Just a post about the mainenance @KevMacD and I did last night, March 30 2016.
As you guys may have noticed, the filters really needed changing. Smoke and smells were becoming very apparent in the space during cutting. This was really bad on Tuesday after running some acrylic through the cutter.
We changed out 6 of the smaller 20x25x1 filters and replaced them with new ones. We also took the larger 20x25x4 filters and vacuumed them and shook them out. It wasn’t the best way to clean them but we didn’t have replacements. I think it might be a good idea to look for a more sustainable filtration system in the coming months. We may be able to get reusable filters instead of one-use ones - this would reduce the long-term cost of filtration and, more importantly, cut back on the amount of foresight we need to put into cutter maintenance.
We have put pressure monitors on the laser cutter filter system to measure how clogged they get. Here is a picture of the graph before and after the cleaning:
The bottom graph is a pressure differential across the filter. A differential of zero means essentially no air flow impedance. We can see that before it was clogged, the differential was about 7.5mBar. After we cleaned it, this differential went down to 2mBar. Qualitatively, the cutter was clearing the bed much quicker and we didn’t notice any smoke or smells permeating into the space.
It would be interesting to see if there’s a particular substance that’s causing the filtration problems. Maybe we could get people to voluntarily log their material, where they got it, when they cut it, and how long the cut took?
Presumably we’ll know how long and at what power, thanks to the laser power monitor. We should monitor that for a while and see what the data looks like. My assumption is that the filtration pressure will increase too slowly to be able to match it to any particular cut. Things like ambient temperature and humidity might have more of an effect than any particular job.
I had heard a report of a faulty stepper motor on the laser cutter and came down to check it out last night, (April 4 2016). I had it do some big circles and some engraves but found no issue. It might be an intermittent problem though. If anyone sees anything weird, let me know.
I also replaced the collimating lens in the head of the cutter. It was pretty damaged and dirty. I’ve left it on the top of the cutter if anyone wants to take a look.
I did a test cut, am able to just cut through 6mm ply at speed 20 power 60, which is a little better than before (sp15, pwr60)
The filters were last updated two weeks ago. We’re monitoring the air pressure differential across the filters to better understand when they need to be changed next.
The optics (mirrors and lens) were replaced and aligned last week.
We measured the laser output power with a Mahoney Laser Power Meter borrowed from Science World, and got a reading of slightly over 79 watts (out of a theoretical 80 watts) so we feel that’s pretty good. It cuts like a dream too!
The malware was removed from the laser PC. It should be safe to use USB sticks again.
Upcoming:
There were some vague reports about a problem with one of the laser cutter axes. I’m hoping to get some more specific details so we can try to reproduce it and fix it. @Logan_Buchy , @kevmacd, and I did notice a very small issue with the Y-axis motor/driver last week when we changed the mirrors. The symptom was a very small discontinuity in some curves when they are cut. Like a small vertical jump up at about “2 oclock” when cutting a circle. We’re unsure whether it was the artwork file, LaserCAD, the stepper motor, controller, or some other mechanical slipping. If anyone else has noticed anything like this, please provide some details or photos.
We own a new laser tube but are in no rush to install it as long as our existing tube is cutting so well. Simply replacing the mirrors and lens made a huge improvement on performance.
@newton.jason made an improved water chiller to install sometime in the next month, which will let us keep the laser tube at its optimal temperature.
Various pie-in-the-sky dreams of replacing the whole controller, or reverse-engineering its UDP-based protocol in order to ditch LaserCAD for bettersoftware.
If you want to stay in the loop, join us in #laser on Slack.
Laser maintenance scheduled for Tuesday, April 19th.
@lukecyca@newton.jason and I will be installing a new chiller which should keep us running smoothly as the weather warms up. We will also try to look into the axis issues that we have heard reports about. If you have had an issue where the cutter positions itself incorrectly, please save the cutter file that causes it and let one of us know where to get the file - it would be helpful for diagnosis.
This was the result of me trying to etch with a Y swing, I noticed when I started working that the Y axis was stopping quite loudly when manually moving the arm out of the way with the y+ button, it wasn’t affecting my work since I was etching with an x swing, but when I tried to go the other way to clean up the work it made a horrible noise every time the Y motor changed directions and kept slipping out of position. My settings were speed 300 power 20, so it was going pretty fast. I also had a less drastic occurrence when I tried to “cut” at the same speed for an outline of my work, as it finished the sides of my rectangles it was losing registration.
I believe this is an issue with something simply being loose, whether it’s the stepper motor being old and stripped internally or a belt not being able to deal with the torque, I’m not sure.
I know this sounds like an edge case, but if there is any chance of an axis being missaligned mid cut, it makes the projects I’ve been waiting to cut a non starter. Long work times * minor slips != precision work.
Hi Laser people, I used the laser cutter yesterday to cut some acrylic. It worked beautifully, BUT, at the start of the second cut, the header went to the bottom left of the bed and made a bunch of loud clicking noises before starting to cut. Then, the cut started to go a few inches outside of the “run box” area that I had checked 3 times prior to starting the cut. I had to hit stop and start the cut again centered in the middle of the bed to ensure it didn’t go off the edge again. Long story short, is that at the end of the day, the cut finished perfectly, but I’m hoping that someone can check the laser cutting machine to make sure the calibration of where the header is versus the bed is still correct. It was almost as if the belt was skipping or something, but my cut was at a slow speed setting, so I don’t think this should have happened (I believe the speed was set at 12, power was set at 25 for this cut). If you have any questions, or my descriptions need clarification please let me know. Peace.