-
Aluminium printer/milling machine build.
I've started to build a machine I plan to use to print aluminium structures. It will use a welder and feeder to print Aluminium. Then after the Aluminium is cold it will mill away any errors/excess the welder has made.
It's going to be used to print aluminium structures 2.2m x 2.2 x 15m
I think I am going to need a lot of help especially on selection of components.
Here is the design criteria;
1. Accuracy only needs to be about 1mm but over the full 15m.
2. It could take a year to print each structure. So weeks to setup is acceptable.
3. It will be OUTSIDE because the y axis is going up 15m vertically. The Y axis HAS to go up vertically because molten metal and gravity.
5. I will build the y axis as it prints. Like the top of a crane or building form work climbs the structure it is making.
6. I will set 4 aluminium posts into the ground with helical gear rails attached to the sides. This will be the y axis which the rest of the printer will climb, I will weld the structure that is being printed to the posts as the height increases. I am printing ridiculously rigid structures which will be far more rigid than the CNC printer itself, so the height will not be a problem as the structure being built is welded at intervals to the climbing posts. Even when the gantry is at full 15m height it will only be a meter from being physically attached to the structure being printed.
7. There will be no physical machining contact between the welding head and the object being printed. The only physical machining contact with the printer will be the spindle used for milling what the welder laid down.
8. The milling spindle is only there to follow the welder around and clean up any excess, shaving off a few millimeters. No deep cutting/milling required. Same grade of aluminium every time behind the welder.
9. Both the welding/printing head and milling spindle will be located close to each other. It will either be printing or milling never both together.
10. I plan to use AI and a camera to make measurements from a reference(not on the machine) and adjust the welding/milling as required.
11. If the machine distorts/bends/vibrates while in operation then I will cut it, straighten it then reweld it.
From my design requirements I believe the smallest motor spindle is all I require. Am I wrong? missing anything? The welder has to be water cooled so cooling water is going to be on the gantry may as well get a water cooled one and avoid the noise. If am only going to be removing a few mm from the just printed aluminium then a 400W motor should do? Yes/No? Is the quality of the aluminium finish going to be reliant on the quality of the motor? Will a good cutting tool and small cuts give me as good a finish as a high quality motor taking chunks off?
I also decided to use Helical gear rails throughout for linear movement because of the long lengths involved and the possibility to add extra rail when needed. Are there any better solutions, cheaper? I can just afford the helical gears solution so unless there is a better and cheaper option then I think I am just going to bite the bullet and go for helical gears.
I am trying to find the cheapest rail solution. I think linear bearings are too expensive(15m x 2,5m x 2,5m) and the accuracy way more than I actually need. I am thinking of using the aluminum beams that I am going to build my gantry on as the rails and use regular bearings as wheels. Will I have problems with the helical gears if the gantry is not on linear bearings? I see this is how most cheap 3D printers do it, but they use belts for motion and not helical gears. I never bothered considering a belt setup because my belt lengths would be 10m long. I could not find anyone that was using these type of belt lengths for CNC or 3D printing. And the 25mm belt cost $12 per meter. Can belts be used successfully at those sort of lengths? Saw a Youtube video where the stretch on a 500mm belt was visible.
Anyway I am going to visit the scrap yards and Aluminium suppliers this week and find 12.5m of the biggest aluminium box sections I can afford and weld them up into a 2.5m x 2.5m square for my frame and then another 2.5m beam that will traverse them. First build my x and z axis without servos, connect a cheap motor and measure how much vibration and deflection I get when taking off a few mm of aluminium weld, then strengthen/dampen as required. Weigh the beam I end up with and then get the servos/motors to shift that.
I would be very grateful for any information/opinions on rails and motion solutions that would suit my application.
-
Re: Aluminium printer/milling machine build.
Have you made a picture of this thing? I'm trying to visualize it - especially the part about it building its own Y axis as it goes - but not having much success.
I'd suggest using steel beams rather than aluminum ones. Steel is much stiffer, and it's also cheaper. I have seen 3D printers based on MIG welders, so that's not hard to picture, but I'm not seeing how this could possibly be rigid enough over that huge span to carve away at the weldment without chattering madly, especially since you're using wheels on your beams instead of real linear rails.
-
Re: Aluminium printer/milling machine build.
Hi,
great sounding project.
I agree with Andrew, use steel in the construction, it is way cheaper to build a structure of given rigidity out of steel than aluminum.
To be honest I think a 400w spindle is a bit of a joke. This project will cost many thousands, what matter if you up the ante in the spindle power to 2.2kW, they are only a few hundred
dollars?.
I am rather dubious that the bearing arrangement you have described will be sufficiently accurate to ensure optimal mesh of the helical gear and pinion. I would have thought that the mesh
needs be +-0.02mm or there abouts....and that would probably exceed the bearing idea.
The only other idea to a rack and pinion is a rotating nut ballscrew. They are used on very large machines and I suspect prohibitively expensive for your project....could be wrong of course.
Even transporting a 15m long ballscrew will give you grief.
Craig
-
Re: Aluminium printer/milling machine build.
Hi G-Spot - Some feedback. 30 years ago I used to program welding robots and train people to robotically weld. One of the exercises I designed was to get the welder to write their name on a plate then start stacking it up and see how high they could make it. So I was 3D printing metal a long time ago :) At about 50mm high the signatures would get wobbly. That's because of the weld shrinking and generating lots of stress that pulls the stack around. So you have a lot to figure out. There are large scale welding 3D printers around. I'd do a lot of research and make a small a scale version first. I'd look at laser welders this is the best technology to get what you want to happen, happen.
Your Q's
10) using AI sounds great but again its not easy. As the weld progresses the structure moves. There are several camera based weld following/steering systems around so there are precedents, do some more research
11) good luck with that approach, It won't work. This sort of machine has to be correct at the get go. Again a small scale version will provide a lot of failures and learnings
400W spindles have very small shafts and fatigue very fast. Mine rarely got over 300 hrs before they snapped and that was majority timber. When I used them on aluminium they bent and once straightened they then failed. I would use an er20 or an ISO20 spindle 1.5kW minimum prefer 2.2kW. Milling AL weldment is a tough thing. Welds are soft and gummy you will need lubricant and high pressure air to keep the tool clean and sharp. I used to manually dress AL welds and even burrs gummed if you were not paying attention. If the machine head is a bit wobbly you will choke the tool real quick. Single flute tools are the way to go to help on this issue
In regard to the finish this comes down to the dynamic stiffness of the total machine. I have been researching this off and on for a few years. What you propose will have many vibration modes that will be easy to excite. You need to look at 3D printer drivers that have input shaping, That will be the best defense against this type of vibration. You are proposing a light weight structure that is in no way what a mill of this size would look like. They are massive for a reason. If you look at 15m high structures such as bleachers, scaffolding, temp buildings etc you will see they wave around in the breeze. You will have global and local vibration issue to solve.
Helical or straight gears? Hmmm helical will be difficult to get the correct mesh over such a length in such a structure. I'd use straight with a tensioner like basic R&P cnc's use. The spring loaded drive takes care of the intolerances. Rack comes in 1.4m lengths and you will need to align all of those somehow. Longer is available but costs a lot and transport is always an issue. They can arrive bent. Its easier to align straight gears then helical. By align I mean get the pitch across the gap correct you use a short piece of rack across the gap. You can't do that with helical due to the wind in the gear.
It is possible to use belts but I'd use a 50mm wide for the long axis. But I think straight R&P will be better for you.
Linear bearings are actual cheap. By the time you get straight tube, several bearings and then make carriers accurate enough your well past the cost of the rails and cars. I have tried and won't go there again its too painful. Plus home made goes out of tolerance regularly.
I would not spend any $$$ until you have sorted this on paper or CAD. I can see a lot of pain in this project. I have been involved in all aspects of your project and in each bit there are high hurdles to overcome. These compound exponentially when placed into the same machine. I'm not saying don't do it, but go small scale first... Even large companies and universities collaborating in this area have taken years & Mega $$$ to get something together that works.
Good Luck on your adventure and keep us posted... Peter
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
awerby
Have you made a picture of this thing?
I only know how to use ACAD 3D-Studio and it's the Johnny Depp version which I need to rehack onto my PC. So that will take at least a week to get working again.
I am keen as this is probably going to be a commercial project, eventually, if I am lucky..lol.., to use something a lot simpler and cheaper. What do you use?
Imagine a 4 post car lift. Going to attach a square frame which prints the x and z axis. Standard 3D printer design but moving the top of the printer up and down and not the bed.
I live within 50 miles of the biggest Aluminium smelter and mill in the country so I am not getting much difference between the price of Aluminium and steel for the same dimensions, like only 15% more for the Aluminium.
From my experience in sailing I am not convinced that a steel structure is more rigid than aluminium. In sailing the more rigid boat wins. If your mast or boat flexes you spill the wind. But there isn't a single modern racing boat with a steel mast, the trick is they use steel stays to brace the Aluminium mast. They use a little bit of steel where it works best, in tension, to make the aluminium structure more rigid than steel would be. Of course Carbon fiber is what is used now but before that came along it was all aluminium masts.
I also happen to be working on my own DIY construction project where I am making a pre-stressed concrete beam 20m long x 1.5m x 0.2m. I spent the last 2 years sinking 15 6m deep reinforced concrete piles into the ground with about 50 tons of concrete on top. I now have the ability to prestress large objects up to 20m in length to 100s of tons. Had to design and make a machine capable of digging 6m deep holes only 30cm x 30cm through stone or soil that could be operated by 1 person. Been there done that got the t-shirt. Only cost me $100 for the steel and 3 months from start to first hole finished. In case you are wondering why I didn't just hire a pile digger, there was a massive flood here 18 months back and for 3 months you could not hire any. Anyway my machine can go through stone and concrete while the ones you hire are augers and cant. Also my machine could do undercut piles which only piling machines costs hundreds of thousands can do which cost thousands to hire.
Was thinking of using large Aluminium box sections only 5mm thick. Fill them with concrete with dozens of high tensile steel rebars running down the length then pull them between my end posts leave for 30 days then cut the rebar away from my end posts, thread the ends and then use them for my machine.
Not sure why so many DIY builds go for the post stressing option on their concrete interiors. The amazing thing about prestressed concrete is after the cement is dry you no longer have to carry around the machine that did all the stressing. The energy it exerted is now locked in your cement. So if you now encase the prestressed concrete in your machine you are adding the energy stored inside to resist flexing to your machine. If you use the post stressing method then your machines tensile strength is being used to stress the concrete. And because the rods running through your concrete are not attached to the cement they provide a pathway for vibrations to travel directly through the concrete bypassing any dampening properties your cement may have.
If you try to insulate a house exterior wall from vibrations if you have anything rigid between the 2 walls like bolts etc then it bypasses whatever insulating material you put in the middle. Same with submarines, no use filling a layer between the outer and inner hull with vibration absorbing material if you then attach the inner hull to the outer hull with hundreds of bolts.
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
joeavaerage
Hi,
great sounding project....
Thanks Craig
Yes I usually look at the most expensive option then the cheapest and try to get something in the middle.
I also hate noise. I recently switched from electrically produced air to petrol because I have a residential electricity supply, now I am always looking for electric tools and not the air ones because I can't stand to work with the racket the petrol compressor makes. So I am definitely going to go water cooled.
I also hate gearbox problems. When they go wrong its hard to tell why when all you are left with is pieces. So I am going to take yours and Peter's advice and go with linear rails of some sort.
I already started this project before COVID hit but had to shelve it until now. But I did spend a couple of months researching balls screws and as you pointed out getting long ones delivered without damage is the biggest problem. Half the stuff I get delivered to me here in South Africa comes with physical damage. And shipping is criminally expensive because of how bad the Customs and Duty clearance is. Anything more than 700mm in dimension is usually $250 for shipping.
Paul
-
Re: Aluminium printer/milling machine build.
Hi,
Steel Youngs Modulus =207GPa
Aluminum Youngs Modulus =70GPa
Steel is three times stiffer than aluminum, fact.
Filling hollow tubes, be they aluminum or steel is a waste of time. You need rigidity and concrete filled tubes are not it. The same tube but with double the wall thickness is better.
Craig
-
Re: Aluminium printer/milling machine build.
Hi G-Spot - pre or post tensioning a structure does not make it stiffer. It does make concrete stronger by placing more material in compression. As concrete is weak in tension. The internal strains are in equilibrium and do not contribute to the structural stiffness.
Steel masts especially stainless steel have been used in the past. But weight high up in a sailing boat is important or the reducing of weight that is. By the time you make steel thin enough to achieve the required weight it is too thin and can buckle. So after wood which is a great material, then steel, then aluminium came composites... Aluminium is viable because it can be extruded which is a cheap way to form metal.... Peter
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
peteeng
Hi G-Spot - Some feedback. 30 years ago I used to program welding robots and train people to robotically weld.
Awesome!!! My strength and formal qualifications are in electronic engineering and computer programming. I have been building my own welder for this project, that was the first part of the project, but I had so many unanswered questions on the welding side that stopped me from choosing the correct components and I already had a couple of thousand dollars spent on components and didn't want to spend more blindly so I decided to buy the best TIG machine that I can interface to my machine, get the answers I need then finish my own welder, and like you say Laser is the way to go, and the prices are dropping to within the reach of DIY now.
I went for TIG and not MIG because with TIG the arc and adding the filler material are separate operations. I want to use a camera with infrared to see the temp of the metal and then add the aluminium to the weld pool. I have a whole bunch of theories about how I can control the weld pool using software(AI) that I want to explore.
I have done a lot of research in the past using cheap cameras and Small Board Computers to measure objects accurately and plan to get the rails of my machine laser etched with registration marks then use the camera and computer to position the machine and not the position of the motor shafts or encoder. I plan to use a mechanical brake in conjunction with jogging the motors to obtain resolutions far exceeding the resolution of the motors alone. This is why I am going to go for the straight cut gear rails, as long as they can move the axis then it wont matter how worn or how much backlash there is as long as they don't jam I will get excellent resolution. Simple closed loop routine that jogs the motor about the point you want to be at then apply brake and check.etc etc. My resolution on the axis which I use this strategy will be dependent on how well etched my rails are and not the ballscrew or geared rail I use. And as long as it is not an axis that requires rapid speed and cutting precision, like the y axis on a 3D printer, it will be a winner. I predict that it will take up to 30 minutes to weld each layer and no cutting or welding is done when moving the y axis and it is the 15m axis.
I need to make my first attempt 2.5m by 2.5m because we talking about ships here...lol and anything on a ship is supersize compared to other engineering. I can earn good money immediately with the machine just working to 5mm accuracy only welding, the parts are traditionally sent elsewhere for milling. If worse comes to worse I can just stay up all night and do them by hand. Even if it only works as a giant set square it will save hours compared to working with cardboard cut outs and visual approximations and hours of grinding.
I think I am going to make this version good enough to make the money that will pay for the next version......as opposed to to something that will bankrupt me before I literally get it off the ground.
I am going out early tomorrow to visit the scrap yards that keep industrial beams, aluminium and steel. I will report back on whatever is available and would be grateful for your input before I make a choice.
Thanks for your excellent advice and information.
Paul
-
Re: Aluminium printer/milling machine build.
Hi,
mild steel has a tensile strength of about 500MPa. Hardened and tempered 4340 ( the stuff my Grandpa always called '90 ton axle steel' and his eyes glazed over) has
a tensile strength of about 1000MPa (depending on the temper), so about double the strength of mild steel.
Take a 50mm x 50mm bar of each 1m long, supported at both ends, and then load it with a 20kg weight in the center. Which deflects the most? Mild you might say,
after all its weaker right?. But no, they both deflect the same because the Youngs modulus of mild steel is the same as 4340, both being 207GPa
If you used an aluminum bar of the same dimensions (50mm x 50mm x 1 m) and loaded it with 20kg it would deflect three times as much as steel, because its Youngs modulus is 70GPa.
It beggars the imagination, but strength is NOT the same as stiffness.
For instance if you used a 100mm x 100mm x 5 aluminum section, its highly probable that any load you put on it is a small fraction of what it can withstand, ie it won't break but it will
spring or deflect. If you use 100mm x 100mm x 10mm aluminum section neither will it break but it will spring or deflect less.
Craig
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
joeavaerage
Hi,
mild steel has a tensile strength of about 500MPa. Hardened and tempered 4340 ( the stuff my Grandpa always called '90 ton axle steel' and his eyes glazed over) has
a tensile strength of about 1000MPa (depending on the temper), so about double the strength of mild steel.
Craig
Yes I understand the difference between strength and stiffness.
If you apply tension to something you make it stiffer.
If you apply more tension to a washing line then it deflects less for a given load. But you reduce it's strength.
And a thin walled steel tube filled with concrete is a lot stiffer than just the steel tube alone.
"The Effects of Filling the Rectangular Hollow Steel Tube Beam with Concrete: An Experimental Case Study"
https://www.researchgate.net/publica...tal_Case_Study
-
Re: Aluminium printer/milling machine build.
Hi,
BS. Concrete is about 50GPa, compared to steel of 207GPa.
If you fill a thin walled steel tube with concrete you increase its stiffness by the stiffness of the concrete alone and given the modest Youngs modulus of concrete not by much.
Double the wall thickness of the tube as the stiffness increases markedly, way WAY more than filling with concrete.
Quote:
If you apply tension to something you make it stiffer.
BS. All you do is shift the load point up the curve, but the slope of the curve , ie the Youngs modulus remains the same.
Quote:
If you apply more tension to a washing line then it deflects less for a given load.
The washing lines ability to withstand a load is not due to the stiffness of the line, but due to tension.
Craig
-
Re: Aluminium printer/milling machine build.
Hello Paul - Readers - Complex concepts trigger warning :)
Your project is interesting and tough on so many levels. Lets talk about geometric resolution or accuracy to begin with. The geometric control system that most CNCs use is called deterministic. What you are describing is deterministic control. This means that the structure determines where the tool centre point (TCP) is. The machine actually does not know where the TCP is we assume that it is at the correct place because we told it to go there. You mention 1mm (so I assume that means +/-0.5mm) over 15m. This means the control system and the structure have to be good to 0.1mm which means it has to be made to 0.01mm. This is typically done by machining lands to the required accuracy using bigger machines then the machine your building (called a mother machine) In your case this is not possible as its a multi piece lightweight structure and its very big. You cannot control a TCP from within a deterministic system unless the entire system is built to the required accuracy. In your case this is impossible. So lets talk about humans. Our bodies are indeterminate and very complex. We use several systems to be able to touch our nose or pick up a glass of water. Particularly we use a system called Proprioception (PP). This is an electromagnetic referential system that is external to our mechanical deterministic system. The PP gives feedback to our motion systems and steers (reactively and predictively) our limbs so they get to where we want them to get to. Plus it not only handles position it also handles velocity and forces. Amazing. You are going to need a machine perception system.
I have been involved in a similar system that repair welds large mining equipment particularly extremely large excavator buckets, much bigger than you are talking about lets say 20m by 30m by 10m high....The company has gone down that road and stalled and started a stalled a couple of times. But size does not matter. The issues are the same as if it's on a benchtop or on a mining site.
So since you can't solve this issue in the deterministic universe your machine (and others) will have to have an external laser, lidar, precision gps or ultrasonic system (the perception system. Or machine perception system MPS) that measures where the TCP is at all times absolutely and then compares that to the deterministic information, create an error differential then feed that back to the controller for correction. This is done on some machines via glass scales and on very large mills its done with lasers these days. So I imagine you will have to have a scaffold or flagpole above your machine (as it needs to be separate from the deterministic machine), a transmitter/receiver on the machine head and a lidar scanner looking down on your job doing the MPS work. Your cameras will do the local work within a local geometric reference frame at the machine head and this will be integrated into the global reference frame and corrected in real time.
Then there is the issue of being a large lightweight machine and it will vibrate. Plus thermal expansion/contraction will be very large and I'm not sure how you will compensate for that, perhaps the MPS can cope...
All of this is not trivial... as you may have already guessed. Peter
as a note a lunar lander has literally fallen over on the moon because they did not spend the M$$$ to check the laser inertial system, they assumed that it being a commercial system it would work. Plus they left the system initialisation as a manual switch that had to be human operated prior to launch and it was not on a checklist with a big RED TAG so of course it was overlooked, so the mission which costs say $80M has basically failed. Inertial control is tricky. Musk has had heaps of rockets blow up trying to land the critters but his over the hump on that now. Why do I say this? because Paul many of these issues you are about to get entangled with are all the same stuff just smaller scale... Control, Control, you must learn control... Yoda
re: tension in washing line. The apparent stiffness increase is due to the foundations of the line not the line itself. If your lines are attached to tree twigs there is no gain in stiffness. If they are embedded in tonnes of concrete, then it's the foundation stiffness that improves not the line stiffness. Yoda probably had something to say about that as well.
-
Re: Aluminium printer/milling machine build.
Here's research that confirms filling a steel tube with prestressed concrete improves it's strength,stiffness and ductility even more so than just filling it with normal concrete.
Both experimental and analytical results show that the prestressed strands could significantly enhance the confinement effect of the core concrete under bending, which, in turn, improves the prestressed CFST beam performance in strength, stiffness and ductility.
https://ui.adsabs.harvard.edu/abs/20....144Z/abstract
-
Re: Aluminium printer/milling machine build.
Hi G-spot - You have to be careful when reading this sort of work. They are done to prove something in particular usually hand in hand with an industry partner who wants a particular outcome and all of those statements are relative. Strength improved relative to a thin hollow beam YES, stiffness improved against the hollow beam YES and ductility improved against the hollow YES again. But it could have been a thicker tube and all the comments are then the same. Construction industry loves concrete so to use a light steel tube then fill with concrete is sort of attractive... You have to broaden your vision sometimes to find the "best" structural solution. Peter
thick hollow tube is stronger than thin hollow tube - obvious, thick hollow tube is stiffer than thin hollow tube - again obvious and thick hollow tube is more ductile than thin hollow tube (can you guess) :)
As an after thought i suggest you consider timber for your structures vs metal. Being involved in boats I expect you are familiar with timber, epoxy and fibreglass. Mass timber and laminated timber is now a very popular building material even for multi story buildings. Its stable, light stiff damp... Easily screwed to , repaired etc etc. Most of my routers are made from formply and its proven to be stiff, damp stable for its purpose. Peter
-
Re: Aluminium printer/milling machine build.
Hi G-spot - I read the article and the reason the stiffness of the prestressed beam improves is that in the non stressed beam the concrete cracks, this means the structural efficiency in tension is zero. When the concrete is prestressed the compression holds the cracks together and the load is transferred via the steel members. This is discussed in the paper its not my interpretation. So there is a mechanical reason why the apparent stiffness improves. The concrete people are always looking for ways to improve their product. The metal people don't as its pretty much a given. Portland concrete is low modulus, low strength and it cracks. Its main construction benefit is it can be cast in place... There are concretes that don't crack and there are concretes that self heal. The Romans used them 2000 years ago, that's why their huge domes are still standing... In this papers case the tubes could have been made thicker or the pre-stressing strands could have been used by themselves so it was a tensegrity structure (sort of) Many ways to skin the cat. Its the concrete people driving that research, they need solutions........ Peter
-
4 Attachment(s)
Re: Aluminium printer/milling machine build.
OK been looking for steel.
New price is $1:15 Kg
I managed to find a scrap yard with a great selection of beams at $0:70 Kg so I am going to take the 50% cheaper option and use it to get thicker bigger beams than I could afford new.
They even have railways tracks, so tempted to use them and make my own bearings, 1000Mpa and hardened by trains, 100 years of stress relief.
Now I must choose a size, I need 10m and my budget is for 500kg.
Any recommendations for web and flange thickness ?
Is it better to go for beam height or flange thickness? I know that flange thickness is better if you want it to be stronger but web thickness is important for twist and buckling.
I think for a machine base/frame then resisting twist is just as important as load bearing strength. They are not going to be used for load bearing in the direction of gravity.
I want to go for I beams because they are easy to model in FEA and easy to increase stiffness later.
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
peteeng
The concrete people are always looking for ways to improve their product. The metal people don't as its pretty much a given. Portland concrete is low modulus, low strength and it cracks. Its main construction benefit is it can be cast in place... There are concretes that don't crack and there are concretes that self heal. The Romans used them 2000 years ago, that's why their huge domes are still standing... In this papers case the tubes could have been made thicker or the pre-stressing strands could have been used by themselves so it was a tensegrity structure (sort of) Many ways to skin the cat. Its the concrete people driving that research, they need solutions........ Peter
I lived in Rome as a teenager. When I arrived there I bought a guide book and visited every great monument, took me about 2 years to cross them all off. The Pantheon is amazing and I visited it on a rainy day when the rain falls through the hole in the roof. The fact that it doesn't have a capstone at the very top and instead has to support itself just on the strength of the concrete makes it awe inspiring. And that's when I decided to join the masons(the concrete people) and I have been pushing it ever since...lol
There are 2 different types of concrete. One mixed by builders and one mixed by scientists. If you mix it with measuring jugs and scales and make sure the temperatures while mixing and even more importantly when curing are kept constant then it is like freaking kryptonite. With steel or other materials you can pull out a blow torch and it melts away. Concrete can break a man who tries to defeat it.
People need to stop looking around them at builder's concrete when judging concrete and try making their own under lab conditions.
-
Re: Aluminium printer/milling machine build.
Hi G - Design the machine before you buy anything. Its free to design something. If you have CAD and FE then make all those decisions first. Making decisions based on cost like you are doing this early always ends in grief. Define what the structure has to do and design it to work. And remember the CAD model is perfect - the real stuff is twisted, crooked and imperfect. Peter
-
Re: Aluminium printer/milling machine build.
Yeah right.
About 4 trillion dollars per years is spent on concrete and buildings by builders, globally.
There is probably exactly nothing that high-end builders donĀ“t know about concrete ..
In Finland for example concrete can be cast in sub-zero temps, with the right additives.
2000 years ago the romans already had concrete that could be cast underwater, and they used it to build viaducts -- some still in use today.
ANY industry that spends over a trillion dollars per year at anything will quickly achieve a mini-max of results/cost/ease-of-use within a very few years.
PV panels are an example.
So is concrete.
So is steel.
So is alu manufacturing.
No lab anywhere is going to do concrete better than builders spending hundreds of millions of dollars per year at it over decades.
Endless materials are better than concrete. Depends on what and how your measure and how much You can afford to spend.
E.g. The best laminated wood beams, are about 30% stronger than steel by mass, and stiffer, and can take any shape including complex compound curves.
The best carbon fiber beams are very light vs strong, but were abandonded by SpaceX after a few years in favour of stainless steel.
And they, SpaceX, are the most successful, the best, engineering company on earth.+/-
With pretty much limitless money.
Buckyballs and other exotics are theoretically stronger by about 10x, but You cannot buy them by the ton at Your local steel merchant or builders supply.
Spiderwebs are much stronger than steel, by mass, but there exists the problem of getting a 100 M spiders weaving a web for You, on time, to budget, to spec.
Real anecdote. Feel free to laugh. Or invest.
I researched this.
Really, I did.
Apparently If You feed spiders amphetamines You can increase web production a lot.
Potential investors were very impressed when I suggested a farm with 100 M spiders in the sahara desert, fed on amphetamines.
This was to build a space elevator, around 2002.
There are technical challenges, one of which is the potential energy in a space elevator 36.000 km tall, should it fail.
Firstly it will pretty much circle the globe when falling, and secondly it is likely to crack all the continents and vapourise a lot of seas.
So who exactly will insure it, permit it ?
The permits process is probably a 20-year process.
Financially, 2T$ should do it, and Elon Musk and or Jeff Bezos could carry it off, maybe Larry Ellison.
It c/would potentially give humans free spaceflight, and asteroid mining, and endless raw materials from the belt, all kinds of goodies.
Quote:
Originally Posted by
G-Spot
There are 2 different types of concrete. One mixed by builders and one mixed by scientists. If you mix it with measuring jugs and scales and make sure the temperatures while mixing and even more importantly when curing are kept constant then it is like freaking kryptonite. With steel or other materials you can pull out a blow torch and it melts away. Concrete can break a man who tries to defeat it.
People need to stop looking around them at builder's concrete when judging concrete and try making their own under lab conditions.
-
Re: Aluminium printer/milling machine build.
Hi Hanermo - good to hear from you. The Space X rockets changing from carbon fibre to stainless steel is an interesting one. The main reason was production speed and availability. SS rockets can be made faster, he needed about one per week and it took a month to make a CF one. Plus there's not enough CF on the planet to build the amount of rockets he needs (roughly speaking). Peter
-
1 Attachment(s)
Re: Aluminium printer/milling machine build.
Reinstalled my FEA software, unfortunately the latest version is full of just as many bugs as the last version.
But after many hours fighting it I finally managed to get it to spit out the deflection of the beams I was thinking of using with 500kg at the centre point.
Even at 50 metric tons this beam(2.5m x 200mm x 200mm x 10mm) is only deflecting 3mm.
I see that HAAS have a deflection test for their spindle which is 0.0762mm with 1000lbs(~500kg)
https://www.haascnc.com/service/trou...---ad0599.html
Anyone know what the average accuracy of top end CNC milling machine is with 500Kg force on the spindle?
-
Re: Aluminium printer/milling machine build.
Hi,
a smaller machine like a Hass mini-mill would be around 50N/um, whereas a good industrial size machine like a VF1 about 150N/um. Really top end machines
required for the most accurate parts from tough materials up to 750N/um.
A good hobby machine suitable for aluminum cutting and with care steel cutting is about 20N/um. Personal experience says that trying to design and build a 50N/um
machine is a big challenge......probably beyond what you might reasonably called hobby materials and techniques....for instance machines of 50N/um or better are all,
or at least 95% of them, are cast iron and/or stress relieved steel.
Craig
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
hanermo
Yeah right.
.
Yeah right, not knowing that chemists in a lab decide how the biggest building companies on the planet are going to mix their next batch of cement and not some wizened old site foreman.
Builders mix concrete for profit and not maximum strength, always, if it will be in spec for the job then that's all they care about. So useless at their jobs that they have to have most of the concrete they make lab tested after it has been laid.
-
2 Attachment(s)
Re: Aluminium printer/milling machine build.
Hi G-spot- The test is to determine spindle bearing float but if I look at the numbers the machine deflects at around 90N/um... say 0.001" at 500lbf. For the Z direction I'd expect it to be much greater than that but then at least its a number... Here's some very old data. Machines are much stiffer now. Peter
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
joeavaerage
Personal experience says that trying to design and build a 50N/um
machine is a big challenge......probably beyond what you might reasonably called hobby materials and techniques....for instance machines of 50N/um or better are all,
or at least 95% of them, are cast iron and/or stress relieved steel.
Craig
I am going to weld it like a tank.
First I am going to preheat the parts before I weld them.( I think for the steel I am going to use it is 100C)
Then I am going to stick it in my furnace at 600deg for an hour then let it cool.(I checked up on this because I need to order the burners and thermocouples to suit the temp range)
The cost of the burners and thermocouples(accurate to 3 degs) are about $200 for 10 sets, so I am going to stick a thermocouple on all the pieces and make sure I am always at the right temps when I am working.
Also I have a cement truck or two coming for a job I am working on, so I intend to lay down a 500mm thick reinforced slab with holes in in to make a straightening jig.
I used to know a guy in the truck chassis straightening business, he showed me how they pull these size frames into shape with heat and chains attached to large jigs.
If things get really out of line, then I am going to put the frame down on a flat firebrick surface and heat it up to 1100 C, then it will melt flat...lol.
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
peteeng
Hi G-spot- The test is to determine spindle bearing float but if I look at the numbers the machine deflects at around 90N/um... say 0.001" at 500lbf. For the Z direction I'd expect it to be much greater than that but then at least its a number... Here's some very old data. Machines are much stiffer now. Peter
Thanks Peter, that's exactly the info I needed. Now I can get going in CAD, already have a drawing but using those 200 x 200 x 10 thick beams which were ridiculous over-kill as the FEA has shown. So I am going to scrap that version and make version in FEA using the data you kindly shared.
-
Re: Aluminium printer/milling machine build.
Hi G - You don't need to be too technical with a stress relief. If the metal is red then it has relaxed. Support it well because at 600C it will sag under gravity...
The usual guide is 1hr soak per 25mm thick section, but if it's red its done. Cherry red definitely done.
Sorry Tanks have no relevance when it comes to machine design, the more welding the more the distortion, the more hassles downstream. Minimise welding. Your journey hasn't begun yet, still optimistic thought bubbles and enthusiasm. Its called the Fuzzy Front End.... But I encourage you to keep smiling... Peter.
Preheat is useful if the parent is some funny alloy that has cold or short cracking,. If its mild steel then preheat is useful if you can bring the entire part up to a temp say 200C or hotter. This evens out the thermal stress created by the hot puddle cooling. I would recommend small mirrored welds done in sections and let cool. Take a long time to do the welding vs getting the whole thing done in short time. This allows the structure to settle in between seasons. Straightening cars to 1mm is a bit different to machines at 0.01mm. I have hot corrected large lathe drive screws with oxy in my youth, steel is like butter at the correct temp... Peter
If you have an oven then tack the assembly together, preheat in the oven to 200C then pull out and start welding. Use heavy protective leathers., I have several scars from bumping hot metal... Personally would not go down this path but you have time to figure that out... get busy in CAD and FE... Peter
-
1 Attachment(s)
Re: Aluminium printer/milling machine build.
Here's the sensor info if anyone else wants to make their own De-stressing oven. $ 4.25 each including thermocouples, you can get the boards by themselves and then use a higher temp probe if you want to forge or melt steel. But they are more than good enough for 600C.
Correct me if I am wrong but structural steel requires 600C for an hour for each inch.
These sensors can be bought as cheap as buttons everywhere, they hook up to an Arduino and you can read and log the temp within 3 degs across the range.
Cheaper solution than getting your stuff milled first then hoping you can bolt it together straight.
I costed the fire bricks and the insulation for my machine which is 2.5m x 2.5m and it is still a lot cheaper and easier route than bolting.
Cast a flat surface with self leveling cement, jig your machine to it, then weld up. Best of all you leave the sensors in your machine when it is built. Then you can preheat your machine to the same exact temp each time you do machining, or you can log all your machining with temps then make corrections to your accuracy as you machine based on the existing temps.
I also want to be able to de-stress anything I print so having this ability will really save me a lot of headaches in the future.
You cant use a handheld thingy for something big, because unless you wrap something big up well in insulating blankets you will battle to get it up to 600C, super easy to burn a hole in whatever you are heating if you can only see it to measure the temp after taking 5 minutes to remove blankets. Arduino connected to a phone, you can watch the temps without losing all your heat by opening it, you will see rapidly rising temps and lower the gas at the burner in that area. Yes I am aware that propane is not good for forging or smelting because of the carbon in the burnt gas but no such problems with 600C. If I had to do this commercially I would rig up an induction heater and then use the Arduino to do the whole thing, bring it up slowly to 600 then hold for an hour then slowly bring it back down to atmos temp.
-
1 Attachment(s)
Re: Aluminium printer/milling machine build.
Hi G - You have to be very careful with the concrete. It explodes due to the trapped water. Its a very powerful explosion. So you have to insulate the floor very well so it CANNOT get above 100C. This is not trivial when your ovens going to be 700degC. Heat Treat ovens are usually 500mm or more above the floor... steel framed then firebricks etc etc. Peter
Heres an axle I designed coming out of heat treat at 650C. You can see the oven floor is off the ground... two reasons - protect the floor from the heat and allow the creation of a trolley. I don't think you realise the energy required to heat the oven is huge. Firebrick insulation etc is very leaky - good luck. I have designed 3 ovens for heat treating aluminium. The energy required is more about heating the oven then the part... Peter
I was involved in fire tests for building products when I was a student. The lab had a specially made house which used a particular fire hardened concrete. We did a test one day involving plastic chairs and the floor started exploding. It was like a machine gun, chunks of concrete flying at whizzing velocity everywhere. Very scary. We were close as we were reading the instruments but not for long, everyone ran! Peter
-
Re: Aluminium printer/milling machine build.
Hi,
Quote:
I costed the fire bricks and the insulation for my machine which is 2.5m x 2.5m and it is still a lot cheaper and easier route than bolting.
Fire bricks are not the right thing for a heat treating oven. Fire bricks are thermally stable, can usually resist flame products, but are moderately dense and moderately thermally conductive.
For a heat treatment oven you need insulating bricks. Here in New Zealand they are $12.50NZD (plus tax) each. Not too bad for small ovens but at the large sizes it becomes extreme.
Insulating bricks are very low density and highly thermally insulating, quite a different beast to fire bricks.
https://thermalnz.co.nz/products/ref...on-bricks.html
Is there not a company or companies that can do it for you? I suspect that the cost to have it done will be well less than building your own oven.
Craig
-
Re: Aluminium printer/milling machine build.
Hi,
issue to tease your brain: how are you going to hold the fire bricks/insulating brick up in the ceiling of your oven? Having some sort of frame or columns to hold them up
is only going to interfere with the working volume. Boring a hole and riveting/bolting to some external frame is going to allow heat to conduct via the rivets/bolts cooling the
working volume and heating your frame.
You might try shaping the brick so that they form a dome.
Maybe some bolt let into the surface of a brick to about half the depth of the brick and then cemented in place with a refactory cement.
As you can guess I have given very considerable thought to this matter, with a view to making an oven myself. Truth is that to make an oven of useful size becomes expensive, and then
you might use it once or twice and seldom ever again. The prospect of getting commercial custom for such an oven is pretty limited. Most heat treatments involve carburising or nitriding or
quench and temper cycles. This is not an area where you can wing it, industrial customers are demanding and exacting.
Craig
-
Re: Aluminium printer/milling machine build.
Hi G - I understand the ingrained attitude of doing everything yourself, I tend the same way. But in this instance building a heat treatment oven is way off the critical path for this project. It's a many years project within itself. If you have not built a large oven yourself there's so many pitfalls and rabbit holes that when you turn on the switch and it does not work then your whole project is 2 years behind and many, many $$$ behind. There are several ways to do this without stress relief. You need to investigate various designs and methods first. You do not even have a general arrangement. A good GA is the usual official starting point for a project. It can be looked at reviewed and critiqued. Round 1 designs usually end up in the bin... I think around version 10 you start seeing the real path forward and by V20 your starting to polish the design. Keep at it - Peter
-
6 Attachment(s)
Re: Aluminium printer/milling machine build.
Design update
Fixed my design size based on the following;
1) Max width allowed on the public roads here is 2.6m
2) Maximum height of room where machine will be operated is 2.4m
3) Maximum room space is 3m x 3m
4) Rail and screw sizes are 2000mm, 2500mm, 3000mm (the ones I have any chance of being able to afford)
5) Sheets that I intend to weld are plentiful in 2m widths
Fixed my design type as moving gantry based on the following;
1) Welding sheets of metal 2m wide at ground or near level gives me the ability to weld up sheets to makes up a single piece of 2m x 15m or any length if I stick the machine on a truck.
2) Any other type of design means I have to have a table or supports to lift the sheets onto and I would only be able to weld 2 sheets.
3) No clamping required for many welding printing jobs.
4) Safety, your gantry weight does not change so you can dial in your servos to not exceed limits, fixed gantry means moving bed and work-piece, rapid accelerations or deceleration could cause work-piece to be catapulted.
Design philosophy I am going to use based on;
1) Work experience at the top of masts has taught me that trying to lean out means everything goes to ****.
2) If you are moving an x and y axis up high and using M20 rails and 20mm connecting plates then you are always going to be off centre by a minimum of 140mm plus half your beam thickness. Which means on a machine with a beam 200mmm wide you are off centre by a minimum of 240mm. Then half the diameter of your spindle on top of that.
3) The problem with movement(vibrations) is because you are working so far off centre 300mm not that you are working so high.
4) Tilting your beam doesn't solve much.
I am going to use FEA to optimise a design with perfect symmetry, where the centre of the cutting tool is aligned with the centre of the beam.
I started out with a work area of 2m(x) x 2m(z) x 1.2m(y). I am using 2500mm rails and screws on this design and sacrificing 500mm to symmetry
Constraints I am using is that the maximum size beam/pillars can be is 300mm x 300mm (cost, availability and weight)
I used a 100mm x 100mm beam with the spindle at the end that travels up and down my gantry beam for the y axis
First image is stress analysis the gantry 300mm x 300mm beams and pillars with 2m between them and 1.2m below them.
Second image is the optimisation based on 5000N of force pushing up from the spindle column
-
2 Attachment(s)
Re: Aluminium printer/milling machine build.
Oh WOW! this is the type of AI that impresses me.
This is the bare minimum of steel you need from those original 300mm x 300mm solid blocks to get the job done. Works out at 15% of the weight of the original solid beams.
I now know what my minimum cost making it from steel will be.
Also what is super interesting is how it has put the legs on opposite diagonals of the bases.
Dont forget this design is operating as a press. The final design will factor in the torque and forces from the tool in the horizontal plane, the acceleration of the gantry forces etc, so it will need more steel than this and will definitely not look anything like this when those are factored in.
Oh yeah the spindle column is 200mm x 200mm not the 100 I put in my previous post
And the outer dimensions of this machine are 2.6m x 2.6m x 1.5m the work area is 2m x 2m x 1.2m when I talk about dimensions in mm I am talking about cross sections and not length.
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
joeavaerage
Hi,
Fire bricks are not the right thing for a heat treating oven. Fire bricks are thermally stable, can usually resist flame products, but are moderately dense and moderately thermally conductive.
Craig
I already have a lot of ceramic fiber cloth, enough to cover it half a metre thick, the frame is only 200mm high. The gantry will lie flat at ~200mm also. Will use at least 10 propane burners and compressed air + a leaf blower or 2. If I was trying to melt it I would be worried about heat escaping quicker than I could put it in.
I have an electric heater already, I had to build a test load when I was designing my welder, so I had to be able to sink 300 Amps. bought the roll of heater wire direct from the manufacturer and made a large heater that I stuck outside, was more like a light.....lol fastest heat source ever. if you stood in front of it and powered on it would hit you like a wave.
Lots of experience with fire, used to be bush fire fighter, lived off grid before solar power was a thing where everything was done with fire, water for house was heated with a fire boiler. I have been trained in forging and loaded and unloaded kilns when I was studying.
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
peteeng
Hi G - You have to be very careful with the concrete...
Hey concrete can withstand up to 500C without a sweat, they build all the public fire places from the stuff here.
Just gets the surface worn down a bit. Anyone charging for chemicals to put in it to make it fire proof must be in on a con, I not surprised there were unpredictable results.
Admit it Peter you are so anti concrete :)
Awesome oven design where you combined the door opening mechanism with the trolley to remove the work piece.
-
Re: Aluminium printer/milling machine build.
Hi G - I have put a lot of time and effort into concrete for machine parts. It has a place in the CNC universe. Your projects are very aspirational and I'll follow them with interest. Your AI work I expect is based on stress optimisation not stiffness optimisation. Keep at it. Peter
-
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
joeavaerage
Hi,
issue to tease your brain: how are you going to hold the fire bricks/insulating brick up in the ceiling of your oven?
Craig
I have so much building materials here, If I could melt all the scrap steel I have I could probably cast a machine. Would make a net from high tensile steel fence wire, tie the back of the blankets to that with glass fibre and then lower and higher it like the circus does with the big top. If it's a once off then I am only going to be concerned that the blanket cannot get close to any of the burners.
I have already sourced fire proof mats that are used in industry to hold back fire for a short while and protect concrete and other structures. They work for up to an hour and are like $100. Would have laid that down on top of the concrete, then firebricks on top, then a layer of fireproof mat on top first, then multiple layers of ceramic fiber insulating mat put a sheet of stainless steel in between a few layers.
Get some of my hippy friends round and we can throw turf and sods on the top like it's some sort of medieval earth cleansing ritual.
Concrete is an OK insulator, especially at thicknesses more than 100mm, that fireproof mat will be more than enough to keep the concrete below 500C especially when there are firebricks too, I would be using a minimum of 10 thermocouples, not all of them could ever be faulty, the only source of fuel is the propane, there is next to no chance that the temps would exceed 600C.
I sure as hell would be making sure there were 2 main valves, one far away next to the gas cylinders, and one in the work area.
All work operating burners, carried out to the side and not above. Been there, found myself in the middle of fireball before lol....
-
6 Attachment(s)
Re: Aluminium printer/milling machine build.
Quote:
Originally Posted by
peteeng
Keep at it. Peter
Wow I reckon I will be cutting sheets before the end of the weeks, this FEA has just answered questions that I think would take me 10 years to work out manually.
OK I reckon this design is as close to the machine I will make. Basic shape, curved stiffeners on the sides. This is with only 15% of the base material, I will up that to get within top machine specs.
The height of y axis of 1.2m was ridiculous because to achieve symmetry with a 500mm bearing spacing on the base of my gantry I needed to be within an equilateral triangle whose height is 420mm, so I made the max machinable height 400mm so the bottom of the rails on the beam will be exactly at the top of an equilateral triangle with the 2 base bearings the other points. This means that the tool head will always be operating inside the triangle.
The red ball in one the pics is the exact centre of mass of the machine. Means when you operating at a height of 200mm, the mid point the tip of the tool will be at the centre of mass.
I don't care about the only 400mm y axis. This machine will be what I lift up using screws on posts on each corner if all goes well, so it will have an extra y axis at a later date.
So I am almost fixed on a height at 400mm unless I splurge extra and get 3000mm long rails and screws which would allow me a height of somewhere around 900mm.
These optimisations are amazing, can make the thing the stiffest just using thick plates welded in strategic areas.
I am going to try and get to a smoothed and double checked optimization then make it out of balsa wood and test it.