Reducing Quill Backlash and Setting Z Axis Gain on a RF-30 Mill/Drill

This article deals with a simple modification to a RF-30 mill/drill that reduces quill backlash. I then address the task of setting the correct Steps per [DRO inch] in the CNC program, Mach3.

Over the range of 0 to 0.4000 inches, I measured an error of less than +/- 0.002 inches. However, I also saw a large random error at 0.2000 inches that has yet to be figured out. So consider this article a work in progress.

If you are interested, please see

http://rick.sparber.org/ZABG.pdf


Your comments are welcome. All of us are smarter than any one of us.


If you wish to receive future article announcements automatically, please send me an email with “Article Alias” in the subject line.

Thanks,

Rick

Thanks Rick! I've added your Quill Backlash Reduction Method to our Milling category, as well as to your builder page: Rick Sparber's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="/quill-backlash-reduction-method"><img src="/uploads/115042/quill-backlash-reduction-method.jpeg" alt="Quill Backlash Reduction Method" /></a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="/quill-backlash-reduction-method">Quill Backlash Reduction Method</a> <span> by <a href="/builder/Rick+Sparber">Rick Sparber</a></span> </div> <div class="tags"> tags: <a href="/tag/spring">spring</a>, <a href="/tag/mill">mill</a> </div> </div> </div> </div>

This thread has been moved to the Must Read subforum. Congrats (and thanks) to Rick for making such a valuable contribution!

Quote:

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Originally Posted by rgsparber

This article deals with a simple modification to a RF-30 mill/drill that reduces quill backlash. I then address the task of setting the correct Steps per [DRO inch] in the CNC program, Mach3.

Over the range of 0 to 0.4000 inches, I measured an error of less than +/- 0.002 inches. However, I also saw a large random error at 0.2000 inches that has yet to be figured out. So consider this article a work in progress.

If you are interested, please see

http://rick.sparber.org/ZABG.pdf


Your comments are welcome. All of us are smarter than any one of us.


If you wish to receive future article announcements automatically, please send me an email with “Article Alias” in the subject line.

Thanks,

Rick

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Rick I have a Grizzly mill-drill which I believe is the same as yours. I found that only raising the fine feed takes the backlash out.Similar to a cabinet or contractor saw where height adjustments should always be done raising the blade,rather than lowering.
I have a digital scale mounted on the Z axis.When only raising the spindle and hitting the height wanted the scale shows a variation of 0 to .0001.I want to preface this by saying ,most of the time.I have had the endmill drop a few times with a heavy cut.When I first started milling a few years ago I did not pay attention to the position of the endmill in the holder. Now I always make sure the end mill flat is down as far as it will go before tightening the set screw.My digital scale is not like your DRO but is accurate enough for my hobby work.
mike

Mike,

Thanks for the details.

A DRO bolted on the quill directly measures quill movement. It is far more accurate than dead reconing with a stepper motor. Sadly, Mach3 cannot accept feedback from a DRO.

Rick

As I often do when I finish a project, I googled it to see what else similar comes up, your project is about the only one to appear and I read it with interest. I too had, in my case, a Clarke branded mill with a backlash problem, I chose to go the other direction to you as I have pulled the quill up rather than push it down.
I have written this up fully online here Milling machine Quill DRO and backlash eliminator!
I hope it will be of interest.

rog8811,

There certainly are a lot of similarities between our mill modifications. I hadn't thought much about how gas struts worked. Thanks for the education. The best I can figure, the original take-up spring in the Z axis feed is only to raise the quill. It certainly does not address backlash. As we both showed, you have to put a force on the quill to address backlash. Then the force acts through all gears to eliminate it. The trick is to apply enough force to overcome the downward pull of a large end mill. Apparently you have done that.

Thanks,

Rick

Quote:

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Originally Posted by rgsparber

rog8811,
The trick is to apply enough force to overcome the downward pull of a large end mill. Apparently you have done that.

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Indeed yes, My shell cutter cuts smoothly now and the with the heaviest tool I have, my boring head, it has taken all the flutter that I used to get from it out of the system, it has transformed the machine :)
Also DRO's are such a boon with zero only a button press away.

I have had my 5/8" end mill pulled out of its collet on a heavy cut. The force is most certainly downward. I believe this is because the end mill tends to screw itself into the material. My guess is that a shell mill has an upward force.

As far as adding a DRO, it dramatically changed how I approached machining. CNC takes it up another notch.

Rick