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

Well done! :)
Are you satisfied with the result?

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.

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

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

X, Y, and Knee motor mounts done.

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.

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)

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

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 :)

Mcgyver, thank you for the kind words.

Okay, so much for the easy stuff. Now on to the head scratching stuff for me---the wiring and electrical. It's about this time that I start reading up on the Pacific Scientific drives and I find out that if I run them on 120VAC, I'll only have half the power to the motors. I'm already borrowing the 240VAC from the water heater circuit so I know I'm going to need some more 240VAC power.

Of course I plan to run the wiring in the attic space during the summer while it's hot up there. I also changed out the service panel from 100A to 125A and use tandem and quad breakers leaving a few slots left for the future. I end up with a 30A 240V circuit for the mill, another 30A 240V for the drives, and 2 more 120V circuits for powering the breakout board, computer, DRO, lights etc. all with a home run ground wire to a ground rod just on the other side of the wall from the mill to try to avoid a ground loop.

Next I have to figure out how to wire some 240V 40A contactors for the mill and Drives, through an Estop switch and a switch to go from manual to CNC, and also let Mach2 know about the Estop. I came up with the following wiring schematic. I tried to keep the high voltage stuff away from the low voltage signal stuff as much as possible so I have a separate enclosure for the contactors versus the breakout board. I used an inexpensive service panel enclosure from Home Depot for the Sound Logic/ Campbell breakout board that was large enough in case I need a second board for more inputs or for a ModIO board for a pendant/ MPG later.

I've also got a gratuitous photo of the VFD in the enclosure on the mill as I have the Sharp Digital variable speed head. Someday I may figure out how it hooks up to control spindle speed via Mach2.

One of the problems every Mach2 user faces is not enough inputs. I find out I'll need to gang the limit switches on the end that is not shared with home. That is, +X, -Y, and -Z ends get combined after putting an isolation diode on each signal end. The other issue is that the Sound logic/ Campbell breakout board is designed to look for an active low signal, whereas the Industrial Hobbies optical limit switches I have are active HI. I had to get help from an electrical engineer friend (thanks Jim Davey) who immediately figured I needed a 1K ohm pull down resistor from signal to ground of the shared limits to make things work. I also had to play around with the orientation of the diodes. The band on the diode goes toward the breakout board. The combined limits connect to the Aux limit connectors so that you can specify a separate input pin in Mach2.

I had to make up some new motor and resolver cables and my instructor recommended ferrules on the ends of the wires as they go into the screw terminal connectors. After looking at the usual electronics places where the ferrules and crimping tools were in the order of several hundreds of dollars, I found a crimping tool and ferrule kit for a reasonable price at Ferrules Direct by searching on the internet.

After I starting connecting all the cables, I had to figure out where to route them. I wanted them to go over the right side above the VFD enclosure but was worried the Z DRO scale may snag on them. In addition, I thought it would be a good idea to try to keep the chips off the scale so I decided to enclose the scale further. I left a slot so I could screw the nylon cable supports to it.

I finished securing the limit switch tubing/ cables and the DRO reader head cables.

I tried running the knee without the gas spring assistance. It was drawing too much current for my motors at 40 ipm rapid in -Z, and I was getting an over current fault on my drives. I wanted to put the gas springs up at the front as I had seen Peter Renolds do it, but the Y axis motor was too close to the knee to allow it.

Rather than remake the Y axis mount at this stage, I decided to use some 6" structural 6061T6 channel to support the gas springs at the sides of the knee so that the gas springs could still be positioned vertically. Initially I placed one on either side of the knee between the jackscrew and the ways, but I think since most of the weight of the table and saddle is at the front of the knee, the lift behind the screw made the knee catch as it moved along the ways.

Now I thought I was stuck. Then I decided to try an asymmetric force application front to rear, but still relatively balanced transversely. I added another set of ball studs at the left front of the knee with a 200 lb. gas spring and a 100 lb. gas spring on the right rear. Because the distance in the X axis of the side mount is about twice the distance in the X axis of the front mount, the moments are relatively equal side to side, but more upforce at the front of the knee than the rear.

This is working alot better. I am running it at 30 ipm rapid on the knee and 120 ipm rapids on X and Y. This is plenty fast for a beginner like me, even though I'm sure I could go faster on X and Y with no problem. I think if I need a faster rapid in the knee, I will have to do the ballscrew conversion.

RJ,
I see from one of your pics you had the ball screw & nut disassembled for the machining. How did you put it back together? I removed the ball screw from the nut to get the table off (now realize I didn't have to) and have been told I made a big mistake as I will have to send the unit back to the factory to be reconditioned at Great Expence. Any advice you can give my would be greatly appreciated. Thanks, Jack.

Jack F,

I am sorry to hear about your ballnut problem. I always kept the ballnut on the ballscrew throughout my retrofit as I had been forewarned. I have read some posts somewhere, not necessarily on this forum, where people have reloaded their ballnuts, so it can be done. I think the key was making sure you still had all the balls as I think the size of the balls is critical. If you can find all the balls, I'm sure someone on this forum can help you.

Regards,
Rick

it looks to me like you do good work. i have an enco moll i,d like to do the same thing to. this mill was in the owners basement. i had to disasemble it to remove it . it was quite a job. did you buy a kit to convert your mill? i,ve checked on some of them and i can,t afford them.
i,m a retired toolmaker/machine builder but don,t understand the magic of cnc,s but i think i could learn to love them.

thanks for any info you can give me. Dar

Dar,

Thanks for your nice comments. I didn't buy a complete kit, but I did get lucky and found someone (HS&S) from whom I bought the ballscrews and motor mounts that fit my mill. The motors and drives were surplus so I made the adapters to make them fit my mounts. For a toolmaker/machine builder, you shouldn't have any problems making motor mounts or making things fit. You probably just need to know what's involved for you to figure it out.

I would like to recommend you contact Roland Friestad who wrote a series of articles for Home Shop Machinist titled "Computers in the Shop" at http://www.cardinaleng.com/ as I ordered a bound copy of reprints from Sep/Oct 1989 - May/June 1994. He goes over the basics of what you need to know to convert a mill to CNC and has blueprints for an ENCO 9 x 42 knee mill as well as a Mill/Drill conversion as far as motor mounts, ballscrews, and selecting motors. Also, Roland is a really nice guy who will be happy to talk to you if you have questions. After I read the reprints, I felt I had enough info to start to be conversant.

After you get the ballscrews and motors mounted, you need to figure out how to control them. I highly recommend looking at Mach2/Mach3 (http://www.machsupport.com/artsoft/index/index.htm) and joining the Yahoo group as it is a great support group for new users. There are alot of links at the machsupport.com to point you toward connecting to a PC through a breakout board as I have, and motor drives and power supplies for the motors.

I'm not an expert as this is my first project, but I will try to answer any questions about what I've done. Hope this helps you get started.

Regards,
Rick

thanks Rick
i have contacted him and will buy the book.
thanks again Dar

Any chance of a video being posted of your terrific conversion in action?
...nice pics too!!

jmg

Rick, I'm an ardent Newall fan. Tell me, what made you decide to use Newall over glass or magnetic strip scales?

Any chance of a video being posted of your terrific conversion in action?
...nice pics too!!

jmg

Hi jmg,

Thanks for your comments. I haven't taken any video of it. If I do, I will try to post it.

Regards,
Rick

Rick, I'm an ardent Newall fan. Tell me, what made you decide to use Newall over glass or magnetic strip scales?

I haven't had much experience with other types of scales, but it seemed to me that the sealed nature of the Newall scales would be better than glass scales-nothing to worry about keeping clean, even if I don't end up running flood coolant.

Regards,
Rick