Category: Electronics Workbench

The process of switching the laser cutter from “normal” operation to the Ortur YRC-1 rotary and back again requires a checklist:

Which looks like this:

The same thing as a PDF will be more printable or readable.

Previous posts cover what goes into making it work:

• Adding a stepper driver & mode switch
• Rotary wiring, cables, and connectors
• Adding a home switch in a custom cover
• Using a 3 inch focus lens for more clearance
• Printing petite chuck jaws for less interference
• Printing an autofocus pad
• Printing conical tailstock centers
• More on Home Offset and Focus Distance
• Tweaking the autofocus pen = switch

Notes:

• Always disable the rotary’s stepper driver before connecting or disconnecting its cable.
• The Ortur YRC-1 rotary has a pulley ratio of 1:3, so the step/rev value is three times the DIP switch setting on the stepper driver. For this setup, 1600 → 4800 step/rev.
• The honeycomb frame is a parallelogram, not a rectangle. I align the cardboard baffle / fixture to the bottom edge of the frame and the rotary to the bottom edge of the fixture opening, but your machine will be different. The angular alignment may not be off by enough to matter, but consistency is a virtue.
• The Rotary.lbset and Linear.lbset files live on a file server with daily backups. Such backups will come in handy when you inadvertently overwrite one of those files with the other one. Trust me on this.
• The Rotary.lbset file does not have Rotary Mode enabled, because the KT332N does not home the Y axis in that mode. If your rotary lacks a home switch, then it doesn’t matter and you’re on your own.
• The KT332N controller has a [Reset] button that allegedly does a power-on reset and reloads all the changed Machine Settings. This sometimes does not work as expected: power-cycling the controller is the only way to be sure.
• The autofocus operation must hit the focus pad, which can be ensured by positioning the pen near the pad, jogging the platform a few millimeters under the pen, tweaking X and the gantry while peering down parallel to the pen, then doing the autofocus.
• The focus pad has a crosshair clearing the chonky Ortur 3-step jaws, but I set the controller’s [Origin] at the foot of the pad’s base for more elbow room.
• The Z axis distance field in LightBurn’s Move window does not accept formulas, so you must divide the workpiece diameter by two. Using a focus stick to verify the ensuing nozzle-to-workpiece distance is a Good Idea™.
• The LightBurn Job Origin dot must be on the top row, because the KT332N does not go into regions with negative coordinates. With the chuck on the left and the [Origin] just to its right, the upper left dot locks the LightBurn selection to the physical limits.
• Selecting [Use Selection Origin] puts the Job Origin at the upper left (per the dot) of whatever you’ve selected, not everything on the LightBurn workspace. [User Origin] then locks the selection to the [Origin] set on the controller.

As the saying goes, it works for me …

A box of air filters that Came With The House™ (and fit nothing therein) surfaced during a recent heap probe and prompted a quick-n-dirty project:

It replaces a tired box fan (barely visible at the top) that’s been shoving air around the basement to equalize the humidity.

The quintet of 140 mm fans seems quieter, although they don’t move quite as much air. Given that I have no way to know how much air circulation is enough, it’s likely sufficient.

The strip of black tape covers a hole for the knob on the fan power / speed control, although I cranked it up to full throttle and expect to leave it there:

The controller sits on a platform cut from 1.5 mm cardboard:

The 3D printed holder came with the controller. I cannot imagine how they have enough time to print a holder for each controller; maybe it’s a QC check for a 3D printer manufacturer.

I intended the controller to sit on the other side of the middle fan, but realized I had to cut the opening after mounting the fans and got the chirality wrong; the wiring in there layout leaves something to be desired.

The fans mount on a sheet of cardboard cut from one side of a Home Depot Extra Large Box and the bottom of the filter box comes from the other side. Because I don’t have a deep emotional attachment to the filters, they’re attached to each other (and the bottom sheet) with hot melt glue. I do have a slight attachment to the fans, but four dabs of glue hold each one in place. More gaffer tape holds the fan sheet to the front of the assembled box, in the unlikely event I must get in there again.

Hey, it’s Christmas: good things come in boxes, right?

The focus “pen” = switch on the OMTech laser stuck out far below the nozzle:

The nozzle is 18.5 (-ish) mm above the surface with the laser beam focused to a tight spot. The brass (-ish) tip of the pen flew about 5 mm above the material, requiring considerable attention to the placement of magnets, clamps, and similar accoutrements around the material on the platform.

Having dismantled the pen while replacing its wiring, this seemed like a good time to figure out how to get more clearance under its tip.

Removing the pen nose shows the tip on its 3 mm screw inside the spring pushing the tip downward:

I replaced the original spring (on the bottom) with a softer spring, mostly because the tip exerted what seemed like entirely too much force on the material. That makes no difference for acrylic & plywood, but anything squishier required deploying the focus gauge after I remembered the problem.

The other end of the screw is impossible to photograph in situ, but the tapered head seats in a recess leaving several millimeters of air below the proximity sensor. I made a little steel slug to reduce the pretravel by filling that gap:

The spigot on the slug (turned from 7/32 inch steel rod) aligns it with the screw head, with high-viscosity cyanoacrylate adhesive holding it in place:

The surface finish of my slug matches their tapering, so I figure it’s about right.

A setscrew near the top of the pen clamps the proximity sensor with a few millimeters of adjustment:

The slug reduces the pretravel to nearly zero with the sensor at the bottom of its range.

The brass tip had been twisted onto the screw as far as it would go, so I cut a few millimeters off the screw to put the tip closer to the pen nose:

Even with reduced pretravel, the tip nearly vanished into the pen body before tripping the sensor, so I unscrewed it two turns = 1.4 mm.

With the pen back in the machine and plugged in, measure the switch travel with a step gauge:

Protip: Measure the as-cut height of those steps, then either shim the bottom of the gauge with tape of a suitable thickness or add that much to the layout and cut another set.

With a good step gauge in hand:

• Slide it underneath to just touch the tip
• Note the measurement = A
• Slide it further until the switch trips (red LED on)
• Note the measurement = B

Figure B-A, round up to the next millimeter, then set that value as the Home Offset for whatever axis moves the platform. My tweaked pen had 2.5 mm of travel, so I used 3.0 mm:

Adjust the pen position to put the tip more than the Home Offset below the nozzle (I picked 5 mm) to ensure the switch will trip before the nozzle contacts the platform, then do an Autofocus.

Measure the distance from the nozzle to the platform (mine was 5.5 mm), subtract that from 18.5 mm (the known focused distance for my laser head, as above), and set that as the Focus Distance:

Another Autofocus should then put the nozzle exactly 18.5 mm (or whatever your machine needs) off the platform / material.

This shows the pen now flies 5 mm below the nozzle:

The step gauge shows it’s 13.5 mm above the platform, much better than the previous 5 mm.

The switch trips juuuust before the nozzle hits the material:

I should lower the pen a millimeter, but that’s in the nature of fine tuning.

Happy Dance!