EZ-Trak losing Y axis Zero

[melamark]

Hello Fella's,

My EZ-Trak has developed an annoying problem of losing Y axis zero. I have determined that this is only happening during rapids. It has never lost position when running at machining speeds. I suspect the encoder is the culprit, but really can't afford any downtime right now due to a crushing schedule, of course.

So, until a service tech to thoroughly solve the problem, is there a way to globablly slow down the rapid speed. If I can do that, it will temporarily solve my problem. I can live with slower rapids if I don't have to rezero all the time.

If I put a feedrate with a rapid command, will the Ez-trak obey? Or will it use some default rapid? Where does it get the default rapid speed if none is specified?

Sorry for the long list of ?s.
Thanks!
Mark

[HuFlungDung]

You could eliminate the G00 and use G01 F100 (or whatever max feed you feel is safe) in place of the G00.

This should be possible within the post settings of your cadcam software, but maybe not so easy if using conversational.

[NC Cams]

I you know how to use the built in PFM, you can reset the jog default speed in the paramters table.

Otherwise, you'll have to plug in your speed factor in G code or else adjust the speed down on the screen via the feed override keys.

EDIT:

HAVE YOU CHANGED THE HDD LATELY??? If you did and put in one bigger than 540K, the machine can lose zero because it is putting position info outside the 540K window that the software is only capable of recognizing.

Solution: back up your files, FDISK to 540K for primary partition and then reload the whole O/S and Eztrak software into primary partition. You can use the other partitions for anything BUT the Extrak O/S's use.

Make sure the BIOS is NOT using LBA and make sure the cache is being written to disk before exiting, too. These will also cause origin losses to one or both azis zero points
END EDIT.

[machintek]

Since this happens in rapid (max accel/decel): A loose belt; a loose pulley, a loose coupling to the encoder at the end of the motor. Teeth worn off the belt. Loose connection ( encoder plug, AXSBOB, BMDC).
Take a few minutes and take a quick look.
How much does it change?

George

[melamark]

Thanks for all the input above. After swapping servo cards and seeing the abnormal behavior remain on the Y axis, I eliminated the boards as the source.
Next I swapped the motors on the X & Y axes and the problem DID switch to the X Axis, meaning the cabling was good and the problem was inside the motor somewhere.

I took the encoder cover off the offending motor and found it had a lot of shavings in it - not from machining, but from the encoder hub. I appears the encoder hub was not properly assembled when I sent the motor out for rebuild 2 years ago. The hub was not pressed on the shaft all the way down and the set screw was not in contact with the flats on the shaft - it was scraping on the end of the shaft and created all the shavings. As Machintek noted, this was why I only saw the problems during the rapids with heavy accel/decel.
So anyway, I cleaned things up, properly mounted the encoder hub, and the machine is flying away at full speed. Problem solved, no cost involved (well labor and downtime...) but at least I have restored confidence in the machine.

Thanks Again!
Mark