We’ve seen a few advances in the finishing processes of 3D prints over the last few months that result in some very attractive parts that look like they were injection molded. Smoothing ABS prints is now a necessary skill for anyone looking to produce professional parts, but those of us using PLA for our RepRaps have been left in the cold. After some experimentation, the guys over at protoparadigm have come up with a way to smooth out those PLA prints, using the same technique and a chemical that’s just as safe as acetone.
Instead of acetone, the guys at protoparadigm are using tetrahydrofuran, or THF, as a solvent for PLA. Other PLA solvents aren’t friendly to living organisms or are somewhat hard to obtain. THF has neither of these qualities; you still need to use it in a well ventilated area with nitrile gloves, but the same precautions when using acetone or MEK still apply. It’s also easy to obtain, as well: you can grab some on Amazon, even.
The process for smoothing PLA prints with THF is the same as smoothing ABS prints with acetone. Just suspend the print in a glass container, pour in a tiny amount of the solvent, and (gently) heat it. The evaporated solvent will smooth all the ridges out of the print, leaving a shiny and smooth surface. You can, of course, hand polish it by dedicating a lint-free cloth and a pair of gloves to the task.
When you want to print a 3D object you run into problems if there is a part that has nothing below it. The hot, soft filament coming out of the extruder will droop with gravity if not given something to rest on while it hardens. The solution is to use a second material as a support. But then you’ve got to find a way to remove the support structure when the printing is done. That’s where this beauty comes in. It’s a heated stir plate for dissolving PLA.
The PLA is printed using a second extruder head. Once the part is cooled [Petrus] puts it into a heated bath of sodium hydroxide (lye). The solvent will remove the PLA but not harm the ABS. Speaking of ABS, [Petrus] also mentions that this can double as a temperature controlled hot plate for polishing ABS prints using acetone vapor.
There’s all kinds of good stuff inside of this beast so do check out the full plans to learn more. Our favorite part is the stir bar which is a piece of threaded rod and a couple of nuts. To make it safe to submerge in the chemicals he 3D printed a pill-shaped enclosure for it.
[Chris] has been having some real problems getting PLA to stick to the build platform of his Printrbot. This is of course not limited to this brand of printers, and affects all extruder-based hardware using the PLA as a source material. He came up with a couple of ways to fix the problem.
The first is something we’re quite familiar with. The image above shows [Chris] applying a thin layer of hairspray to the platform. This is a technique the we use with our own 3D printer. The sheets of paper are used as a mask to help keep the sticky stuff off of the threaded rod. For more info on the hairspray trick [Chris] recommends that you read this article.
The second technique uses a slurry made from saturating a bottle of acetone with ABS leftovers. In the clip after the break he shows off a glass jar of the solvent with scraps from past print jobs hanging out inside. After a couple of days like that it’s ready to use. He takes a paper towel, wets it with the solution, and wipes on a very small amount. He does mention that this will eventually eat through the Kapton tape so apply it rarely and sparingly.
Continue reading “Making PLA stick to a 3D printer build platform by using hairspray or an acetone ABS slurry”
If there’s one problem with the RepRap, it’s the cost of filament. Sure, there’s also the computationally difficult problem of slicing 3D models, but a 5 to 10 times markup on turning plastic pellets into filament is the biggest problem. It’s even a bigger problem than the problems of compatibility and interchangeable parts that comes with everyone forking a ‘standard’ printer design dozens of times. The cost of filament, though, is the biggest problem, right up there with RepRap developers focusing nearly entirely on different printer designs instead of the software, firmware, and electronics that are also vitally important to the RepRap project.
Nearly a year ago, we caught wind of a competition to create a home-based filament manufacturing station that takes cheap plastic pellets available for about $5/kg and turns them in to 3D printer filament that usually sells for $50/kg. A winner for this competion has finally been announced. The winner, [Hugh Lyman] just won $40,000 for his home filament creation station, the Lyman Filament Extruder
The goal of the Desktop Factory Competition was to create a machine that produces filament suitable for 3D printers with a total build cost of under $250 USD. [Lyman] met the goal by using a few motors, 3D printed parts, a PID controller, and off the shelf auger drill bit (that’s the actual model and supplier he used, by the way) that is able to reliably churn out plastic filament.
If you want to build your own Lyman Extruder, all the plans are up on Thingiverse, but LulzBot, the awesome people who gave us a 3D printer, hope to sell a pre-assembled version of this extruder sometime in the future, hopefully with a chain guard around that sprocket.
There’s one problem with the popularity of plastic-extruding 3D printers such as the RepRap and Makerbot; since they’ve become so popular, the price of plastic filament has skyrocketed over the past few years. Without a way to produce filament at a hackerspace or home lab, the price of 3D printed objects will remain fairly high. Project Spaghetti hopes to rectify that by building a machine to make plastic filament for 3D printers.
The folks behind Project Spaghetti – a loose amalgamation of makers going under the title of Open Source Printing, LLC – have successfully built a machine that is able to produce short lengths of plastic filament.
Early machines used a plunger to press small pellets of ABS plastic through a heated steel pipe to produce filament. There are a few problems with this approach, especially when the temperature is set to 480F, but the team was able to make a bit of filament with this design.
Although the team is using a piston to force melted plastic out of a nozzle, they do have a screw-drive ‘plan B’ in the works. This design should allow for continuous extrusion for theoretically endless reels of plastic filament, every RepRappers dream and a neat way to win 40 grand. Continue reading “Making plastic filament at home”
We visited the MakerBot Industries booth to give them one of our badges (post pending), say what’s up and meet the creators behind the creators of our lapel-sticking creations. They were excited to see us, so excited in fact that they gave us a small spool of the PLA they are about to carry in their store.