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Old 12-21-2016, 01:49 AM   #1
MachineTom
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Default Conversion Of Grinder CNC

An uncommon machine in a Home shop is a Surface Grinder. But in this case this is my 3rd SG. Built as an Automatic in the 80's it had a hydraulic X axis and a stepper type Y axis. In the 90's it was reworked to have a digital Y with a linear slide and Z axis, and a manual x axis.Click image for larger version

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I purchased it when the company sold out to a China company.
The unit used Compumotor steppers and microdrives. These are a single drive unit, drivers, controller all in one box. Communication with a PC via RS232 port, and hookable to a RP240 2 line operator.

Antique you might think, but for this application just right. With the grinder I got some books, BASIC EXTENDED is the language. Many readers here were not yet born when that language went out. But again for this application it fits.

So all I had to do was rebuild a well used grinder from a manufacturer that is out of business, learn a dead computer language, and install controls to make this into a workable SG.

A wiring diagram would have been handy. But not anywhere.
Click image for larger version

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I will focus on the CNC end of the project not the mechanical side.
The steppers are nema 34 size units, the Z has a feed of .050" per rev. while from a milling point of view is very fine indeed, a.010 is a big cut on a grinder, So I put a 3:1 reduction to the stepper.Although the stepper has a 25000 steps per rev. feeding a little bit at a time is the game.

Click image for larger version

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The driver for the Z was loaded as a startup program, so as soon as the driver is powered up the program is running. The buttons on the left side control a jog function, the larger black button is for a fixed downfeed of.00025", and the toggle is a high/low speed when jogging. Not yet programmed is the automatic downfeed for Z. But its working great as is, now. The holes will be filled with a couple more switches, for home return.
Click image for larger version

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The Y axis is controlled by this operators box. The program lets me select how much each step over each cycle of the table advances. Limit switches are adjustable for maximum travel.
Click image for larger version

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there is a trigger switch on the X axis, which closes to tell the controller to advance the set step.Click image for larger version

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The drivers were mounted on the door for electrical controls, good assess and protection.Click image for larger version

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As it is now I can set the step over, set the depth of cut, and walk away while the machine does its grinding. I don't miss the exercise, cranking the table,4 turns left, 4 turns right, quarter turn feed,then 4 turns left...

The Y axis is stepper controlled, the motor sticking out the rear in the photo. The old feed screw was shot, so I made a new one, and added a square shank, that connected to the original stepper motor drive shaft, then added a mount for the new stepper.

I found these antique parts to be easy to purchase off ebay, the website from Parker is still available, and downloads are free. There is a software package called Motion Architect, that will provide the software base. You do need to write the movement code.

I now intent to automate my Dividing head, and the linear stage that came with the grinder, to cut gears for an upcoming project.


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Last edited by MachineTom; 12-22-2016 at 05:40 PM.
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