Kerf removal

[John Johnson 2]

Is there a tool available to remove the keft easily. Yes one could sand each piece bu there has to be an easier way.

[Rich Harman]

Kerf is the bit of material that is removed by the cutting tool. So there is no such thing as a kerf removal tool since by definition, the kerf has been taken away already.

Maybe you mean something like a deburing tool?

[John Johnson 2]

You are joking right ?

[Rich Harman]

Just trying to be helpful.

[john banks]

Not following either John. There are software techniques to compensate for the kerf and I can advise on these if you use RDCAM. Careful alignment/focus and long focal length with appopriate power can give parts that are cut in hardwood that are maybe 5" x 5" x 0.2" and will stand straight up on a level surface with no post processing.

[Joe Pelonio]

Spindle sander, though I rarely find the need to worry about the kerf.

[Mike Null]

I agree with Rich. The kerf is the area that has been removed by the laser (or saw). If you have rough, charred or melted edges where the kerf was cut then there are several tools you can use, none of which were specifically designed for the job. I use a sanding block, files, scrapers, a router or whatever else seems like it would work.

[jason harris]

Depending what you have cut a 'jointer' or 'buzzer' (depending what part of the world you live in pick the right name) will work well but thats only for straight edges with enough length to work on those machines.

[Richard Rumancik]

John, if you elaborate on what material you are cutting and what the problem is (corner, entire edge, part shape) and what your objective is, I'm sure someone could direct you to an appropriate tool or method.

Rich was just describing what a kerf is; he assumed that you really meant there were burrs on the part (ie sharp bits of material left along an edge) hence his suggestion of a deburring tool (which is indeed a real tool which you drag along a sharp edge to shear off the particles.) Like every field there are technical terms that help us communicate.

[Lee DeRaud]

Another approach is to cut the workpiece a bit oversize and then cut shape you actually want from 1/4" MDF and then use that as a template for a flush-trim router bit to clean up the edge. The good news is that this method even works on thick wood that the laser can't actually cut by itself: you can use a bandsaw/jigsaw/whatever to do the rough cut. The bad news is that it doesn't handle inside corners well.

[John Johnson 2]

When one cuts 3mm Plexiglass the edge is left at a slight angle. If that edge is glued to another piece of Plexiglass then the edge produces a problem. Yes of course one could sand it, scrape it and router it, but I was wondering whether there isn't an elegant solution. The solution should only straighten the edge and not remove any more material once the edge is straight.

[Mike Null]

John

On my machine 3mm acrylic cuts with a "straight" edge. That is unless you're looking very hard for a minuscule angle it is not readily visible. The finish is not quite polished but a light touch with a flame would provide the polish if I needed it.

[John Johnson 2]

I am very happy for you that you get straight edges. My edges has a marked angle.

[Scott Shepherd]

I am very happy for you that you get straight edges. My edges has a marked angle.

It would help to know what machine you have.

You can reduce the angle by changing the focus down into the work. You'll find a sweet spot that gives you a good straight cut for that thickness. Try focusing .060" below the surface and see if that helps.

[Greg Facer]

Try moving the focus point onto the material, that will even out the angle if done perfectly, and the melting of the solvent glue might do the rest. Having said that, a router or jointer taking off 1/32 or even less is the regular way to do, as any glued edge will be flat....won't work if inset from another edge though!

Or, try a longer lens, less power density but straighter kerf, but acrylic is the material least affected but the focal length, as it acts as a waveguide keeping the beam tight.

Full disclosure: much of this is what I've read as much as my experience.

[Rich Harman]

The speed that you cut can affect the angle as well. If you cut too fast (barely cutting through) the top of the cut will be wider than the bottom. Slowing down should open up the bottom of the cut giving a straighter edge.

[Mike Null]

John

If I'm cutting 1/4" material the angle is much more pronounced.

[John Johnson 2]

Now this is an interesting thing to think about. I think that you may have the solution.

[john banks]

John, do you have an angled kerf only on acrylic or does it happen with wood as well? Reason for asking is to try to determine if this could be an alignment issue or whether it is related to the melting of the acrylic?

[Adam Ajans]

There can be several reasons for an angled edge on laser cut acrylic. First of all, your machines laser ray might not be aligned correctly. Check this by using a thick (1") clear acrylic piece. Put it under the laser head and press the "test" button to make a spot on the acrylic. Look from the side of the acrylic piece if the hole made by the laser follows a straight path. If not, align your mirrors.
Second is the Issue of laser output power. If your laser tube isn't strong enough, you won't be able to get a straight cut. Try to drop the cutting speed until you get a straight edge. If the cutting speed you're getting a straight edge at is too slow for you; I'm sorry but you'll have to get a more powerful laser tube.

[Richard Rumancik]

John, I'd suggest that you cut a square and check the angle on all 4 edges. You could use soimething thicker than 1/8" acrylic to make it more evident. If there is any angle, then they should be equal especially on opposite sides of the square. If they are not then alignment needs to be tweaked.

Once you are sure the laser is aligned the best it can be, then I'd suggest a longer FL lens. I didn't see whether you specified the lens you are using in this thread . . . but since you probably have power to spare with 80 watts you could afford a longer FL lens as long as the larger spot size doesn't bother you. (maybe 2 1/2" or 3"?) Then you could get a straighter cut.

If you are trying to build acrylic boxes etc then even a small angle can be a problem. Squaring the edges of the components with a secondary machine can be done but is an additional operation but you are usually limited to processing straight edges. (Some people prefer removing the edges before bonding as it removes the highly-stressed edge which can be prone to cracking and crazing.)

Another option is using fixturing to square the sheets, and using a gap-filling adhesive.

Unfortunately there is no simple solution to this problem.

[Rich Harman]

An alternate way to check for a straight beam is to fire it on a piece of material to make a dot, lower the table a few inches and fire again. If the two marks are centered then your beam is straight.