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Calibration problelm

Discussion in 'Troubleshooting and Build Support' started by TigerPilot, Aug 2, 2011.

  1. TigerPilot

    TigerPilot Well-Known Member

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    I know we went trough this many times before but I still can't solve it. I cut the part in the picture. If you look at the circle I've marked you'll see that the sides are a little flat. The difference between the two axis's is about 0.03". It's consistent in the bigger circles as in the small circle. I don't think it's backlash since I've cut the part with the multipass and there are no steps in the cut surface. It's smooth. If there was backlash there should have been steps somewhere. The slits are the size of the bit. The bit fits snug into them. All this means, to me anyway, it must be calibration. But which axis. I found it very hard to calibrate precisely since it is wood I'm using and using a caliper is not as exact either. Every time I calibrate I think I've got it and when I check some other time it's not as I had it. I've checked if something is loose but the gantry is sturdy with no play and the drive rollers don't move when the power is on. The circles have to be exact or the small parts cannot be used. It would make no difference on the big tooth wheel but the small circles have to be precise. Any idea what or where to check next?

    Attached files [​IMG]
     
  2. TigerPilot

    TigerPilot Well-Known Member

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    Can someone, please. cut this file on his PP. It should be cut in 1/4" MDF with a 1/16 bit. I just can't get my machine to cut a circle. When I cut a rectangle, with multipass, it comes out perfect within 1thou. When I use the attached file to cut a 1" circle not one measurement comes out even close to 1". The closest one is about 30thou less and the other are all over. It's not even an egg just some kind of abortion. There are two places where the problem can be. 1) my machine and 2) the phlatcode. If someone else can get a perfect circle with the attached code than it's my machine.

    It has to be in MDF, foam will not show the problem as much. Attached files 1inch Circle Test.cnc (7.5 KB)Â
     
  3. rjarois

    rjarois Moderator Staff Member

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    yoram, just for the heck of it, try the circle program in mach-3 and see how the circle comes out. randy.
     
  4. kram242

    kram242 Administrator Staff Member

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    Thats a good idea Randy, maybe its in the control software.
    p.s. that's a cool looking gear Yoram!
     
  5. TigerPilot

    TigerPilot Well-Known Member

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    I'll try it, Randy. I'll have to see where in the wizards it is. It just frustrates the heck out of me. I can cut twenty circles and they all come identical and I cut them with multipass and the cut slot is just the size of the bit all around. That means, I think, that there are no loose parts or backlash. It does mean that, doesn't it?
     
  6. rjarois

    rjarois Moderator Staff Member

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    yoram, it should cut the same in multi-pass, all its doin is stepping down. maybe the wood is slipping...try a foam carrier and try. randy.
     
  7. TigerPilot

    TigerPilot Well-Known Member

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    You miss understood me, Randy, the multipass cut is the same. That's the whole point. the cut slot is the same all the way down and the bit fits into the slot just perfect. If I had slip the cut would have steps, which it doesn't.
     
  8. jovian

    jovian Member

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    I am seeing a similar problem with my circles. Both in foam and lite ply. Havet tried a multipass to check backlash on the foam. I know wood i was having a problem on the x. Also my y is losser than i like. I got a lot of tuning
     
  9. dhc8guru

    dhc8guru Member

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    I have noticed large circles cut fine (anything over roughly 1") that small circle in the photo has an egg/squarish shape to it...My machine cuts the exact same way. I am getting up to speed on learning mastercam. I am going to make some test cuts with patterns made in mastercam to see if there is a difference. I am not convinced the controller software integrates well with .DXF files. It seems like the software doesn't smooth the lines well or maybe a line arc smoothness setting in the CAD software needs to changed so the CNC software see's smoother arcs and circles.
     
  10. TigerPilot

    TigerPilot Well-Known Member

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    dhc8guru, I'm using Mach3 so that I don't have the problem of the controller software. I know that if I'll cut planes in foam they will come out perfect but I bought the machine with plane second on my mind. I wanted to cut wood first. Up to 1/2" wood. If I will not be able to do it the PP will unfortunately have to go into the corner. I liked the small footprint of the PP with the option to cut material at almost unlimited length but, alas, that may not come out as planed, for me. And now that a few more come up and say that they have the same problem, I'm kind of disappointed. I'm not giving up just yet. I will try a few more days.
     
  11. dhc8guru

    dhc8guru Member

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    Wow, half inch wood. Don't know how big of a sheet of wood your machining? Even multipassing, just being able to keep the wood in place shuffling through the rollers is going to be a challenge.
    You may need to put guides on the table to keep the wood in place. I would think you maybe exceeding the limits of the machine.
     
  12. TigerPilot

    TigerPilot Well-Known Member

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    The question is not how thick the wood is, dhc8guru, since I cut in with the multipass and each cut is like a new sheet. I'm cutting it in 1/32" steps that means I'm cutting everytime a piece of wood only 1/32" thick. The problem is that if there is play and?or backlash than the but come out inaccurate. Which is what happening to me.

    This is what I've cut out of 3/8" ply with a 0.787" (2mm) bit at 15ipm feed rate. I'm just not experienced with these things and I can not analyse it, to tell where the problem might be. I wrote the measurements. On the left is the circle that should have been 1" diameter. On the right is the hole it came out of. On the hole I measured the top and the bottom. The top number is the top and the bottom, the bottom. Anybody with experience can tell me where to look for and/or where to adjust the backlash? I'm way over my head here. Attached files [​IMG]
     

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