Clausing 12" 100 Mk3a CNC Conversion V2

[BrassBuilder]

Some of you may remember my Clausing CNC conversion from here:

http://www.cnczone.com/forums/vertic..._100_mk3a.html

Once I got "done" with it, I wasn't happy with the tolerances and only ran the lathe a few times before I stepped back and took another look at it. Since this was a total rebuild, I'm starting a new thread on it. I held off starting a build thread until now, because I was not sure this was even going to work.

The main problem was that the lathe would not hold consistent tolerances. I could not get it "tuned" no matter what I did. I think the big reason for this was the wear in the bed. If I got the carriage adjusted within a few inches of the chuck, then I couldn't move the carriage past the half way point in the bed. If I adjusted it where it was at the tightest point (farthest end of the lathe), then it was really loose at the chuck. This meant that when I tried to get the steps set, the carriage could be off .005 on one move and .015 on the next. It was impossible to get the steps set under these conditions. This was not acceptable for me. Although I was not making space shuttle parts, I felt I could do better.

So....off to ebay I went.

The first item that I found was a set of THK 25 rails that just happened to be the perfect length for the bed. But I needed a way to mount them...

This is where I really did not want to go with the project. Up until I was done with it the first time, the lathe could go back to stock. I still had all the original pieces and planned on putting it back to original if the CNC idea didn't work out. In order to get these THK rails installed, I needed a flat area and unfortunately, I had a V-way in the way.

It had to go.

A friend has a big Bridgeport, so we hauled the bed out to his mill and milled the V-way off on the front side. This way was for the original carriage and since I was building a new carriage, I didn't need the V-way anymore.

Sorry...no pictures on what we did.

I then made 8 brackets (four for each side) to support the new extensions.

The next two pictures show the brackets and the extensions. This is all 6061 aluminum. The brackets are 5/8" think and the extensions are 1/2" (or were). Once they were installed, we took the bed back out to the Bridgeport and milled it perfectly flat with each other. We also milled a "reference edge" on one side for the THK rail to butt against.

Installed one rail against the reference edge and then aligned the second rail off the first one with the use of a jig.

More to follow after the pictures.

Mike

[BrassBuilder]

Building the carriage.

1. The first picture is after getting the 1" thick aluminum machined flat and the first holes drilled. Obviously, I do not have them countersunk yet.

2. The ballscrew and THK rails in place.

3. A better picture of the machining that needed to be done.

4. Lined up the rails the same as the other ones. The jig worked great.

5. The completed carriage. The motor hangs off the back side under the lathe.

Mike

[BrassBuilder]

For the most part, that is the big changes. Once I got done, I ran some tests and.....the stupid thing was still off. Once I got it set to move 3" consistently, if I did a 6" move, it would move 6.005. If I did a series of moves such as .010, .020, .030, .040, I would get readings of .011, .021, .032, .043...it would slowly creep ahead. At this point I wanted to sit down and cry and throw a tantrum.

Instead, I started investigating and reread back through some of my threads. I finally got it narrowed down to possibly noise in the system. This started a quest on researching "noise" in CNC systems and posting this thread:

http://www.cnczone.com/forums/steppe...cnc_noise.html

After a complete rebuild of the control box (this was actually worse than building the lathe), I got this thing moving consistently within .0005 and for what I am doing, that is good enough for me.

Looking back, would I have done this knowing the hassle it was going to be?

No way.

Am I glad I did it?

Yes. Definately. Positively Yes.

There is so much that I learned (specifically getting THK rails installed and lined up and control box wiring) that anything I do from here on should be easier.

What's next?

I still need to install limit switches and I want the lathe to be able to cut threads, so more wiring and electrical stuff to do. After installing the new aluminum on top of the existing bed, the SR25 rails, and building the new carriage, I lost a few inches of my lathe (diameter). Instead of a 12" lathe, I probably have closer to a 7-8" lathe. I am going to place a 2" riser under the headstock and extend the tailstock to make up most of it. This should not affect the rigidity of it much.

After that....

Well...I have three sets of THK SSR15 rails sitting here and my mini-mill has three axis....and I'm starting to get some ideas on combining the two....hmmmmmm.....

And I've been looking at building a 3D printer....and I sort of got my eye on the RepRap system....but instead of buying all the plastic parts on ebay and since the drawings are freely available...and I just happen to have a CNC mill available...I may start by cutting out all the parts out of aluminum instead.

And I have a whole pile of Series 100 mk3a lathe parts to sell on ebay

So much to do....

Mike