Epilog Mini24 at 75dpi

[Matt Davis]

Hi all,

While troubleshooting another problem yesterday, I did some engraving at 75dpi. I discovered that when the Y axis advanced between rows of dots, it would do so with a lurch, and an audible thump to go with it. I could actually see the entire I-beam shudder when it would do so. When examining the completed engraving under magnification, I could see the ends of many of the rows had gone off course, even to the point of overlapping the rows above and below them. I'm assuming this is because of the sudden jolt and vibration. Granted, I don't notice this at higher resolutions, probably because the movement is so slight. But, I'm concerned the problem may still be there, just at a lesser level and possibly degrading overall engraving quality.

I pulled the sides off the machine and went through checking the various belts and pulleys, cleaned everything, but to no avail. It still thumps and shudders at 75dpi. The carriage all moves freely and easily by hand when the machine is off, so I'm kind of baffled. I guess what I'm down to is a possible defective Y-axis motor. I'll probably be calling epilog tomorrow morning to confirm this. But, in the meantime, I'm curious if anyone else with the same machine has noticed anything similar when engraving at 75dpi

Thanks!

[Richard Rumancik]

Perhaps something is wrong, but I suspect that it is just that the velocity profile of the y axis motor was not really optimized for use at 75dpi. The step is .013" approximately at 75 dpi. Most engraving is done at higher dpi, which means that the step is smaller (.0066" at 150 and .0033" at 300 dpi). So the motor won't be able to accelerate as much over a shorter distance and hence there would not be such a jerk on the gantry.

What are you engraving at 75dpi? Or is it for testing only? If there was a production need for it, Epilog could have probably tweaked the firmware to make a more gentle step at 75dpi but in all likelyhood there isn't that much engraving happening at 75dpi. If you have a requirement, you could ask Epilog to consider the issue in a driver update. The problem probably isn't really present at higher resolutions.

[Dan Hintz]

Perhaps something is wrong, but I suspect that it is just that the velocity profile of the y axis motor was not really optimized for use at 75dpi.

This is my first-look assessment, as well.

[Matt Davis]

Thanks for the replies. I was using 75dpi solely for testing purposes to check the laser match setting in the calibration menu. I've been troubleshooting some engraving quality issues (fuzzy edges) and am now reasonably confident it's the tube finally giving up the ghost after an 8 year run. While vector cutting still works ok, it's been having issues rastering fine vertical lines for a while now. I've been able to nurse maid it along by reducing the rastering speed, but now I'm seeing a pretty serious degradation in quality even at these settings. I'll be making the call to Epilog in the morning.

[Matt Davis]

I thought I should close this by letting anyone interested know what I found out. Epilog did confirm that 75dpi is used almost exclusively for testing purposes and that "strange things happen at that resolution", so no worries about my Y-axis.

Now...here's something else I learned that anyone else who owns an older mini might want to keep in mind for future reference. When I started troubleshooting my engraving quality issues, I began with replacing my lens....no dice. I finally gave in, accepted reality, and replaced the tube a couple of days ago. The new tube allowed me to engrave fine vertical lines again, but the edge quality on text was still somewhat poor. Tech support felt the issue was with vibration and had me go through and re-tension my X-axis belt and a few other items. When I pulled the lens/mirror holder assembly off to examine something else, I noticed that something was rattling inside the holder. It seemed a little odd as I had just replaced the lens a few days earlier, and was certain I had reassembled everything correctly. I disassembled, and reassembled it again, but still "rattle rattle". Tech support told me that most likely the O-ring that hold the lens securely in place had deteriorated and wasn't doing its job anymore. The O-ring looked fine to me, but fair enough I'll get a new one. Later last night, I was looking things over again, and pulled the original lens back out and compared it to the new one. The old lens was significantly THICKER than the new one Epilog had just sent me! Now everything made sense. I dug through my parts bins and actually managed to find a new o-ring of the right diameter, but thicker than the original. I installed it with the new lens, the rattle went away...and the machine engraves beautifully now!

So, moral of the story. If you have an older Mini, and you replace the lens, make sure to compare the thickness of the new lens to the old. You might need to replace the O-ring with a thicker one. Otherwise, all sorts of havoc may ensue.

Thanks for reading!

[Mike Lassiter]

Details are everything. Frustrating to go thru stuff like this, but you generally only have to once. You will know next time. Experience is a good teacher if we remember the lessons later. One thing that is of value to all is that experience doesn't have to be our own. People sharing theirs here with others is a beautiful thing. Can you imagine having to make every mistake yourself, and nobody to offer help. Here help has been given in minutes. People come here all hours of the day an night.

Sharing here may just save someone a lot of grief when they can least afford it.

Oh, and Matt that was good detective work, and again it was a very small detail with big consequences.

[Keith Upton]

Thanks for closing out this thread. I just bought a Mini 24, so reading things about these lasers specifically is always nice... even nicer when the solution to the problem is posted as well.

[John Bronleewe]

Thanks for closing out this thread. I just bought a Mini 24, so reading things about these lasers specifically is always nice... even nicer when the solution to the problem is posted as well.
Agreed. I've been lurking here from time to time for a few years now. Just ordered a Mini 24 - 60w today and I'm looking forward to its delivery and some good times ahead. Thanks to all here for your help and sharing information. I plan on doing the same once I'm up and running.