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IndustryArena Forum > MetalWorking Machines > CNC "do-it-yourself" > Milli a new composite mill kit
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  1. #1501
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    Re: Milli a new composite mill kit

    Hello Pippin - I have been digging around for other resin and ATL Composites have a similiar resin to the Luci-Clear. ATL are testing my carbon coupons. They do not advertise it on their website so if your interested you need to call them and ask.

    https://atlcomposites.com.au/

    Peter

  2. #1502
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    Re: Milli a new composite mill kit

    Hi All - I have been studying damping again and came across an article on laminated metals. Very interesting. I also ran a few modal models comparing steel with aluminium and it turns out that the vibration modes are geometry dominant with the modulus playing a very small role. I made a cantilever 1000mm long of 50x100mm section and ran the modal solver comparing the two materials. The vibration modes where very very similar. eg the first pair is steel 41htz AL 41.5htz. The second pair are 81.2 and 81.3 htz so the take away here is make things as stiff as possible. Which is the usual mantra. Every reference seems to have different damping factors for materials of quotes the values from other sources. So my current leaning is towards laminated aluminium. I've had word that the CF samples have been passed to an engineer for test so hopefully I get the modulus back soon.. Peter

  3. #1503
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    Re: Milli a new composite mill kit

    Hi All - The Milli project has been parked for a while due to various things. I've been on a small trip which has given me some thinking/doodling time that has been productive. Project Milli has had two main aspects 1) material development and 2) machine configuration. The material development side tried to make a cold castable and conventionally machinable material similar to aluminium. This failed except if I use carbon fibre or (drum roll) aluminium. On the machine configuration side I keep coming back to the Mori Seiki M1 but I dislike the saddle. We'll yesterday I think I conceptually cracked the saddle issue so its time to do some more detailing to see if that works. So I'm waiting for the modulus test of some CF coupons to arrive and I can develop the new Milli in F360 and try the F360 FE module... so there's movement at the station as they say around here... Peter

  4. #1504
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    Re: Milli a new composite mill kit

    Evening all and Sundry - I received the carbon fibre test report today. It achieved a tensile modulus of 38GPa and a UTS of 280MPa. So now I have enough info to compare metals, glass laminates, CF laminates and concrete variations. 38GPa is half what I get at test for a CF mast laminate using stitched fibres. The recycled material is mainly woven cloth which is crimped and is about half the efficiency of straight fibres so 38GPa is an expected result. But good to have the paperwork. Considering I can get 34GPa out of Eglass its a tough call to go to the CF unless I get it free. Then the CSA grout is 34GPa out of the bag easy to use, just add water... but steel is 200Gpa and Al 70Gpa so I'll think it through... Damp steel is the go... Peter

  5. #1505
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    Re: Milli a new composite mill kit

    Hi All - Here is the stress strain graph of the tests. Coupon 6 slipped in the jaws so was excluded from the results. Peter

  6. #1506
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    Re: Milli a new composite mill kit

    Why doesn't strain start at 0%?
    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)

  7. #1507
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    Re: Milli a new composite mill kit

    Hi Pippin - I presume you mean (0,0). To make the graphs clear they step the curves over a set amount for each data set. Otherwise they would be over each other and difficult to interpret. The actual data will start near (0,0) I say near as the machine and clamps and coupon have elasticity and if you regress the data backwards it won't go thru (0,0). The slope of the curve is the interest not the axis intersections.... coupon 2&6 show some slip so they had to be neglected or just use a particular part of the curve. Peter

  8. #1508

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    Re: Milli a new composite mill kit

    Hi peter

    Hope you are doing well. I just go through your whole 2 years thread in two days. Very Informative.

    If you are on Instagram then look at this.
    https://instagram.com/great_cnc?igshid=N2ZiY2E3YmU=

  9. #1509
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    Re: Milli a new composite mill kit

    could exchange with our engineers for CNC maching, casting, or other custom items : )
    https://custometalplasticast.com/

  10. #1510
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    Re: Milli a new composite mill kit

    Peter could you or others share (if not proprietory )some of the specifics of your technology of laminating laser cut steel - additive manufacturing. I've tried some searching without much success for actual "nuts and bolts " techniques that a small shop could use for dyi cnc machine construction . The builds in your routers for the z axis come to mind. Things like specific epoxies ( or ? structural MMA's),,surfaces preps, clamping techniques /systems or ? vacumn bagging etc.
    BTW Happy New Year and thanks so much for all you've taught -I've learned a lot and still hoping to learn more.
    Chuck

    Sent from my SM-S908U using Tapatalk

  11. #1511
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    Re: Milli a new composite mill kit

    Hi Chuck - I'll go thru your Q's:
    1) I have found there are good and poor laser shops. Especially ones that can bend accurately. So if the design requires bending and keeping things flat you need to spec your requirements accurately on the drwgs and talk those thru with the metal shop before they make them...
    2) Your epoxy supplier can assist in resin selection. As there are 1000's of resins and suppliers work with your supplier. As a general statement you need a structural adhesive. It can be epoxy, PMMA, urethane or hybrids. You can also use contact adhesives.
    3) Surface preps - follow the suppliers guides
    4) clamping - vacuum is good as it is even and strong. But clamping or built in bolting holes can work
    ask specific questions if needed. Its a huge subject. happy New Year to all Peter

  12. #1512
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    Re: Milli a new composite mill kit

    Morning All - For those using concrete to make machine parts. The Romans made self healing concrete that has lasted 2000 years. Peter

    We Finally Know How Ancient Roman Concrete Was So Durable (msn.com)

  13. #1513

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    Re: Milli a new composite mill kit

    hey Pete

    what do you think about using al2o3 nanoparticles as a filler for epoxy?

  14. #1514
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    Re: Milli a new composite mill kit

    Hi Ard - I have made a few billets using ALOX and epoxy. ALOX is around E=200Gpa maybe E=300GPa so "should" give you a stiff material. Being a crystal, it has different stiffnesses in different directions, so its average stiffness would be about <200 I think same as carbon fibre. However its impossible to machine so you would need to use metal inserts for the hard points. The German UHPC material uses large grain (10-15mm) ALOX to make their high modulus (claimed E80) concrete. All of the concrete and mineral castings I have been able to qualify have been compression tested and I believe they are skewed results due to compression eg liquids in compression have very high stiffness but we can't take advantage of that.... My recent carbon fibre tensile test only achieved 40GPa in tension and that was random long fibre CF at E=210GPa. So I'm struggling to see how ALOX or any other materials can get past 40GPa (round figure) in tension. For machine design we need a) an isotropic material or b) an elastically well-defined orthotropic material so we can confidently design the part. I am organising some new tests using aluminium powder and short steel fibres with epoxy. These are choosen as I can machine them on std mills and my machinists are happy to mill them. I have been playing with materials for decades and currently I have given up on finding the new wonder material for machine parts. I think that laminated steel or aluminium is the best solution at present. Known properties, as damp as cast iron, easy to do. Steel is tough to beat due to its high stiffness with good design pay attention to vibration (do modal analyses) and it comes out on top. Laminate it and its a great material. Peter

    My current view is I can buy E40GPa CSA grout out of the bag cheaper than using anything involving epoxy due to epoxies high cost and low modulus epoxy E=3.5GPa. Nano size does not matter in concrete tests the bigger the particle the higher the modulus achieved.

  15. #1515

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    Re: Milli a new composite mill kit

    You're right not much can be done about epoxy's E=3.5GPa (table is from here)
    https://www.researchgate.net/publica...Nanocomposites

    I meant more about the actual adhesive strength going up, if that's a property worth investing into.
    https://www.researchgate.net/publica...sive_and_Steel

    I can easily get to (as mentioned in the second paper) 4%wt of the epoxy for $200 (80-180nm particles) have a good source for these, smaller particles $$$

    yes I am doing metal inserts al6082 for the rails and steel for the column, rail inserts are thicker for stiffness but use al so its easier to cool them, column insert for the carriages are steel because its much thinner and doesn't need cooling.
    Attached Thumbnails Attached Thumbnails 2023-01-17 02_14_16-(PDF) Mechanical Properties of Epoxy_Al2O3 Nanocomposites.png  

  16. #1516
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    Re: Milli a new composite mill kit

    Hi Ard - Well that research is pretty much a pointless exercise. There are many epoxies with over 100MPa flexural strength so I'm not sure what drives this sort of work. Adhesive strength of epoxies is very high no need to try to better it. For the best adhesion waft a propane flame over the surface prior to applying the epoxy. The flame boils off surface moisture and activates the surface for better adhesion ie it increases the surface energy. Look up plasma surface prep or corona prep or flame prep. Its now std practice in aerospace and automotive bonding. Laser prep is also appearing. Surface moisture would be the number one issue to getting a good bond assuming the surfaces are clean. Look up water break test that's a good thing to do as well.

    Surface Preparation before applying WEST SYSTEM Epoxy

    Flame Treating Plastics - Epoxyworks this works for all surfaces

    cheers Peter

    video showing flame prep at BMW BMW Car Factory ROBOTS - Fast Manufacturing - Bing video

    acrylic and urethane adhesives are not moisture sensitive so drying the surface is not recommended as they use moisture for curing....

  17. #1517
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    Re: Milli a new composite mill kit

    Hi Ard - This is how I'd do your parts, looking at the column:
    1) I would section it into 20mm or 25mm slices. Since steel is 7800kg.m3 and Ep/granite is say 2500kg/m3 (my alox casting is 3200kg.m3 alox is quite dense) 2500/7800= 0.32 so you want to loose 70% of the steel if you want the same weight. Or say lose 50% have a play with generative design and see what it gives you. So spider web the slices in an optimal way. 20mm or 25mm steel is easy to have cut via laser at the plate shop.
    2) Each slice will have a set of counterbored or countersunk holes so each layer can be bolted to the next. Epoxy up each layer and bolt up or press or vacuum bag them and build up the part in sections. The first slice you get rough machined if you want.
    3) This way you have no mould and a hollow optimised part
    4) Once the verticals are bonded take it to the machinist and have the front final machined and the base squared up, add threads to the bottom so the base can be bonded on
    5) take it home bond and screw the base on take it back and have the base finish machined
    6) You maybe able to assemble in the rough and then only have it machined once, have to think that through.
    7) Now you have a very precise, stable, very stiff part that you can include cooling if you want. Some laser shops have a tilting head so you can have the "back" of the slices at the correct angle so its a smoothly designed part.

    You could do it in aluminium. The laser cutter I use can cut up to 16mm thick AL. You could leave it solid and it would be stiffer and same weight as EP/Granite. But thick alum is dearer as it is slower to cut then steel. I think I'd use steel. Use a structural epoxy putty and it would be a very good part. You can also sculpt the outside a bit in the layers to give it some pizazz. Then have it painted candy apple red with a clear pearl finish and it will look a million $$$. Peter

  18. #1518

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    Re: Milli a new composite mill kit

    I very much like this triangle-ated frame, the weight is really well distributed and acceptable and has great work area, on your double column the gantry was like this so you know it's stiff, but the problem of the spindle being too far away from the bed still remains, laminating would definitely solve the issue, will see how it goes, I think I'd laminate from the side though, that way you don't need to pay the extra for the 4th axis laser/plasma/waterjet cutting.

    Lately I've been thinking, since I'm concentrating on high speed machining, maybe I should get rid of tool holders in general to save some $, $20-$50 per toolholder that can be invested in better/more endmills and use one of those direct clamping collets: https://www.acrow-tools.com.tw/uploa...0301161255.jpg

  19. #1519
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    Re: Milli a new composite mill kit

    Hi Ard - But will it be Candy Red or Neon Green? Peter

  20. #1520
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    Re: Milli a new composite mill kit

    Hi All - I have talked to the testing lab and they have agreed to do a couple more tests. So I'm going to make some aluminium granule, steel fibre and hybrid samples to test. Then I think all the data is in. I'm thinking of doing a CSA grout one as well. Peter

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