Laser jumping, irregular lines

[Scott Moore2]

I have a Morntech 100 W laser with a 24x36 bed. It's very new. I just purchased it in late May. Recently, in the last couple of weeks, I've had troubles cutting. If I try and do a circle, for example, I get a jiggle at two spots in the circle. Whether it be a square or a circle, I cannot get a complete cut. There's always a gap. And anything with a circular pattern will be irregular.

Does anyone have any idea what this is? What's the cause of this?

I've included a picture here of some circles I cut to show how some are squished, have weird jiggles, and most of them have a small gap where the circle didn't get completed.

242374

[Greg Holt]

First thing I would be looking for is mechanical backlash in the X axis.

Maybe the pulley is not secure on the motor shaft. My first guess.

Perhaps a loose belt. That should be obvious.

Something else less obvious ?

Greolt

[Scott Moore2]

Thanks Greg, yeah, from looking at some other threads here it looks like it might be the X axis stepping motor. But I wanted some input. I did look at the belts and all the connections. Everything looks tight and solid.

When it does the "jiggle" I can sort of hear it skip if I listen closely. But it sounds more like it's intentional, as in I hear the machine's motors slightly change frequency as it does it's little thing.

For any closed vector, a square or rectangle, or octagon etc., sometimes there will be a slight jitter or laser burst in the middle of a straight line. It is always on the Y axis, or height, not the width or X axis. But it appears to be the X axis is the one jittering. It's a strange hickup. The Letter S usually gets a bad hickup too, and a perfect circle is impossible.

[Kees Soeters]

If you're sure that all the mechanical parts are ok, check the electronics: loose or corroded connectors between controller and stepperdrivers, or even from the driver to the stepper. Your powersupply can also be the problem. A lot of "heavier" components can work themself from the PCB's .. A crack in a soldering can give strange errors..

One thing you can do quite easily is pull a connector, clean it with breakcleaner (the one you use for your car's breakes) and put it back.. do that for all connectors. (ofcourse you have to pull the mains-plug first!)

Cracks in soldering can be found by tapping with the backend of a big isolated screwdriver while working

If you take the PCb out, you can visualy search for those cracks. (mind some capacitors can be charged.. discharge those first and check the voltage with a meter..)

Kees

[Glen Monaghan]

Are those "hand drawn" or free form circles, or are they supposed to be true circles as would be created by a graphic program's circle tool? Are they supposed to be identical copies or is each one drawn a bit differently? If they are supposed to be true circles, and especially if they are supposed to be identical, it looks like you have serious, serious problems with your machine because every one of those looks different and none is remotely "true". The edges wander all over the place, some are sort of egg shaped, ever one looks a bit different.

The gap may be due to improper backlash compensation, but that doesn't explain the wavy edges and non-circularity. Does your machine just rely on counting stepper motor steps or does it have encoders on the X and Y axes? If it uses encoders, try cleaning them and their sensors, and make sure the encoder strips/discs and sensors are not loose or wiggling around.

-Glen

[Shawn Handley]

My epilog was doing that. It turned out to be a combo of a dirty x-axis motor spindle (the actual belt driver), a dirty x-axis linear encoder strip, and a dirty x-axis linear encoder reader. My raster looked like a acid trip and my circles never had an end... or had an end.... the start did not equal the stop.

My old epilog had a stripped bearing mount on the x-axis block which caused a wobble very similar to the one in the picture.

Grab it all (all blocks, rails, bearings...) wiggle everything around, see what moves. Post back here.

[Ross Moshinsky]

We had a similar problem and it turned out to be a faulty rail and bearing. It took the bearing to break to determine the problem and to finally resolve the issue.

[Scott Moore2]

Thanks everyone. I'll post the result here when we finally get it figured out. I've asked Morntech to fly somebody out here and they're waiting for parts. This machine is only a 5 months old, and given all the problems we've had (this is not the first), I'm asking them to fix it. The machine only has about 40 hours of actual render time on it, so there's absolutely no excuse.

In terms of quality, I've found the Morntech machine to be absolutely horrible. The workmanship was total garbage - loose screws, hoses coming off, arcing in a half dozen places, super poor customer support and responsiveness. This has turned into a $10,000 nightmare for me. I'm frankly ready to call an attorney. I'll give it another week or so for them to get somebody out here then I'll call the lawyers and my L&I insurance for backup.

[Mark Sipes]

As a lerning point for all of us, "What was the major factor for you deciding to go with this company?"

[Scott Moore2]

I looked at other companies. I would have liked to purchase a Universal or other American made laser, but they were easily four times as expensive. I also looked at companies like Coletech, but I was weary of importing directly from China.

Morntech sold me on the fact that for slightly more money, they import the machines to California, check them, and ship them, thus eliminating quality control issues, as well as the paperwork and hassle of importing. They also sold me on the fact that they have spare parts and expertise in California. Their ebay ratings seemed to be good, so I trusted all would work out fine.

As it turns out, I broke a bulb while fixing their messed up machine (arcing in many places), and it was faster and easier, as well as cheaper to import a bulb from Coletech. Morntech didn't have any bulbs in stock. I also subsequently ordered a 1.5" lens. They have none in stock, and I've been waiting a month. And now trying to get help from them in California is like pulling teeth, requiring many phone calls, threats of legal action etc. So, well, I didn't make a good choice there. I would highly recommend that nobody use them based on my own experience. Why is it that Coletech, for example, can email me and call me from China within hours or minutes, but Morntech will go days without answering me?

Anyway Mark, that was my reason for choosing them. I was so very wrong.

[rich santana]

Hey Scott, I had a similar problem a couple weeks ago. I thought it was terminal, but it ended up I just had a loose lens. Try the brainless things first. You might have a 'Doh' moment.

[Scott Moore2]

I'd like to thank everyone here for all their help. This was all very helpful. In the end I figured it out. But I should still warn people away from Morntech. They're nice folks, and they offered to fly someone out finally (at my expense), but really they were too little too late.

Here's what it was:

There is a bar along the back of the machine that controls the Y axis. There are belts on the right and left side. One of the screws on the bar was lose (a hex screw). I thought the bar was all one piece, but it's screwed together. One of the screws (shown in the picture below) came lose, causing the left and right belts to move at different speeds. The funny thing is I looked everywhere and checked all over, and couldn't find the problem.

By the way, the circles were true circles, not hand drawn. Yes, it really did get that bad. After weeks of agonizing, it was literally three turns of a hex nut and it was fixed!

http://myart.bellevuefineart.com/morntech/morntechlaser-9908.jpg

http://myart.bellevuefineart.com/morntech/2012-10-03%2016.58.46.jpg

Thanks again everyone. I hope this resolution helps somebody someday!

Scott Moore

[Rich Harman]

That is a torque tube. Actually I think it is more of a rod since it is solid. Since it was loose I can almost guarantee that the X axis is not perpendicular to the Y axis now - unless you aligned it before tightening.

[Walt Langhans]

Why is it that Coletech, for example, can email me and call me from China within hours or minutes, but Morntech will go days without answering me?

Excellent question. All I can say is that I've been looking into buying a machine, and the customer service and responce time that I have gotten from G Weike Laser, and Shenhui has been truly outstanding. I too have been wary of importing from China but they have pretty much won me over.

[Scott Moore2]

Thanks Rich. It appears to be working flawlessly, although I could be wrong. I'm admittedly an amateur at this.

[Rich Harman]

If it is out of alignment you probably won't notice until you make parts that need to fit together well, or cut something that needs to have precise right angles.

Easy way to check - engrave or cut a large square. The bigger the better. Measure the diagonals. If they are equal then the axis' are perpendicular.

Another way - using a large piece of scrap engrave a long line vertically, then engrave a long line horizontally that intersects the first line. You can do this using just the manual controls. Use a carpenter's square to check that they meet at a right angle.