Sharp Mill retrofit

[RJ.]

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.

[RJ.]

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.

[RJ.]

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.

[RJ.]

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.

[RJ.]

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.

[RJ.]

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

[RJ.]

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.

[RJ.]

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.

[Jack F]

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.

[RJ.]

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

[Dar]

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

[RJ.]

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

[Dar]

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

[jmg]

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

jmg

[RICHARD ZASTROW]

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

[RJ.]

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

[RJ.]

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

[K_Labs]

I've been reading your post for a little bit here and I thought you said somewhere that you used servo motors. Well not verbatum but you said Servo encoders. Could you clarify?

[will gilmore]

thread is from 2007. RJ hasnt posted since so I wouldnt hold your breath for a reply

[RJ.]

I certainly hope you weren't holding your breath.

They are Pacific Scientific AC brushless servo motors with resolvers, not encoders.