Airflow Specs Through The Compact Filter

I have been having a lot of problems with my Compact Filter not, well, filtering out smell. It has caused a lot of complaints in neighboring offices. One of the common things I have read is that the filter speed needs to be adjusted to keep the same airflow through the filter as it gets used (clogged). Does anyone have this spec? It shouldn’t be difficult to design an airflow sensor and have the fan adjusted automatically to ensure proper filter flow.

Well it is kinda a pain to measure air flow in my experience as an instrumentation tech and would need to have a well tuned PID loop on the power adjust for the fan. If you are getting smells still it would be best to inspect your filter and check for leaks in the system. maybe do a small test engrave or cut before you print to make sure you have the setting adjusted high enough?

My thoughts were to use a step function that would adjust speed to fall into certain bands. Add a dead zone around each transition point to prevent dithering and I think that should do it. I just want something that works as easy as the glowforge itself. I actually have huge regrets in buying the filter, but it is after the return period. I thought I would try to make it work before giving up on it entirely.

If you can build a sensor and controller you might as well, i just work on these things on an industrial level and went to school for 4 years for my trade and they are still a pain to deal with. I think the best instrument you have is your nose imo. I was lucky when it comes to the air filter and was able to cancel my order before it was ready to deliver. Is there a way you can vent outside? (as you are using the filter i would guess not) You might have same issues with smell but you could in theory install a charcoal filter in line before it goes outside to mitigate those and a higher cfm fan to help dilute it once it gets outside.

I am an electrical engineer and design embedded systems. I can design around it, I just need to know the design airflow.

The main issue you will run into is your measurement point, how turbulent the air flow is, it will make an accurate or consistent measurement nearly impossible. there is only so much dampening a signal can do in that situation and will end up having the controller ramping all over the place or be so dampened that it will not respond to changes in air flow. Same limitations come when you are measuring any fluid flow.

“Turn it up until it doesn’t smell” is kind of simple in comparison to extra engineering work.

For the record, I’m a great fan of engineering and even overengineering. But Glowforge has suffered considerably from the latter (*cough* limit switches).


I appreciate the comments, but what I am really looking for is the min/max cfm the filter needs to be effective.

I don’t think you’re going to get an official answer, it’s not the kind of thing Glowforge likes to tell us. If for no other reason than it’s subject to change.

Unofficially, ancient discussion on this forum suggests that Glowforge itself (without the filter) is designed to push out 200 CFM. When you turn on the “filter attached” switch, I think it just disables the exhaust fan, but keeps the intake fan running (I could be completely wrong here). So I’d assume somewhere in that neighborhood would be necessary to ensure that the GF doesn’t become pressurized and push smoke out the cracks.

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I’m so sorry to hear that you’ve been having trouble with the Compact Filter. My apologies about our slow reply. The Compact Filter is designed to run at about 350m³/h which converts to ~206 CFM you can find this information available here in the manual.

The Compact Filter has adjustable fan power to improve the life of the cartridge. When you start to detect an odor, you turn up the fan; when the fan is at maximum speed and you start to detect odor, you replace the filter cartridge.

Could you please let me know if you are still experiencing any trouble with the Compact Filter?

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