The Switch Doc rebuilds his cat toy launcher with 3D printing

The Smart Extruder

For some reason, the MakerBot distributor that I bought the printer from shipped me a very early unit with a very early design of the new Smart Extruder (Figure 2). I powered up the printer for the first time and it didn't work. It wouldn't even level the build plate. The first call the technician asked me to update the firmware (which took about two hours). No change. Still failed. I called MakerBot (got a person easily and every time after paying the MakerBot Care); they were appalled that I had such an old Smart Extruder and next-day air shipped me a new one. I was impressed. However, I plugged in the new model extruder and it did exactly the same thing. No joy. I had a lemon MakerBot.

Figure 2: Smart extruder.

After several other calls and some other suggestions, MakerBot had me ship the entire printer back, and they cross-shipped me a new MakerBot. This got me thinking. I started looking at reviews on the Web and I found lots of comments and complaints about the Smart Extruder, especially early on. I emailed MakerBot marketing and asked for a comment, but they ignored me. The tech support guys told me they had problems early in the product life, but they had fixed the problems with the new Smart Extruders. Once they found out that I was writing an article, they stopped commenting about anything and referred me to marketing. I should have kept my mouth shut about writing this article.

I opened the box, checked the serial number on the Smart Extruder (it was much newer), updated the firmware, and started my first print. Absolutely perfect. The new Smart Extruder works like a charm. I still had the old extruder and compared it to the new one. I could see some of the changes to the heat sink and structure that seemed to address the web comments.

The last issue I had with my new purchase was that they changed the spool size from the MakerBot Replicator 2 to the 5th Generation. Ouch! I had a bunch of filament. Turned out it was simple to fix. I found a Thingiverse project that added an additional spool holder that used the old size spools. I printed it with the MakerBot and the problem was solved.

Now that I have all the new equipment, I am very pleased with the MakerBot Replicator 5th Generation. Someday, I will like the webcam and app too. Overall? I am satisfied with my purchase.

Learning 3D Printing

I knew nothing about 3D printing when I started. I had never used a mechanical CAD system, and I had never designed a single 3D file. I'm an electrical engineer and have used CAD systems my entire career, but not a single mechanical design program. I used the sample files and printed chains and bolts when I got the printer, which was cool, but I had a MouseAir V2 box to design. I've always approached learning new systems by forcing myself through the learning process and doing a real project.

I started by using several CAD systems to try to design a box and do something simple. I tried 123D Design, Tinkercad (Figure  3), BlenderCAD [5]-[7], and several others. I could draw designs and push them to the MakerBot using the tool chain. However, I quickly learned the difference between drawing 3D designs and engineering 3D designs. It was impossible to place items accurately using 123D Design and devilishly difficult to place in Tinkercad. I was coming to the conclusion that I would have to use a professional CAD system such as SolidWorks [8].

Figure 3: Tinkercad initial design.

However, Daugherty suggested I look at OpenSCAD [9] (Figure 4). I did, and I was in love from the first moment. OpenSCAD is the programmer's Solid 3D CAD modeler. You write code to create the 3D solid models. Want a box? Here is the code for a box:

                cube ([190,140, 40]);
                cube ([186,136, 65]);
Figure 4: OpenSCAD design screen for sample box.

Plus, I get sub-millimeter positioning. This box is 190x140x40mm with 2mm walls. Now I get programmable accuracy that I can adjust when something doesn't quite fit. Everything is positioned exactly where I want it, and I can change its position via code. This is 3D modeling for programmers. I completely abandoned all of the others and have exclusively built models using OpenSCAD. You will find many designs and modules available on Thingiverse and on the web for gears (Figure 5), rack and pinions, rounded corners, and more.

Figure 5: OpenSCAD design screen for gears downloaded from Thingiverse.

One downside to OpenSCAD is there doesn't seem to be a good path from an OpenSCAD model to building a plastic injection mold MouseAir is going to be marketed as a kit, and it is way too slow (and too expensive) to make, say, 300 units when each top/bottom unit takes 12 hours to print. A rule of thumb with 3D Printing is each hour of printing costs about US$  10 in production: $120 for a MouseAir box doesn't work. A plastic injection mold should be able to make one for about $4 (ignoring the $4,000 or so for the mold cost!). I can see a conversion to SolidWorks in the future.

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