Backlash Compensation

[erik_f]

This was interesting.
https://machmotion.com/blog/what-is-...-to-correct-it

[chiloquinruss]

"backlash compensation" - I don't think so! There are some great posts on here discussing keeping things properly tuned and replacing worn parts (IE pinions etc). I had an instance awhile back with some china end mills that were not cutting to my liking and what I discovered was a lot of 'bit flex'. Symptoms were similar to what I would expect from backlash but turned out it was in the bit itself. My machine is over 10 years old and I cut mostly cheap HD ply, so it gets a lot of long run use. The replaceable parts are cheap, quick to change, make my machine a good wood working tool. Russ

[erik_f]

Thank you for the feedback guys.

[Brady Watson]

A Shopbot is 'reasonably' tight and backlash free when you measure .003-.007" of play in any one axis. I'd recommend getting a good dial indicator set up and measure everything including gantry AND table deflection when you press down on them with moderate force. There comes a point where you can't get a bolt together machine any tighter and you just have to do the best you can or look at other options. The gearboxes themselves will show .004- 006* in many cases when new.

[scottp55]

Slightly off topic....Brady...5 yr old Desktop....Any time frame to replace anti-backlash nut on Z-axis, and spring for spindle support?
What are indications of the need to replace?
LIKE the one piece older Desktops with welded frame, and machined Y-rail area...vs. the new bolted together for my applications.
Sorry for the off topic....and appreciate any info/threads Brady(Thanks in advance).
scott

[Brady Watson]

Scott, What kind of play have you measured on your machine?

I don't have a lot of good things to say about plastic lead nuts when real ballscrew/nut combos can be had for dirt... They are fine if you don't cut over 2 IPS in most cases on these machines.

[scottp55]

OK,OK......THIS week I'll buy a dial indicator set Brady
Still pretty tight on second passes, BUT Z seems to drop a hair on every RR(5 RR's will eliminate a light pencil mark on wood).
Was just wondering if those years of cutting buttons at low Z had stretched the spring.
I'll get some hard numbers when indicator(and steel plate?) come in.
Sorry I asked the question without any numbers Brady
scott