Full Version: Uh oh, laser overheat trouble

From: Nick (KOZASNJZ) [#1]
 6 Jun 2005
To: ALL

Well this is a first for me and even for the Gravograph tech I spoke with. While working on a genuine walnut plaque where I was attempting to inlay some 2" coins into the wood (not fully, just set them maybe 1/16" - 1/8" deep) I got an error message from the machine stating that the laser was "over-temp." Of course this happens the hour before my customer needs it and as of 45 minutes later, I'm still not operational. I've got the top cover and front panel completely open along with the back panel where the laser tube is and a fan on full blast to try to cool this little lady down. The tech suggested that I check the DB9 connection between the laser source and the RF amp but everything there seems to check out. Any other suggestions, I anticipate this will be a waiting game but if there are any tricks, please fill me in.

From: Nick (KOZASNJZ) [#2]
 6 Jun 2005
To: Nick (KOZASNJZ) [#1] 6 Jun 2005

By the way, I'm operating with a New Hermes LS 800

From: laserman (MIKEMAC) [#3]
 6 Jun 2005
To: Nick (KOZASNJZ) [#2] 6 Jun 2005

Nick,

What power is the laser?

I know that it is a synrad laser tube and they have a thermal switch that trips once the laser tube has hit a certain temp.

I am a little surprised that it has tripped doing a job like you are describing.

I know on the older laser tubes we had a method of by passing these switches you may want to inquire about this possibility.

From: Nick (KOZASNJZ) [#4]
 6 Jun 2005
To: laserman (MIKEMAC) [#3] 6 Jun 2005

It's an 80 watt laser, I was very suprised to get that message when I've worked the machine much harder in the past (in my opinion, though it was not doing a solid area of engraving as in this case). After about an hour or so with the back panel off and a box fan blowing at high speed, I looked around and jiggled some wires, checked some connections and did an overall inspection then decided to plug it back in and fire it up and SHAZAM! She's back in business. There was a little push button module which was very near the tube that I pushed but I cannot say 100% that pressing it is what did the job. I guess we'll find out next time >.< ::knock on wood::

EDITED: 6 Jun 2005 by KOZASNJZ

From: Harvey only (HARVEY-ONLY) [#5]
 6 Jun 2005
To: Nick (KOZASNJZ) [#4] 7 Jun 2005

Sounds like a thermal overload breaker. If it made a slight click or you felt a slight click, that was the reset.

Most thermal switches are buckle switches that trip at a certain temp. Some will automatically reset when the temp goes down significantly, some require a manual reset. The ones with a button are manual reset.

The idea of the manual reset is that something went wrong if it tripped, so it requires a tech to check out the unit and then reset the breaker.

Besides a failure of the system, possibilities are inadequate cooling, (not enough air moving or input air too high a temp), or a defective switch.

EDITED: 6 Jun 2005 by HARVEY-ONLY

From: Rodney Gold (RODNEY_GOLD) [#6]
 6 Jun 2005
To: Nick (KOZASNJZ) [#4] 7 Jun 2005

Hiya
We often have or had thermal overloads with both Synrad and Coherents. I have never seen a reset switch on either , but Im not at all familiar with your machine. Mostly the sources we have used required some time to cool down and then reset themselves.
An 80w laser is pretty much on the edge of air cooled capacity . you will find that as you get to the 100 w mark , sources tend to be water cooled so environemntal conditions like a hot day with high humidity can cause this.
One of the reasons the sources overheat is that the heatsink fins on the source get clogged up with dust , a paintbrush and a can of air (stuff photographers use) can be used to clean these as well as cleaning the fan blades and air holes etc. Leaving the cover open is a bad strategy , at least with our machines it is , as the whole enclosure is designed to flow air the best way over the source and closing it and using the supplied fans works better. We have fitted extra fans to our lasers as well as beefing up the power supply to the lasers and no longer have overheating problems , we also use an aircon in our laser room.
Sudden and unexpected thermal overloads on our machines have often been a precursor to RF board failure or source failure. I would check that the machine isnt down on power. We use a 3mm piece of acrylic to check ours periodically, we know it will cut at x power and z speed , if we have to reduce the speed or up power - we know we have a problem and depending on how much we have to up the effective power , whether its alignment or the source itself.

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