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  1. #101
    Join Date
    Jul 2018
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    6249

    Re: Designing new Router called Maximus

    Hi All - Been digging into the Tool plate. Seems the corrugated plate makes a difference. With a 1000N load it makes a 0.1mm diff. I've modelled the plain design with the corrugated front and the corrugated back with a plain front and the corrugated back always wins. This means if I go this way the width is wide and spindle mounting is perhaps limited. So I have to make a decision if the 0.1mm is worth the width or cost as the guttered design will be more costly. But then I like its looks as well. So I suppose it will also come down to how the shape fits the motion parts. Time will tell...

    I'm also intrigued with the timber machine builders. Timber has a lot of advantages for small machines plus I could make them on Scoot, although I have done Al in Scoot but it complains if I use DOC >0.3mm. So I did some calcs to see what an MDF, plywood and aluminium laminate gantry would need to look like to be same the stiffness as Maximus. Rather big!! Max is 230mm high x 170mm wide. An mdf section 50mm thick would have to be 550mm high and 450mm wide to be the same stiffness. Now the bearing beams for Max are 300mm long so if the beam was 300mm wide I wouldn't mind but 450mm is too big. It would be a bit smaller in F17 ply about 400x400mm and I fiddled a bit with aluminium but still too big. So I would have to knock down the stiffness target to 5N/um for the timber one I think unless I was building a really big machine. My hope was that I could have the gantry bearings bolt directly to the gantry web with no extra structure. If I changed my design rule of using nuts everywhere I could do it in aluminium but I'd have to thread the rail holes. Maybe worth it in future.

    Seems the course is set for Maximus now... Peter

    By the way the E for MDF is from 2600Mpa to 3500Mpa which is the same as epoxy resins at 3000Mpa to 4000Mpa. F17 plywood is about 14000MPa stiffness. I choose F17 because that's what formply is and I use formply for a few things. I like using very thin epoxies that are designed for infusion as they have no thickeners in them. They saturate timber much better than laminating epoxies which have thickeners added.

  2. #102
    Join Date
    Dec 2003
    Posts
    1206

    Re: Designing new Router called Maximus

    I would imagine that the sort of people who need to cut three inches from billets of titanium in a single pass have the resources to buy large and strong machines.In fact just buying the metal would take a lot of cash.Which would lead me to believe they won't be buying router kits.
    I saw the gains you achieved by boxing in the sides of the machine and just have to ask the question-why use vertical sides?We both seem to have an acquaintance with the world of boats and for a very long time there has been an acceptance that shrouds should meet a mast at an angle of thirteen degrees or more.Would it have helped your figures to have used such an inclination on the sides of the machine?It leaves me a bit bemused when I see other design proposals on this site,which have nowhere hear this level of engineering analysis,and which have gantries securely braced in one direction only.You have done the calculations to bring your proposal to a high level and set all of us a superb example of how to create a strong machine without using hundreds of kilos of metal.I hope the use of mental and computing resources,rather than just throwing metal at the job becomes the new normal.

  3. #103
    Join Date
    Aug 2014
    Posts
    232

    Re: Designing new Router called Maximus

    I know you're joking, but for the benefit of anyone new to machining:

    Your buyers will not be able to machine G5 titanium on a router type machine - titanium is awkward to machine even on a rigid mill or lathe, it doesn't like being cut, and if you want the tools to last more than 10 seconds you will need lots of coolant. Titanium is a very poor conductor of heat, the chips won't take away much heat so the tool gets extremely hot if run too fast or no flood coolant. Try a simple test in a lathe - take a piece of 10mm G5 rod and turn 1mm off of the diameter for 20mm in one pass with a brand new sharp carbide tool. If you got the speeds and feeds right the finish will look good, but when you measure it you'll probably find it isn't round, more likely trilobular.

  4. #104
    Join Date
    Jul 2018
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    6249

    Re: Designing new Router called Maximus

    Hi Routealot - Was joking about cutting titanium. That's really a big boys game Making sides that are at an angle is difficult. Cutting sheet square is easy and probably won't gain much stiffness with the angle. I can give the ply supplier a cutting list and pick it up. If I want it mitred to angles thats a hard area. By angling the sides you don't gain stiffness per se. What happens is that the structure becomes "strain hardening" or "strain stiffening". This means that as it deflects it gains stiffness. In this case we don't want it to deflect very much. In Routealots thinking this is because angled sides are more like triangles then as squares. Squares behave like a parallelogram under side load and hinge at the corners. So the corners have to be very stiff in this case.

    Shrouds at thirteen degrees (I've designed down to 8degs) are limited in angle as they stretch under load and then the rig can become unstable. Plus there is a large increase in leverage as the angle gets smaller so the wires get stretched even more. That's why highly loaded monos use poles at the deck to improve the rig angles. To correctly analysis a yacht rig it has to be done in a non linear solver. Not many Naval Architects or even mast builders can do this until recently. If you keep the shrouds out at big angles then linear solvers are fine can be done in excel. Non linear solvers include gravity, the wire catenary and the wire stretch to check it does not become unstable at the loading envisioned. I prefer free standing masts and over the last 30 years of working with masts and rigs I thought they would have become the norm. Aircraft learnt very early that rigging is a huge amount of drag and wires and fittings are failure prone. Yachting changes very slowly.

    Getting back to Titanium as Zorbit explains. Ti work hardens like stainless steel but even harder. Plus being very very strong its chips are very strong and hard and can damage tooling. Plus the strings are very strong as he has found and they wrap around the machine and parts and are difficult to remove. Tools have to be extra sharp and cutting depths have to be as heavy as possible. Plus Titanium is not stiff so it deflects more than steel. So everything has to be right to do a good job on Ti. I think I'll make Trilobular the word of the day. I'm away for 2 weeks from thursday (3 days away) so won't get much done on Maximus until I get back.

    The companies cutting Ti with 3" tools make very expensive swarf. The pre-swarf tonnage must be worth millions in an operation like that. Peter

  5. #105
    Join Date
    Jul 2018
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    6249

    Re: Designing new Router called Maximus

    Hi All- Looking at the 15mm vs 20mm conundrum again... The Hiwin bearings have a Co static rating of 15mm 16.2kN and 20mm 23.9kN. This means at an applied load of less than Co the bearing will not suffer any damage. Damage is usually brinelling of the race by the balls. So I looked at the model and extracted the bearing reactions with an applied load of 10,000N or 10kN. The tool plate bearings are closer together so see more load. The gantry bearings see about 6-7kN and the tooling plates see 7-8kN. These are within the Co of the 15mm bearing and the operational load is unlikely to be 10,000N. Maybe 1000N so why go the 20mm?? I just checked and the 16&23kN are for expensive bearings. The BST bearings are Co15=8kN and 20mm=13kN so the BST would still do the job. My only niggle is that the 15mm use 4mm bolts and these feel too small. The 20mm uses M6 which are much stiffer. I think that convinces me to go 20mm again.... Damn I have to remodel the bearings.....Peter


    From the image you can see that there are 411 connections in the router model. Each connection can be spec'ed as bonded, sliding, slid with friction, disabled or separating. It's a bit of a drag working thru the connections checking that they are all correct. But it's much quicker then doing it the usual FE way of checking mesh and contacts, takes hours and hours. Some models take days to set up.

    Better check the moment as well. The bearing moment is 0.076kNm say 0.1kNm. This is near the limit of the 15mm BST bearing (0.15kNm) but remember the 10x design load so would be Ok. The Hiwin has a 20mm moment capacity of 0.221kNm. Linear cars can take moments in all directions and the roll direction is usually the strongest. Mr roll, Mp pitch and My yaw. cheers Peter

  6. #106
    Join Date
    Jan 2008
    Posts
    1523

    Re: Designing new Router called Maximus

    Suggestion (you may have already looked at this): model a larger box section for the Z axis whilst keeping the spindle tucked in as close to the gantry as possible.

    Eg a square section rather than a rectangular section.
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

  7. #107
    Join Date
    Jan 2008
    Posts
    1523

    Re: Designing new Router called Maximus

    Regarding your gutter design:

    Have you modelled in the ball screws and nuts? My experience is that the large size of ball nuts often dictates component spacing. E.g 16mm ball nuts are thicker than 15mm profile rails. I wonder if the ball nuts will get in the way of your gutter.

    Does it really need to be a fancy bent profile, or do you get the same benefit from a thick plate with pockets / space milled for the bearings? May be substantially easier and cheaper. Accuracy much easier to achieve. Bent plate will require post machining anyway.
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

  8. #108
    Join Date
    Jan 2005
    Posts
    15362

    Re: Designing new Router called Maximus

    Quote Originally Posted by peteeng View Post
    Hi All- Looking at the 15mm vs 20mm conundrum again... The Hiwin bearings have a Co static rating of 15mm 16.2kN and 20mm 23.9kN. This means at an applied load of less than Co the bearing will not suffer any damage. Damage is usually brinelling of the race by the balls. So I looked at the model and extracted the bearing reactions with an applied load of 10,000N or 10kN. The tool plate bearings are closer together so see more load. The gantry bearings see about 6-7kN and the tooling plates see 7-8kN. These are within the Co of the 15mm bearing and the operational load is unlikely to be 10,000N. Maybe 1000N so why go the 20mm?? I just checked and the 16&23kN are for expensive bearings. The BST bearings are Co15=8kN and 20mm=13kN so the BST would still do the job. My only niggle is that the 15mm use 4mm bolts and these feel too small. The 20mm uses M6 which are much stiffer. I think that convinces me to go 20mm again.... Damn I have to remodel the bearings.....Peter


    From the image you can see that there are 411 connections in the router model. Each connection can be spec'ed as bonded, sliding, slid with friction, disabled or separating. It's a bit of a drag working thru the connections checking that they are all correct. But it's much quicker then doing it the usual FE way of checking mesh and contacts, takes hours and hours. Some models take days to set up.

    Better check the moment as well. The bearing moment is 0.076kNm say 0.1kNm. This is near the limit of the 15mm BST bearing (0.15kNm) but remember the 10x design load so would be Ok. The Hiwin has a 20mm moment capacity of 0.221kNm. Linear cars can take moments in all directions and the roll direction is usually the strongest. Mr roll, Mp pitch and My yaw. cheers Peter
    4mm mounting SHCS work fine in the 15mm rails they are 60mm apart I have opened up the holes so 5mm can be used if you are in a heavy loading situation, but if you machine pockets for the rails, which is a normal way to install them, then there is not much loading on the mounting screws 20mm rails are good but if you don't need them which is in most cases for a machine that is not doing heavy cutting the 15mm work fine
    Mactec54

  9. #109
    Join Date
    Jul 2018
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    6249

    Re: Designing new Router called Maximus

    Hi Pippin - I don't want to use tube sections as they require threading and some require internal stiffening to achieve the local stiffness that I have picked. That's why The Maximus beam has the internal stiffening (earlier posts cover this area of the design development). Plus the SHS section that's close is 250x250x6 which is way to heavy for this machine concept. I may have to back off the stiffness spec when I get it costed anyhow. Whether its square or rectangular the tool plate area stack height would be the same. Maximus is a kit router aimed at a similar market to the Al extrusion type market. Yet it will be the same stiffness as a light mill hopefully. An earlier post compares plate to the sheet metal design (#33) and the equivalent tool plate is terribly thick and heavy (30mm aluminium). The target cost of the kit means parts can't be machined, similar to the extrusion kits, they don't get machined. The machine design is in Round 1 but near R1 end. R1 figures out the structural requirements and limitations of the design and the "best form" of the parts. No motion parts are considered in R1 to make the path clear. I'm about to start Round 2 which will include the motion parts. Yes the gutter may go because of the screw drive but the drive does not have to go down the middle. If it goes to the side or the top then the gutter does not matter. Every part must contribute to the stiffness of the machine and every part must be looked at closely and opportunities found. Many kit routers suffer from lack of stiffness. Seems its the first thing Makers try to fix in this category. So the aim is to provide a very stiff machine that forms a great growable (hackable? in the lingo) skeleton for the maker.

    Hi Martec -Thanks for the info. I too am sure that the 15mm will work. My main concern is the tool plate car bolts when they are in tension. I'd prefer the M6 vs the M4s. And the 15 & 20 are very close in $$$. I have drilled out rails in the past as well, but being a kit it should be plug and play. As soon as I go near a machinist the price blows out. It has to be all done on the laser or by the Maker. I try not to have holes threaded by the Maker as some can't or won't do a good job of it. And having the laser shop thread holes is uneconomical as well so it's a rule "no threaded holes" or machined lands...

    But the rails are OK. Rails are dependant on their support structure. I'm thinking about the ply bench and how best to mount the rails. I think at this design load they will need metal reinforcing or I go to a metal bench and a timber stand... more thought bubbles needed... but the bench is up to the Maker so I just have to give good guidelines for what's needed,

    I, like others also have the concern I'll need a little more space in this area so the 20mm maybe the go. Until I get it modeled I can't vote yet. Peter

    Re - modelling the bearings. I use the manufactures STEP models for the CAD work. In this case I have to rework them a bit to create the compliant rail area plus give various nonfunctional bits more clearance so when Simsolid does its auto connection thing it does not find the plastic end caps and connect them to the steel rail ! cheers Peter

    I've attached a zip file as a test for MP4 files in future. Its Brevis my second kit. It's a benchtop carver, laser, printer platform. Zip seems to be the way at present until admin allows MP4s to be uploaded...

  10. #110
    Join Date
    Jul 2018
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    6249

    Re: Designing new Router called Maximus

    Hi All - In my search for real machine stiffness values I keep coming across big machines. They seem to quote machine stiffness whereas the small machines just say they are rigid. This one has a massive 350N/um stiffness. And to carry the Titanium theme its for machining titanium. Peter

    Would really like someone to measure their machine stiffness out there and describe its utility. I sent a note to CNC Router parts asking them the stiffness of their machine and they responded that they did not know. cheers

  11. #111
    Join Date
    Jan 2007
    Posts
    626

    Re: Designing new Router called Maximus

    Quote Originally Posted by peteeng View Post
    I sent a note to CNC Router parts asking them the stiffness of their machine and they responded that they did not know. cheers
    Thats a bit of a concern..... I would have thought they would have that sort of info.
    I was considering one of their kits.

    Steve

  12. #112
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    Jul 2018
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    6249

    Re: Designing new Router called Maximus

    Buy one of mine Rob - you know its stiffness and i'm on the same island. which model were you looking at? Peter

  13. #113
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    Jul 2018
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    6249

    Re: Designing new Router called Maximus

    Hi All- I'm off on a small trip so won't be looking at this for 11 days see yuz 14th May plus...

    Rounding up the stiffness info. There are a few small mills out there measured by a UK machine group at 1-5N/um. The guys with 1N/mm want to stiffen their machines. Academic papers quote 10-100N/um and seems its the big machines that get serious with quoting machine static stiffness and they range up to 350N/mm which was stated as near infinite stiffness! Maximus design target is 10N/mm and I shall design a light version and heavy version by changing the plate thicknesses. Once I'm through Round 2 which integrates the motion elements the static stiffness will be reviewed and then finalised eg heavy will be 12-10-8-6 etc and light will be 3-5N/mm etc.

    By the way the large machine makers have onboard sensors that monitor dynamic stiffness/loading and datalog loadings to check that the spindle and tooling is looked after. They also have the tool loading on the DRO available. Anyone who can measure and publish their machine stiffness here that would be excellent for the general machine info world. Machine stiffness requirements is a common question in the forums...

    Part of my trip is dropping in to see couple of 3D metal printing companies. I think this area needs to be investigated for making parts. See yo'all soon. Peter

  14. #114
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    Jul 2018
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    6249

    Re: Designing new Router called Maximus

    Hi All- contemplating the timber bench and how the rail loads will go. So looked at the bearing reactions and they are not too bad. The design load is 10000N so divide that by 10 as the max service load. The longitudinal load is only 34kgf which is 3.4kg service load and its pushing down so will distribute fine. The transverse load is 309/10=31kgf which is in shear which again I think the ply will take easy. The uplift on one of the bearings is only 21kgf which is 2kgf in service so that won't pull the screws out. So I think the plan is to go with wood, set the screws with PVA or epoxy, use long metal thread screws for maximum support and the deals done. I'll revisit this formally when I get back these seem to be low for a 1T applied load.

    My latest router Brevis uses a melamine laminated bed and the threads felt very good through them so I think the top of the bench "stands" will be melamine to keep it simple. The stiff melamine will distribute the loads nicely to the ply. I was thinking of using aluminium under the rails but that's more cost and effort. I was reading a work on a large 5 axis machine. It had long concrete stands for its axis some 2.0m high. They weighed 200T initially and they got this down to less than 100T with some analysis. Big is heavy...

    I'm off now so back the 14th may... Peter

    I've attached a tip truck image, that's the sort of thing I'm analysing at the moment. They like to know where it's going to crack before it does. They also prefer it not to crack!

  15. #115
    Join Date
    Jan 2007
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    626

    Re: Designing new Router called Maximus

    Quote Originally Posted by peteeng View Post
    Buy one of mine Rob - you know its stiffness and i'm on the same island. which model were you looking at? Peter
    Hi Peter,
    I will certainly look at your package....don't worry....lol
    I fellow CNCer here has already made enquires and the cost was found to be a bit prohibitive compared to DIY.

    I have never heard of so much talk about stiffness in a CNC Router so I am very impressed.
    It hurts my head but I am nevertheless impressed....lol.
    Steve

  16. #116
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    Jul 2018
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    6249

    Re: Designing new Router called Maximus

    Hi Sterob - Well it's talked about alot all over in forums and suppliers sites but no numbers are put to it. My router is stiffer then your router, I want a stronger router when they mean stiffer etc. So I have been trying to put real numbers to the issue so a proper comparison can be made. Seems all the big machine manufacturers specify it, they understand the importance of machine static and dynamic stiffness. So we've all learnt a bit along this journey. Maximus is a bit bigger than I wanted but then I didn't know the numbers to shot at. Now we know, it can be given some perspective. Peter

  17. #117
    ericks Guest

    Re: Designing new Router called Maximus

    Do you have a website that shows your maximus machine?

  18. #118
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    Jul 2018
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    6249

    Re: Designing new Router called Maximus

    Hi Ericks - Post number 97 has images of it so far. Its being designed on this thread. I'm travelling the next few days and will be back on the thread 14th may. Only 10 pages so have a good read from the start. I've attached a couple of screen shots here. Peter
    Attached Thumbnails Attached Thumbnails Ma x1.jpg   Max 2.JPG  

  19. #119
    Join Date
    Jan 2007
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    626

    Re: Designing new Router called Maximus

    Quote Originally Posted by peteeng View Post
    Hi Sterob - Well it's talked about alot all over in forums and suppliers sites but no numbers are put to it. My router is stiffer then your router, I want a stronger router when they mean stiffer etc. So I have been trying to put real numbers to the issue so a proper comparison can be made. Seems all the big machine manufacturers specify it, they understand the importance of machine static and dynamic stiffness. So we've all learnt a bit along this journey. Maximus is a bit bigger than I wanted but then I didn't know the numbers to shot at. Now we know, it can be given some perspective. Peter
    You are doing a great job Peter.

  20. #120
    ericks Guest

    Re: Designing new Router called Maximus

    Quote Originally Posted by peteeng View Post
    Hi Ericks - Post number 97 has images of it so far. Its being designed on this thread. I'm travelling the next few days and will be back on the thread 14th may. Only 10 pages so have a good read from the start. I've attached a couple of screen shots here. Peter
    Thanks....sorry i was under the impression you already had machines for sale

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