Big Spider

by ElectronicKit, published

Big Spider by ElectronicKit Oct 19, 2010

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Just in time for Halloween - a 102mm x 150mm MakerBot printable spider. Printed in black (or glow-in-the-dark ABS) this thing would look pretty real. 3rd photo down is a cheat, I photoshopped a white ABS spider photo to get an idea of what black would look like. Modelled after a googled diagram of the real thing, the proportions should be pretty close except for the 10X size.

The spider head is not real detailed having only a couple of (closed) fangs hanging down.

What I learned from working on this is that modelling animals is way harder then doing geometric objects. There are no straight lines only short segments of changing length and diameter. Makes me appreciate that much more the modelling done to generate the animals, busts and figures posted on Thingiverse.


There are non-fatal errors reported by SkeinForge when you generate the GCODE, but both object sides print fine.

The halfs of the spider's body are printed at a 45 degree angle to fit onto the 100mm x 100mm MakerBot platform. Be sure you center up your XY table good before beginning to print. A heated build platform for ABS is required for this 102mm length object.

For SkeinForge, Set INFILL DENSITY to .03 in the FILL menu. I printed the body halfs raftless because they are glued together on the flat sides and that goes a lot easier with just a small amount of sanding with some 220A sandpaper. As others have noted, you can get a real good ABS glue joint with acetone (paint thinner). I used a clamp to line up and hold the 2 halfs together, then brush applied the acetone along the seam. Once glued this way the parts are welded together for keeps, so line them up carefully.
Follow the instructions and precautions printed on the can of acetone - the stuff is flammable, not good to breath and bad on the eyes, so be aware.

UPDATE 10/22/2010 - Sorry, the legs I originally uploaded were about 1/3 smaller then they should have been. A leftover from trying to get the legs to fit into holes on the body. I have replaced that file with one that generates legs which are 72mm overall in size as pictured on the finished model.

The stl file for the legs below prints 3 legs at a time, so you need to print 3 copies to get 8 usable legs.

ABS curl was not a problem, but you should use a raft for printing due to some modelling issues (the legs taper, so I had to provide some support). Using a raft on a non-heated build platform works fine with these skinny spider legs. When printed, the legs are strong and solid enough to support the 102mm body. Note when printing legs, it looks like it is not working until about 6 layers are generated.

For SkeinForge, I set the BASE LAYERS to 1, and left the INTERFACE LAYERS to 0 in the RAFT menu. In the FILL menu, I used .3 for INFILL DENSITY. No additional support material is needed.

My 1st shot at doing this project was to boolean cut 8 holes for the legs to fit into. After 3 attempts to get the sizing right I gave up and put a cut out slot where the 2 opposing rows of 4 legs can be glued. One advantage of that is you can do some custom positioning of the 8 legs for effect.

I first clamped the body upside down on my work bench, applied enough hot glue for all 8 legs and then rough fit each leg onto the body by holding the leg in place for several seconds. After unclamping the beast, I flipped it over, put a spacer (bottle cap) between the body and the bench top, then did some final positioning of the legs before the hot glue completely set up.

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Big Spider by ElectronicKit is licensed under the Public Domain license.

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My old MakerBot CC 3D printer XY platform was 4" x 4" (100mm x 100mm) so everything I designed originally had to be for printing on less than that area (like 3.5" x 3.5"). Looking at XY build platforms of the 'average' 3D printers in the last few years of 6" x 6" and 8" x 8" would surely allow a panel of 4 legs / build. I sort of buried the headline, but that is why there are only 3 legs in the STL file as I recall.

I made it all the way thru printing and assembling this before realizing... hey, this spider only has 6 legs!! Why on Earth group the legs in 3s instead of 4s?!

Very impressive. Great job of cutting the model to make it printable.

Thanks! Note that I had goofed up wth the original file upload of the legs as noted in the LEGS instructions above.