Engraving Acrylic problems...

[Steve Krahn]

Hello!

I have been having problems with producing acrylic engravings lately. My problem has been getting worse in the last while. My machine is a Rabbit QX-1290 with a 100W tube. When I first got it, I only needed 13% power to engrave on Rowmark plastics. However, at this point I need about 18% of my power in order to produce something that is good enough. Good enough is not the quality that I like though. Everything else I engrave seems to work at the same amount of power that I began with. So only my acrylic engraving seems to be suffering from this.

The first thing I tried was to re-align the machine. I got it to within perfect alignment as far as I know. This is what I got at the table. The one at the end of my thumb is my final alignment test.
399507

These are some of the samples that I engraved so you know what it looks like at regular power.
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If anyone has any ideas as to why this is happening, I would appreciate some wisdom in getting this fixed!

[Bill George]

Try cleaning your mirrors, I have used DNA but there could be better stuff to use. Then go to the carriage and lens clean all that the mirror and lens, make sure that you keep track of which side of the lens is up. You might find the lens loose in the holder and that's the issue.

[Steve Krahn]

I forgot to mention that I have also cleaned all the mirrors and lenses quite a few times through this whole ordeal as well. Before, after, and during. I will check again to make sure the lense is solid.

[Bill George]

I forgot to mention that I have also cleaned all the mirrors and lenses quite a few times through this whole ordeal as well. Before, after, and during. I will check again to make sure the lense is solid.

Well it either has to be in your optics or the tube and I am assuming you checked the lens at the end of the tube, unless someone else has a better idea.

[Scott Marquez]

Steve,
Help me understand the attached picture with tape and your alignment test.
All of the burn holes seem to have a burned circle around them, is that the case?
Thanks, Scott

[Clark Pace]

What about general cutting. Issues there?

[Steve Krahn]

Scott, the 'donut' is an out of focus shot in order to make sure it is centered in focus. The larger marks are about 1" out of focus.

Clark, I also forgot to mention that cutting acrylic is also suffering.

[Jerome Stanek]

After running the laser for a while does the head heat up. the beam could be bouncing off the side.

[Bill George]

Scott, the 'donut' is an out of focus shot in order to make sure it is centered in focus. The larger marks are about 1" out of focus.

Clark, I also forgot to mention that cutting acrylic is also suffering. Are you using the alignment procedure off Ray Scotts website? I don't understand "out of focus" and I have done a lot of mirror alignments.

From RabbitLaserUSA by Ray Scott, Owner

[Steve Krahn]

Are you using the alignment procedure off Ray Scotts website? I don't understand "out of focus" and I have done a lot of mirror alignments.

From RabbitLaserUSA by Ray Scott, Owner

Yes Bill, the method I used comes from this site (http://www.rabbitlaserusa.com/Manuals/BeamAlignment.html). Step 42 is the part that explains the "out of focus" idea.

I am not at my machine right now, so I will have to do some more checking into it when I get back to it. I had actually not thought to check the lens at the end of the tube itself.

[Bill George]

Yes Bill, the method I used comes from this site (http://www.rabbitlaserusa.com/Manuals/BeamAlignment.html). Step 42 is the part that explains the "out of focus" idea.

I am not at my machine right now, so I will have to do some more checking into it when I get back to it. I had actually not thought to check the lens at the end of the tube itself.

All your mirror targets you posted had hollow circles Scott. I just stick masking tape on each mirror in turn. centered and on to the next. Black dot on each, not a perfect dot but not hollow. Same on the last one only as suggested it must be centered in the tube and a small dot a result out of the lens. BTW my link was removed, but not by me!

[Kev Williams]

RECI states this about their glass lasers: "When the working current is 4mA and the tube is in the state of preionization, the laser can be used for high-frequency impulse engraving." ---

Now, what I see in your yellow plastic pic, is the laser is firing halfway decent thru 'long sections', places where the tube has time to fire fairly continuously, and is barely firing at all in the short sections, such as the narrow vertical and nearly vertical lines in the letters. This is happening at your lower power settings. But the wood piece is engraved nicely, and I'm sure was engraved at higher power settings...

What this says to me is that maybe this isn't a simple dirty mirror or lens problem... the lower power results seem to indicate that for whatever reason, your tube is now requiring more initial energy to enter and/or keep the tube in preionization state... This could be indicative of the tube beginning to fail, or it could be you have an iffy electrical connection at the tube... ?

[Steve Krahn]

RECI states this about their glass lasers: "When the working current is 4mA and the tube is in the state of preionization, the laser can be used for high-frequency impulse engraving." ---

Now, what I see in your yellow plastic pic, is the laser is firing halfway decent thru 'long sections', places where the tube has time to fire fairly continuously, and is barely firing at all in the short sections, such as the narrow vertical and nearly vertical lines in the letters. This is happening at your lower power settings. But the wood piece is engraved nicely, and I'm sure was engraved at higher power settings...

What this says to me is that maybe this isn't a simple dirty mirror or lens problem... the lower power results seem to indicate that for whatever reason, your tube is now requiring more initial energy to enter and/or keep the tube in preionization state... This could be indicative of the tube beginning to fail, or it could be you have an iffy electrical connection at the tube... ?


Your last paragraph seems to be spot on as far as what my problem is. When using higher power on the acrylic, it appears to almost accelerate the power and instead of sharp edges, I get an angle up from the engraved area. But only in the direction the laser is traveling. So it seems as though it is taking time to power up and down again. I will have to look into finding out how to troubleshoot that.