Why are my laser cuts not lining up?

[Eric Allen]

Any idea which item you did that fixed the issue? Did you notice any of the pulleys loose? I have a kind of "surging" effect in the Y axis with mine. It has yet to manifest as a cut issue, but it does seem to draw a great deal of power in the three surge points as my office light dims a little when it hits those, might be kicking in the boost mode on the UPS unit to overcome the extra power required. I believe it also slows down a tad, so it's probably having the effect of giving more laser power in the slight "pause" as it overcomes whatever is causing it. I've been slowly trying to narrow it down to the item that causes it to require more power to overcome those points. The front bar that stabilizes the Y axis has been bent from day 1 of purchase, and I suspect it is timed with that, but haven't gotten to the stage where I have time to tear it down and verify. The issue hasn't manifested as a serious enough problem to require me to shut down, but once all my work is caught up I'd like to make sure it never does. The "surge" or drag points seem to be evenly spaced, so that narrows the field a little at least ...

[Richard Rumancik]

Eric, if the stalling of the laser carriage is such that it dims the lights I'd say you have a serious problem. But I would never have thought that a minor stall effect would feed back through the power supply to UPS and then to the mains (reflected in the flickering lights.) The motors (whether stepper or servo) are controlled by pretty sophisticated drivers that control voltage and current under all conditions. It's not like a lone AC motor tied directly to the mains.

Are you positive that the UPS is operating properly and can handle the maximum draw of the laser? There are some rules for selecting a suitable UPS based on watts and VA (volt-amperes) of the laser; generally you have to have some good margin. I'd make sure the UPS itself isn't being overloaded. You can research this if there is any doubt. You might need to get some advice from Epilog.

Does your laser allow you to manually move the carriage and gantry around? If so, do you feel the binding points? I think I'd try to get this resolved before it affects something else.

[Eric Allen]

The UPS is substantially overspec'd, I researched it heavily back when I was shopping. The hell of getting older, I remember very little of that research It doesn't register a load with just the computer, with laser and computer at max power it runs about 50% loaded. It's a nice sine wave setup, fairly certain all is good in that department. In spite of the lights reflecting the draw, it hasn't been enough to kick in the boost function, at least while I was watching. There are 3 consistent locations of obvious loading when moving the carriage by hand, several suspects come to mind.
My current lead suspect is wiring. I was running a similar cutting operation during the day yesterday and didn't notice the surging effect, if it was pure mechanical loading it should be more consistent with the obvious mechanical loading points day or night. You wouldn't think my LED shop light would be enough, but maybe it's that little nudge over the "line" Tearing down the laser is easier than running a new line (major trusses to support the roof tiles and cathedral type ceiling for 15' to snake through), but I'm betting a new 12 guage line is probably the solution. Naturally, it's the longest run in the house, but at least no conduit requirement here

Eric, if the stalling of the laser carriage is such that it dims the lights I'd say you have a serious problem. But I would never have thought that a minor stall effect would feed back through the power supply to UPS and then to the mains (reflected in the flickering lights.) The motors (whether stepper or servo) are controlled by pretty sophisticated drivers that control voltage and current under all conditions. It's not like a lone AC motor tied directly to the mains.

Are you positive that the UPS is operating properly and can handle the maximum draw of the laser? There are some rules for selecting a suitable UPS based on watts and VA (volt-amperes) of the laser; generally you have to have some good margin. I'd make sure the UPS itself isn't being overloaded. You can research this if there is any doubt. You might need to get some advice from Epilog.

Does your laser allow you to manually move the carriage and gantry around? If so, do you feel the binding points? I think I'd try to get this resolved before it affects something else.

[Richard Rumancik]

How old are the batteries? If the batteries in the UPS are still good I would have thought that they would prevent load changes from getting reflected back. Maybe you should do a test of the UPS with a different load. I would not suggest you do it with the laser; you could find another load that is 75% of rated and plug it into the UPS (instead of the laser/computer). Then turn the load on and off and see what happens. If you had a bad battery the smoothing effect of the UPS would be lost.

Also, you could unplug the UPS from the source and see if it is actually working as a UPS. That would give you an idea of battery condition.