Piper Cubs are a classic taildragger. This is an electric powered model by eFlite. About 1/7 scale and powered by their Power 25 motor. Battery pack is a 3S 3200. An older ARF designed for the NiMH battery technology, with the new LiPo battery packs it is reported to have flight times up to 17 minutes. A plane worthy of wearing the taildragger bee.
I was inspired by the user friendly GUI in K3D. Creating object shapes in K3D was pretty easy. However, it doesn’t have a handy export to the STL format. In fact, it took a while to find the way to export to an .obj file which Meshlab can import and convert to STL. And along the way I learned a few lessons.
In K3D, the export to the .obj format is accessed through the create mesh > objmeshwriter. This creates a thing that can be edited. Key input is a mesh and key output is linked to a file name. A subtle point here is ONE mesh is the input. Therefore, if the file has several meshes they must be merged two at a time into one before being input to the objmeshwriter. It is good to know that early on, as often the same shape can be created by distorting one mesh rather than merging multiple meshes.
Once the object is finished and consists of one mesh, then the objmeshwriter will save a copy with the specified file name as an .obj file. However, I think a bug in K3D results in a mirror image along the X axis (at least in my Ubuntu Lucid version). This threw me for a while, but once I figured it out I just import again and save again to an .obj file and it is corrected.
The .obj can then be imported to Meshlab and saved as an STL file.
The STL file can then be imported into ReplicatorG. I wasted a bit of time here before I discovered that although the units in K3D were noted to be meters, ReplicatorG automatically assumed mm. So I need not have wasted my time trying to scale the objects down.
All open source, from creation to extrusion.
- the MuseAfter a few days to play with software and the Thingomatic, I’ve learned a bit about it’s strengths. The first thing that amazed me was I only had four or five failures in the first twenty things made. Twice the filament stopped feeding on very long prints over two hours. Snugging the feeder screw back up fixed this but the prints were ruined. If I had been very clever and really good at G code I could probably have restarted the prints, but I did not.
The other failures were very tall prints with very narrow bases. If the base comes loose then the head can drag the print around. Printing on a raft instead of trying to lay the part directly to the build platform fixed this. In some prints, orientation of the part could help this too.
I learned that the best looking parts have bold details. A Makerbot M coin I downloaded from Thingiverse printed very nicely. When I tried to print coins with finer lettering I got varying degrees of quality. If the lines became too fine, then nothing was extruded. So, in general, when designing stuff, think bold. Details that are at least 3 or 4 mm will print better. Or, learn G code which would allow for the printing of one single extrusion width and detail.
I also got better quality putting letters on top of a flat surface rather than having intersections. Though the STL file looked the same, with intersections Skeinforge tries to follow the contours of buried detail and the flat surface surrounding the detail is not quite so clean. Setting the letters on or just above the flat surface will cause the G code to lay a flat surface with straight and smooth passes. Then it will go back and extrude on top of it. A very very small gap will disappear as the hot plastic drops, provided it is not so great that the plastic cools on the way to the surface. A gap of 0.1 mm should be no issue.
One cool part I found on Thingiverse is a chicken head knob. There are ridges, but overall quality is good enough for a cool custom knob and the strength feels useful.
My Makerbot 3D printer was finished in about 20 leisurely hours over one week. I went very slowly when I got the electronics portion. I was extremely impressed with how the laser cut plywood bits went together. Fit was great, and the box like construction was very square and solid when done. All rods and bearings went together with no binding.
The online instructions were very thorough, so I have not included in progress pictures. There are only a couple of things I would suggest for anyone building a makerbot. The power supply had been updated, and needed a couple of holes drilled to fit right. This is the only thing that did not bolt right up, and it seemed due to Makerbot upgrading the power supply (which was very impressive). The nuts vibrated off of my build platform, so I will add some thread locking or nylock nuts. The only other thing I got backward was the direction of the threaded bushiing for the Z platform (it should face up). This was a little tight to fix once assembled, but not too bad.
Only one fit was tight. A T-slot was close to the slots for the Y axis stepper motor. The fix was fairly easy. I assembled it the other way around with the head of the bolt in the T slot and ground half the head of the bolt away. Remarkably little fitting of this kind was needed to complete the kit.
I highly recommend building with the acrylic or heated build platform first, before trying the automated build platform. My 3rd print had some negative Z data in it and caused the head to crash through the build platform. It still works, but an automated platform would have had damaged film. Lesson learned, I now raise parts and drop to the platform to ensure no negative data.
After finishing the build, I took a break. I expected some issues and wanted to have the patience to work through them. First check - XY table was reversed. Invert in the software, done. Next check was fine, the calibration routine worked perfectly. The extruder worked. Time to print something. My first print came out great!
I am very impressed by the quality of the kit. There is extra Kapton tape, parts to make your choice of build platforms, it even includes a USB cable and filament to get you started! It was very complete and the online instructions were excellent. For anyone that wants to assemble (as opposed to build/tinker/design) a working 3D printer I can recommend the Makerbot. In particular, they also matched the controller boards, firmware, host software (ReplicatorG) and had driver files all finished. I was so impressed by the electronics I ordered another set to build a 3D router.
Using K3D and Meshlab many 3D parts can be designed and printed.
- the MuseDay one of the Thingomatic assembly went very well. The Makerbot kit is well thought out, packed, and labeled. They suggested 45 minutes for the X stage. I took my time and completed it in about twice that. But the Y stage took just about the 3 hours they noted and the Z stage took about a half hour. Once you get the hang of the parts assembly went well.
The Makerbot kit and the RepRap are quite different. The Makerbot feels more like a kit with complete instructions. The RepRap was more like building something where you had to fill in some gaps and figure it out along the way. Also, the basic structure of the Makerbot is laser cut plywood which goes together very precisely and results in very intuitive and square assemblies that need little adjustment. The feel is very solid, and it is easier to see how things should be with the Makerbot kit.
After just 8 hours, including a break for dinner, the X Y and Z stages were completed using the online instructions. The next step is the plastruder and I need to pick up some correct high temperature solder before tackling that stage anyway. I think assembly is more than half finished.
The only tweak I noted is that adjusting the X stage stepper motor is difficult because the rods run right over the cap screws. I think hex head bolts may be advantageous and easier to adjust. I opted to leave the wood bits unfinished because I like the look of the laser cut parts and also to ensure that the tight fit is not altered by a finish. I considered shellack but it does not have high temperature resistance. I may paint parts with a brush when finished, but the plywood is very high quality and I don’t think a finish is critical.
The other option choice is what kind of build platform. The kit includes bits for an automated platform that can unload parts after printing (ABP), a static heated build platform (HBP), and an unheated acrylic platform. I opted for the HBP. I was not concerned about running multiple parts unattended, but do look forward to the reduced warping offered by a heated platform.
Fit and finish of the kit was outstanding. The X axis slid easily on the rods after assembly with very little tweaking. The overall impression as it goes together is that it is quite solid and will last.
While trying different host software to get the controller board to function, I learned that ReplicatorG has built in drivers for various versions of Makerbot 3D printer. In the menu was specific options for the Thingomatic with a heated build platform as well as the automated build platform (which ejects the parts after printing). Looking forward I can see that getting the plastic to extrude at the right rate while controlling the printer speed and position could take a good deal of trial and error. Makerbot has a “Mk 6 Stepstruder” that is part of their latest kit. In addition, their kits have labeled pieces and they have detailed online instructions for assembling the specific kit. It was much more challenging to piece together various versions of hardware, firmware, and host software that form the RepRap project. So I made the decision to order a Makerbot Thingomatic for serious hobby plastic part 3D printing capability (plastruder).
The Huxley project will morph into a RepStrap project. That is, another 3D device based on the RepRap project. With three axis being controlled, I feel confident that a 3D dremel/router could be constructed. It could also be controlled very slowly which may be more robust. Having one “additive” 3D printer and one “subtractive” will add flexibility in making parts from 3D computer generated files, which is the goal.
- the MuseFinally! The PC communicates with the board!
The last few posts have documented the frustration in getting a simple step in the assembly process finished. The daily posts give the reader an idea of how difficult it can be when you seem to be at a dead end (you are not alone).
The short answer turned out to be firmware, and the method ReplicatorG. Read on for details.
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