Hi All, thanks Ericks- Here's one on Aluminium Extrusions and I found one on UCCNC CAD to DXF - Peter
Hi All- Still waiting, I spoke to the Sales Manager and he's on the case now. I've been looking at racks, here's a catalogue. Peter
Apex Dynamics :: Rack & Pinion
catalogue too big so here's the link....
Hi All - This week I become a very squeaky wheel and send RFQ's to other companies. Two people have left the sale Dept it seems and they are bogged. But there are other suppliers out there. I've been very busy with a diagnosis and repair project so had lots to do. Those fires are out so its back to Maximus. Next important thing to do is build the half sheet model Maximus M. Peter
Yeah, it always has to pass through some automated testing to be sure that customers will get the top-notch product. Testing step is the main step for those companies and firms who really care about their products, no matter do they hardware or software as well. Without tests - they can lose their reputation.
Hi All- No news, I rang the Manager and he's on the case now, they have had staff shortages. I'll also send out the design package to other suppliers. Can't forward the project much until the first quotes are in...Cheers Peter S
Hi All - Hopefully this is the week the quotes come in. Being a designer and a materials nerd there's always something bubbling in the background. I've been working on some machine component casting material for a while. It's a combination of epoxy, carbon fibre and another high stiffness whisker. I'm doing some vacuum casting trials this week (if the whiskers arrive) and making a block for some machining trials. Working towards a cast small Mill as the next project. Will keep you all informed. 50% Stiffer then epoxy granite just as damp and a bit denser.
One of my commercial projects at the moment is designing some 0.5mm thick carbon fibre bicycle tubes for a client to make a 500g bike frame. This has opened the door to some nano whiskers to use, interesting stuff.
Here's some very high speed machining to look at. Haven't done much on my router lately been rebuilding a laser for the local Mens Shed. But now that's finished I can back to my to do list.
https://www.youtube.com/watch?v=l2my4RMJZWM
Cheers Peter
Epoxy composite sounds interesting. I'm keen to hear how it goes.
The sand and rock components of epoxy granite are of course partly used due to low cost and high availability. How do the fibres compare?
For a metal mill, weight and large sections are not usually an issue so stiffness of epoxy granite doesn't seem to be a limiting factor generally (just use very big sections). Obviously different considerations for a gantry router where you have to move a large part and therefore weight optimisation is important.
7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)
Hi Pippin - Epoxy is relatively expensive no matter how you look at it. I've looked at some urethanes but the gel time is too fast for the vacuum process I use. There is a very good acrylic resin with indefinite gel time but it needs an oven to kick it off. But I will need an oven eventually to correctly cure and stabilise the epoxy... Carbon Fibre is V expensive so the trick is to use the least amount but get the best effect. I have been working on a recycling scheme for CF through some of my clients so its good value if they can get me enough of it. The HM whiskers are a commercial product and I'm waiting on various cost breakdowns vs volume. So until that whole puzzle and $ equation is sorted I can't tell if its economic or not, at the moment it looks reasonable. Performance wise on paper it looks V promising and I see no technical hurdles as I've made similar yet more complex materials before. So need to make a block and see how it mills and drills.
Casting parts will open up possibilities with shapes and part consolidation that plate billet parts can't achieve. I can route the moulds/plugs on my router Scoot. The bench Mill project is torn between a Bridgeport config or a gantry config. Datron have very nice Ep/Granite gantry machines. The moving gantry gives you the max size table for least footprint. The bridgeport gives you max stiffness as the tool is always within the bearing footprint. The mill has a target footprint 700mm deep and 800mm wide. Pros and Cons. These things will come out in the wash. Peter
Thought you might be interested in the following papers (same authors). They report using epoxy granite to achieve the same stiffness as steel or cast iron at a reduced weight and greatly increased damping. The section sizes are bigger, but despite this the weight is less due the low density.
http://annals.fih.upt.ro/pdf-full/20...-2012-2-13.pdf
http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf
7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)
Hi Pippin - Thanks for the documents. I have been designing & building composite structures for over 30 years so no need to convince me of their virtues! I'd like to build in carbon fibre but it would be an expensive exercise for a hobby machine but it would be a very good production machine material.... Epoxy glass would be as stiff probably stiffer and much stronger then Ep granite. But a machine part does not need high strength and to some extent it does need weight to counter inertial forces. The material I am about to make will have a density of 4000kg/m3 as the fibre is quite dense. The fibre is 4x stiffer then granite so I expect the bulk modulus to be around 55GPa whereas Ep/Granite is about 35GPa. Being a composite it will be damp so I think it's a good thing. I shall make production moulds for the main parts. I have decided on a moving column design vs a bridgeport config. This takes better advantage of the rails and cars by not using a saddle and keeps the tool within the kern of the bearings. But I need to get Maximus done!! I have started talking to another supplier for quotes on Max's parts. I think the original supplier has a very large project on at the moment and is not interested in small jobs. Keep making Peter
Here's the current visualisation model, its block geometry no detail yet until I get the concept figured. Would you like one
Nice design....!!
Hi Ericks Thanks.
Pippin thanks for the docs. They do confirm some of the data I have.
For the layperson. Cast iron is the traditional machine tool material because it is easy to mass produce. Its damping feature is a strong secondary benefit. It also has surface friction features that are of benefit over steel as well. Depending on who does the research & what exact materials are used cast iron is 2-3x damper than steel. This can be described by the value zeta. Which is number that represents the vibration diminishing. In one of the above papers steel is 0.007, CI is 0.018 and EG is 0.022. The bigger the zeta the more damp the material is, so in rough terms the batch of material they used and tested EG was 0.022/0.018=1.22x damper then the CI they used. This number can be thought of as the % of energy absorbed in each cycle so steel absorbs 0.7% each cycle Ci absorbs 1.8% and EG is 2.2%. The researchers made equal stiffness beams and compared their weights and damping. The mill i'm designing is intended to be a benchtop size. So weight matters as it needs to be freighted and assembled on a decent bench. From helping others in the topic of damping, the material dampness is not the sole solution to a damp machine. Thin sections typically used by extrusions and std tube products are a clear culprit. Thin sections are easy to excite, especially thin square or rectangular shapes.
If we cast steel machine parts in thick or solid sections they would not vibrate as much either. With the rapid movement towards large scale metal printing we shall see the major machine manufacturers using other materials that are very stiff and live. But they will do extensive modal analysis of the parts to design out the vibrations. Perhaps that will be a new thread when I start doing modal analysis on this mill. I hope to get a block mould made this week and make a block of Tetrium material for testing. Cheers Peter
Now show me what you can do and draw me up a cnc laser frame
Hi Ericks - Need more detail for that. Is it a LED laser? a CO2 laser with direct beam? or lots of mirrors and smoke? 6"x6" or 40ft long and 10ft wide? Peter
Your Tetrium sounds interesting!
A number of papers report 5x damping with epoxy granite compared to cast iron.
A moving column machine is interesting. Benefit of a short lever when the Z axis is low and not having a saddle (not easy to make an ideal saddle). Downside is large column mass to move.
Moving column seems to be a common design for 5 axis machines.
My epoxy granite mill designs (purely CAD stage) are based on double column VMCs like the Okuma M460. https://www.okuma.co.jp/english/product/vmc/index5.html
7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)
Hi Pippin - Measuring the dampness of a material can be done in many ways so there is experimental error to consider. For instance in the paper you attached they did a modal analysis and compared it to the experiment and found a 16% difference. One thing they did not consider is that in the experiment the beam is in air so it was air damped as well (that's the main reason a tuning fork dims over time for instance) . But in an FE model its in "vacuum" so to speak so no air damping. To include air damping you need to do a coupled CFD/FEA analysis and that's a bit complicated. Another variable is that they do not state the alloy or its heat treatment condition which in CI means there is a huge variable in the grain boundary conditions. It's the grains rubbing against each other and rubbing on the intergranular deposits that provide the internal friction. Every CI alloy is different so I expect every alloys zeta will be different. Same for steel and other materials. Every researcher seems to get different zetas, but the ranking is usually the same which is the important bit I suppose.
The Okuma is like a very sturdy gantry router or bridge mill or portal mill. It has a saddle and that's something I was trying to get away from. A saddle on a bridgeport or a gantry means the bearings have to be organised in a small place. Plus the saddle is sort of an extra piece that needs to be dealt with. The travelling column sidesteps that and I think it's a good solution. The M460 although double column doesn't have the table go under the bridge? I would have thought this is one reason to do it. Although it does say its a mod of another model so they may have used the base to save development time and designed new columns. marketing I suppose two columns are better than one? Peter
Look up crossed bearings. These are linear cars built back to back. So you wont need a saddle. It also means that the rails are orthogonal ex factory. I've looked at them off and on...
Ericks - Like this one except metal and tidied up? Peter
https://www.youtube.com/watch?time_c...&v=OIlNAUVZZaM