can i use a external fan along with the filter
i guess you can exhaust the exhaust of the exhaust - but at that point, why not just get rid of the filter and exhaust the exhaust?
An external fan eliminates the need for the filter, but if you get creative with the ducting you can switch between the filter and the external fan/vent.
You should not use an external fan between the filter and the Glowforge however as the filter has its own fan that is calibrated for the filter. Adding an additional fan can overpressure the filter, leading to damage.
You’ll have a hard time balancing the air flow.
What’s your desire for wanting to do this? Do you want to shut the filter fan off so it’s all quieter?
You don’t want to force air into the filter - you want the filter to pull everything into the filter.