My 3D printed repair is complete. A long journey but a perfect fit in the final product.

Earlier this month, I decided to use my 3D printer to replace a missing foot on a patio chair. If you have been following my previous articles, you will know that I have been using Autodesk 123D Catch and Meshmixer to produce a model for the 3D printed repair. Finally, when the model was finished, I printed the part.

You can imagine my joy when I pushed the new part into the chair leg and it fit perfectly. Now, if only my wife’s first response would be “well done” instead of “but, it’s yellow!” Maybe I can paint it.

The original foot (left, above and below) is a very complex shape. I used Autodesk 123D Catch to stitch together a 3D model of the part from around 40 still photographs, taken from different angles. The resulting 3D printed repair part (right, above and below) turned out pretty well after I touched it up in Meshmixer. Not perfect, but good enough. The size and shape is so close that I was able to push the new part into the chair leg by hand. And, it’s a snug fit. Maybe this one won’t go missing.

 

3D Printed Repair Printing was the easy part of this project

The part is printed in 101 layers. It took 90 minutes to print, and used 8 meters of ABS filament. Its overall size is approximately 60 mm wide, 40 mm tall and 20 mm deep. The part was printed with the most flat side down (on the print bed) and the sculpted side facing up.

There were two things about this 3D printed repair part that needed special attention.

• First, warping. ABS is likely the more durable material for this type of part. But, unlike PLA material, ABS tends to warp at the edges. If it does, then the edges lift off the print bed. At best, this results in a warped part. At worst, the lifting may cause the print to come loose while it is printing. And that ruins everything.
• Second, support. The chair replacement foot does not lie completely flat on the print bed. It’s not a simple cube. You need to instruct your 3D printer to add support material where needed, such as to provide support in the empty spaces between the ribs. This support has to be printed in such a way that it is removed easily.

In the picture to the left, you can see how I addressed each of these issues. This picture shows the 3D printed repair part about one quarter into the print. The first issue, warping, was addressed by attaching an anti-warping pad or disk to each of the four corners of the model. These pads are around 12 mm in diameter and 1 mm tall. The second issue, support for overhangs, was created automatically by my slicer software. These supports are the squiggly, loose looking pieces between each of the ribs. Later in the print, they will support the solid horizontal overhang (shown in the pictures above).

You can also see some squiggly supports between the edge of the 3D printed repair part, and the anti-warping pad, in the lower left. You need to make sure that there is some support material between the anti-warping pads and the part itself. Otherwise, it will be hard to remove your pads from the final print. Normally, the support material is very easy to pull off by hand.

You can also see the small brim that I have printed around the part on the first layer. Together, the brim and the four anti-warping pads provide a large surface area of adhesion to the print bed. This prevents warping at the edges. Thanks to fellow Canadian Claude Theroux who made my life easier by posting models for the anti-warping disks on Thingiverse.

So it’s done, it works, and yes, it’s yellow.

As a former management consultant, I know the importance of a “post project review”, so here goes: The cost of this part was under $1.50 for plastic and electricity. Of the roughly 48 hours I spent on this project, the breakdown was:

• Creating the model using 123D Catch – 80% (including multiple picture taking sessions and lots of learning)
• Fine tuning and repairing the 3D model using Meshmixer – 15% (including learning to use it)
• Actually printing the part and sticking it in the chair – 5%.

Needless to say, these were not “billable hours”.