Reply To: Laser – J Tech Photonics Tips and hints

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Jay Johnson

Hi guys- Looks like you are all doing awesome work on upgrading the mostly printed CNC. I just got informed on the forum here, so I will now be looking at the thread to see if I can be of service on answering questions. It looks like you all have figured out how to get everything working, but here are a few suggestions from some of the earlier responses.

Focusing: We wrote a blog post the has an alternative to using your eyes to find the best focus and rather use a number of lines at different Z heights to engrave into a test piece of wood. Then you look at which is the smallest line. The post is here:
We normally recommend anywhere between 1″ and 3″ for the focus height. Yes, most of our machines in the pictures and videos are set up at about 3″. We have found not much of a difference in this range as long as you get your focus small as you can.
Also, as many have noticed, the easiest way to turn your laser down for focusing is to use the PWM command in marlin. You can see when the threshold of the laser is met somewhere around M106 S5 or so. It might be a bit lower (M106 S3) or a bit higher (M106 S10). Just find which is the lowest for your laser and then use the focusing technique from the manual.
The laser gauge is a good idea. Just make sure your lens does not move. We sometimes use PTFE tape to secure the lens in the housing. Never use super glue or anything that will fume as it will destroy the lens coating.

Safety: The shielding is great for making a laser shield, but we also still recommend using your goggles at all times unless you have a full enclosure that is also interlocked. This means that if the enclosure is breached, the laser will turn off. The front green connector is the interlock which you can use to put switches for the openings. If you have kids around, I would suggest taking the key out of the driver and hiding it when not in use. Always make sure everyone in the room has a pair of goggles as well…

Fumes: We use a shop vac to suck the fumes from the work surface and put a charcoal filter on the output of the vacuum. It is even better to put the vacuum outside and vent out of the space completely. When processing any material that is not organic you need to take extra special care. Most of the fumes from non organic materials will be even worse for you to inhale.

Anodized Aluminum engraving: This process is a chemical process (the anodization will bleach white), so it is very material specific. Most of the samples we have tried work, but we have also seen some that don’t from customers. The one from our video is from Brady ( We have engraved our Mag Lights as well and it works great.

Software: All of the software on the website will work with the marlin firmware. The inkscape plugin is something that developed a long time ago and has been shared on several sites over the years so there are a lot of variants of it. It can be a bit buggy sometimes, but heck, it is free. Most of the issues it has is when you are importing images into inkscape that the plugin has difficulty in figuring out the size and/or units. Most of the time it will work fine when you draw from inkscape itself (text and such). You will use M106 as the laser on command and M107 for the laser off command. The S command is added based on the power level % setting. If you have questions on the software you can post a specific one and I’ll try to answer quickly.

I’ll be checking the forum now and will try and respond to future posts which are relevant to us.

Best Regards,

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