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  1. #1
    Join Date
    Nov 2020
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    361

    Design Concepts

    There's a massive content drought going on right now so I though I'd revitalize the community with something. It's an older project. If I were to build it, it would probably cost $20k+ and an arm and a leg. It was designed to fit a standard sized garage here in germany(3x5m). It's based on Modig's Rigimill. It uses concrete anchors ala Unisorb Fixators. I'm just dumping the whole WIP folder so it's messy. It was meant to have a 2-axis milling head but I never completed that. I found out that separating the 4th and 5th axis from one another is more feasible (more on that later).

    _model7.prt is the main .prt assembly file, (step of the main assembly also included)

    If loading the parts in Fusion takes too long just remove all servo files(.prt), they are from grabcad and I had someone mention that loading them in takes forever and never ends.

    By the way it takes me 10mins to open the .step but only 30s to open the .prt

    My favorite part about this is the under rail cooling pipes.

    .prt : https://www.mediafire.com/file/f5q2c...0xinf.rar/file (messy but has drawings of cool parts)

    .step : https://www.mediafire.com/file/yzqed...embly.stp/file
    Attached Thumbnails Attached Thumbnails thumbnail_2.png  

  2. #2
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    Nov 2020
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    361

    Re: Design Concepts


  3. #3
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    Nov 2020
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    361

    Re: Design Concepts

    Guy converts motors to spindles, both ER collet and ATC.

    https://www.youtube.com/watch?v=zwd3K-CH2H4

    https://www.youtube.com/watch?v=p_0xkxgVjBI

    His granite based machine.

    https://www.youtube.com/watch?v=bkmn34lKe_E

  4. #4
    Join Date
    Nov 2020
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    361

    Re: Design Concepts

    Today's concept is a moving column. Main goal was a max weight of around 200kg for each part, so it can be disassembled and moved(by use of large men) when necessary, as well as reuse of metal parts throughout the design to keep machining costs down(the more pieces of the same part you order the cheaper per piece it is). A bonus is an addition of a 4th axis on the spindle by use of a cross-roller slewing ring(RU series) a harmonic reducer and a servomotor with a brake. For the 5th axis a rotary table was planned by use of a worm gear, never got that far though and finally decided against using a worm gear at all, not that its a bad practice or anything, lots of companies that make these with worm gears, either tooth types or cam roller types.

    The parts were to be cast after aligning the plates with external jigs made with alu profiles. By now you are probably wondering why I chose this way instead of casting and sending the parts to machining. Where I live, its prohibitively expensive to have anything machined at a shop, not to mention multiple transport costs involved in the process or the general unwillingness of companies to work with private customers.

    To price machined parts I use xometry and protolabs.

    .prt(https://www.mediafire.com/file/dmq16...olumn.rar/file)

    .step(https://www.mediafire.com/file/j9u1b...olumn.stp/file)

    After this concept I switched from designing with uhpc to work with granite slabs instead, for the simplicity of bringing the surfaces to micron level precision through lapping and to eliminate the amount of parts that need to be machined. More on that later.

  5. #5
    Join Date
    Jul 2018
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    6548

    Re: Design Concepts

    Hi Ard - so you are having "rough" granite parts made then bonding steel machined parts to these? Peter

  6. #6
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    Nov 2020
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    361

    Re: Design Concepts

    Quote Originally Posted by peteeng View Post
    Hi Ard - so you are having "rough" granite parts made then bonding steel machined parts to these? Peter
    Hey Peter, good to hear from you.

    No, custom granite parts are also too expensive here and shipping from china, I don't see how that would be viable either. Current idea is to buy a precision 4um slab locally ($1500) 1200x1200x165mm and cut out parts from it. This is why the design also goes back to a double column. Best stiffness to weight ratio. Also skipping machined plates as well, rails and mechanical components directly mounted on the granite. If needed I could glue the rails to the slab. I would not plan to reuse them.

    Steel also switches to aluminium for things like the bridge and headstock, this cuts machined parts costs by 50%. With this, spindle has to switch from torque based to high speed. This allows for a possibility for a very special setup where I can double the workpiece area without changing the overall machine size. I'll cover this later on. Think rotary table, if you set it up that the spindle Y travel is slightly more than half the workpiece size you can rotate it 180° and machine the other half. Really excited about this part.

    Currently waiting on some sample quotes for frameless motors, to build my own harmonic/rv cycloidal actuator. Not making the reducer myself but build the actuator up from components.

    Currently looking at using FB-2 (https://www.harmonicdrive.net/produc...s/pancake/fb-2) and Nidec NH1-D77 or D100 frameless motor(https://shop.sdp-si.com/catalog/?cid=p9997).

    Oh nice, just as I was copying the link D77 price went up from 230 to 310. Brilliant.

  7. #7
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    Nov 2020
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    361

    Re: Design Concepts

    ...in other news a granite router makes the headlines.

    Nothing much interesting going on in this basic concept, except the Z axis. Z carriage and spindle adapter are solid pieces and mounted on the sides like the big boys do, stiffness compared to other setups off the charts. The caveat is the spindle is part of the stiffness equation and Z travel is wholly dependent on the length of the spindle. This can easily be solved by making the adapter longer, but its all about compromises in the $ dep. The gantry legs are also solid aluminum pieces.

    uses this spindle : https://aliexpress.com/item/1005001955171225.html

    .prt(https://www.mediafire.com/file/tgetk...outer.rar/file)
    .step(https://www.mediafire.com/file/eg7tp...outer.stp/file)

    ...and as always beware, the .prt folder is a mess.

  8. #8
    Join Date
    Nov 2020
    Posts
    361

    Re: Design Concepts

    Todays concept is a double column 5 axis mill turn based on dmg's dmu 200p.

    .step(https://www.mediafire.com/file/efr4r...anite.stp/file)
    .prt(https://www.mediafire.com/file/l8hlh...small.rar/file)

    It's body parts are cut out of 165mm thick 00 grade granite plate. The B(45° swivel) and C(rotating table) axes are powered by a frameless motor + RV cycloidal reducer. Why cycloidal and not harmonic? because harmonic flex splines have poor torsional stiffness. Alternatively one could use a ready made robotic joint actuator.

    The spindle is a SAB150 from olispeed, $3-4k, runs hsk 32 or 40 and is a high speed spindle.

    The rotating table has 2 versions, square like in palate changer type and a big round one like in vertical turning centers. This big one allows the work area to be doubled, if you rotate the workpiece by 180°. This really neat feature allows this build to have a massive 600x600mm work area approx.

    The frame is connected to the steel table with vibration damping pads from Maedler that screw to both elements and have an elastomer in between.

    The rotary axes use a super stiff 3 row roller slewing ring series YRT.

    Cons.

    For a long time I was sure this would be my final choice, but I need my machine to be modular to the point I can take it apart for transport. In this case the problem arose, how to reliably connect the 2 columns to the base so that alignment is easy. I could not figure it out without glueing precision aluminum guides to both the base and the bottom of the columns. Extra machining parts would cost approx. EUR1000.

    Another issue that became apparent is low torque on B and C axis would allow only for light cuts because there is very little space in both to use components that would compliment the very stiff frame.

    The final nail in the coffin came in form of ATC. The main requirement for my machine is to be max. 795mm in width so that I can fit it in a standard european doorframe. Because of this I'd either have to have the ATC on the top of the machine or removable on one of the sides. with the 45° swivel head as well as in a normal 3 axis configuration the only way to have ATC is on the side.

    Hence I've decided to rest this build in the graveyard.

    At this point I went back to the drawing board and started going through all the frame types I researched over the last 2 years, I have found a candidate for the next project and its design is already underway. More on that later.

  9. #9
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    Nov 2020
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    361

    Re: Design Concepts

    Found a really great site that showcases a lot of machine frames:

    3D machine tools models

  10. #10
    Join Date
    Feb 2021
    Posts
    19

    Re: Design Concepts

    Server not found!!

    It's Russian? Hmmm...

    Quote Originally Posted by ardenum View Post
    Found a really great site that showcases a lot of machine frames:

    3D machine tools models

  11. #11
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    Nov 2020
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    361

    Re: Design Concepts

    Quote Originally Posted by MoonShot View Post
    Server not found!!

    It's Russian? Hmmm...
    yes I noticed it's down, I hope its only temporary though: here's a snapshot from the wayback machine:

    https://web.archive.org/web/20210119...odels_eng.html

  12. #12
    Join Date
    Feb 2021
    Posts
    19

    Re: Design Concepts

    Nice! Looking through them has me thinking I didn't consider enough options when designing my machine, but I'm not done yet and I can still gather ideas from it.


    Quote Originally Posted by ardenum View Post
    yes I noticed it's down, I hope its only temporary though: here's a snapshot from the wayback machine:

    https://web.archive.org/web/20210119...odels_eng.html

  13. #13
    Join Date
    Jul 2018
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    6548

    Re: Design Concepts

    Hi Ard - The search for perfection is indefinite. I recently upsized my CAD graveyard to 1Tb but you can go to16Tb I think... Peter

  14. #14
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    Nov 2020
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    361

    Re: Design Concepts

    Quote Originally Posted by peteeng View Post
    Hi Ard - The search for perfection is indefinite. I recently upsized my CAD graveyard to 1Tb but you can go to16Tb I think... Peter
    Yup, I did find a really good frame design but then I realized that I had gone in yet another circle to the first frame I was working with...only after doing it for 2 years I have a very different mindset and not as many limitations as I put on myself back then. Because the general diy consensus was that an HMC is too hard to do or wasn't done in the diy sector yet I foolishly adopted the idea at the time. But not anymore.

    and my graveyard is only 1.6Gb but I do delete a lot of mishaps, so maybe it would be double the size if I didn't...

  15. #15
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    Jul 2018
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    6548

    Re: Design Concepts

    Hi Ard - I think a HMC has many advantages, no reason a DIY can't do it... 2 years of embedded effort will make this one a great machine whatever the config. The world is a weird place at the moment everyone should be safe and happy but unfortunately they are not.... Peter

  16. #16
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    Nov 2020
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    361

    Re: Design Concepts

    Hey guys,

    durcrete just released a series of eight UHPC design webinars. It's in german but there's english description on the bottom right side of each slide.

    https://www.youtube.com/watch?v=au3eD3ZmAvI

  17. #17
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    Jul 2018
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    6548

    Re: Design Concepts

    Thks Ard - comments on shrinkage is a worry. The CSA has much much less . Peter

  18. #18
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    Nov 2020
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    361

    Re: Design Concepts

    Quote Originally Posted by peteeng View Post
    Thks Ard - comments on shrinkage is a worry. The CSA has much much less . Peter
    I am pretty annoyed at this fact, they were claiming no shrinkage previously in all their ads. Now this complicates things. If you wanted to use external jigs to align the inserts prior to casting, to avoid machining, this is no longer possible because of the shrinkage. You'd have to cast in threaded anchors and then glue the block inserts with steel filled epoxy as a in between layer and then screw them to the inserts, with this you could use aluminum because it would no longer touch the concrete. All in all, I think the price would be more or less the same if you used granite slabs. The only advantage would be free form of castings at the overall cost of manufacturing complexity. Lets not forget molds too.

    Wish there was a cost effective way to process or order custom granite parts. Shipping from china at least doubles the part price. I don't exactly want to go Michelangelo on rough granite and do it by hand...

  19. #19
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    Jul 2018
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    6548

    Re: Design Concepts

    Hi Jon - Have a look at Sika-212 HP non shrink grout. 0.03% growth at 28 days (or sikagrout ultra same expansion). That's less then epoxy. They don't quote modulus but ask and they will tell. Maybe around 50GPa.... I pick Sika because I think your in Europe? If so ask the Sika tech people they will have a good product for you. Peter
    Attached Files Attached Files

  20. #20
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    361

    Re: Design Concepts

    Quote Originally Posted by peteeng View Post
    Hi Jon - Have a look at Sika-212 HP non shrink grout. 0.03% growth at 28 days. That's less then epoxy. They don't quote modulus but ask and they will tell. Maybe around 50GPa.... I pick Sika because I think your in Europe? If so ask the Sika tech people they will have a good product for you. Peter
    Thanks Peter, I'll write the name down.

    Ideally I'd love to find/design a system (that uses little metal) with which I could reliably and precisely build up a frame from granite slabs. to avoid doing any cutouts in the slab, to keep the workload low and geometry at its most basic form(not that lapping will be any fast). Something that allows me adjustment in all 3 axes, think something like unisorb fixators but 3 dimensional. Alas I'm probably daydreaming.

    I like the idea of casting parts but I highly doubt I could do it precise enough without machining the inserts.

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