Grizzly G0704 Cnc Conversion

JimDawson

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Or can CNC programs take the slack into account and compensate to get the accuracy you want?

Under a few conditions backlash compensation works, but not many. Cutting a circle for instance, it won't work. It will work for doing a hole pattern, but in general it will not work when continuous cutting. The only real way to get accuracy is to have zero backlash.
 

cozmogeek

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The ballscrew upgrade is really expensive. I want to see how it does with the leadscrews first.
 

TomS

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The ballscrew upgrade is really expensive. I want to see how it does with the leadscrews first.

Look at what Linear Motion has to offer on eBay. Their pricing for ball screws and nuts is very reasonable. I spent about $125 for three pre-machined ball screws with nuts, and three each fixed and floating bearing blocks about a year ago when I converted a PM-932. The contact person is Chai and his customer service is very good.

Tom S.
 

brav65

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Look at what Linear Motion has to offer on eBay. Their pricing for ball screws and nuts is very reasonable. I spent about $125 for three pre-machined ball screws with nuts, and three each fixed and floating bearing blocks about a year ago when I converted a PM-932. The contact person is Chai and his customer service is very good.

Tom S.
+1 on linear motion and Chai. I got 4 ballscrews and nuts along with a spindle motor and linear bearings. Good guy, and if you buy direct he will give you an additional 10% over eBay prices.
 

cozmogeek

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+1 on linear motion and Chai. I got 4 ballscrews and nuts along with a spindle motor and linear bearings. Good guy, and if you buy direct he will give you an additional 10% over eBay prices.
Thanks for the heads up about the discount. I'll have to look into it soon.
 

brav65

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You can give him the specs for the coupling interface you are using as well as the bearing blocks and they will turn the ends for you. I just sent a hand drawn sketch. His email is linearmotionbearings2008@aliyun.com

I have no connection with them, just a happy customer.
 

cozmogeek

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I got the X and Y done and everything wired on Monday since it was a holiday.
I just got my Z axis done. I used the 3d printed direct drive nema 23 mount. I used linuxcnc and the jog keys on the keyboard (arrows) to make those aluminum standoffs for the Z motor. That's the first thing i've ever milled...yay!
Now I need to spend some time getting linuxcnc configured. I got a USB pendant too that I need to get setup.
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cozmogeek

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I have made some more progress on this. Last week I ordered the ballscrews.
I tried tracing text with a 1/8" endmill and the results are pretty ugly:
LsBeBWvh.jpg
You can see the backlash in the results. When drawing the O and D the start and end of the letter don't line up. This was before I realized that the bearing wasn't seated all the way so I had a ton of backlash. After I cut this I measured and it was .04" (LOL).. I tightened it up correctly and got it down to .003"
So then I setup the backlash compensation and tried an engrave operation instead and it was much better other than my board not being straight.
7VfZENbh.jpg

Over the weekend I made the motor mount standoffs and the X axis mount (manually using the jog controls on the keyboard):
usMdM3nh.jpg
Tonight I plan to replace the 3d printed X mount with this new one.

The Z axis mount is different for the ballscrews than the leadscrew version so I'll have to wait for those parts to arrive before I can replace it. I'm not sure about Y yet. It is more complicated since it has the spacer with the holes for the bearings.

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