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Manual XY "cnc" type of machine. Doable?

Discussion in 'General Talk' started by Zeuligan, Jan 29, 2018.

  1. Zeuligan

    Zeuligan New
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    I'm a computer modder and often find myself short of accuracy when creating my parts. I do everything by hand. So, it's a lot of filing, sanding and measuring before even the simplest part could be created. I work mostly in Acrylic, but have the need for aluminium, up to 8mm-10mm thick.

    My dream and a real CNC, but I live in an apartment making it impossible to unpack and mount a CNC every time I need to create parts (as of calibration etc – I'm told). I also understand that cutting 10mm aluminium isn't something you do with a hobby machine, so a beast capable of 10mm aluminum is not a machine you move.

    So, to my idea or rather thought.

    Would it be possible (everything I possible, but let's call it plausible) to create a manual XY rig? Mostly like an CNC, but without the electronics. Reason for this thought is the cost, but also to start to build on, what in a future could be a real CNC, using real parts, like C-beam for a manual setup.

    I'm visioning a construction of pre-mounted beams you can slide together (when needing to cut) then mount a motor (I got a Makita and a Dremel). Clamp it to a table, Lock one axis (like X) and put start and stop brackets for Y and just push the Y back and forth, manually lowering the Z until the piece is cut.
    Thinking about digital caliper for controling position of the axsis.

    I do understand that the precision leaves A LOT to ask, but compared to a file and drill by hand, it should be a huge upgrade.

    So, smart CNC, Openbuild pros and genius engineers. Is this the dumbest idea ever? Should I just leave it until moving to a house and get a real CNC or is it actually an idea that could be done? Pref below 2-300$ in C-Beams, wheels and other needed plates?

    PS. Can you even mill Aluminum by hand with a router like a Makita or is it just small of a machine? DS


    I'll add a picture of a concept I'm currently working on, showing a very simple piece in 8mm aluminum (started learning Fusion 360 a few days ago, so sorry for lack of details ).

    [​IMG]
     
  2. Gary Caruso

    Gary Caruso OpenBuilds Team
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    You can do thick aluminum with a trochoidal milling scheme, even with a belted machine.
    You won't need to calibrate every time you move it as long as the table you put it on is reasonably flat.
    I have hand cut aluminum close with a band saw and table saw (woodworking tools) then used a template and a flush trim router bit to get it perfect...
    CNC is so much easier!
     
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  3. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Aluminum can also be cut with template guides. It's less than ideal but it can be done. Just don't expect to be able to do 10mm in a single pass. (Expect more like 40 passes.) The biggest problem with cutting aluminum in an apartment is the place will look like a glitter bomb has been set off. But as far as a hand crank assembly, it's possible as I've done it myself. Again, less than ideal but it can be done. As for acrylic though you'll just want to stick to template guides. It's far too difficult to hand crank fast enough to keep the acrylic from gumming up.

    As far as apartment sized machines, it wouldn't be all that difficult to work up something on the scale of a Handibot that could easily be stored in a standard file box, something with a through-route base plate you just set on the cutting surface. Sure you would have to move and reset it a few times for larger cuts but it wouldn't have to be taken apart and rebuilt between projects.
     
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  4. Scotty Orr

    Scotty Orr Master
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    The OB O-Bot! hmm........
     
  5. Zeuligan

    Zeuligan New
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    This is actually new and positive info for me. Haven't heard you can actually move a CNC between jobs (someone called me not so nice things in a FB group, for even suggesting such a thing hehehehe). Maybe that puts CNC back on the agenda again. Trochoidal milling was a new term for me, but after some Youtube I now know that what I thought was just milling is actually Trochoidal milling :D Thank you for that lesson and insight.


    Handibot was cool, but 3000$ is way over my budget for a first machine. Was hoping to solve a working machine under 5-700$ and then upgrade while building stuff. The open build C-beam machine looks ace for example (but to expensive outside US and no fun with 350% freight to Sweden)

    I actually have a work room in the celler of the apartment building (with a drill press, work bench etc). So don't have to mill in the appartement, I just need to be able to store and move a "portable" type of CNC between a cellar storage room and the work room when milling.

    Hand crank assembly, will remember that term :)

    Thank you both for our awesome answers and I feel at least comfortable enough to start to draw a machine using open build parts and see how much it will cost me to get a working hand cranked mill setup as step 1 towards a real CNC


    Does it matter if I choose Lead or Belt for Aluminum milling?
     
    #5 Zeuligan, Jan 29, 2018
    Last edited: Jan 29, 2018
  6. Gary Caruso

    Gary Caruso OpenBuilds Team
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    If you want to slot cut, lead screws... if you stick to trochoidal it doesn't matter much.
    With Fusion they call it adaptive cutting, this keeps chips from clogging the bit and the slot. The easy way to Trochoidal is with Estlcam.
    I think the video you watched might have been from Estlcam? This is what I use and I was able to do 12mm aluminum with a belted machine, 4mm DOC at a time.
     
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  7. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Not sure you can get down to the $500 to $700 range when you start figuring in VAT but you should be able to get down reasonably close if you can handle cutting your own starter plates. As far as shipping, there are a number of OpenBuilds distributors in Europe so you don't need to ship all the way from the US.

    Attached is a rough concept of what I was talking about. It's just a modified version of something I already modeled and could still use a lot more simplification to bring down cost. But it would allow you to through-cut in sections on larger items and cut smaller items or acrylic on an inset waste board.

    500Bot.jpg
     

    Attached Files:

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  8. Zeuligan

    Zeuligan New
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    Thank you very much for that. You are all so helpful <3

    One question, not sure if it's relevant, but I notice that when using lead it is C-beam that is the choice and then the wheels are inside the beam. When using belt (like the OX) then the wheel are on the outside. I'm thinking wheels outside (on for example the v-slot 80mm) will be much wider apart than inside a c-beam. Should that bring ore stability than wheels on the inside? So, what happens if you use the c-beam but use the wheels on the ouside for x an y also (just like the OX do on the Z).

    Wheels outside or onside, does it matter for stability and what materials that can be milled?

    If that made sense :)
     
  9. Rob Taylor

    Rob Taylor Veteran
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    Another option in addition to trochoidal milling/adaptive clearance strategy is the use of proper roughing/finishing passes. This would require a simple tool stickout setting jig or zeroing plate, but it's amazing how much material you can push a large diameter roughing end mill through compared to a smaller finishing end mill, with lower cutting forces and higher feed rates.

    Wheels as far apart as possible for minimum deflection- because it's a direct product of the torque on the frame from the cutting forces being overcome by the rigidity of the beams, plates and wheels themselves. The further apart the wheels are, the less force they need to apply to overcome the torque (T=Fs and all that) and therefore the less deflection force they see on themselves. Obviously this ends up being a compromise between rigidity and machine size & axis travel. You've just got to pick a point you're happy with.

    Most machines around here are on the less-rigid, larger travel side because they can get away with it in soft materials like MDF, acrylic and aluminum. The high speed routers also help with that- you're effectively using an HSM strategy, which means high feeds, high speeds, and low chipload per tooth for low cutting forces. This also helps with the fact that aluminum transmits vibration very well and probably wouldn't cope well with traditional milling methods without hefty mitigation for surface finish.
     
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  10. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    I understand your concern on the internal wheels but wheels on the inside are fine in this case due to the counteracting wheels on the far end of the gantry. While the narrow gauge would tend to allow an individual plate to roll inwards, the rigidity of the gantry frame combined with the wheels at the far end prevents this inward deflection from happening. (You'll note I didn't use the internal wheels on the Z-axis, something which is fairly common in designs here on OpenBuilds. I don't trust internal wheels in single plate applications.) The inset wheels also work better in this case because it allows for easier bracing of the side channels, which help prevent them from rolling inwards.

    As far as belts go, using both internally mounted wheels and inset belts is possible on the C-beam. It just takes a bit more coordination in the plate design.

    While belts can be used on systems used to cut aluminum, lead screws offer more power and a better resolution on the cut.
     
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  11. Zeuligan

    Zeuligan New
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    I got a really stupid followup question :) (Planning to build my own CNC, just can't put it of any longer hehehe).

    The gantry plate for a c-beam in the shop. Can I just add an other c-beam to that (like in the design above) or do I have to create my own custom side plates to anchor the Y beam to the X beams? I will create a machine with a movable gantry and a small area (so I can move the machine) like 400x600 active area) and it will need to be able to mill Acrylic up to 10mm and Aluminum up to 10mm . But I don't dare to order any parts (plan to order in a little at a time to get the hang of it) but don't want to order stuff that I can't use.


    Does it matter if it's Grbl or Mach3? Feels like the real controllers are Mach3, but also 10 times as expensive. What I'm asking, can I make do with some cheap Arduino Grbl + Stepper controllers as a start?
     
  12. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    If I'm following what you're asking, yes, C-beams can be used for side vertical risers. There are already several examples of this on the forum. The design above (with the exception of the big metal base plate) was created around the idea of no special or user cut plates. Everything can be obtained from the OpenBuilds parts store.

    As for the Arduino Grbl + Steppers, that is also fine. And should you decide to move on to Mach3 in the future there is really no waste. The Arduino just gets pulled for some future project and replaced with a Mach3 compatible board.
     
  13. Zeuligan

    Zeuligan New
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    I'm getting of topic from my original question in this thread, so will end this thread with one last question just to clarify what I ment

    Will the "ordanary" C-Beam Gantry Plate work (wide enought?) to fasten C-beams vertically with the angled brackets / like in your example or will I need to get the Gantry Plate XL to have enough space to fasten the vertical c-beams?
     
  14. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Actually the plates shown are C-Beam® Gantry Plate - Double Wide which are wide enough. You will need to use Cast Corner Bracket clips though to compensate for an odd hole spacing at the center of the plate.

    As far as getting off topic, it's your thread. It can meander wherever you want it to go.
     

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