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  1. #1
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    Nov 2020
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    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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    227

    Re: Design Concepts


  3. #3
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    Nov 2020
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    227

    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
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    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
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    Jul 2018
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    3488

    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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    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.

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