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Taking the CNC Plunge

Discussion in 'PRECISION-MATTHEWS' started by TomS, Aug 6, 2014.

  1. TomS

    TomS Active User H-M Supporter-Premium

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    No. I roughed out a 1.240" through pocket in a piece of 1/2" thick aluminum. The gcode I sent you is the pocket finishing pass.
     
  2. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Can you post a better picture of the cut finish?

    Have you tried a 2 flute end mill? With a 2f carbide end mill I would run that at 6000 rpm (my max) 22 ipm with a 40% step over for the roughing and a finishing pass at 10 ipm and .015 cut, both run as a climb cut.

    The only 4 flute end mills I use on aluminum are the corn cob roughers. I prefer single flute chamfer end mills for chamfering.
     
  3. Davd Flowers

    Davd Flowers United States Active Member Active Member

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    Ok so the second pass

    Finishing pass with a spring pass?? Ok going to back up a bit. have you checked the backlash of your X Y ball screws and what are your drivers set too? Micro stepping? What file format is the cad model in?
     
  4. TomS

    TomS Active User H-M Supporter-Premium

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    I'll try to get a better picture. Haven't tried a 2 flute because the finish is so bad with the 4 flute.

    I normally would run this job at 8000 rpm and 60 IPM with .1 stepdown and stepover for roughing. Finishing is done at full depth (.5) and stepover at .01 and 30 IPM. I've played with speeds and feeds to see if the surface finish get better but no change. I ran some mild steel parts before I changed out my electronics and the surface finish was superb. I'll try and get a picture of that part as well.
     
  5. TomS

    TomS Active User H-M Supporter-Premium

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    Yes, finishing pass with a spring pass. My drivers are set for microstepping. I'll have to look at the specific setting. Can't remember because it's been so long since I set them up.

    I have some backlash. About .002" in X and Y but as I said in my previous post the mild steel parts I made before the electronics upgrade had a very good surface finish.

    The CAD model is Fusion 360 format. I've attached it below. Change the file type from .txt to .f3d and it should open.
     

    Attached Files:

  6. Davd Flowers

    Davd Flowers United States Active Member Active Member

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    Dont know if you feel safe about running some one else's g code but if you do... Stock is 3"x 3"x .5" and X Y zero is center of stock and z zero is top of stock. I used a .250" engraver for the chamfer, but any size would work as long as it comes to a point.
     

    Attached Files:

  7. Davd Flowers

    Davd Flowers United States Active Member Active Member

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    I would be curious to see what the finish looks like if you set your drivers back to half step...
     
  8. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Are you running the ESS on a dedicated 5v power supply?

    For your finishes to degrade after changing the electronics suggests a problem with the settings or possibly electrical interference. I will see if I can get screen captures of my ESS configuration for comparison.
     
  9. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Toms setup is very similar to mine and I'm running my drivers in micro-stepping with no issues.
     
  10. Davd Flowers

    Davd Flowers United States Active Member Active Member

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    Same amount of backlash? IIRC a half step on a 5mm pitch screw yields about .0005" Dont really see the point in micro stepping. What am I missing ??
     
  11. TomS

    TomS Active User H-M Supporter-Premium

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    Yes, I have a dedicated 5vdc power supply to the ESS.

    Here's a picture of a steel part I made before the electronics changeout. Notice the very smooth machined edge.
    20170720_083723_resized - Copy.jpg

    A picture of the pocket in my test piece. Notice the faceted finish.
    20170720_084639_resized.jpg

    This is the part I made last week that prompted this thread. The exterior profile surface finish is "ugly".
    20170720_084350_resized.jpg
     
  12. TomS

    TomS Active User H-M Supporter-Premium

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    I'll see if I can find some time today to run the code. If not then it will be a week or so. Heading out of town in the morning.

    Thanks for your input. I really appreciate it.
     
  13. TomS

    TomS Active User H-M Supporter-Premium

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    For reference my X and Y axis drivers are set for 1000 microsteps.
     
  14. Davd Flowers

    Davd Flowers United States Active Member Active Member

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    The finish on the first steel part is pretty amazing, no faciting at all.
    On the aluminum one, i see some chatter marks as it comes past the ear. (Much better pics btw) Ive had similar when my headstock gibs were loose. It was more apparent on the backside of the part then the side facing you. Maybe try milling a square noting the axis on it and compair finishes on each side??
    Not saying that its the problem your having, but making note of the axis on the part may help point in some direction.
     
  15. TomS

    TomS Active User H-M Supporter-Premium

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    I ran your code. Results were the same as the parts I posted above. What CAM program do you use?
     
  16. TomS

    TomS Active User H-M Supporter-Premium

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    The faceting is the same all the way around the pocket/hole. Looks to me it's not axis related.

    My headstock gibs, if anything, are a bit on the tight side. I haven't checked the X and Y gibs yet but it's on my to do list.
     
  17. Davd Flowers

    Davd Flowers United States Active Member Active Member

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    I'm using sprut cam all though I have been tempted to switch to fusion 360, but I would have to learn thier cad as well. I use alibre for cad and like it better than fusions.
     
    Last edited: Jul 20, 2017
  18. Davd Flowers

    Davd Flowers United States Active Member Active Member

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    Im at a loss....I do get some faceting but its pretty minimal. Ill have to see if I can get a pic uploaded for you to see.
     
  19. TomS

    TomS Active User H-M Supporter-Premium

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    A comparison pic would be great.

    I've just about exhausted the possibility of a mechanical problem, except for checking the X and Y gib adjustment. I have to believe it's an electronics issue because I was able to get good surface finishes before I installed the new stuff. I'm hoping it's a simple fix.
     
  20. Davd Flowers

    Davd Flowers United States Active Member Active Member

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  21. Davd Flowers

    Davd Flowers United States Active Member Active Member

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    Trying to figure out how to post picture.. hard to see the faciting but if you look to the right side you can see some of it..
     
  22. TomS

    TomS Active User H-M Supporter-Premium

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    I can see the faceting. Not that bad though. Wish mine was that good.

    If you don't want to learn Fusion CAD you can import files with .igs, .iges, .sat, .smt, .stp, and .step formats. I also have read where you can import .dxf files too.
     
  23. TomS

    TomS Active User H-M Supporter-Premium

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    Jay - I agree with you that it's a configuration issue or electrical interference. That's the only thing that's changed since I ran parts with good surface finish. Screen shots of your configuration would be great.

    Thanks
     
  24. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Will do. I should have some time tonight to do that. Between work and remodeling a bathroom there has been no time to play!
     
  25. TomS

    TomS Active User H-M Supporter-Premium

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    Thanks. Good luck with your remodel project.
     
  26. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Tom PM me your email. I thought I had it but I'm not finding it. I had to take photos of the screen since my machine pc does not have a way to properly save screen captures. The files will reduce too much if I post them here to be useful.
     
  27. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    Another thought. I can get poor finishes if the coolant isn't filtered or the coolant spray isn't flushing the chips away quickly enough.
     
  28. TomS

    TomS Active User H-M Supporter-Premium

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    Don't think it's coolant because straight cuts in X or Y leave a very smooth finish. The rough surface finish appears on radius', angle cuts, and circular pockets.

    I've read quiet a bit about improving surface finish and found a few tweaks for my CAM software and Mach3. Tried them out today and no change. Next I tightened the X and Y gibs until the motors stalled then backed off the gib adjuster until the motors would move the table and saddle to there extremes without missing steps. Still no improvement in surface finish.

    I've got a Gates drive belt on order to replace the eBay import belt I'm running now. You never know.

    I've heard that some people have had surface finish problems with angular contact bearings. I don't understand that comment mainly because high end precision spindles almost universally use AC bearings. On the other hand I could have a bad bearing. If the new belt doesn't help the situation I'll start looking for a new lower bearing.
     
  29. jbolt

    jbolt United States Active User H-M Supporter-Premium

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    If the straight cuts are smooth I would not suspect the bearings.

    I'm not sure this is related to your problem but have you tinkered with the CV setting in Mach3?

    http://www.machsupport.com/wp-content/uploads/2013/02/Mach3_CVSettings_v2.pdf
     
  30. TomS

    TomS Active User H-M Supporter-Premium

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