Telop Mode and uncoordinated moves

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13 Apr 2017 14:26 #91312 by Henk
HI all

I was wondering if this is possible in LCNC without custom components etc.....

We have am hobbing machine at work that has been around the block a few times and is now getting increasingly unreliable. It is a conventional machine with change gears and many, many relays in the panel. This machine is in desperate need of rewiring and the best would possibly be to use a PLC to control the machine, keeping all the gear trains etc. In the future, i would like to do a full retrofit however so instead of using a commercial PLC, i want to use LCNC so that i can later add servo motors etc and make it full CNC.

The machine motions are controlled via clutches that are engaged to either rapid or feed each axis. Would it be possible to control these motions from LCNC bearing in mind that coordinated moves would be out of the question.

My idea was to use a commanded position, compare it to the current position and activate the appropriate clutch. The problem i foresee is that the velocity for each axis which is either fast or slow and noting in-between will cause following errors. I was hoping Telop mode will allow two axes to move to a target position in an nu-coordinated fashion but im not sure.

Any ideas on how this should be done are appreciated.

Thanks
Henk

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13 Apr 2017 14:57 #91319 by andypugh
It's easy to avoid following-errors, just wire the f-error inputs in HAL to the commanded position, not the feeback position. (Or, set the limits very wide, to retain some monitoring function)

There is absolutely no point in converting to CNC and retaining the mechanical gear-train.

With the workpiece slaved to a spindle encoder you can make absolutely any gear ratio you want, and can also hob two different tooth-counts on the the same blank in one setup.

I don't have a "real" hobbing machine, but my milling machine does quite well at the job with some rather simple HAL changes:

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13 Apr 2017 16:04 #91323 by Henk
Hi Andy. Thanks for the tip.

We have a pfauter cnc at work as well and we just completed the conversion to LCNC on that. The old bosch control was long dead. We are very happy with that machine. We used a custom component to do the axis syncronisation on that.

There is a lot of mechanical work to do on this second machine before i can go the full cnc route. In the meantime i need to ise the machine and cannot afford it to be out of action for too long.

Anyway, ill do some tests and let you know.

Thanks
Henk

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