My Cnc Conversion

[JimDawson]

The only other thing that comes to mind is to make sure the axial play is actually in the ball nut rather then in the lead screw support bearings. The lead screw support bearings should be preloaded a bit. Short of that, installing larger balls in the nut is the proper fix. I'm surprised that the Anilam screw does not have double nuts.

 

[chevydyl]

Neither screw has double nuts, and the anilam screw is made by RBC, the overall nut length is longer than the x screw, it sticks out the back of the yoke almost 1/4". I'll have to do some bench testing on it before I tear it apart as well.

 

[chevydyl]

finally figured out how to get my Rapids up with electronic gearing. I tried high kernel speeds and it just made things twitchy, so I asked on cnc zone how to do it, then it came to me. 120000 steps per inch, divide by 4 is 30,000 set in Mach 30k steps per inch, the. In the servo drives set them to follow 4 quad counts per step input pulse, my resolution becomes .0000067 so I could actually divide one more time for a 1:8 ratio and have a resolution of .000013 and I think my Rapids would double but 115ipm is plenty for this mill at the moment.

 

[TomS]

Thanks for the kind replies.
The engraving was done with an accupro .250 60deg carbide blank, 4200rpm, 6.67ipm doc .010-.015 not enough spindle speed or too deep of cut, it was pretty burry, rubbed on some scotch Brite and took em down. Not sure if this bit was actually made for this or not but it's what a friend had for me to use to test some text.
Jim, the x axis screw has no backlash, setup an indicator touch the screw the table moves, y axis.....005 dial movement before the saddle flicks the needle. I feel like there is room for improvement, the screws are from different manufactures, one is from an Anilam controller (y) the other from an acu-rite (x) control. Both take out brand new, but the seller was calling them (old type) maybe anilam used to have their screws loose so they'd last longer idk. Do you have any suggestions on anything else it could be besides the bearings on the screw?

Thanks for the engraving info. It helps a lot to have a starting point.

Tom S

 

[JimDawson]

finally figured out how to get my Rapids up with electronic gearing. I tried high kernel speeds and it just made things twitchy, so I asked on cnc zone how to do it, then it came to me. 120000 steps per inch, divide by 4 is 30,000 set in Mach 30k steps per inch, the. In the servo drives set them to follow 4 quad counts per step input pulse, my resolution becomes .0000067 so I could actually divide one more time for a 1:8 ratio and have a resolution of .000013 and I think my Rapids would double but 115ipm is plenty for this mill at the moment.

Sounds like that would work. 115 ipm is about right, I have mine set at 100 max. Plenty fast. 1/3 micron resolution is close enough for any home machine, and most full on industrial machines for that matter. Once you get the Y-axis lead screw worked out you are going to have a very accurate machine.

 

[chevydyl]

Jim I actually went back and retuned to 100 max. It runs pretty good right now.
I still gotta familiarize myself with bobcad, having trouble cutting a square extrusion on the end of round stock, the part ended up being oversize and it finished the program in the center of one of the flats leaving a little indention, so I'll have to hone my skillz to make sure it continues off the part for a seamless finish.
And on the engraving, doing it over I had MUCH better results with the same part at only .005 to .008 deep. Maybe try 10-20ipm feed, the part must be flat of course, factory alum finish won't do, must take a face skim or the letters will be different widths. I also did a different style text BobCAD default, with a .075 2fl ball nose, the letters were shiny and turned out great, I have read that others had great results using small center drills as well, they are much much stronger, and if your using high speed steel your spindle rpm limit really improves finish.

 

[JimDawson]

........the part ended up being oversize.......

I just takes a bit of practice to get it right, you're almost there!

One hint, mic your end mill, and plug that number into your CAM tool size value or into the cutter comp if you have it. Most end mills are not on size, normally a few thou under, that will cut an oversize outside profile.

 

[Firestopper]

I just takes a bit of practice to get it right, you're almost there!

One hint, mic your end mill, and plug that number into your CAM tool size value or into the cutter comp if you have it. Most end mills are not on size, normally a few thou under, that will cut an oversize outside profile.

True, I allways measure the endmill as I have some regrind's. The cutter comp works great when you plug in the correct size.

 

[chevydyl]

Thanks for the advice, the issue was my tool path in bobcad, I did something wrong, I talked to tech about the program crashing and they also helped me figure out what I did wrong, I will start mic'ing my cutters, I choose a tool in cam but see no data about size in Mach for comp, I'll look into it, I explained to firestopper on an AGE2 control how a friend used cutter comp.