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C-Beam cnc

Discussion in 'CNC Mills/Routers' started by Kyo, Jun 24, 2016.

  1. Kevon Ritter

    Kevon Ritter Veteran
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    Long time lurker here,

    I've been looking into building a 2'x4' to replace my really crappy cnc shark. (That thing is a piece of garbage.) I was originally going to use 40 series profile from 8020. It's so expensive though since everything has to be that much bulkier to handle the loads I would like to apply. So I just decided to build a tiny machine with the intentions of machining aluminum. I had a few designs already for the larger machine, but there was no point in reinventing the wheel for something this size. I absolutely dislike belts. I feel like they would be just as bad as the HDPE flex that the Shark is putting me through. Lead or ball screws were the objective. So when I saw this, I got excited. It's a smaller version of my larger designs, and is far less expensive.

    With that said, I have all of the mechanical components on order. They are sourced from Openbuilds, Chris (plates), and fleabay (flange bearings). I plan on using 269oz steppers, DQ542MA drivers, and the Pheonix. The Shark pretty much broke today (well it didn't but when the flex kills larger endmills with 0.6mm passes at less than 250mm/min, I consider it worthless), so now I'm in full swing with the electronics too. The Pheonix is currently unavailable. The plan is to cut aluminum, which I have done plenty of on even the crappy Shark, which has even smaller steppers.

    Kevon
     
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  2. Kevon Ritter

    Kevon Ritter Veteran
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    That vertical mount is a pretty nifty idea. It would be better if the cross bar had threaded holes every 50mm or so. That would allow you to clamp uneven pieces if you needed to.
     
  3. John Christian Lien

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    Currently building a bigger version of this maschine with taller y-axis side plates. Just created a thread on the forum for all to see, and also posted the upscaled side plates (dxf file) for anyone who wants that :)
     
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  4. digicoustic

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    Just curious if anyone has done a build using the 3mm Stainless Steel plates available on ebay?
     
  5. Kevon Ritter

    Kevon Ritter Veteran
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    For $15 more, you can get 1/4" aluminum from Chris.
     
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  6. digicoustic

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    Yeah, that's what i'm thinking. I was just trying to weigh the advantages/disadvantages of Stainless Steel vs Aluminum. Chris is waiting on a part for his machine which he advised should be up and running within a day or so.
     
  7. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    1/4" aluminum will be more than three times stiffer than 3mm steel plates. To get apples-apples, the steel plates would need to be 4.45mm thick. Yes, the little bit extra for the aluminum ones is more than worth it.
     
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  8. tcurdt

    tcurdt New
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    Is that really true? Let's say stainless steel has strength of 517N/mm2 and Aluminium of 240N/mm2. Doesn't that suggest that

    3mm * 517N/mm2 (steel) <=> 6.35mm * 240N/mm2 (alu)
    1551 N/mm3 (steel) > 1524 N/mm3 (alu)

    even the 3mm steel plate would be stronger that the 1/4" aluminium?

    What's the math behind your 4.45mm?
     
  9. Kevon Ritter

    Kevon Ritter Veteran
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    Strength based on thickness isn't linear like how you have it.
     
  10. tcurdt

    tcurdt New
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    Do you have a pointer on how the math should look like then?
     
  11. Kevon Ritter

    Kevon Ritter Veteran
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    Sorry for the short response. I was at work.

    It's been forever since I've touched material properties, but this is essentially what we're looking at. I'm not saying that this is the full story, but this is definitely much closer that simply multiplying a value by a thickness.

    We should be able to just substitute yield strength in for Eb. With all else equal, our new equation would be T(aluminum)^3 * Eb(aluminum) = T(SS)^3 * Eb(SS). Now we just plug and chug.

    Without doing much searching, I used 302 SS although 304 is a more common standard. For the aluminum, I used 6061 T6. With the numbers in the chart below, a 302 SS 3mm plate is equal to a 3.877mm plate of 6061 T6 aluminum. I figured it was safer to use values from the same graph than to search around from different sources.

    Now don't take that as an absolute. I could be wrong on the specifics. I'm only just trying to show that material properties are rarely linear.
     

    Attached Files:

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  12. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    You're confusing strength with stiffness. How flexible a material is has nothing to do with its strength and stiffness is what is in play here not strength. Stiffness of the system is what keeps the bit in contact with what it is chewing on rather than merely skipping against the edge of the material.

    The equations are fairly simple. It's basically moment of inertia (I) times modulus of elasticity (E).

    I = b x h^3 / 12 and E for steel is roughly 2.9 times that of aluminum. As b (width) is the same on both sides of the equation it factors out as does the divisor of 12. h is the thickness (t) of the material.

    So:

    t(aluminum)^3 = 2.9 x t(steel)^3

    t(steel)^3 = .25^3 / 2.9 = .0054

    t(steel) = .1753" = 4.4529mm
     
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  13. Kevon Ritter

    Kevon Ritter Veteran
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    I'm glad to see that we are both using the same equation. The part that had me unsure was wether to use elasticity or yield.

    Elasticity for anyone following along.
    198GPa for 304 Stainless Steel
    68.9GPa for 6061 T6 Aluminum
    Ratio = 2.87:1

    If you redo the math I did, you would come to the same conclusion as Rick.
     
  14. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Yes, yield is where flexural bending becomes permanent. Let's hope nobody takes a machine there. o_O
     
  15. Nickg

    Nickg New
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    Guys, very long time lurker here, as i have bugger all knowledge about CNC, came across this build and loved it, great concept, great documentation, Kyo, take my hat off to you sir! thanks.
    Today I went to a Machine Shop, to see if they could make me the plates. The place was bit like they were stuck in the 1980s, they had CNC machines, the size of cars, and were doing some serious engineering. But when I showed them, the Stetchup files, they said where are the dimensions? Then I showed them the DXF files using, the A360 free viewer, again no dimensions, also whats shown on the screen doesn't seem to have any depth. They said they work with STEP files, does anyone have the files in this format, or can they be saved in this format? My understanding is / was that the files shared by Kyo, are 3D meaning that all the info is in the file, for example, size, width/depths of holes, etc and a CNC machine, would be loaded with one of the files and bob's your uncle, out pops a plate, or am I miss guided?
    Thanks for the advice.
    Nick
     
  16. Kyo

    Kyo Veteran
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    The shop should have no problem getting dimensions from the dxf files directly when they do the cam to cut the plates. To get dimensions from within a viewer app the measurement tool would be used. The following dimensions could change depending on chosen bearings and plate thickness. For a stock build the following would apply.

    Plate Thickness: 1/4" / 6.35mm ( all plates )
    Bolt Head Recesses: 1.6mm ( front and rear x-axis plates )
    Bearing Pocket: 16.1mm dia x 5mm deep pocket with 18.1mm x 1mm deep flange ( front, rear, side y-axis plates )

    You can also export files from sketchup as step/iges. Please find below a zip file with the iges exports from the v2 sketchup file as well as step exports and the base sketchup file.
     

    Attached Files:

    #256 Kyo, Jan 18, 2017
    Last edited: Jan 19, 2017
  17. Gary Caruso

    Gary Caruso OpenBuilds Volunteer
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    I would have Chris cut them for you, he does great work and you wont be charged a fortune.
    [email protected]
     
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  18. Nickg

    Nickg New
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    Kyo thanks for this. I have sent files to the machine shop let's see what they say.

    Gary thanks, the issue would be the postage, I'm in Spain
     
  19. Kyo

    Kyo Veteran
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    No problem :thumbsup:
     
  20. Kevon Ritter

    Kevon Ritter Veteran
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    I got my frame parts in today. I forgot to get regular ball bearings for the z and I'm still waiting on the plates to be made, so I'm just at a stand still.

    I have to say that I am very impressed. I was scared that the v wheel setup wouldn't be as tight and rigid as I was wanting, but it's definitely miles ahead of the crappy Shark. The CBeam feels great too. I'm curious to know how it would hold up at the full 1000mm for the gantry though.

    And don't worry. I won't be spamming this thread with my build.
     

    Attached Files:

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  21. Maxdd

    Maxdd New
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    Kyo what was your opinion of your RPi 3 to Phoenix USB CNC controller w/DQ542MA drivers setup? Is there a huge advantage in the G540 w/your new GRBL shield? Thanks!

    Max
     
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  22. Kyo

    Kyo Veteran
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    Hi Max,
    I am a huge fan of Raspberry pi's I use them to run my 3d printers, cnc's ect. They make great cheap control PCs.

    The Phoenix usb controller and my Gecko g540 usb controller are very similar and accomplish the same thing. Run grbl. However we focus on two different style of drivers.

    Hayri focuses on individual drivers such as the Openbuilds dq542ma , pololu , generic Chinese drivers from ebay, ect. by breaking out the signals to screw terminals. This allows you to select what ever driver you want to run in your system depending on budget and needs.

    My usb controller focuses on the Gecko G540 and other parallel port based systems using the same db25 pin out. The Leadshine MX3660 and MX4660 come to mind. The G540 has the added benefit of having fully opto isolated input / outputs I make use of for limit and home switches; spindle / coolant relays ect. Making for a plug and play system only requiring a single ribbon cable from grbl controller to driver. I also use the same idc26 pinout as the ESS so if a change to mach3 / 4 is ever wanted you do not need to rewire your machine, uplug the ribbon cable from my usb controller and swap in the ESS.

    Running grbl with individual drivers like the dq542ma I can recommend Hayri's Phoenix controller.

    Running grbl with a driver package like the G540 my usb controller would get my recommendation.

    Interested in running Smoothie? Waiting for Openbuilds soon to come out controller might be just the ticket for you. WIN A CNC CONTROLLER PACKAGE! [Closed, Winner TBA]

    I do not think a single controller is the correct answer for each and every project. Each has their place. Go with the one that is right for your application and needs.

    While I will not go into full details or prices here as that would border on advertisement vs Comparison. I will drop a little teaser while we are on the subject.

    My nano / grbl interface board is on it's last run.
    Nano_G540.jpg


    I am moving away from the Nano and ch340 chip. To a dedicated 24V GRBL / Estlcam controller. :thumbsup: (not yet available )

    G540_Controller.jpg
     
    #262 Kyo, Jan 20, 2017
    Last edited: Jan 20, 2017
  23. Glene

    Glene New
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    Hi Everyone. I'm new here. Hopefully this question finds someone to answer it and it doesn't take up too much time. I go to the Files and Drawings, and open up the Plates.zip file and double click the, say x-axis Rear Plate Rev 2 and it opens on my system with a program called DWG TrueView 2013. I can see the drawing in two forms, one called Model and one called Layout 1. I don't see where there are any dimensions called out. Is there a way to 'turn dimensions ON' ?
    Are the drawings meant to be templates or are they meant to be used for accurate machining ?
    Any help on this small question would be great.
    Thanks,
    Glen
     
  24. Kyo

    Kyo Veteran
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    Hi Glen,
    The 2D cad files are for machining. The dimensions are embedded into the file compared to a traditional paper blueprint with dimensions called out. Any good machine / job shop will be able to use them. Just let them know the plate thickness and pocket dimensions as posted above.

    I am not sure about Trueview not having used it myself, But most traditional cad software will allow you to check any dimension with the measurement tool. A good cross platform free option is Draftsight. Works very well and is what I use to double check all my dxf exports from fusion / sketchup. You can also use the sketchup file and measure the plates directly from within sketchup.

    If a template is needed I did post some 1:1 pdf templates a little ways back in this thread towards the top of page seven..
     
  25. tcurdt

    tcurdt New
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    I am a bit confused about the spacer story at the side plates. According to the instructions it's a 6mm spacer plus a 1mm shim and then either the mini wheels or the big wheels - but from the specs it looks like the wheels don't have the same thickness. The big wheel is bigger than the mini wheel. What am I missing?
     
  26. Kyo

    Kyo Veteran
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    We had a nice discussion about this with some very well done drawings I can not seem to find the correct thread / post at the moment. Mini wheels get the 1mm shim between wheel and spacer the full size wheels do not. This is to keep them in alignment on the V-slot channel.
     
  27. tcurdt

    tcurdt New
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    I got a bit further myself already by checking the Sketchup Model. As for the thread - would it be in this 9 pages? or where to search?

    So in the sketchup I saw the shim for just the small wheels - but then the question is whether the height of the big wheel is the height of the mini wheel + 2mm. Found it a little hard to find the correct information. Now IIUC the thickness of the wheels is 8.80mm and 10.23mm - but that doesn't really matter because the bearings make up the real thickness. So for the small one should that be

    2(bearings) * 4mm(height of the bearing) + 1mm (wall inside the wheel) = 9mm

    and the big one

    2(bearings) * 5mm(height of the bearing) + 1mm (wall inside the wheel) = 11mm

    11mm - 9mm = 2mm

    Correct like that?
     
  28. Kyo

    Kyo Veteran
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    That is correct, 2mm total difference. 1mm each side of the center line. As we are only using a plate on one side the mini wheels need that 1mm shim to come into alignment.

    Found it; C-beam machine Page 37 towards the bottom.

    [​IMG]
     
  29. KM4_2855

    KM4_2855 New
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    I am hoping to begin this project soon. One thing I would like to experiment with in addition to normal cmc work is milling PCB. Is there any mods I should consider for increasing resolution?? The documentation is great which convinced me this is the way to go. Thanks for such a great design.
     
  30. tcurdt

    tcurdt New
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    Plenty of big for PCB milling :)

    I guess one could use belts on all the motors to increase the resolution in expense of travel speed.
     

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