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  1. #61
    Join Date
    Feb 2005
    Posts
    578
    Me thinks you should add two nuts on either side of that lead screw and pinch the bearings together. This will totally fix the screw to the machine and decouple it from the motor.

    See you later,
    Steve

  2. #62
    Join Date
    Dec 2004
    Posts
    1316
    I agree Steve, but as it was just a mockup I left them out.

    Jason

  3. #63
    Join Date
    Dec 2004
    Posts
    1316
    Hey guys, work was hell this week. I got some time to design and cut the bearing support for the other side of the leadscrew (The side of the gantry opposite the motor).

    The second picture shows a size comparison between them and the motor plate.

    Made the screw holes to hold the #10 screws with minimal lateral movement and the bearing fit is snug enough to stay in on its own without the need for nuts.

    Got my 1/8 and 5/32 spiral upcut Whiteside bits this week and immediately switched out the straight 1/8 bit for the upcut version to compare them.

    The spiral bit cut through the material more easily than the straight bit.

    Feed rate: 1016mm/min 40"/min
    Depth per pass: 4mm approx 5/32"
    Bit size: 1/8 upcut spiral
    Attached Thumbnails Attached Thumbnails Bearing supports.JPG   Plate Comparison.JPG  

  4. #64
    Join Date
    Dec 2004
    Posts
    1316
    Got that motor plate installed last night along with the lead screw support.
    I also cut a new motor plate that allows the use of #10 screws without widening the hole. I bought #10 screws from different stores and they were slightly different in diameter.
    I also modified the motor plate so that the bearing hole is all the way through and the fit is not as tight as before for the skate bearing (608).
    Some pics of the installed parts along with new motor plate code.

    Jason
    Attached Thumbnails Attached Thumbnails Motorplate2.JPG   leadscrewsupport2.JPG  
    Attached Files Attached Files

  5. #65
    Join Date
    Dec 2004
    Posts
    1316
    I also changed the X axis lead screw to 5/16 - 18 stainless steel threaded rod and it works well, the only thing is that the alignment has to be spot on. For some reason the motors are stalling while jogging at 1700mm/min, I am certain its the lead nut still being a bit tight.

    Jason

  6. #66
    Join Date
    Apr 2003
    Posts
    1873
    Jason,
    I have enjoyed watching your progress.

    Just an observation here that may be a potential for alignment and vibration problems.

    It appears that you are using a rigid motor/screw coupling, these work fine for perfectly aligned shafts with perfectly machined ends, however, the coupling method and standoff setup used likely will not lend itself to the necessary alignment precision. Why not use small pipe cut to precise lengths with equal thickness washers at each end to distribute the end forces after tightening and some type of flexable coupling.

    The other area that might be troublesome is where the screw goes through the rear bearing, to me this would seem best with a nice slip fit and not locked rigid with locking nuts. This would allow some movement due to expansion/contracting from temperature changes. Perhaps keep the locking nuts and accomplish this by a nice slip fit between the outer bearing race and the nylon bearing journal.

    A locking nut on each side of the motor end bearing seems good idea.

    Just an observation/opinion and not necessarily a problem.
    Ken

  7. #67
    Join Date
    Dec 2004
    Posts
    1316
    Ken,

    Thanks for the suggestions. It seems I got away with slight misalignment before due to the use of the 1/4-20 threaded rod which gave a little flex, this is not the case with the 5/16-18.

    The small pipe would be a good idea. I used the standoff couplings you see to get it done quickly but soon found out that the couplings are not all the same length, different batches I guess. I suspect use of the pipe will clear any tightness if the lead nut is not the problem.

    If the alignment is still out then I may have to remount the motor plate. The truth is I made an error when I was mounting the plate in forgetting to tighten up the lead nut tensioning screws to prevent any droop in the lead screw (JGRO leadnut is a 2 piece one) and this may have caused a slight misalignment.

    If there is still a problem I will get a flexible zero backlash coupler that allows for misalignment.

    I agree the thermal expansion/contraction is an issue with a rigid system but I am not sure what you mean by the term "slip fit".

    Jason

  8. #68
    Join Date
    Apr 2003
    Posts
    1873
    Jason,
    What I refer to as a slip fit for bearing ID to shaft OD is a fit not so loose as to feel slop but a fit that allows the bearing to be moved up and down on the shaft race by hand with some, but only minimal resistance.

    Ken

  9. #69
    Join Date
    Dec 2004
    Posts
    1316
    Thanks Ken, now I understand.

    Jason

  10. #70
    Join Date
    Dec 2004
    Posts
    1316
    Got a new coupling made for the leadscrew-motor shaft and I put in a new motor plate so that my motor screws thread into the MDF. The whole setup now works like a charm.

    Jason.
    Attached Thumbnails Attached Thumbnails new coupler.JPG  

  11. #71
    Join Date
    May 2005
    Posts
    195
    Keeo up the post. Man I really appreaciate you sharing your progress.
    What is possible? What you will!

  12. #72
    Join Date
    Dec 2004
    Posts
    1316
    Sharing is what its all about in the zone. Thanks for the encouragement.
    I should have some time this weekend post pics of work cut on the machine.

    Jason

  13. #73
    Join Date
    Dec 2004
    Posts
    1316
    Did a test cut today for a clock I drew up in CAD. I forgot to offset the X and Y axis so the machine did not start from the center of the stock (chair) . The circular alignment of the numbers looks good so I can cut as soon as I get my Vcarve software.

    Jason
    Attached Thumbnails Attached Thumbnails Clocktest.JPG  

  14. #74
    Join Date
    Oct 2005
    Posts
    225
    Would you mind telling me(and everyone else) what electronics and motors you are using?
    Thanks,
    southernexplorer

  15. #75
    Join Date
    Dec 2004
    Posts
    1316
    The 3 axis Hobbycnc setup with the 127oz/inch motors. I would advise the 200 oz/inch motors. Its not that the 127 oz/inch motors don't work well but I have pushed them to their limits at this time.

    Jason

  16. #76
    Join Date
    Dec 2004
    Posts
    1316
    oops.

  17. #77
    Join Date
    Dec 2004
    Posts
    1316
    I made a coupler with my machine and it came out quite well. I will need to use thicker stock as 1/2" stock is a little small. I used 10-24 set screws to secure the shafts. When I hook it up to my small Hawk mill I will report on its performance.

    Jason
    Attached Thumbnails Attached Thumbnails Coupler1.JPG   Coupler2.JPG   coupler3.JPG  

  18. #78
    Join Date
    Aug 2004
    Posts
    3215
    they look really nice, and yes you will need thicker material i tried that and the setscrew just pulled through the material so i went ahead and got the lovejoy's (as lionclaw sujested) the outer pieces are metal.

  19. #79
    Join Date
    Dec 2004
    Posts
    1316
    Joe,
    What size set screws did you use?

    I choose the 10-24 as they were the largest diameter and coarsest pitch I could use based on the stock I had.

    I found that if the shafts have a flat side the set screws do not have to be as tight as a fully round shaft so I have not had any pull out problems so far.

    Jason

  20. #80
    Join Date
    Aug 2004
    Posts
    3215
    Quote Originally Posted by Jason Marsha
    Joe,
    What size set screws did you use?

    I choose the 10-24 as they were the largest diameter and coarsest pitch I could use based on the stock I had.

    I found that if the shafts have a flat side the set screws do not have to be as tight as a fully round shaft so I have not had any pull out problems so far.

    Jason
    They are 10-24 also, but i made a small drill hole so it may have set to far down into the leadscrew and not enought threads in the coupler itself.

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