One of the most common materials to cut and engrave using a laser cutter is wood. A particularly pesky problem with using a laser cutter to cut wood is that there will be laser cutter burn marks right around the edges of the cut. I’m assuming you’ve clicked through to this article because the burn marks are undesirable (and you’re not making an attempt at the art of pyrography!), so let’s read on to see how to deal with this common issue.
How do we laser cut wood without burn marks? First, it’s important to note that what’s typically causing the burn marks to be left in the first place is not the high-powered beam hitting the surface of the wood itself, but rather the fumes and debris emitted while the cutting process ensues. There are a number of things one can do to avoid charring like using tape, dampening your wood a little bit, using a higher powered laser, or experimenting with different kinds of wood more conducive to laser cutting.
Now, these burn marks don’t occur on every material you cut; laser cutters will either incinerate, vaporize, or melt certain materials depending on their composition.
I’ll be going over shortly in detail:
- What exactly causes these burn marks to occur so prominently when cutting some materials like wood and not others
- How to take preventative measures beforehand to ensure such unseemly burn marks don’t ruin future projects
- Some quick tips to remove light charring on pieces that have already been cut
Factors That Lead to Laser Burn
As I already stated earlier, Fumes and/or debris residue is nearly always created when the laser cuts the wood.
Because of such high temperatures, these fumes scorch the surface right around where a laser beam cuts material.
When you stop to think about what is happening, a CO2 laser is basically just finely burning through some material like wood. Therefore one should naturally expect there to be at least some browning or amber color along the edges of a cut project.
Although some degree of this is to be expected, it quickly turns problematic when there is significant charring and soot that is no longer aesthetically pleasing (typically when the burn marks are too dark or leave “laser tails” on select portions of a cut).
The most significant charring and scorching will appear on chiefly combustible materials. Other materials like acrylic will usually appear slightly melted or glossy, but barely noticeable where the laser beam has cut.
Sometimes burn marks will occur where the laser comes in contact with the cutting bed as it slices through on the reverse side of the material.
So ideally, you’ll want as little contact between your project and the cutting bed as possible.
Preventing Laser Burn
So now that we’ve briefly looked at some of the reasons why laser cutter burn marks happen in the first place, let’s look at a few ways that one can minimize some of these ugly marks that might ruin your project, or otherwise make it turn out in a way that’s suboptimal.
One sort of makeshift measure that seems to work for a lot of people is the use of regular, everyday masking tape that you can find and purchase at office supply or arts and crafts stores.
The idea is that you want to cover the entire wooden surface with masking tape prior to cutting your project. After your design is cut, you will painstakingly have to remove all the tape.
Apparently this seems to work well because it prevents the edges of the engraving from getting stained. Any major charting marks will be left on the tape itself which can be peeled off in the end.
Although the removal of tape may be a time consuming process, it may turn out to be worthwhile in the end if your design is not sacrificed to ugly brown marks.
Types of Tape to Use
Different types of masking tape have varying mounts of tack. Low tack masking tape should be sufficient for most projects, but there may be some instances where you will want to rely on higher tack tape.
If you’re cutting wood that has an uneven grain to it or a high moisture content (birch plywood would be an example), you will want to rely on higher tack masking tape, for the low-tack variety may not offer sufficient protection since it will peel off too easily.
This is a similar process to using masking tape. Again, this material can be found in your everyday arts and craft store. The lower the tack the cheaper the material is to acquire in general.
If the low tack quality application tape doesn’t hold too well, try a higher tack.
You apply all of the application tape to the entire surface of the wood to be cut.
Make sure to smooth out all bubbles beforehand, otherwise that could lead to results that are even worse.
Other Preventative Techniques
The tips I’ve already mentioned are probably the most common. But here’s a couple of other things you can try if those seem to not be working as well:
- Try adjusting the focus of the laser. To do this you have to switch The settings on your machine to “manual“ and then back out the focus of the laser. Supposedly a slightly lower, more diffuse focus will keep the level of smoke at bay while still allowing for the fine cuts to be made on the material.
- Immerse thin plywood or other woods in water prior to cutting
- Avoid cutting wood that is too thick
- Make sure you are always using air assist when you’re cutting. This is usually just compressed air that is directed to the point where the laser beam meets the material. This constant stream of air can reduce scorching on a variety of materials.
Testing various woods
It turns out that certain kinds of wood are more susceptible to charring than others.
This usually has more to do with the glue binders embedded in the material rather than any inherent property or grain of the wood itself.
Because of the glue embedded in materials ike plywood and MDF, these materials will typically leave more burn marks than pure wood. So perhaps avoid these woods if it’s a headache for you.
Some great woods to experiment with are:
Since the exact composition of various wooden materials you will be using is not always known, it’s best to do preparatory cuts before you commence to finish projects. That way you can play with the different settings on your machine and reliably predict what charring effects will take place if you use the same for final artwork.
To reduce burnt edges, there’s a few things you can play around with on your laser machine to see if it produces any positive results for you:
- Adjust the PPI or frequency (try setting it to a lower number like 400 or 500)
- Adjust the speed of the cut A lower speed may reduce burn marks, but you may find that you’ll need to run a couple passes before it actually cuts completely through your material.
- Typically if the machine is run at too high a power level then the project will be more prone to burn marks
Removing Ugly Burn Marks
An ounce of prevention is superior to a pound of cure. That said, sometimes it’s too late since the project is already cut, but it isn’t charred to the point of being unsalvageable.
There are a couple things you might want to consider.
- Sanding the material this one’s kind of obvious, but if you don’t have too much charring,try just using a little bit of fine tooth sandpaper on the edges as long as it doesn’t jeopardize the fine detail of your project.
- Something as simple as a little Windex while scrubbing with a toothbrush or other similar brush may do the trick in small areas
- Pumice liquid soap with toothbrush or fabric brush. This basically acts sort of like sandpaper in that it will allow you to scrub soot off tiny cracks and crevices of the design.
- If you tried some of the other tactics and you only have a minor amount of burn marks and stains on the engraving edges, try denatured alcohol. This is often used on wooden furniture, we can also be used to remove burn stains. Just apply a little bit to a cloth and rub on the areas of charring.
My Final Two Cents
I hope this helped you and you don’t end up with too frustrating a problem or too high of expectations with laser cut wood.
I’ve personally seen dozens of projects from 3D puzzles, toys, jewelry, and much more being cut out of wood from laser cutting machines. There was almost always some level of brown or amber color on the edges.
This didn’t ruin those projects for me, as I saw it as just a natural byproduct of cutting wood and was used to it. But I perfectly understand that sometimes that charring goes beyond the tolerable amount.