6. 3D Scanning and printing

This week is all about Scanning & Printing.

The Individual assignment for this week: - “Design and 3D print an object (small, few cm3, limited by printer time) that could not be easily made subtractively” - 3D scan an object (and optionally print it)

Group Assignment

See Reykjavik Site

We all printed similar test models on different printers. I used the Prusa Mini+ I’ve had since 2020. I’ve used the machine enough to the point I don’t think I learned anything specific. The assignment did get me to re-tune my printing profile.

Hero Shot

Additive Design

I did a bit of brainstorming trying to figure out what to make. I settled on designing something very flexible as a demo piece for the lab. I eventually settled on doing a sort of Ball-joint chain where each link is a set of two spheres where one sphere wraps around the next sphere in the chain.

Fusion

I started off by making a rough sketch of what I had in mind before settling on the required parameters. I decided on the following:

Name	Unit	Expression	Description
Space	mm	NozzleDiam+0.2 mm	Space between surfaces in the joint
BallDia	mm	5 mm	Diameter of ball joint
Dist	mm	6 mm	Distance between joints.
Num	none	50	Number of Joints in pattern
NozzleDiam	mm	0.4 mm	Nozzle Diameter

Using these parameters I made a refined sketch:

After revolving the sketch and rounding the hole it looked like this:

Then I did two separate patterns, One circular and one linear.

Here’s the circular pattern with section analysis enabled, showing the inside of the joint

and here’s the linear pattern with section analysis enabled.

The first version I printed had an opening on the bottom, not large enough for the joint to fall out but enough to allow for 90° angles:

But this also meant if I twisted the piece just right I could “unlink” the chain like so:

I decided to print a version where each joint is completely enclosed so instead of the bottom surface being defined as BallDia/3 relative to center I instead used ( ( BallDia * 1.5 ) / 2 ) - Space This removes 0.6 mm from the bottom of the sphere meaning I can slice it with no overhangs.

Printing

Printed on the Prusa MK4 with 50 joints using the default MK4 Input Shaper profile at 0.2mm SPEED and standard 15% infill. No supports and no brim (I like to live dangerously)

Thanks to the flat bottom PrusaSlicer can print this without any overhangs on the external perimeter. Note the lack of blue lines: Purple is bottom surface, Yellow is perimeter and orange external perimeter.

I cleaned the buildplate thoroughly using dish soap in the sink before drying and placing it on the printer. I also wiped it down with Isopropyl Alcohol to make sure it’s spotless. I could use Magigoo or some adhesive but the bottom surface would not be as smooth as printing directly onto the plate. I just need to make sure the first layer sticks perfectly as there isn’t a lot of contact surface to work with. Luckily this worked on the first try. Total print time was 51 minutes.

The final version came out perfectly, See the Hero shot at the top for a demo. I think I’ll print another one of these at home in some fancy filament and see if I can make a nice bracelet.

Scanning

Decided to try out two scanning methods. First I’ll be trying KIRI Engine a freemium android scanner app. Seems simple enough. I decided to scan my mouse since it has some interesting contours. It’s a Logitech MX Anywhere 3S.

The app itself is one of those all too common pro subscription models. I used the photo scan with auto photos propping the mouse up on a rotating plate slowly changing the vertical angle while rotating the plate. The final scan came out surprisingly well.

I used PrusaSlicer’s in built cut feature to slice the mouse away from the base of the plate. The cut tool also closes open faces automatically.

Here’s the mouse after cutting and adjusting. My theory for the chunk missing from the hump is due reflections from the sun throwing off the scan.

I printed out a miniature mouse, Here’s the original and scan together: