Superience

The parts for the carcass were already precut from Lowes so all I had to do was drill the holes for the furniture connectors. The connectors consist of a 3/8 dowel cross drilled and tapped 1/20 and a flat head bolt with a recessed hex. If you have put together any ‘flat pack’ or Ikea furniture you know what they are. They are easy to mount, self align and hold tight. The case has three levels, the top for the laser and XY mechanism, the second level for the Z lift table, fan, power supplies and electronics and the bottom for the water tank and coolant pump. The whole assembly is on 3″ casters.

As I mentioned the fan is a $12 bathroom fan that vents out a 3″ hose. The air will come in at the front of the unit, get sucked down past the table and out the back.

I opened the box with the sprockets for the lift table and instead of one 1/2″ bore and six 1/4″ bore sprockets there were six 1/2″ and one 1/4″ sprocket. I had planed to turn down the ends of 3/8 threaded rod to 1/4 because I already have a bunch of 1/4″ bearings, but now I need a new plan. I thought about making some bushings for the sprockets. I then thought about threading the ID so they would screw onto the rod.

So I took a rod coupling and turned the od to 1/2″. Each coupling made two bushings. The theory is that I will be able to rotate the bushing and as it moves down the threaded rod I will be able to preload the bearings.

I mounted the motor on a scrap aluminium plate and slotted holes in the shelf to slide the motor for tensioning the chain. Currently there is a 120v reversable gear motor installed. If I can come up with an autofocus system I will exchange the motor for a stepper or servo.

Four brass threaded inserts will travel with the table. The total assembly is a 3/4od x 1/4id bearing at the top, 12″ of 3/8 threaded rod, the sprocket with bushing and a 1 1/8od x 3/8id flanged bearing at the bottom. A SPST center off toggle switch controls the table.

Hey it is finally starting to look like something besides a pile of parts!

I started to do the wiring for the stepper motors. I had a short piece of igus energy chain for the Y axis and the X axis had this spring assembly that contained the wiring. It is a very simple way of containing the wires and the hose for the air assist. I wonder if long springs are commonly available? It looks neater than the igus chain and is less critical in alignment.

I constructed an ‘air assist’ nozzle from a piece of 1″ pvc pipe and a chair leg protector. It is a perfect friction fit over the lens mount. The yellow hose will slip fit into a 1/4″ hole drilled into the side of the pvc pipe. I don’t know if it is technically an air assist as I do not think that it will aid in moving material out of the cut, but hopefully it will keep the lens clean of smoke and debris.

OK, this is getting frustrating. I was trying to do this on the cheap. I have a pretty good collection of junk and I thought with a few choice flea market and eBay finds I could cobble something together quickly. But the mis-mash of optics are not cooperating. So I took a step back and rethought the mirror layout. I moved the .5″ mirror next to the laser and the larger (but damaged) gold mirror out onto the Y axis. A few tweeks of the mounts and the optical path finally aligned. Yay! One thing that I noticed is that the beam coming out of the laser is not perfectly axial with the tube. Not a big deal but annoying. The focus is good but there is a very slight halo around the hole. I am assuming that this is from the little speckles on the damaged mirror.

With 10ma of current you can slice through a piece of Plexiglas or a paint stir stick. Now I have a bit more confidence so I am going to knock it all apart and start mounting it into a cabinet.

I picked up a bathroom exhaust fan at Lowes for $12 and a package from Surplus Center has arrived with some sprockets for the Z lift table.

I found a set of “Front Surface IR Mirrors” on ebay the other day that said they were from a CO2 laser project.

At first glance the photo looked strange then I realized that they were diffraction grating mirrors. If you notice you can see straight through the one on the right. I thought that they would be great for making a beam combiner along with a laser pointer so I placed an order. The arrived quickly. The three holes were perfectly sized to run a #6-32 tap through and there were small recesses that were a perfect fit for some small springs. I drilled three matching holes in the Y axis mount and it was finished. I cranked the power down low so I could align the beam. After the first quick pulse I could see that there was something wrong.

The surface of the mirror was visibly distorted. I grabbed the IR thermometer and gave another quick pulse. The face of the mirror was 30 degrees above room temperature. I guess that these were NOT for the right wavelength.

Headed out to the carriage house to mount the laser and do a final alignment of the mirrors.

IMPORTANT… This is what NOT to do.

I had read somewhere that you could use strips of scotch tape and the laser on low power to ’see’ where the beam was pointing. Just look for the puncture marks and tweak your alignment. Sounded logical. So I placed a strip of tape across the mirror mount, there is a good 3/32″ between the tape and the pristine gold mirror surface. First shot was high and left, second was right in the center. Perfect, now on to the next mirror. New strip of tape on it and fire a pulse. Nothing. I hold down the button a bit longer and there is a very rough hole. I look back at the first mirror, it is covered with a bunch of dots. When the tape was vaporized it splattered onto the mirror. I tried to clean it off with a surgical swab and alcohol. This removed the sticky residue but the gold coating is still slightly damaged.

I then switched to using a sheet of paper held in the path. This was less exact but at least cleaner to the mirrors. The mirror on the Y carriage is only .5″ and the holder that I made reduced the aperture to .375″. Tilt that on a 45 degree angle and it becomes very critical to align. I thought I was pretty close and gave it a high power shot and made a bit of smoke as the beam hit the edge of the fiberglass mount and heated it up. Finally I got the beam around the mirror maze and onto the firebrick laying in the bed. Calling it quits for the night.
Next up. Move the smaller mirrors closer to the laser where the alignment is less critical. Try and access the damage to the mirror with the splatter. Hey that is why they say the mirrors and lenses are ‘consumable’ items.

Any alignment tips are appreciated. I can see why having a red guide beam is handy.