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John Simonson
08-09-2014, 9:19 PM
I have a 50w Chinese engraver running RDworks software. I am having a problem with rotary engraving and I was wondering if anyone might know what the problem could be?

In the picture below you can see in the "s" when it starts engraving it burns a line to begin and then it continues to engrave perfectly. Does anyone know how I can stop it from burning a line?

294590

Thank you in advance for all of your help!

Glen Monaghan
08-09-2014, 10:01 PM
Given the orientation shown in the picture, I am assuming it's engraving with scans going in the vertical direction, starting at the right and working to the left). It appears to me that the substrate isn't turning for the first few lines, so those lines are burning on top of each other. After that happens a few times, the substrate starts rotating with each scan and engraves properly.

You didn't say what type of rotary device you are using, but check for slippage (between substrate and rotary device), binding (of the rotary), obstructions, etc. as the job starts up.

John Simonson
08-09-2014, 10:19 PM
You are correct in the scan direction and working from right to left.

This may sound dumb but I do not know what type of rotary I have. Hopefully the picture helps identify what type it is.
294594

I watched the engraver multiple times while it started and it doesn't move for the first few second. I thought it was getting hung up but that doesn't seem to be the issue. Any setting or any other ideas you think it may be?

Mike Null
08-10-2014, 7:53 AM
I do not have a rotary device but I would check what Glen is talking about plus your art file. It is possible that your art file is flawed or that your input with respect to diameter is inaccurate.

I would check a couple of other drawings to see if the lag happens on all of them.

Dan Hintz
08-10-2014, 8:19 AM
I watched the engraver multiple times while it started and it doesn't move for the first few second. I thought it was getting hung up but that doesn't seem to be the issue. Any setting or any other ideas you think it may be?

Check for backlash. While the system is powered, can you jog the rollers back and forth any amount by hand? If so, the motors is trying to turn the rollers, but the backlash hasn't been taken up yet. When the piece starts turning, that's when the backlash has been taken up.

Doug Griffith
08-10-2014, 8:55 AM
If you can't fix the slippage/backlash problem, you may be able to cheat it. Put a piece of aluminum tape 1/4" before the first letter. Then add a vertical line to the digital file 3/8" before the first letter. The burning while not rotating will happen on top of the tape that can be removed after the job. It's a cheat but sometimes you need to get a job done.

Dan Hintz
08-10-2014, 1:50 PM
If you can't fix the slippage/backlash problem, you may be able to cheat it. Put a piece of aluminum tape 1/4" before the first letter. Then add a vertical line to the digital file 3/8" before the first letter. The burning while not rotating will happen on top of the tape that can be removed after the job. It's a cheat but sometimes you need to get a job done.

The problem with that is the first letter will have a cut-off section. The best way to deal with backlash is to pre-load the rollers. Roll them in the direction they will normally roll during processing until the slop is taken up.

Doug Griffith
08-10-2014, 1:55 PM
Actually, the cutting off will be shifted forward to the line that engraves on top of the tape. It's like adding a throw away first letter. The real first letter becomes the second letter.

Mike Audleman
08-10-2014, 2:20 PM
I think I have the same ebay laser machine. The roller attachment looks the same.

When I first started trying out glass (right after getting the machine, a mistake, but I digress) I was having a similar issue. I attributed it to slippage. I had a bag of fat rubber bands that I used for holding stuff while glue set. I wrapped two around the glass to give it some friction and the problem (mine anyway) was solved. Glass and other smooth objects may have issues with those knurled rods. The rubber bands give the object some stickiness for the rods to grab on to and the results (ones that didn't crack anyway) were substantially better looking.

Looking closely it appears the etching is much deeper in a line indicating the laser is hitting it many times. Try a couple rubber bands around the object to prevent slipping. If thats not the issue, didn't cost ya anything to try :)

Also, make sure you move the head to the top left of the bed. Then move it down an inch or so. Hit origin to set the origin. Unhook the gantry and hook up the rotary attachment. Move the gantry into position over the object's center using your hand. By moving the gantry an inch or so from the top before unhooking it, the machine "thinks" it has that room at the top and won't complain about overscan room. It doesn't know if the gantry is hooked up or if the rotary attachment is, but you do.

Chuck Stone
08-10-2014, 4:46 PM
Also might want to check any of the rollers and see if a set screw has loosened.
That would cause some backlash. Might as well check the set screws on the gears
too.. anywhere you can get some play.

Dan Hintz
08-10-2014, 8:11 PM
Actually, the cutting off will be shifted forward to the line that engraves on top of the tape. It's like adding a throw away first letter. The real first letter becomes the second letter.

Ah, gotcha now... add a virtual/fake letter to the engraving, so to speak?