Upgrading a k40 Laser Cutter Bed

At about $400, a k40 Laser Cutter is a wonderful low-cost entry into the world of laser cutting and engraving, and also a great platform for hacking and upgrading.

The biggest limitation of a k40, however, is the size of the engrave-able area, which is limited to just 8x12 inches.  This suffices for many projects, but often is a source of frustration when trying to create something larger, or even just for efficiently using materials that come in 12x12 sheets.

While enlarging the k40 bed is a common desire, the most popular upgrade along these lines is a full 12x24 rebuild of the laser gantry, gutting both the electronics and gantry parts of the case, building a custom gantry in its place, and relocating the electronics to an external case.

12 x 12 cutting / engraving area

For myself, I wanted to try something more restrained; a 12x12 cutting area retrofit to fit entirely into the existing cutting bay.  I found inspiration when I came across a budget laser engraver kit for just $99 on Amazon.

When assembled it would be tight, but seemed like it would fit in the existing k40 bay with a little encouragement.  My plan was to laser cut some adapter pieces to hold the y-axis mirror and laser head, then adapt the gantry, gut the k40, and swap in the new for the old.

Unfortunately, after gutting the k40 internals, I found out I had mis-measured.  The back of the k40 has reduced vertical clearance due to the laser tube compartment hanging down from above, and the x-axis from the diode laser could never fit underneath it to allow the full 12" of y-axis movement I wanted.

The only way I could get it to fit was to reuse the original k40 x-axis, mounting it in place of the one from the diode laser with some acrylic adapter plates.  

My laser cutter was now inoperable, so I hand fabricated various pieces from acrylic and plate metal to hold everything together well enough to make the laser cutter operational again.  This included a new mount for mirror 2, attaching it to the end of the x-axis...

and a holder for the laser head, adjusted to tuck underneath the laser tube compartment.  These would get rebuilt later once everything was up and running, but in this early version, it was finally fully functional after a fair amount of tweaking, and had a full 12x12 cutting and engraving area I wanted.

Movable cutting bed (z-axis)

After getting the laser operating again with the enlarged cutting area, my attention turned to the cutting bed.  Since I sometimes cut 1" foam sheets such as for camera case inserts, I wanted a bed that could move up and down to adjust for different material thicknesses, all without affecting levelness.

My idea was to create a frame for the bed that would be supported on all 4 corners by captured nuts and threaded machine screw legs that turned in sync by gears driven by a circular toothed belt.

A small gear-motor would drive the gears in either direction in response to a DPDT toggle switch to move the bed up or down.

A spring-loaded idle wheel maintained tension on the belt, and could be released it I needed to turn one of the screw legs manually to level the bed.

Here is the completed bed (upside-down), built from scrap aluminum fence post material and the above-mentioned gears, belt, and motor.

And here is the completed bed right-side-up during motion testing.

Catching up on Small Projects - Oculus/Meta Quest

I haven't written in a long time, and thought I'd do some quick posts of small projects I've worked on.  The first is for a number of small projects I've completed for the Oculus (now Meta) Quest VR headset.  

Like many people, my family got our first Quest 2 during the pandemic as a way to "get out" more during lockdown.  To this day, I still use my Quest 3 fairly often, sometimes playing for a whole afternoon on the weekend when I'm hooked on a particular new game.  During such long play sessions, opportunities to improve the experience presented themselves, leading to a few quick projects.

3D-Printed Back Weight

The first quick project was a way to help balance out the headset to make it more comfortable.  While there are a number of great after-market head straps to adjust pressure points and fit around the head, the headset still tends to be front-heavy, which I found would give me a neck ache after hours of continuous play.  

While some people use external battery packs strapped to the back of the headstrap, I like to play plugged in, and created a curved, hollow 3d-printed back-weight which I filled with copper slugs.

Staying Charged when Playing

When playing plugged-in, the choice of cable and charger are critically important.  In order to play continuously, the Quest must communicate with a smart-charger and coax it into a higher-voltage fast charging mode instead of the USB default of 5 volts.  Otherwise, the battery will drain faster than it can charge and will die after a few hours.  To do this, one must have a USB-C charger capable of fast-charging, and exclusively use USB-C cables and connectors along the way.  This is because USB-C connectors and fast-charge cables have extra wires used for voltage negotiation, while old-style USB connectors do not.

Since a lot of chargers and cables lie when they claim to support fast-charging, spend an extra $10 for an inline USB-C Inline Voltage Meter to verify the charging current and voltage (hint: get one with the male connector on a pigtail, as ones sticking directly out of the device easily break off).  Here, we see a Quest 3 fast-charging at 12 volts instead of only five.

Also invest in short right-angle usb-c extension cable which you can attach to your head strap and leave permanently attached to the headset.  This will save wear and tear on the delicate USB-C connector, and act as safety disconnect mechanism when accidentally stepping on, or otherwise snagging the cable.

USB-C Rotary Charging Cable Connector

An unfortunate side effect of playing while plugged in -- especially with shooting or fighting games -- is getting the cable twisted all up.  While I've tried a number of magnetic swivel connectors, these tend to come apart too easily from the weight of the hanging cable, and none have supported the extra wires needed for fast charging.

To solve this, I came across slip-ring connectors, electrical components which can maintain an electrical connection to a rotating device.  They use sliding brushes to keep connections intact across a built-in rotating shaft.  This probably makes them too electrically noisy for data, but seemed ideal for power transfer.  I spliced one into a short USB-C extension cable, being sure to connect power, ground, SBU, and CC lines, creating a handy adapter that automatically unwinds any twists in the line while I play.

Golf Club Controller Extension

Recently, I've found myself taking a liking to a number of VR sports games for sports I've shown relatively little interest pursuing in real life.  Perhaps that's the point of VR: taking in experiences that are too expensive, intimidating, dangerous, or simply too much of a hassle to partake in otherwise.

One such game is Golf 5 for Quest, which I've found to be realistic and fun.  The one thing I wanted, however, was to have an accessory that extended the controller to give a place for my back hand for a more natural grip and swing.  There are a lot of existing "golf" controller accessories for Quest, but they generally fall into two categories:

• A fairly long golf-style club in which you attach the controller to its head
• Arms that extend the bottom of the controller primarily for Gorilla Tag but might be useful for golf too.

I didn't really want to have to attach my controller to something long and be swinging it around the room.  Not only do I hit enough stuff already with the controller alone, but pressing buttons to activate menus and such would suddenly become a pain.  The arm extensions seemed more like what I wanted, but none would work without removing the controller grips I already owned, nor would they feel much like a golf club handle.

This was a perfect excuse for me to use the Mole 3D Scanner I'd purchased about a year earlier as a gift to myself.  I used it to scan my controller handle with its silicone grip on, and build a snug adapter cup I could 3D print.  

The cup fits over the existing grip, making it quick and effortless to add or remove at will.  With the addition at the bottom of some threaded rod, nuts and a genuine golf club grip to slide over the rod, I finally got the simple extension I wanted.