Sharp Mill retrofit

[RJ.]

I finally finished my Sharp LMV retrofit. Mach 2 control, Pacific Scientific AC brushless servos on X, Y and knee. Ballscrews on X and Y. Gas springs on knee.

Regards,
Rick

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[svenakela]

Well done!
Are you satisfied with the result?

[RJ.]

Well, it's still a work in progress. I still have about .002" backlash in the knee I have to look into. But I am happy to finally have it running. X and Y ballscrews are running well with little to no backlash. I still have dials on X, Y, and knee along with a 3 axis Newall DRO because I am a new machinist-hobbiest, and I still expect to use the machine manually alot while I'm learning.

I would like to take a moment to thank my instructors at De Anza College Department of Manufacturing and CNC Technology for their instruction and help with my project and for teaching me some basics of manual and CNC machining. I have so much to learn. Many thanks to Mike Appio, Scott Wigginton, Larry Brown, Mike Engle, Loren Beall, and especially Chris Newell, without whom I could not have done this project .

First cuts on my machine are dedicated to them. It is the Manufacturing and CNC Technology Department logo. Thank you all.

[propclock]

I am thinking of doing the same to my sharp mill.
Where did you get the ballscrews? my table is 50" sort of odd ball,
I have only cnc on the knee so far. I used a dc gearbox motor and timing
chain drive . this allows the full weight of the knee to be moved with ease
and feedback is via a rsf glass scale on the knee. It takes a while to settle
but repeats to better than .0001. some dc bias (offset) on the motor makes
up down motion equal and allows for manual operation with a 8" handwheel

[RJ.]

propclock,

I got my Hiwin ground ballscrews for X&Y along with the motor mounts from HS&S Machine Tool in Santa Clara, CA. See www.hsands.com and call and ask for John Servin.

They used to do Sharp Mill retrofits, and he had a few leftover parts. I'm not sure if he still has anymore. If not, I have the drawings for the Hiwin parts so you could have some made.

The ballscrews I got came long, and I had to shorten the ends of both the X and the Y. I think they were probably made for the 50" table instead of my 42". Otherwise, the ballnuts fit perfectly in the yoke with some drilling and tapping for fastening screws. I will try to post more details of my retrofit as time allows if there is interest. Otherwise, let me know if you have questions.

Regards,
Rick

[RJ.]

It's raining the day the rigger comes to pick up my mill at the tool dealer, so we wrap it up. It's loaded on the forklift then onto the flatbed truck. Then on the way home.

[RJ.]

After acquiring the ballscrews, motor mounts, motors, and drives, work is started to take things apart. I took alot a pictures because I've never done this before, and it's all got to go back together again later.

Started by taking off the X and Y acme leadscrews, loosened the gibs on the table, and slid the table onto a melamine board at the same height by adjusting the knee height. I was surprised how easy it was to slide.

This gets us to the yoke. The stock yoke only references the bore for the bronze acme nuts, but the ballnuts reference the faces of the yoke so I need to machine the faces square to each other and the bore/ mounting flange.

[RJ.]

I used an angle iron as a fixture to mount the yoke so I could square the faces to the bores and mounting flange. I mounted the yoke by the flange to the angle iron after drilling and tapping the angle iron. I used a dial test indicator with a long point to orient the bores square to each other and the fixture on a surface plate.

I first squared the faces of the yoke on the surface grinder, then drilled and tapped the faces for the ballnut mounting screws.

[RJ.]

Next problem is the motor mounting flanges don't match the motor mounts I have so I need to make adapters. A circular pocket is needed so this will be my first CNC program. Luckily the Haas mini-mill VMC I used has a circular pocket canned cycle.

After I make the adapters I need to modify the Y axis mount for the adapter or my motor shaft will be too short. Last photo is the trial fit of the Y axis motor mount assembly.

[RJ.]

Since I'm new to this, I don't know whether I'll need the dials and handwheels or not, so I opt to have no regrets and plan to place dials and handwheels. This requires extending the X, Y and knee shafts. I learn to single point thread on a lathe first. I also learn to mill a keyway and broach a keyway in the dial holders.

[RJ.]

I bought a knee mount from www.cncauto.com and both the knee and X axis mounts needed a little massaging to fit the knee at the desired angle and for the mounting adapters and slack for fitting the pulley.

[RJ.]

Now for my big moment. I need to machine the left end of the X axis ballscrew which requires a keyway and single point threading the end. I don't want to mess this up or I'll be buying another expensive ballscrew.

First I make a support with a leftover ball bearing so the ballscrew won't whip. Then I carefully machined the end.

[RJ.]

Now it's on to spacers. I make a spacer for the left end of the table because the thread on the ballscrew is a little too long for my 42" table. I made the spacer a little thicker as I decided it would be easier to fine tune the dimension for zero slop with a spacer on the ballscrew shaft versus trying to get the thickness of the table spacer exactly right.

My knee mount also needs a spacer between it and the jackshaft bearing holder.

[RJ.]

Assembly time. Added one shot lube lines for the ballnuts. Installed the ballscrews and knee jackshaft. I had to heat the bearing housing in the knee near the pinion to get the bearing back in.

[RJ.]

I used dial indicators to center the ballscrew shafts in the center of their deflections while fastening the bearing mounts. Then motors and pulleys on and set belt tension.

[RJ.]

X, Y, and Knee motor mounts done.

[RJ.]

I thought I would be able to use the feedback encoders on the servos as a DRO in manual mode until I found out they were resolvers. So I decided I had to have a DRO so I bought a 3 axis Newall C80 for X, Y, and Knee. I also pondered home and limit switches and decided on the Industrial Hobbies optical limit switches.

So I took a little detour to install the DRO and installed the home/ limit switches at the same time. The home/ limit is shared at -X, +Y, and +Z.

[ZipSnipe]

Nice work RJ, I,m impressed. Hey you said that your a beginning machinist/hobbyist right? How come such a large mill?(not that theres anything wrong with that Bigger is better)

[RJ.]

Hi ZipSnipe,

When I was in high school, I bought a Taig micro lathe. I got so frustrated with problems keeping the work tight in the chuck, chatter, and shallow depth of cut due to lack of rigidity and mass. When I took my class at De Anza College, I used a Bridgeport knee mill and 13x40 lathes. I was amazed how easy it was to take off metal with no complaint from the machine.

Originally I was going to get something like a 9x20 lathe and 8x30 or 8x36 knee mill; but after taking the class, I just decided to go for a standard size knee mill and 12x36 lathe. Everybody always says more mass is better. Besides, it's my mid-life crisis, right?

Regards,
Rick

[Mcgyver]

Rick, nice work, thanks for sharing so many pics. you will congratulate yourself for years to come on what a clever chap you were in going for a full size mill