So last week the SupplyFrame office Prusa i3 finally gave up the ghost — the z-axis threaded rods unwound themselves from their couplers and the whole thing fell apart. So we needed to get some better couplers as our tubing wasn’t going to cut the mustard anymore. Thankfully Pasadena is full of 3d printer people! Within a few blocks of our office we have New Matter, DeezMaker, and a soon to be announced 3d printer from ToyBuilderLabs.
The one everyone is talking about right now is New Matter who recently announced an already successful fundraising campaign for the first run of their $250 3d printer, the MOD-t. This has been making the rounds recently due to its low price and stated aim of bringing 3d printing into the home of the masses (a tale as old as time, right?). It’s a lovely goal for sure, but they will definitely have their work cut out for them, but perhaps this is the team to make it happen? We decided to head over to their lab since it’s just around the corner from our office and see if we could get them to print some new couplers and maybe take a look at their printer while we were at it, videos and pictures after the break!
The mechanics
They have been working with frog to design a 3d printer that people will be comfortable to have in their homes, and we think they’ve done a pretty good job on that front. It certainly looks pretty, but we’re hackers so we wanted to see under the hood. While they don’t have a working version of the final model yet, we did get to see one of their prototypes up close and personal. We honestly haven’t seen a 3d printer built with fewer components than this, they’ve really managed to boil it down to the bare essentials, while still keeping it functional. Take a look at the pictures…
Their key mechanical design breakthrough is their rack and pinion driven XY bed, they’ve managed to do away with all the bearings, smooth rods, and threaded rod screws and replaced them with a simple mechanism of two pinions that the bed sits upon. The bed itself is a simple block of plastic with the racks attached underneath, this sits on the pinions and is then driven around the XY axes as they turn. This really is quite ingenious, but we had to wonder if this would have any negative issues, for instance could dirt and other crud get stuck in the gear system? Was there any backlash in the gears? Does the build plate bounce around at high speeds?
We asked [Steve Schell], New Matter’s CTO about this:
Any small debris that finds its way onto the pinion rods tends to get swept out of the way as the table slides along the length of the rod (remember the rack & pinion interface both meshes and slides). Large debris could cause an issue, but we just haven’t seen any real source for this type of debris in our testing to date.
We also took a close look at the gear system as it was moving around and there is very little backlash (if any) in the system at all, [Steve] says they were very careful to select the right rack and pinions and ensure their assembly process works to tight tolerances and it seems to have done the job. Finally the build plate is apparently heavy enough to keep it down on the pins even at higher speeds. They get 80mm/s print and 200mm/s maximum slew speed out of the printer which is fairly respectable given the design and they say that they haven’t had any issues with the bed at this speed. Check the video out below for a closer look at the bed during printing.
The removable bed really is a great benefit of the rack and pinion design, no more struggling with the printer to remove a part, just pop the bed off, set it aside to cool and pop another bed in to get started printing again straight away. We asked [Steve] if they planned on selling replacement beds, but they weren’t yet sure on the price or when they would be available.
We do plan to sell spare / replacement beds, but haven’t set a price. It’s not a very expensive component, but we’ll need to factor in packaging, handling, shipping, etc. in order to determine a retail price.
We were also very concerned that we saw no mechanism to level the bed, here’s what Steve had to say:
Since the bed is moving in both of the horizontal axes relative to a stationary extruder, there’s absolutely no need for bed leveling. Our testing confirms this, as we’ve done nothing in the construction or calibration of our prototypes to correct for any sort of bed leveling. All that is required for good consistent adhesion of the first layer is (a) straight pinion rods, which we control with the vendor and our manufacturing process and (b) tight tolerances on the build plate and its molded-in gear racks, which we also control in our manufacturing process.
This brings us round to their manufacturing process. We all prefer open source designs here, and sadly the MOD-t is not open source. But it appears this is largely to due with the manufacturing processes they will be using to produce the machine. While they could open source it, who is realistically going to spin up a fab house with custom boards, injection molded parts, and machined assemblies to reproduce the design? They have also been working hard to find the right suppliers that will allow them to hit their $250 price point and not go broke doing it. For instance, they’re using optical encoders with their DC motors for accurate positioning, this is usually quite expensive on small runs but since they are planning for tens of thousands they can start getting to scales that make it cost efficient over stepper motors.
The software
The software side of things is still in heavy development, they plan ultimately to have a single ‘push button print’ approach from their store in the browser. This really is a necessity for the device to reach the mass market as we really don’t think you can get a wider consumer market to use Slic3r or Skeinforge! So they are keeping the store very tightly controlled, everything on the store should print perfectly out of the box, no calibration, no messing with settings etc. As such the store is essentially DRM controlled, more out of necessity than anything else.
That’s not to say that the machine itself is though, we’ve been assured it takes standard GCode and standard PLA 1.75mm filament. Any controlling software you would usually use on your reprap or similar device will work. Of course, you’ll then be stuck tweaking settings as you are with all 3d printers, but that’s the trade off.
The prints!
New Matter were kind enough to print us 2 new sets of Whosawhatsis’ Buko Z coupler v2 for our printer, these came out fairly nice and were not too difficult to install in-place on our machine without disassembling everything. Of course we screwed up and these couplers don’t fit with our X axis parts meaning we need to raise the bed and spend yet more time fiddling with the printer rather than actually — you know — printing stuff.
Catch the video below for some up close action shots of the MOD-t prototype and let us know what you think of the mechanical design in the comments!
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