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Incremental Downfeed

michaelstranny

Plastic
Joined
Jul 11, 2017
Hello, I bought a new Birmingham 10 x 20 Surface about 3 years ago. The incremental down feed has 4 settings .0002,.0004,.0008, .0012. If you have it set on 0002 it moves 0002 about half the time, but then it will it will move 0004 at times. The same thing will happen if you have it set on .0004. It will move .0004 most of the time, but then down feed .0008 at times. It's always done that. It seems to be happening more frequently. Can anyone offer any insight on this. Mike
 
Mike,

Can anyone offer any insight on this.

I do not know your Birmingham grinder. But my Jones and Shipman 540 has an automatic downfeed. This works with a ratchet and pawl mechanism. If your machine has a similar mechanism, then perhaps at times the pawl withdraws farther than it should and picks up an extra ratchet tooth. But this is just an educated guess, nothing more.

Cheers,
Bruce
 
I have a similar problem not your brand machine. If there is a mechanical switch that triggers the down feed, a condition called contact bounce occurs. Where the driver sees 2 input signals very close together, and commands the servo/stepper to double. On my driver its call "debounce" and it extends the time between equitation of an input command.

Look for a Debounce command in the software setup.
 
A lot of times that is caused by the head sticking in the slides and then dropping after another downfeed impulse.

The grinders I'm familiar with the head follows the thread on the elevating screw,held in contact by the weight of the head.If the head sticks then the screw will continue to turn until the backlash is taken up and then on the next turn the head will be pulled down by the screw, break loose and fall until the backlash/clearance is taken up.Thoroughly cleaning and adjusting the gibs cures that problem.
 
Mechanical downfeeds usually use the rachet and pawl method mentioned above. When my grinders started feeding erratically I cleaned the old, hard grease / crud from the mechanism and re-lubed. Usually fixed the problem for a few years.
 
I looked at the spec's on your machine. It has a servo motor on downfeed, so the issue is likely the limit switch/programming. extending the debounce time is you likely cure.
Can you see the handwheel make two movements, or just the column drops an extra amount. If the later, then likely sticking of the column. Crud, Lube issues.
 
My guess is you miss a tooth on on the one feed then it doubles the next time.

On older machines this is an issue.
 








 
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