[RCW]

I have an old Gorton that was originally NC via paper tape. Does not appear to been used enough to have much wear. It has ball screws and dc motors on x axis and quill. Max torque is for the knee at 1700 in/lbs (with no gear reduction). I want to convert it to run off Mach3.

Today I found a "kit" at

http://www.ebay.com/itm/Cnc-Milling-Machine-3-axis-NEMA34-PC-Mach3-Micro-step-motor-Kit-Stepper-637oz-in/390627298795?_trksid=p2047675.m1850&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D11%26meid%3D16210148953790784%26pid%3D100011%26prg%3D1005%26rk%3D1%26rkt%3D5%26sd%3D150737478359%26

That provokes a host of questions:

1. Has anyone purchased from this suppler? Are the reputable or a Hong Kong fly-by-night? Is this even a good price?

2. What other components would be needed?

3. Are there off-the-shelf gearboxes, or will the hardware all have to be made in-house?

4. Are the kits that are more complete?

5. There are many great posts on this forum, but I'd really like to have a step-by-step guide-book, which--so far--I have not found.

All advice appreciated!

Bob

[RCW]

Anyone out there on "the largest forum of its kind?"

[jalessi]

Bob,


The eBay vendor you are inquiring about has relatively good feedback concerning stepper motors and drives.

"HOWEVER" If you need hand holding, are you sure a offshore purchase is a good idea?

In my opinion the components in the kit you posted are completely underpowered for the task (reliably running a Gorton mill) .

There are several threads (see attached link) that share details on Gorton conversions, you may have better luck if you search through them and enquire directly.

CNCzone.com-The Largest Machinist Community on the net! Over 300,000 members and growing.

Welcome to the Zone,

Jeff...

[RCW]

Thanks very much, Jeff! Very helpful.

Is there a formula to determine the torque rating needed?

Bob

[jalessi]

Thanks very much, Jeff! Very helpful.

Is there a formula to determine the torque rating needed?

Bob

Bob,

This just might be what you are looking for:

Motorsizer - Galil: We Move The World

Have a most awesome afternoon,

Jeff...

[Halfnutz]

Before you do anything do your research well. Look at Centroid, they have been doing what you are planning for ever and have some rock solid hardware and a good reputation at DC motor control and knee mill retrofitting.

Bridgeport cnc retrofit kits for all types of knee mills and Bridgeport clones

Good luck.

[awerby]

If this was originally NC controlled, the most cost-efficient retrofit would reuse the existing DC motors, assuming they still work. Are they just on the X and Z axes, or is there one on Y as well (as one would expect)? Do you have the specs on those motors? Do they have encoders or resolvers? Finding drives that are compatible with them would save a lot of issues in selecting and remounting alternative motors, and you'd have a reasonable assurance that they'd be powerful enough for the job. Once you had the motors and drives figured out, all you'd need would be a breakout board, Mach3, and a computer.

Andrew Werby
www.computersculpture.com

[RCW]

Andrew:

Thanks for responding.

There are/were old (but functional) motors on the X-axis and quill only. There were no encoders or resolvers. The Y-axis had a motor like one often sees on power table feeds. It is moribund and no longer supported by the manufacturer (Servo Products Co., Model 70). Comments on the web--including those by Servo Products Co.--imply reliability problems with that old model.) I wonder if it was even a part of the original package. The knee has a shop-made adapter so that it can be turned with a 1/2"-drive ratchet-handle. The aluminum pulley on the X-axis appears to have been installed and removed repeatedly, or, at least got beat up a little somehow. It would probably work. How much slop is there in cog-belt drives?

The only specs are those on the motor labels. There a very small spindles on the ends of the X and quill shafts that I assume ran the encoder/resolvers. There is so little wear on the machine that I wonder if the NC tape drive ever worked successfully. Anecdotal rumor has it that it only ran for a short time before it became unreliable due to problems with the paper-tape drive. I have no way of confirming that.

The X-axis moves smoothly, almost effortlessly with little--if any--play. Y is slightly stiffer, again with little-to-no backlash that I can detect. The quill is slightly more resistant yet. It is stiff when moved with the manual handle. As would be expected for such a heavy mill, the knee is really stiff.

I hope these answer all the questions above. Please do not hesitate to ask additional questions. I can provide the information from the two motor plates, if that would help.

All input is deeply appreciated.

Bob Williams

[RCW]

Hmm. I got to the third page on the Galil site. Looks like good stuff! However, I am stumped at this point. The page asks for:

Load Mass
Load Force
Screw Inertia
Friction Torque
Lead (per rev)
Efficiency

I have no idea what "Load Mass" means. Is that the weight of the table, vise and workpiece? I have no idea what the table weighs. (A bunch!)

I assume (oops!) that "Load Force" is this is the measured torque on each axis? (4 in. lbs. on X, 15 in. lbs. on Y, 10 on quill and 180 (20 lbs. at 9 in.) on the knee.

"Screw inertia?" If that it the energy necessary to start the ball screw rotating, then it is a number closely approaching 0 on the X axis. Quill and Y are a little bit more, but not a great deal.

"Friction torque?" Is there any way of measuring these apart from the inch-lbs. above?

Lead is .20 on X. On the Y, it appears to move 1" in 5 rev. or .20 as well (the dial is disconected at present). There also no dial on the quill. There is a crude (NOT original) scale. The quill appears to move 4" in 20 revolutions or .20 as well. The dial on the knee indicates that it would move 1" per revolution, and that is confirmed by a dial indicator. (No wonder that mass of iron takes so much torque!)

"Efficiency?" Is that a factor for a gear box or something else? Duty cycle for the stepper?

I feel really ignorant, even for a newbie. Enlighten me, please!

Thanks!

Bob

[RCW]

Thanks for your response, Halfnutz.

I looked at Centroid. They have some pretty impressive equipment. Unfortunately, they appear outside the price range for a hobby. Also, they appear to use a Centroid control system. I think I'd prefer Mach3 (or possibly Linux.

I appreciate your wishing me luck. Apparently, I'll need it.

What are you running?

Bob

[underthetire]

Ajax does have a Mach3 plugin. It works, but not perfect.

[RCW]

Here's the poop on the DC motors.

The motor on the X axis and on the quill appear to be identical. They are marked:

"Adjustable Speed Drive Motor Model 34357352124-OR (or OA?).
RPM: 1725
Enc.: TEFC
HP: 1.4
Volt: 90 Ave.: 2.72
RMS: 3.24
Peak: 16
R Ohms: 5
Time Rating: Cont.
Ambient Temp.: 60
Safety: 127
Replacement brushes: 2-1901

Indiana General Motor Products,
1168 Barranca Drive,
El Paso, TX 79935."

Appears to fit NEMA 24 bolt pattern.