Do you have Backlash?????

[Robbie]

If you are running a CNC this is a must!!! Are you missing corners during polishing? Are you leaving unnecessary lines beacuse your profiles aren’t taking off the proper amount of material? Do you blow up polishers on inside corners? Does your load meter fluctuate on different sides of a top? If so, you may have a case of backlash. Please watch the video to see how to check your machine. Backlash can cost you thousands of dollars a year.

https://youtu.be/XXyP5gfNjlI

[Amroczka]

Backlash has to be checked with a programmed movement (not with the handwheel).... all machines have backlash, and their controllers have a compensation parameter set for the amount of backlash.. i believe most machines only compensate for backlash wih programmed movements..

[Camzl1]

BackLash in its truest form is the residual mechanical movement between the driving gear and the receiving end, the rack. In Northwoods case it is a ballscrew. The nut and the screw. Compensation at the controller is NOT designed to compensate for large amounts of backlash. The most when I worked for CMS was .05mm The best way to test for backlash is based on the the drives not being energized so you can eliminate any servi tune or the servo engagement period. This is not usually do-able because most Servos now a days when they are not engaged they are in a braking state, for safety. So you can check backlash with the machines internal movements as long as you have backlash comp turned off. In the most true sense then someone who is mechanically minded would loosen the servo belts so the ballscrew assembly could be checked individually. For rack and pinion you would have to disengage the gearbox. Something not always easily done.

[Robbie]

Eric you are correct. Checking backlash is performed just as I have illustrated in the video.

[Camzl1]

Thank you Robbie. The previous post from Anthony as I understood it is how we check repeatability. Making a program to go back and forth is not going to check backlash. Again, another more simple statement is for rack and pinion backlash is, the gap between the meshing of the gears is what you are checking. Ball screws it would be the amount of movement past nominal stop.

[Amroczka]

Idk, maybe i didnt explain what i was trying to say clear enough. What i meant was that most machines (if not ALL stone machines) are not programmed to have the backlash compensation (digitally set up in the controller) active when using the hand wheel. So if your checking for backlash with the hand wheel, of course your going to discover some backlash. Whether or not it is exceeding the amount that your controller is compensating for (with programmed movements), you wouldnt be able to tell if you have a problem, unless you checking it with programmed movements (backlash compensated)...

Either way, backlash on a stone machine is usually not the problem when you could be having 4 or 5 times that amount in tool deflection or even stone deflection.

Also just to be clear, my commenting was not intended to discredit anybody. This is just a subject i have interest in and why not build the thread!

[Robbie]

No problem here Anthony. Thank you for your comments, we are here to educate and be educated.

[Amroczka]

I wish we had more videos and discussions on stuff like this is the digital room. Perhaps another thread should be started on tool deflection and running your tools too fast. I think it would be a good topic.