Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
I used an ancient adjustable inside caliper to put the tube the same distance from and aligned parallel to the partition.
Sliding the tube an inch to the left provided enough space to drill & tap two new holes for the Mirror 1 mount to move the beamline 10 mm along the X axis:
OMTech CO2 Mirror 1 mount – redrilled screw holes
I briefly considered crunching rivnuts in there, but the mirror mount expects to sit flat on the floor with no room for rivnuts. So it goes.
Although Mirror 1’s mount has some vertical adjustment, the central stem was already close to its maximum extension, so I cut a 5 mm plywood pad to raise the base:
Laser Mirror 1 – baseplate scan
Despite what the lighting suggests, it’s concave. The image was clean and contrasty enough to just trace into vectors with LightBurn, then Fire The Laser to cut the spacer:
OMTech CO2 Mirror 1 mount – 5 mm Z shim
If you’re wondering how that worked with the tube jacked up, Mirror 1 sitting on the scanner, and the beamline in disarray, there’s considerable benefit in doing things out of the obvious narrative sequence.
Reassemble the mirror, square the entrance aperture to the partition, fire a couple of test shots to center the mirror on the beamline:
Although the most recent mirror alignment exercise put the laser beam parallel to the axes and centered in the aperture perpendicular to the beam, a target directly on Mirror 2 showed the beam was badly off-center:
Beam Alignment – 2M detail – 2023-09-16
Because that target is sitting flat on the mirror, the beam appears wider than it is tall. The horizontal graticule divisions are 1.4 mm apart to allow direct measurements: the spot is really circular and 3 mm in diameter.
Poking around inside the cabinet reminded me that all of the mirrors sat with their adjustments jammed at one end of their range, rather than being more-or-less centered.
Mirror 2, in particular, was up against all three limits. The slots behind these two screws allow the mount to slide along the X axis:
OMTech CO2 Mirror 2 mount – X screws
Seen from the front of the cabinet, those same two screws set the mirror position in the Z axis:
OMTech CO2 Mirror 2 mount – Y Z screws
As you may imagine, using those two screws to secure the mirror at a specific location in both X and Z at the same time is … challenging.
The two screws directly under the mirror set its position along the Y axis and allow a slight rotation around Z to fine-tune the alignment of the perpendicular aperture used for mirror alignment; unlike the other two axes, the mirror wasn’t jammed against the end of the slots.
Moving the laser beam horizontally toward the center of Mirror 2 requires one or more of:
Moving Mirror 2 farther away from the center of the cabinet, but it is already at that end of the X axis slots above
Moving the laser tube toward the back of the cabinet, which also requires moving Mirror 1, which is almost at the end of its adjustment range.
Moving Mirror 1 closer to the laser tube, which its adjustment slots do not permit
Mirror 1 sits on a pedestal with a slotted base allowing adjustments along the Y axis:
OMTech 60W laser beam test – mirror 1
The pedestal could move a few millimeters to the rear, but the screw on the far side is even closer to its limit.
Moving the laser beam spot upward on the mirror requires:
Lowering the mirror, which is obviously impossible given the position of the Z axis slots around the adjusting screws
Raising the laser tube
Mirror 3, inside the laser head on the gantry, was also sitting at the lowest possible point in its adjustment range:
OMTech CO2 Mirror 3 mount – Z screws
All of which suggested I should resign myself to adjusting the beamline:
Raise the laser tube by 5 mm
Move Mirror 1 closer to the laser tube by about 10 mm
Raising the tube gets both Mirror 2 and Mirror 3 off their Z axis adjustment limit, but requires raising Mirror 1.
Moving Mirror 1 gets Mirror 2 off its X axis adjustment limit.
Nothing changes the position of Mirror 2 on its Y axis screws, but that adjustment will help fine-tune the beamline into Mirror 3.
After about five and a half years, the OEM shift indicator in my rear SRAM Grip Shift failed, so I replaced it with a piece of right-angle polypropylene backed with hot pink vinyl:
All done by hand, because it’s easy.
I’d used up my stock of genuine replacement indicators long ago, but they’re now down to two bucks (probably because Grip Shifters are obsolete) and I’ve stocked up in anticipation of future need.
While cutting some oak plywood, I managed to get some interesting (to me, anyhow) pictures of how the assist air interacts with the laser kerf:
Laser cut plywood flames – C
The air flow is about 12 l/min from the pump in the bottom of the laser cabinet and is pushing most of the fumes through the kerf, where they ignite and burn merrily.
The plywood is up on magnetic punk spikes to give the fumes plenty of room to disperse without making too much of a mess on the bottom surface. Unfortunately, the flame can blowtorch the cut parts after they fall through onto the honeycomb.
Another view shows some smoke doesn’t make it through the kerf:
Laser cut plywood flames – B
The bulk of the flame seems to trail behind the beam as it cuts through the wood, which isn’t surprising:
What else would you call things that raise the back of a Moonlander keyboard:
Moonlander elevators – installed
The Moonlander comes with two adjustable struts, one for each keyboard half, which should hold the things at whatever angle you like. I put wood blocks underneath for better support, but finally gave up and laid out a quartet of elevators on scrap 3 mm acrylic:
Moonlander elevators – laser cutting
The upper hole is 30 mm from the base and that’s the only one I needed, so they’re even easier to make than they look.
A backlash test found on the LightBurn forum puts the machine through a series of difficult maneuvers:
Backlash test
That’s burned on the back of a paperboard box at 400 mm/s @ 15%/10% power, which is slightly too intense for the smaller patterns.
The key point is that the machine has no detectable trace of backlash, with all the opposing lines matching up and equal spacing regardless of the approach direction.
The larger targets on the right let the machine reach a speed closer to the nominal 400 mm/s around the arc, so the cut along the tape tab after the right-angle turn comes out a bit wobbly; the smaller targets are fine. The red lines are just under 0.5 mm wide and the wobble is on the same order, so it’s pretty close to being OK.
The pebble caught in this crater has worn flat on the outside and started cutting through the tire carcass into the tube:
Schwalbe Marathon Plus – Stone gash
Gotta love those Marathon Plus tires!
So my bike now has a new tire, tube, and rim on the back.
The old spokes looked OK and tightened up without incident. For the record, the Park TM-1 tension meter puts the drive-side spokes at 25 and the other side just under 20, with the total runout & wobble under a millimeter.
Having now replaced all four rims on our bikes over the course of two years, I sawed the three rims still awaiting recycling into samples:
Tour Easy – 30 k mile rim wear
Unlike contemporary bikes, our Tour Easy recumbents have rim brakes and those original rims are pretty well worn out; they’re not supposed to be concave like that.
The Smell of Molten Projects in the Morning 