Tag Archives: laser cutter

Laser cutter setup: air supply, off-gas and various cutting tests

Finally I find some time to document all the remaining parts of the laser cutter, Workshop Upgrade: Laser cutter and engraver SCULPFUN S9. The cutter itself is just the common off-the-shelf kit, but the air nozzle and enclosure has been custom made. If you want to cut wood, paper, plastics, there will be a lot of bad-smelling and potentially toxic fumes, so better you enclose the machine and provide adequate ventilation. Also, for wood, paper and such, you will need a strong air flow to ensure clean cutting without burn marks.

The setup is now arranged in the basement, so that it can be used quickly and without setup time. There is a metal plate inside, zinc plated steel, so thin materials can be fixed by magnets.

The enclosure, made from 15×15 mm square steel tubing, painted, and the openings closed with white PVC sheet, and yellow (laser-blocking) Plexiglas.

The exhaust is a fan I had handy, a Dalap AP series 125 size, it is quiet and powerful, but surely any similar fan could be used.

There are some openings around the cover (upper) part of the enclosure, accordingly, air can enter and flush out the fumes. The off-gas is connected to an old, disused chimney.

Next, we need a reliable air source. In the main workshop, I already operate a larger air compressor, but it is noisy, and there is no pipeline to the house. Rather than building such pipe system, I decided to setup a second compressor, a quiet compressor, to make the work with the laser cutter more comfortable (hard to focus on any work close to a running compressor…).

It is a Hyundai brand silent compressor, quite decent built quality, and inexpensive for what it is.

With these data, it is running about 30% of the time, when the cutter is taking the full amount of air.

The tank is running with 6-8 bars pressure, by on-off regulation. The line pressure is set to 5 bars, so the pressure to the laser cutter system is stable.

There is already a moisture (water droplet) filter at the compressor, but I added another air filter, a simple model, EIF 4000-04, which is a centrifugal filter including a 5 micron particle filter. This is prevent particles from getting into the needle valve (potentially affecting or blocking the air flow), and removing any water droplets (condensate) in the line.

For easy use, there is a cut-off valve, and precision needle valve (Festo GR-QS-8) to set the air flow at the desired value.

The GR-QS-8 was cheaply available, but sure any similar precision needed valve will do.

The flow meter has a built-in needle valve, but strangely, when using this valve (partially closing it at inlet pressure of 5 bar, outlet pressure basically atmospheric), it causes the metering sphere to rotate quickly and with noise, showing completely incorrect readings. So I believe the design of this built-in needle valve is somewhat flawed.
Be sure to install any valve BEFORE the flow meter, because if you operate the flow meter under pressure, it will show completely incorrect readings. 16-18 L/min is plenty enough for the cutter to work without any burn marks. I have not optimized this much, but maybe you could also work at 12 L/min for most situations.

Cutting plywood works just great, with maybe 0.2 mm cut width.

All the contours are nicely defined.

Even stars or pointed objects can be cut without any trouble. These are just about 3-5 mm size!

With some materials, like, rubber and aramid enhanced seal papers, these don’t cut well, or not at all. And even the vendor (Klinger of brand Klingersil) doesn’t recommend or even support laser cutting of these materials, such seals still need to be cut or punched.

Other seal materials, like, reinforced paper (cellulose) materials including Elring Abil brand materials, these could perfectly fine.

Workshop Upgrade: Laser cutter and engraver SCULPFUN S9

There are various laser engravers or cutters available in the market, so it is hard to make a choice. Finally I got a Sculpfun S9, which appears to be well-regarded in the community as a cost-effective and capable machine. I was also looking for something that is easily serviceable, not using custom controls or special motors – the Sculpfun S9 is built from all relatively standard components so it can have a very long service life even if I eventually need to fix the electronics or replace the controls altogether.

The machine ships as a kit, but there are good instructions for assembly, step-by-step, even the screws packaged for each step in a separate bag.

The machine is fairly portable, so you can also set it on the surface of large panels to do local engraving or similar.

Some first tests, works very well indeed! Just the smell of burned wood and plastic – it is really not a machine for an apartment, and the laser also seems no toy for kids. It is fairly strong and can be dangerous. This laser has a very sharp (maybe 0.1~0.2 mm beam) that cuts through several mm material in a single cut. No good idea to get your fingers in the way.

You can also cut foil. Maybe better to use a knife cutter (because of the smell and vapors), but for some once-off jobs, it is easy to use and also cuts uneven old foil very well in my test. Better use some magnets to push the foil down on a piece of sheet metal.

The main application that I am looking for is to cut custom seals from plain seal stock. The machine cuts well through 1 mm Elring Abil plate, and similar materials. Even thin rings can be cut, no problem (very hard to cut with a cutter knife or punch).

Next step will be to get the machine properly installed. This means, adding an air nozzle to assist with cutting (made from brass), a machine table, and an enclosure with exhaust fan to get rid of the toxic vapors.

The nozzle is made from a piece of brass (several of these pieces purchased at a scrap yard 25 years ago when I was still a kid).

The nozzle has a side inlet, and is designed for about 20 L/min with 1.5 mm diameter, so we are looking at 150~250 m/s linear velocity at the nozzle outlet.

The gas is fed through a 4 mm PU pneumatic tube.

To measure the air flow, we are using a very cheap Chinese gas flow meter. This has a needle valve, but it is not working well – the needle valve puts a spin on the gas, and the indication is incorrect (the sphere starts oscillating and spinning), so I use a separate needle valve (FESTO GR-QS-8) in the supply pipe.

The flow meters comes with flimsy plastic connectors, and these have 5/16″ UNF (24 TPI) tread… not a very common part in Germany to get a transition from 8 mm pneumatic tubing to 5/16″ UNF…

Fortunately, found a suitable thread cutter in my tool selection, so an adapter was made quite easily (from 5/15″ UNF to 1/4″ NPT, then us a 1/4″ NPT to 8 mm push-in tube connector).

The next step has been to make a suitable table, sure you can put the laser machine on some ordinary table, but it has quite some speed and movement and even relatively stable tables will be moving and there is some impairment of precision. So I wanted to give this machine a stable basis that doesn’t shape. It is all welded construction from about 1.5″ square steel pipe. The top is 18 mm waterproof plywood. There will be a piece of zinc-plated sheet metal on top, also to use magnets, and a open cutter support plate on top in case of heavy cuts.

To fabricate such a table, after the welding is done, grind off the scale (this is just plain steel), clean with acetone, and then roll-on some primer paint.

Finally, painted in a blue-gray color, and with the top plate mounted.

Next step, fabrication of an enclosure with a movable cover. All made from 15×15 mm (about 3/4″) square tube, all TIG welded…. looks easier as it is with all the parts and angles.

There will be two large windows, 40×60 cm, to observe the process. I selected GS-1C33-GT Plexiglas (acrylic glas) which is nicely transparent for visible light, but blue light of the laser can’t pass at all.

This is also confirmed by the spectrum, the laser is emitting at about 452 nm.

After some hours of work, the enclosure is ready for painting. It opens nicely and smoothly, also because of a gas spring (200 N, 535 mm total length, 220 mm travel).

It is one of the few occasions that I have use gas loaded springs in my design but it is working well. Just the design calculation is complicated and probably it is always a bit of experimentation to find the right gas spring size and force. But this time, successful at the first attempt. My recommendation, to rather use a slightly stronger spring (say, 200 N if 150 N is calculated) to allow for aging of the spring or other design uncertainties.