I’ve read about sandblasted glass as a print bed surface elsewhere and when I stopped by at our local glazier lately I fetched a pane for testing. This kind of glass comes readily sandblasted from the manufacturer and can be purchased via most glaziers, I even discovered it at some of the hardware stores around. Peeling exhausted Kapton tape off our print beds every couple of prints during daily production workflow becomes rather annoying some day and with such good results originating from increased enviromental temperatures by a heated printer casing I decided to give polyimide-less options another try.
Printing ABS on the pure matt glass doesn’t stick much better than on smooth glass, but wiping the coarse surface with ABS-acetone-solution really makes the difference. While our Wade extruder derivative qualifies as a suitable dummy for serious warping tests it definitely made it big:
Zero warping! As extra benefits the parts get a nice matt and seamless finish at the bottom and can be detached without an air hammer in contrast to a Kapton coated platform…
This test was performed using the following parameters:
Heated print bed at 115°C for the first layer, 110°C for the rest
Heated chamber at 45°C during whole print
4mm sandblasted glass as print surface, wiped with dissolved ABS in acetone
White ABS filament, extruded at 255°C for the first layer, 247°C for the rest
Besides affordability as one major goal there are quite a lot of thoughts out there concerning the sustainalility of the RepRap replication process. It’s about using bio plastics like PLA, made from corn starch and beeing biodegradable, as thermoplastic extrusion material and reducing power consumption of our 3D printing machines.
Most parts of a RepRap can be made of PLA yet – at least for your own private 3D printer that should be capable of printing various things from PLA as well. If one attempts to print huge buildplates and max out the productivity of such a machine you won’t get too far without a heated print bed and preferably even a heated chamber for the whole printer though to prevent warping issues, and that’s where we sadly reach the limits of PLA, since it won’t withstand the high envriomental temperatures from the heated bed (up to 115°C), extruder (up to 255°C) and surrounding air (heated chamber, 45 to 50°C).
But there’s still the point of power consumption, which especially using a heated build plate can be drastically reduced by a simple housing for the entire printer (except electronics due to insufficient cooling, I suggest) that will double improve anti-warping as a heated chamber even without additional heat convection. Print bed temperatures of 115°C itself do easily lead to 45°C enviromental temperature inside the housing.
And while saving energy is good, using green electricity is even better.
This is why we exclusively run our printers with 100% green electricity provided by the german power supply company naturstrom. Of course every electricity comsuming device else at our sites are fed by the same eco-friendly power which means that even a good deal of the distribution process of our printed kits on ebay are operated with green electricity.
By the way: Actually this blog is hosted by the totally recommendable german server housing company manitu and their servers are eating 100% green electricity too.
Way ahead since first steps of our RepStrap we passed multiple milestones with both the RepStrap and our RepRap Prusa build and just printing won’t satisfy ambitions anymore.
So let’s have a take on print quality! X and Y axes proved quite sturdy so far, but there was still some serious trouble getting rid of wobbling at the z axis of a Standard Prusa, so I did it like a serious engineer would have done. Substitute threaded rods with professional TR8x1.5 trapezoidal spindles, support them with two stiffly mounted 608 bearings each and use a durable but flexible coupling to connect them to the stepper. This is where Sugru enters the stage!
On Thingiverse you can find various atempts to design a good performing, flexible z motor coupling, but one of those attracted my attention most: A spider coupling with rubber insert. This is fairly similar to how the professional couplings work – and I liked it. And I had Sugru – and I liked it even more! As cured Sugru becomes something rubber-like I decided to give it a try, took the source files from Thingiverse citizen MiseryBot’s spider coupling, modified them to have the nut traps better fit M3 nuts and of course made a simple Sugru mold for the insert.
It’s performing incredibly well! For the last few weeks our printers were buisy day and night printing our improved Prusa parts set for eBay and the Sugru couplings didn’t weaken a single bit. Z-wobbling is down to zero now and we’re achieving quite decent results in print quality.
Even though the first printer delivers brilliant results so far, we are in a hurry a little at the moment to get the set of plastic parts finished for the second printer, RepStrap’s first child. It seems that printing speed and quality of this machine is limited to the point we stand now, while this is not yet the performance we homed on. A too heavy x carriage and a rather poorly adjustable an inaccurate linear bearing system at all are two sites to be immediately worked on after the Prusa set is finished.
I made a short video of the printer in action yesterday:
We got rid of the spaghetti issues later…
What I am really comfortable with is the overall compact hot end we purchased via reprap-fab.org. I think it might be one of the most staightforward hot ends available so far and it works like a charme. Nozzle diameter is 0.35mm, printing standard white PLA after first runs using “premium PLA-90″ from Orbi Tech – more on that later. All prints up to now were succesfully made on a painter tape covered, unheated print bed.
As already mentioned next door we finally got things wired up and successfully finished our first test prints resulting in even better quality than expected (for the fifth or sixth run at all..). Since our RepStrap was meant to initially start another Family tree of RepRaps – at least one original Mendel Prusa RepRap 3D printer as the nearest milestone – Simon yet got busy in printing a set of Prusa parts from the latest iteration 2 while he is still tweaking settings for enhanced build quality. No major modifications were necessary to the raw build at all, the whole assembly largely works as intended. It does print!
This is part 1 of our documentation and I will have a closer look on used materials, tools and the frame. We will have one post for each detail like the three axes, linear bearings etc. the following weeks while RepStrap’s first child is being completed gradually.
It’s been quite a while ago, when Simon began raving of 3D printing, but it took me several weeks to get into it. Finally – on the fourth of july – almost 4 months ago i put down this via twitter:
This should be one of my last tweets untill today (apart from a few running stats by runkeeper…). Seriously infected by the idea of 3D printing Simon and me started thinking of some kind of homebuilt CNC 3D printer and ended up designing a RepRapMendel inspired so called RapStrap, basically made of wood, threaded rods, aluminium profile, a bunch of standard 608 ball bearings as they usually can be found in skateboard-wheels etc., using a hand full of standard amateur tools. This was ment to be a set of entirely low cost, easy to optain parts aside from some purchased items from industrial suppliers, such as stepper motors and electronic circuit boards.
This is where we got so far:
We recently finished the main frame including all three axes, mounted stepper motors and toothed belts. Time for electronics! For reasons of time saving we decided to order a preassembled mainboard (RAMPS 1.4) via reprapworld.com last week which expectedly should arrive these days.
Oh, did I mention that this is all about open source and open hardware? Well, in case of doubt, now i did.
There will be more information on the construction details later in the build process.
