Cleaner Vector Cuts

[Rick Maitland]

I am going to make up some of those detailed scroll saw desk clocks, but I already know of one problem I am going to have. When I Vector cut wood it leaves the edges of the cut a black chalky mess that is very hard to get rid of. There will be lots of little cut outs and sanding just would'nt be an option. I know many of you have had this same problem so i'm asking for your input....thank you in advance.

[Linda Tetreault]

Rick,
I've sprayed the wood with pledge before lasering which helps & maybe lower the power a little. I've been cutting 1/4" maple on a 35watt & the edges are a nice brown not char. I don't have the settings on this computer, but will check it tomorrow.

Linda

[Aaron Koehl]

Some have used Nitrogen in their AirAssist lines which is supposed to leave a nice edge. Unfortunately, I can't attest to it myself as nobody has taken me up on the offer to post before/after pictures ;)

[Shaddy Dedmore]

I agree with Linda, Maple has left the cleanest edge so far. Followed by Alder. Walnut and Mahogany have been the charriest (OK, so maybe that's not a word). I've bought my 1/4" stock from Colorado Heirloom and from Studio Workshop... pre-finished. For Mahogany and Walnut... I've had the best luck with going to my local hardwood lumber place, getting the 1/4" and using a danish oil to finish. But the time it takes to prep (sand before then lightly sand between coats) was too great... I still like paying someone else to do it, and it's not THAT much more than buying the bare wood. So i'f kinda left Mahogany off my "sell" list.

I don't know if it was the finish i used to a slightly different wood composition, but both the walnut and Mahog vectored a lot cleaner.

When I make boxes, I rub a paste wax on the exposed edges (not the edges that will be taking glue), that cleanes it up, plus helps seal it so it doesn't come off on the fingers. Yet another reason why I don't think making boxes is cost effective for me, takes a lot of time, if I charged flat out what each one had into it, materials, laser, computer, and my time... I wouldn't be able to sell them.

Ah well, I'll find something.

Shaddy

[Brent Brod]

I saw some information where some large commmercial guys were using nitrogen assist when cutting carbon fiber fabric. The pictures looked really good comparing air to nitrogen. The problem I keep coming to with nitrogen is a cheap source. By my rough calculations, you'd bleed a large cylinder down in an hour or so at 30 psi. I'm still considering buying a cylinder just to test with. If it is really great, it might be worth figuring out a cheaper source like a nitrogen generator or even a liquid tank.

If anyone in here is using N2, I'd like to hear about their experience.

[Mike Mackenzie]

Brent,

On the Universal systems we can control the flow of the gas as well as the turning on and off within our driver and can control it by colors. With that said I do see some improvement on the cuts but not enough. We can get similar cuts just using compressed air. We still get a darker edge but no debris what so ever. The nitrogen is not for the everyday laser operator however if you want to use it set up a air solenoid in line and tie it into the start button on the laser system. In a sense what you will get is a signal to start the flow of gas and another to end the flow. The pressure solenoids just use a 5V signal. Doing it that way you won't be pumping the gas right out the exhaust. It also won't be very useful unless you are blowing the gas directly down on the cut. The laser systems that use the air assist that just blows the air across the surface horizontally won't be able to use nitrogen efficiently to achieve a clean edge.

[Rodne Gold]

There are a few strategies you can adopt to get cleaner cuts.
The laser cuts by drilling spaced holes , it pulses.
Firstly if you can control pulses per inch , drop it. This stops the overlaps and thus the heat affected zone on the edges.
Power is king when doing wood cutting , 100+ watts will give hugely better cuts than the lower powers most of us have
Nitrogen is not the answer , ideally with the lower power lasers you want to promote "combustion" IE raise the temp so high that you get more vaporization then burn. So you want to direct air assist at quite high pressure at the cut itself , ideally from the front of the beam to the back
Focus point is also a concern , if you focus on the surface of the wood , the beam diverges to the bottom and thus the power over the area (power density) drops and you start getting a burn. So you need to raise the bad 1/2 the thickness of the wood after focusing so the focus point is in the middle of the woods thickness.
A longer lens also helps in terms of that it maintains the power density over a longer area (but reduces the power density due to a bigger spot size - might be a problem on lower powered systems)
Using a honeycomb table or elevating the wood is essential
Apart from that , we had a lot of problems with warped woods and the fact that composition of the wood changes as does resin content , all of which affect the cut. The "lighter" the wood (in terms of its density) the better the cutting.
Our solution was to have panels of light density fibreboard (ldf) veneered , either on one side only or both sides. This helped a ton as we now got large flat panels that engraved consistently , looked good and could order any finish we wanted. The edges , due to discolouration hide the fact that this is not a solid wood. These days we tend to avoid woods to some extent and concentrate on veneers.
We often also cut wood grain formicas and clad other stuff with it (like supawood done on our CnC machines )

[Kevin Huffman]

Hey Rick,

With our Pinnacle (GCC) machines, there is a setting in the driver called PPI. It controls how many pulses it puts as it does a vector cut. When working with wood and really soft materials you normally turn that down. 500 is usually default and I normally turn it down to 250-300 and it usually gets rid of the charring.

[Rick Maitland]

Thank you Kevin. I bet thats my problem because ive been using 1000 PPI.