Wednesday, September 14, 2016

DIY Faux Ceiling Beams and Laser Cutter Exhaust

Ever since I finished constructing the Monkey Cave, I've thought about adding ceiling beams to complete the look.

Not only could they help even out the difference in height due to the drop ceiling for the garage door, but they could give the Cave some interest and rustic appeal, kind of like Tuscany, minus Diane Lane and plus 3D printing and laser cutting.

Exposed ceiling beams, though, aren't really native to construction in this part of the country.  Instead, I found that most beams are really "faux" versions made of lightweight foam.  Light on weight doesn't mean light on the pocketbook, however as I'd have to spend over $500 to get them shipped, which seemed too much to me to pay for a little Tuscanification.

I also considered making "Box" beams from separate planks nailed together.  While hollow, they would still be quite heavy compared to foam beams.  More importantly, they wouldn't look solid, as it would be very difficult to hide the seams and finish the planks well enough to provide the illusion of the one piece beams I wanted.

Because no solution seemed ideal, for a long time I shelved the idea entirely of adding ceiling beams at all.

Recently, though, the opportunity to revisit ceiling beams came when pondering upgrades to my laser cutting setup.  Up to now, I used a flexible hose to route the fumes out a vent opening in a nearby exterior wall.  But because the hose crossed a walkway and was inconvenient to connect and disconnect, I wanted a more permanent solution.  I came up with the wacky idea of ducting the fumes across the ceiling instead, perhaps hidden within a faux ceiling beam.

Once again, I looked into foam beams, but found that their walls were simply too thick.  To get a big enough opening inside to provide adequate airflow, I'd need at least a 7x7 beam, which would be both too big and even more expensive than before.

Brainstorming for other materials to use, I came across a solution I'd never seen used before: PVC fence posts.  They're light, hollow, come in wood grain finishes, and Home Depot had some "end posts" for sale at a really good price.  They could work perfectly if I could tape up the side openings, connect some of together to extend their length, and perhaps add a faux finish on top to make them look more like stained wood.

To reach the ceiling, I also needed to add a vertical section.  For this I used some oval galvanized ducting.  I added pop-riveted sheet metal to close the ends and outlets at the top and bottom.

I mounted the assembled unit in a corner where there was an offset in the wall, allowing me to cover it up later by extending the front-most section.

To pull air through the duct, I mounted a 12V bilge fan into a short length of post, laser cutting an acrylic plate to seal the fan in place.

The fan would be mounted at the end of the ducting run just inside the vent opening in the wall.  The wiring to power it would run inside the ducting to the laser cutter.

To finish off the beams, I cut up the edge of a chip brush to make it ragged and used it to dry-brush two coats of mahogany gel stain onto post segments.

Despite being fairly loose and random with the paint brush, I was pleasantly surprised by the final effect.  Even with minimal effort, it looked very convincing even close up.

The vent opening in the wall was located a few inches below the ceiling.  To match it, the ceiling beam duct couldn't be mounted directly to the top.  Instead, I decided to use short standoff blocks--fastened to the ceiling with toggle bolts and wrapped with short sections of post--to hold the beams at the proper location.  Besides adding the needed spacing, the standoffs also provided a way to hide the joins between separate sections of pipe.

Designed specifically for faux ceiling beams, Home Depot sells rubber strips made to resemble distressed bronze straps with rivet heads.  Wrapped around the posts at the standoffs, they hide the seams while also providing the perfect accent detail.

I added framing around the vertical duct, covered it with drywall, and then taped and buttered the seams.
I sprayed it with a texture gun and let it dry. When painted, it nicely matched the adjoining wall.

Finally, I added two non-functional beams to complete the installation.  Here is the completed project.

Sunday, April 3, 2016

Hacking the K40 Laser Cutter

Bargain Chinese laser cutter/engravers typically come with funky proprietary controller hardware and software.  While more-or-less functional, the software tends to be buggy, and limits future support availability and upgrade options.

This post details my experience converting my K40 Laser Cutter to use open source controller hardware.

I chose an AZSMZ Mini to use for the new controller.  A variant of the Smoothieboard, the Mini is a compact unit whose built-in features make it very easy-to-use for this application.

I bought an AZSMZ Mini with stepper drivers and LCD display for $80 on eBay.  As my stock control panel was stark and minimalist, I only had to rearrange some of its controls to make space for the new LCD display.

The first step was to build a support for the Mini and LCD board to mount beneath the control panel.  I cut a bracket out of clear acrylic sheet and attached the controller and LCD to it with nylon standoffs.  In front of this, I mounted a new control panel that I cut out of two-color plastic sign-making laminated sheet.  Fortunately, a laser cutter is the perfect tool for doing this kind of work!

With the new control panel mounted in place, the next step was to hook up the controller board to the laser cutter power supply and motion control hardware.

Most others who have done similar upgrades have simply thrown out the old controller (in my case a Moshiboard) and painfully wired up the replacement directly to the existing power supply, stepper motors, and endstops, either directly splicing cables or using a Middleman board to aid in the process.

I, however, decided to take a different approach.  Instead of tossing all the old hardware entirely, I'd make my own adapter board that would allow me to switch back and forth between the old and new.  This would give me the flexibility to use the best software for a particular job, as well as options in case of an incompatibility or breakdown occurred in one specific software/hardware combination.

While power supplies tend to come in many variations, Moshiboard controllers do not.  By designing an adapter board to replicate the Moshiboard connectors, I could simplify the wiring and reuse the existing cabling as well.  While some laser cutters have separate cables for endstops and the X stepper motor, mine combines them in a single flat flexible ribbon cable, so I made an adapter for this configuration.

I was surprised to find out how cheap custom circuit boards are to produce if one is willing to wait a month for shipping from the Far East.

I downloaded and learned a free design program called FreePCB and used it to layout my custom adapter board.  It uses standard connectors and three CTS 206-125 dip switches to choose which controller to enable.  The idea is to switch all dip switches to one direction (with the power off!) to select which controller board to use.

I had 10 boards manufactured at SeeedStudio for a total of 20 bucks.

Wiring up everything was super easy.  The connectors on my adapter board line up in position and orientation with the ones on the Moshiboard, and are attached with short jumper cables.  The only exception is one of the two FFC ribbon cable sockets (the one that connects to the Moshiboard), which I designed to be rotated 180-degrees around so that it could be connected with a very short FFC bent neatly back over itself into a U shape, as pictured below.

Cabling Diagram

The AZSMZ Mini has a built-in voltage regulator, so a single 24V power connection powers both the stepper motors and electronics.  A single wire connects each of the X and Y endstops, and the stepper motors connect with simple 4-wire jumper cables.  The fire line on cutter is active low, so a feature of the Mini simplifies its connection.  The board comes with Mosfets that switch to ground for heater and fan connection, so I simply wired the fire line to the D8 bed heater terminal which is controlled by the PWM1 line.

With the hookup complete, the only thing needed to be done is configuration.

Smoothieboards support easy configuration via a config.txt file that is loaded at boot time from a MicroSD inserted in the main board.

Here is a copy of my configuration.  I had to make adjustments from the defaults to calibrate my motor movement and direction, as well as lower the acceleration and fire PCM rates to get the behavior I wanted.

And here it is the result; all connected up and ready to go.  I've made a few test cuts so far, and all is looking good!

Sunday, January 17, 2016

DIY Filament Factory

Winder box with Filastruder on top
As a frequent 3D printer user, I sometimes go through a spool of filament... well... faster than a redneck goes through second cousins at a family reunion.  While the price of filament has dropped significantly in recent years, raw plastic pellets can still be bought for less than one-third the cost.

To take advantage of this, a number of solutions exist for making one's own filament, including the Filastruder, a kit I received a prior Christmas.   Cleverly designed from largely ordinary hardware, the device extrudes filament by squeezing plastic pellets with an auger bit down a heated length pipe and out a small nozzle.

I'd always had mixed results using the Filastruder, however, as reliable use requires suspending it in the air over a large open space.  Otherwise, that the fragile molten filament can catch on furniture or itself, causing the resulting product to kink, snag, and be otherwise unusable.  This made it a real hassle to use, especially since even a slight air movement from opening a door or walking by could disturb the filament. With little Monkeys about, this was not a realistically achievable scenario.

For a more convenient system, I decided to try making a simple filament winder that could take up the filament as it is produced, keeping it neat and consistent.  While a commercial winder kit exists, I could justify neither the cost nor large wall hanging space it requires when set-up.  Instead, I chose to make one of my own design; one that didn't require the same finicky electronics.  It would also be a challenge which added to the fun.  Lastly, I came up with the idea of building it into a handy portable case that could house both itself and the Filastruder, keeping them free of dust and out of the way when not in use.

I created a frame for a simple plywood box, roughly 20 inches square and 6 inches thick.  I stained it and added a leather handle and some brass hardware, fancying that this gave it the appearance of some bizarre 19th century science experiment or instrument of medical quackery.

The toughest part of the design was finding a way to sense slack in the filament without disturbing the path of the filament itself.  As the new filament comes out molten, I found that even the lightest micro-switch I could find would transmit too much force back up the filament and cause a kink near the nozzle opening.

Other winders use linear sensors, but they require a microprocessor and more complexity, which I hoped to avoid. After trying mercury switches and considering magnetic reed switches and other sensors,

I settled on a lightweight 3D-printed "see-saw" rocker that I weighted down slightly on one side.  The filament moves in a loop down the left side of the box, across the bottom, and up the right side.  When the filament develops too much slack, the bottom of the loop pushes down on a curved acetate surface glued to one side of the rocker. This lifts up the other side, raising a shutter that exposes a CDS-cell light detector to a single LED light source.

The cell is connected to a solid state relay that drives a small gear motor and the take-up spool.  I also added a cheap $5 PWM motor speed control board to allow fine-tuning of the motor speed.

To evenly guide the filament onto the spool, the filament passes through a short length of tubing mounted onto a hinge.  As the hinge moves, the filament comes out at a different place on the reel, keeping it from bunching up in one place.

The hinge, in turn, is linked to a carriage, that moves up and down along a worm gear (threaded rod) driven by a second gear motor.  Two momentary limit switches keep the carriage from moving too far in either direction. They simply switch on and off a DPDT latching relay, wired in a way (one on, one off) so that the motor reverses direction when either switch is hit.

After my initial tests, I also added a small, spring loaded clamp to keep the filament under tension.  This was needed to keep the filament tight on the reel.

Here is the completed winder case.  When in storage, the Filastruder fits neatly inside with hanging space for an empty or full filament spool.

When I'm ready use it, I simply set the extruder on top of the case and pass the new filament down through a hole in the top and loop it round to the winder inside.

I was surprised how well it worked right off the bat.  The rocker assembly tends to stay right on the edge between on and off, moving ever so slightly to periodically activate the take-up motor.  The movements are so small that the filament path moves very little, leading to the most consistent filament than I've ever made before.

I've already successfully used it to create two one-pound (half-size) spools. I'll still probably buy some filament, particularly for special colors and specialty plastics.  When I need simple black or white filament, however (the colors I use the most), from now on I'll probably just make my own.