98: Breaking the Interlock

One of the projects I’ve been working on this week involves some pieces of wood that are far bigger than my laser bed allows. While I’m not finished with the project yet, I thought I’d take a moment to talk about the front door on my VLS 4.60 laser and a fairly simple trick to defeat their magnetic interlocks in cases where you have to engrave something too long for the laser bed.  First, here’s some quick information about the project.

Here are some screenshots of the original box.
Here are some screenshots of the original box.

Those big long wooden pieces are for a custom frame design (by If These Walls Could Talk; check ’em out!)  meant to fit a picture of the Leg Lamp from A Christmas Story. The test piece given allowed me to perform a handful of engraving tests to determine how best to replicate the fragile (it must be Italian!) label on the Leg Lamp’s box.

Several engraving tests have convinced me that I need some spray paint.
Several engraving tests have convinced me that I need some spray paint.

One immediate issue was that the surface of the wooden frame pieces was darker than the inner wood, so even engraving at a high power and low speed to char the wood resulted in text that wasn’t appreciably darker than the wood, while the source material was black spray paint on lighter wood.

Color fill seeped under the masking paper too easily, so spray paint is my next test.
Color fill seeped under the masking paper too easily, so spray paint is my next test.

I then tried some paint fill, but the strong texture of the wood meant that my transfer paper wouldn’t prevent the color fill paint from seeping. My next step will be to try a light spray paint over another paper masked engraving; it should more closely approximate the look featured in the film.

The three edges of the frame I am to engrave. One is a tight squeeze, and two more won't fit at all without leaving the front door open.
The three edges of the frame I am to engrave. One is a tight squeeze, and two more won’t fit at all without leaving the front door open.

But the biggest trick here was figuring out how to fit those larger pieces of wood into the laser. When we were first looking into buying the laser, another laser owner mentioned how the front door interlocks could be defeated to allow people to engrave larger items—like boat oars—if necessary. I never heard from him how to do so and the manual doesn’t mention it at all. Doing this is considered a potential safety hazard, too, for quite a few reasons. The manual explains the following:

DO NOT OPERATE THE LASER SYSTEM IF ANY SAFETY FEATURES HAVE BEEN MODIFIED, DISABLED OR REMOVED. This may lead to accidental exposure to invisible CO2 laser radiation which may cause severe eye damage and/or severe burns to your skin.

The left interlock magnet, tricked by a badge magnet.
The left interlock magnet, tricked by a badge magnet.

With that in mind, defeating the magnet interlock is something you do at your own risk. Do your best not to look at the laser or stick any body parts in there. Also recognize that the exhaust system will be compromised to a certain degree as it’s no longer a closed system.

The right interlock magnet and some of the wood sticking out of the front door.
The right interlock magnet and some of the wood sticking out of the front door.

The front door is held by one magnet on each side, and there is a sensor behind each magnet that detects whether the matching magnet built into the door is present. While some of my weaker magnets weren’t able to trick the sensors, a pair of stronger badge magnets, positioned just right, were able to convince the machine that the front door was closed. My counterfeit badge magnets were attracted to certain parts of the laser body’s magnets, and when I let them slide into where they wanted to go, the sensor could no longer pick them up, so I had to arrange them sticking out (as shown in the pictures) in a very specific position. With this in mind, be very careful when processing your long materials, as nudging the magnet just a tiny bit can cause the laser to realize the door is open and stop the job immediately. For all the trouble that might cause, I’m certainly glad it’s designed to shut jobs down if the doors are opened mid-process.

I hope to write a follow-up post about this project once the frame is built around the Leg Lamp picture; I haven’t even seen the piece it’ll frame yet! Until then, have fun engraving longer materials, but be very cautious when breaking your laser’s interlocks.

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