I put the final touches on my summer project yesterday...

My CNC mill now has a ball screw on the knee. Installing this using a ball screw I had on hand was quite the project. Would have been easier but I'm far too cheap to actually BUY a ball screw. The knee now has a full 12" travel about an inch more than with the acme setup. Here's the pile o' parts for this:

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The support equipment is where the job got complicated. I had to build two air cylinders from scratch. (I did have chromed 2.5" tubing). Again, I'm far too cheap to actually BUY what was needed. Here's pics that I posted earlier
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I have a five axis control card and didn't want to upgrade this plus add another servo drive. As much an issue of no room in the electrical cabinet as cost. So I built the fourth axis servo to quickly bolt on to the ball screw driving end. About a twenty minute change over to use this servo on the fourth axis instead of the knee ball screw.

I had allowed a week in the project for electrical devices. I TOTALLY missed the mark here. It took four weeks of my spare time. Part of the problem was the "Midas" syndrome. All I really needed was forward and reverse limit switches. But I Midas well add the home switch too. I'd been homing off the limit switches for years. its slow and a bit error prone. Since the table was apart I Midas well add X and Y home switches. If I added these home switches I Midas well do the quill too. This turned into a nasty little project of its own as I broke some stuff along the way.

The servo needed a brake for when no power was applied in the case of losing air pressure. Adding this and making it easily removable was a bit of a job I hadn't planned on. Then Midas took over again. I should know I've got air pressure before unlocking this brake so an air pressure sensor was added.

I've probably started a dozen threads asking for help on different phases of this project. This would not have went nearly as well without the help of all the great folks on RCM.

Thanks to all


Reply to
Karl Townsend
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I am MOST IMPRESSED with this, a very fine job, congratulations. Let us know how it works in practice. I still need to put limit switches on the W axis.

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