Variation in Calibration (X & Y)

[gregg]

We do a lot of molds using tabs and slots - but we've recently noticed that the further from 0,0 we get - in both the X and Y axis, the more variation we're getting in the width and length of a slot/tab. It seems to be a linear relationship, getting worse the further from home we get - being off by as much as .040" over the full 96".

How do we correct this?

We have been using our Shopbots for over 15 years, and have been letting it slide, because it didn't matter that much - but now we have projects that we need it to hold tolerance anywhere on the table.
Thanks for any help you can offer.

[Brady Watson]

What model machine are you running & What are your Unit Values (type in VU in SB3) ?

I need to know if you have a PR, PRT or PRS and if it is an Alpha (violet on motor label) with AS911 motors or ASM98 motors or Standard (red/black motor label) with ATX computer tower control box - tan in color (3G), black (4G) - If it has been upgraded to 4G or not (if answer = tan) - or if the control box is aluminum (RBK).

Lot's has transpired in the past 15 years...

When was the last time you greased the gear racks and installed fresh pinion gears? This alone can cause that deviation since the pinions shrink in diameter as they wear.

-B

[gregg]

What model machine are you running & What are your Unit Values (type in VU in SB3) ?

I need to know if you have a PR, PRT or PRS and if it is an Alpha (violet on motor label) with AS911 motors or ASM98 motors or Standard (red/black motor label) with ATX computer tower control box - tan in color (3G), black (4G) - If it has been upgraded to 4G or not (if answer = tan) - or if the control box is aluminum (RBK).

Lot's has transpired in the past 15 years...

When was the last time you greased the gear racks and installed fresh pinion gears? This alone can cause that deviation since the pinions shrink in diameter as they wear.-B

We are running PRT Standard, with A6497-9412KTG motors.
Installing fresh pinion gears may be the ticket - I don't know how long ago we may have done that - but it sounds like a good place to start.
Please let me know how!
Thanks.

[gregg]

We are running PRT Standard, with A6497-9412KTG motors.
Installing fresh pinion gears may be the ticket - I don't know how long ago we may have done that - but it sounds like a good place to start.
Please let me know how!
Thanks.

To clarify, I don't need to know how to "install" them, but to "order" them.
Thanks!

[Brady Watson]

Call ShopBot to order them. They'll need to know how many teeth (probably 25 for XY and 20 for Z) and the width of the rack - 3/8" 'Boston' or 1/2" 'Browning' - measure the width of the gear rack & check that X, Y and Z are all the same. Some years retained 3/8" Boston on one or more axis.

-B