====== Articulated Figure : In place or separate printing for moving joints? ======

{{ :simplejoint.jpg?200|}}So in-place printing is the "holy grail" for 3D printed designs with moving parts. But is in-place the best option in all situations, specifically for small moving joints that could be used in a small (150mm) articulated figure?

Aiming for a model of that size I estimated that the joints would need to be a cross-section of 10mm x 10mm. The shafts (pins) what would allow rotation would be 5mm in diameter. A simple joint design would be as shown to the right, allowing for the joint to flex a full 180 degrees (and so be good for arms and legs).

This model splits down into three pieces which I'll call the link (shown in blue) and parts A and B (shown in red and green). It's worth noting that part B is just a mirror of part A.

{{:simplejointseparate.jpg?400 |}} To print this joint as **separate** pieces just needs the model separating.

I found that the joint worked best when the holes were slightly bigger than the shafts. The diameter of the hole was 5.05mm and the shaft was 5.00mm; this allowed the pieces to be fitted together easily but maintained a level of stiffness that an articulated figure would need.

I also added a slight bevel to the ends of the shafts to make them easier to fit.

No other adjustments were needed to the model.

{{ :simplejointinplace.jpg?400|}} To print **in-place** required a bit more work on the model.

To stop the parts fusing together during printing touching walls needs to be separated. I found that a distance of 0.3mm worked.

This gap was also needed for the holes, meaning they now had a diameter of 5.6mm.

After printing and the satisfying "snap" when moving the joint, the joint itself is looser than the printed-separately one. It's easy to see why, that 0.3mm gap around the shafts isn't tight enough.

{{:img_4231.jpeg?400 |}}Comparing the two joints, the printed in separate pieces is on the left and the print in place on the right. You can see the shafts are a much tighter fit on the printed separately. So for a small articulated figure, it's looking like avoiding in-place printing is the best option if you want stiff joints.

//Printed on a Bambu Lab P1S, 0.4mm nozzle, Smooth High Temp plate, 0.16mm Optimal quality.//