You don’t have to use a K40 laser cutter for long to realise that you need some kind of fume extraction system. K40 fume extraction systems are needed to combat the fume, smoke and bad smells that are generated from laser cutting. Burning plastic doesn’t smell great!
Installing an effective fume extraction system doesn’t need to be complicated or expensive. This guide covers everything you need to know about K40 fume extraction systems.
Why do you need a K40 fume extraction system?
Laser cutting and engraving works by burning away material from the workpiece. Depending on the material this can create a large quantity of fume and in nearly all cases produces a bad smell. Fume extraction is necessary to remove these fumes from your working area, preserving your health and depending on where you have located your laser cutter, your surroundings.
Note: Even with a top-tier fume extraction system, some materials should never be used with a laser cutter, such as PVC. Lasering PVC produces chlorine gas, which will quickly kill off your K40 and you!
K40 fume extraction - overview
The most common method for installing a fume extraction system on a K40 laser cutter is to rig up some flexible ducting from the back of the machine and use this to direct the fumes away from the working area.
The fumes are pulled from the K40 using an inline extractor fan similar to the types used in bathrooms.
The fumes are usually just vented outside. However, in a more advanced (and expensive) system, the exhaust gas is passed through a filter which removes fume particles before venting the filtered gas.
The fume extraction fan provided with most K40s is a small axial fan similar to what is used for air-cooling PCs. These fans are pretty much useless and should be replaced as soon as possible.
Having a good fume extraction system will also result in cleaner cuts, pulling smoke away from the cutting area and stopping it from blocking any energy from the laser beam. Having less smoke at the cutting site will also help prevent residue from building up on the focus lens.
A side note on fan characteristics
Fume extractor fans are much better at pulling air than pushing it (better at sucking than blowing).
This means that it is more effective to have an extraction fan at the vent end of the ducting sucking fume away, rather than at the start of the ducting trying to push it through.
Locating the extractor fan at the end of the ducting will also keep the ducting at negative pressure. This will prevent fumes from leaking out into your workspace. If there are any leaks on your ducting, having it at negative pressure will cause it to suck air in rather than pushing fumes out.
It is also worth noting that fans running in series are not additive. Having two fans one after the other in the same ducting would not give any increase in airflow. Check out this article for the science behind fans running in series/parallel.
This means when using a ducting and external fume extractor fan system, the fan supplied with the K40 won’t actually be of any help at all and in fact, could even impair the performance of the main fan. Once you install a proper extraction system, remove the supplied fan and bin it.
K40 fume extraction - components
Here is a list of the required components for building a K40 fume extraction system:
Extractor Fan
The most important part of the fume extraction system is the extractor fan. Bathroom-type inline extractor fans are very well suited to this purpose. These types of fans give good suction, are inexpensive and are very quiet.
These fans generally come in 4” and 6” diameters, with the 6” size giving more throughput but being more expensive. In my experience a 4” fan is adequate for the job.
For UK users, here is an Amazon link to the exact extractor fan that I use in my system.
For US users, here is an equivalent.
Both of these fans are 4″ units that provide excellent suction at a very reasonable price. This style of fan is easy to mount to a wall and easily connected to ducting using jubilee clips.
As mentioned earlier, locate your fan at the end of the extraction system, not at the start.
Make sure you connect it to an external power outlet, not the PSU supplied in the K40. The PSUs supplied with K40s provide barely enough power to run the K40 unit itself, it is not a good idea to place additional demands on them.
Ducting
Ducting is essentially a flexible pipe that is used to route the smoke and fume from the back of the K40 to the extractor fan and to the outside.
Depending on what size extractor fan you bought, you will require the same-sized ducting. Connect the ducting to the fan using jubilee clips or similar.
Adaptor / Dust Hood
The ducting can easily be attached to the back of the K40 case using an adapter such as this: Big Horn dust hood (this adaptor is suitable for 4″ ducting).
Once again, ensure you pick the correct diameter adaptor for use with your chosen fan/ducting. No need to go expensive here, just pick something cheap that will get the job done.
Optional - Filtration system
Having a filtration system built into your extraction means that the gas that you vent will contain much less fume and particles. The main problem with filtration systems is that they are expensive – in most cases, an effective filtration system will cost multiple times the amount for a K40 unit.
Filtration systems can be made DIY style for less than the cost of a manufactured unit, however will still be quite expensive due to the materials required to make them.
K40 Fume Extraction - Fume Venting
Now that your fume extraction is sucking away all the nasty fumes away from your K40, where are you going to vent them to?
It is simple to just vent it outdoors, however, consideration must be given to your surrounding area. I doubt your neighbours would be too happy if you started venting laser cutter fumes into their garden for hours at a time!
If you are restricted on where/how to vent your fumes, perhaps give more thought to installing a filtration system.
K40 Fume Extraction - Maintenance
As time goes on and you clock up more and more hours on your laser cutting, it is likely that residue will build up on your extractor fan, which will reduce its effectiveness. It is a good idea to give your fume extraction system a good clean out regularly to keep it running in good order.
The inside of my fume extraction fan. Time for a good clean!
K40 fume extraction - Conclusion
To sum up the key points of this article:
- Fume extraction is a key part of an effective K40 laser cutter system.
- The fume extraction supplied with most K40s is useless.
- Extraction fans should be located at the end of the system, not the start.
- Filtration is a useful but expensive addition.\
- Consideration must be given to where the fumes are being vented.