Random musings of a software developer
Someone had a dual-monitor desk stand for sale (something like $10) and I bought it without much in mind for it. I liked the sturdiness of it and it’s been in my foyer for several weeks.
Yesterday, I designed a VESA mount in PLA and printed it over the span of fourteen hours and it turned out to be perfect. It now accommodates the first of two filament spools for the 3D printer.
The dirty little secret in the world of 3D printing is that things go wrong (a lot). This week’s problem to solve is the frequent cross-threading of the rolls of filament itself. Filament manufacturers don’t seem to understand the requirements necessary for doing this right so it’s up to the rest of us to fix the problem ourselves.
Each time cross-threading occurs during a print job, you lose the entire print since the feeding of that filament just stops. In this photo, the printer has actually lifted the entire holder assembly off the workbench:
To deal with this problem, I decided to re-invent the spool holder itself by changing the inner topology from a rectangular shape to parabolic. It now delivers filament in a straighter path to the filament sensor block on the printer, minimizing cross-threading.
The reusable spool guide design incorporates eight individual parts which attach together using standard aluminum hex head bolts.
Decided to 3D print a cookie cutter for a surprise later. Yum. It might have cost $0.25 in filament at the most, perhaps three dollar’s worth of cookie dough, some frosting and the time to make it.
That title quote is by Jean-Paul Sartre but I was torn between that one and the following for this post:
One great use of words is to hide our thoughts.
~ Voltaire
Was thinking it would be fun to design/print a Scrabble set this morning. And while it was printing I thought it would be even cooler to print extra letters and use them for signage, say, on your desk at work or something. Pretty awesome toy if you think about it; you could have a mugful of letters on your desk and say how you feel on any given day.
I had to tweak Cura’s (slicing software) printer profile to get the holder to print within the print volume since it’s pushing the limits. And I used the new GetToDahChoppa program I wrote for the multi-color printing.
Anticipating a dual-extruder upgrade soon for the Robo C2 printer—imagine printing in two colors for the same part—I’ve designed and printed a dual-spool holder for those two filaments. It’s an upgrade for the printer and works much better than the original holder.
The original spool holder stuck out of that rectangular hole in the back of the printer, sometimes falling out during the middle of a print job. Aesthetically-pleasing but impractical, I’ve now replaced the original.
I’ve created step-by-step instructions for creating two versions: one for the full kilogram rolls and one for the half-kilogram variety.
Another design challenge with the Robo C2 printer is the way that the print bed is cantilevered from the back of the printer. It’s a bit like a diving board and similarly wobbles at its front-most extremity as you’d expect. This isn’t really optimal for 3D printing because it results in poor quality with taller parts and especially those which are oriented toward the front of the printer.
I’ve therefore designed a cantilevered stability plate to afix to the bottom of the print bed itself which should provide some firmness in this dimension. Eight M3 type aluminum bolts are the only thing needed other than this part.
Apologies for the lull in blogging but I’ve been fussing with Autodesk Fusion 360 lately. The current design in 3D printing would be an authentic-looking Knut from the Harry Potter film series.
So for the first coin, I thought I’d try the copper/bronze-looking one since I have some copper-infused PLA filament, some copper-infused artist liquid-stuff and plenty of pennies for electolysis at the end.
I managed to do the front side with a convincing Tratello font for the text and a complete rendering of the details. I will attempt to do a photos->mesh conversion for a better face, however.
A raft on the part’s bottom is often necessary so that the part will adhere nicely to the workspace. Unfortunately, that tends to mar up one side of a coin so that approach doesn’t work here. I’ll then want to slice the coin into front/reverse and print both halves.
The standard weight of a plastic coin wouldn’t feel right in your hand so the strategy would be to put something inside of two halves to make it seem realistic.
After the actual print, everything you do to make it nice is called post-processing. In this case, this might include assembling the two halves of the coin with glue of some kind, sanding, tumbling in a magnetic rock tumbler device with copper-plated media for a few days, brushed-in application of a copper-infused liquid for touch-ups and finally, wiring and dropping each into an electrolysis chamber so that ionic copper may bind to the outer surface.
So far, I’ve got one half of the Knut designed and made two test prints. The inside space perfectly matches a penny (which adds weight to the coin and helps to speed up the print time). The filament produces a metallic matte finish and doesn’t appear to have the tell-tale lines you normally might see in a printed part.
The bad news is that my 0.4mm extruder nozzle is too big for this job. I need a tiny opening to print at a higher resolution. So I’ll be ordering some smaller nozzles like this 0.15mm version.
I have a spare power supply from a computer as well as a recycled hard disk. I’ll remove the top from the disk and then glue some very strong magnets around the top perimeter in alternating orientations every 60°. I’ll need to use my existing rubber drum from a rock tumbler kit for the media and parts.
As for the media, this will be a combination of penny-magnet-penny glued sandwiches plus a collection of copper-clad screws (over steel). This then makes everything inside want to give up copper in the millions of collisions with the copper-infused plastic parts, as influenced by the external rotating magnetic field. After a couple of days, the coins should have a healthy amount of superficial copper added plus a polishing of the printed detail.
