3D Scanning and printing

This week I made some 3d printed tools and 3d scanned using photogrammetry.

I wanted to make simple tools this weeks, so I experimented with simple joint mechanisms. Some references that I used to develop my designs:

• compliant Mechanisms Research (CMR by BYU)
• Why machines that bend are better
• Compliant mechanisms by Devin Montes - video
• These transformed chopsticks

Design

I first made a scaled-up version of a simple Gemclip and some other simple geometry clips. I bent one end to add a dimension, that does not allow it to be made using only one subtractive method.

I first made it in 2D in plan to the size and proportion I wanted, and then extruded it in Z. Later I bent the inner part so that the model could no tbe made only subtractively easily, as now it had an undercut.

Then I used some parts of these tranformed chopsticks reference above that I found

And then made normal tweezers and then modified the geomtry to make it compliant like the chopsticks above.

The models

Next after, watching some videos on making compliant mechanisms, I made a simple pick-and-place plier to test out the bending.

Some tweezers we used for holding down electronic components:

I wondered if it was easier to use the tweezers with a reversed action, where applying force releases the object. And by default it holds the object. For this, I used this mechanism designed by Devin Montes - video and transformed it for the tweezers.

Creating toolpaths

I used Cura to make toolpaths for my 3d prints. I uploaded my stl files, set my machine, choose PLA as my material and used these settings:

Printing

I used an Anycubic Kossel Plus 3D printer to print with a black 1.75mm PLA filament.

Printing the gemclip: The finish was alright, as the first layer spread a little too much, causing it to be broader then the actual form. The first layer has a layer height of 0.3mm, and all the consecutive ones were 0.15mm. I used a cutting blade to finish these edges.

In the next print, I used the same layer height for all layers. I printed a simple pick and place plier using a bent compliant joint.

Simple nose-end tweezers:

Used the transformed chopstick geometry, modifoed it for the tweezers:

The bending details were too small, they broke while I was trying to clean them up.

Overall, I made some small experiments with simple tools. I hope to remake the tweezer with the semi-compliant mechanism again after modifying the design.

Useful reference:

For next time

Photogrammetry

I used Agisoft Metashape to make a pointcloud. I followed this tutorial by Agisoft.

I clicked 53 images of the object on a plain background from all around. Steps to make a pointcloud:

1. Workflow > Add photos
2. Workflow > Align Photos (this step take some time depending on the number of key point limit and tie point limit you set.)
3. Some photos failed to align, but I got 9003 points
4. Workflow > Build dense cloud - medium quality.
5. Workflow > Build Mesh
6. Workflow > Build textures

The process:

The output:

3D Scanning

I used a Roland Modela MDX-20 to scan the same object. I used the step-by-step manual for this.

Stuck the bolt and nut using a double sided tape on the raised level bed. I set the scanning area, as close to the object as possible. And a scanning grid of 0.5mm on both X and Y axes.

The output:

Design files

All 3D models for printing
Probe scan of a lump of clay
Photogammetry of nut and bolt
Probe scan of nut and bolt
These transformed chopsticks