Nearly constant flame during cutting

I haven’t seen much of any fire/flame when cutting various materials in the last year. I use almost exclusively Proofgrade. But then I cleaned my crumb tray last week and have had nearly constant flames trailing behind the laser whenever cutting since then - especially on acrylic. Obviously that can cause problems. It is also not cutting through using PG settings in the last week or so, whether I’m using acrylic or wood. I am having to consistently change the PG settings to get it to cut all the way through and this has increased the edge burning, of course.

Any suggestions or thoughts to fix these issues?

Thanks for letting us know about this.

Based on the details you’ve provided, there are a few things I’d like you to check:

  1. Turn off your Glowforge

  2. Inspect and clean the items covered in the things that need wiping instructions, as well as the mirror in the printer head

  3. Take photos of the printer head lens and the mirror

  4. Wipe the top of the carriage plate and bottom of the head using a lens wipe

  5. Replace the printer head according to these instructions

  6. Gently try to rock the printer head forward and backward then left and right to make sure it’s seated firmly

  7. Turn your unit back on, try another print. If possible, capture a video

  8. If you continue to see this behavior, please reply with the date and time of the print along with the video and the photos you took in step 3.

Let us know how it goes.

1 Like

How’s your air assist fan working? Are the flames standing proud or blowing towards the front of the case?


Great question! Definitely blowing for sure.

What did you clean your crumb tray with? Could there be residue?

I used Simple Green since it was recommended by so many folks here and on FB. It’s possible that I didn’t rinse it as well as I thought I did. So I recleaned it again tonight with just water and dried it completely with a hair dryer. Same result. Near constant flame cutting proofgrade acrylic using proofgrade settings. I’ve ruined 2 pieces of thick white acrylic tonight and have a project for a client due Monday, so I am on the struggle bus for sure!

Weird. I get flame sometimes when cutting acrylic, but it all gets blown way downstream.

Exactly. I’ve cut probably 100+ things in acrylic with no problems until now.

If the flames are trailing behind the laser the large head fan is likely not blowing enough. If the crumb tray is badly seated it could cause problems but I would not expect those problems.

It has been my experience that when there is a lot of smoke or flame the laser does not cut as deeply so the flaming may be a part of that… but any resistence in that fan can cause a lot of flaming. I have come to see that such unexpected flaming as notice that the fan needs cleaning.


I will definitely check that again. Thanks for that insight!

FWIW, I’ve had this same experience and I had constant flaming. When I checked the air assist fan it didn’t look all that bad and I was sure that wasn’t the issue. It was. :slight_smile:


I use a pipe cleaner and run it around inside the little scoop from underneath. Amazing what falls out.


Here is the process to clean your Air-assist fan:

  1. Turn off your Glowforge
  2. Open the front door and carefully remove the crumb tray
  3. Remove the printer head
  • Holding only the finished black surfaces, grasp the printer head as shown. Pull gently up and back to disengage the magnets and remove the head.
  • Push down fully on the wire ribbon tab to unplug the wire ribbon from the printer head. Pull the wire ribbon gently away and tuck it into the laser arm.
  1. Unhook the belt
  • Push the carriage plate to the center of the laser arm so it’s out of the way
  • Reach under the laser arm on the right side and feel for a black belt and pulley
  • Take the belt off of the laser arm
  • Placing your thumb between the belt and the laser arm near the pulley, push down on the belt while sliding the belt to the right towards the pulley. The belt will slide off of the pulley. Don’t be afraid to use pressure.
  • Unhook the belt from the motor on the left side
  1. Remove the carriage plate
  • Place both index fingers on the rear corners of the plate and both thumbs on top of the front wheels. Use your other fingers to support the plate. While keeping the laser arm stable with your thumbs, use your index fingers to pull the plate towards you as far as it will go. Then push down with your thumbs to angle the plate down and towards the back of the Glowforge until the plate pops off of the laser arm.
  1. You’ll find a black plastic fan on the underside of the carriage plate. Please inspect it for damage or debris and send me a photo of the fan blades.
  2. If you see any debris stuck in the blades, you can use some canned air clean them.

Once you’re done inspecting and cleaning, you can replace the carriage plate and try a test print:

  1. Reattach the carriage plate
  • Hold the carriage plate as shown

  • Placing your index fingers on the back corners of the carriage plate and your thumbs on top of the front wheels, hook the rear wheels on the groove under the laser arm. The front wheels should be mostly visible.

  • Pull the plate forward until the front wheels clear the laser arm then angle the plate up until the the wheels are in line with the rail. Release the plate – it should grasp the rail firmly.

  • Pick up the right side of the belt and make sure it is not twisted. The outside of the belt should be smooth and the inside should have ridges.

  • Hook the belt onto the pulley on the right side.

  • Make sure that the left side of the belt is not twisted and is smooth on the outside and ridged on the inside

  • Attach the belt on the left side

  • Using your left hand, set the belt on the front half of the motor (the silver piece on the left hand side below the laser arm) and support it with your fingers by placing them under the motor. The belt will not be fully on the motor. Use your left thumb and fingers to clamp the belt firmly in place and apply pressure.

  • Still holding the belt and motor firmly with your left hand, use the pressure from your left fingers to guide the belt clockwise around the pulley as your right hand slowly pushes the carriage plate to the left. The belt should roll onto the pulley until it is secure.

  1. Prepare to Print
  • Gently slide the carriage plate back and forth on the laser arm to ensure that it travels smoothly. If it doesn’t, remove the plate and try again.
  • Replace the printer head and crumb tray according to these instructions
  1. Turn your Glowforge back on, record a video of another test print, and let us know how it goes!

If you have any questions or concerns, please let me know.


Aww man, I hadn’t thought of that and I’ll keep the pipe cleaner trick in mind for maintenance. I did the full-on remove the carriage plate for the cleaning and I was so pleased with how much better it started cutting. These things creep up on ya and you don’t really notice how bad it’s gotten.

1 Like

I had no idea that was there. Thanks @pip , going to clean that next time I do the head.


It’s been a little while since I’ve seen any replies on this thread so I’m going to close it. If you still need help with this please either start a new thread or email

Think someone forgot to do the actual lock.


It is very useful information that I have bookmarked in any case, and good that others (particularly new owners) find it to understand what is happening when those flames happen.

Hey, an unlocked topic that should be locked. How is everything @BigBlueMark? You are one of the shining lights on this forum. Keep them comimg!


Thanks, brother! Doing pretty well. Life keeps getting in the way of me and my Glowforge spending more time together, haha!