3D Printing and Scanning#

There are several 3D printers in FabLab Kamakura. In order to check the performance of each of them, we decided to print the same model and check the accuracy of the finished model.

3D model testbed#

For checking quality, we decided to print kickstarter-autodesk-3d/FDM-protocol. This model allows us to see the performance of many things at once. In addition, it includes a method for calculating the score for each item, so you can see the results of the printing process. We can check …

Dimensional Accuracy
Fine Flow Control
Fine Negative Features
Overhangs
Bridging
XY Resonance
Z-axis alignment

Prusa Mini #

Image from the Prusa Site, forgot to take a nice image of our Prusa Mini

Using PrusaSlicer(on OSX 11.2.1), I imported the test geometry and choose the following settings:

0.20mm SPEED
Generic PLA
Supports: None
Infill 20%, no Brim

After slicing, that gives us the following:

Used filament: 13.87m
Cost: 1.05 ($?)
Estimated Printing Time: 4h4m

Here is the exported Gcode file: georg_prusa_test_ksr_fdmtest_v4_0.2mm_PLA_MINI_4h4m.gcode , (exterinal link, 7.3M)

Turning on the Printer#

Cleaning the Print Bed#

With Isopropyl alcohol, because it evaporates fast and leaeves the print bed nice and non-sticky.

Auto-bed Levelling#

One USP of the Prusa Mini is it auto-bed leveling. Before printing a sensor reading of the bed is taken, and the bed is adjusted accordingly, resulting in better print quality.

Importing the Data#

Is done via USB Stick, the interface is in color, no touchscreen and a rotate-and-push dial (similar to Bento Lab)

Starting the Printing#

I started the print process, here are some images during printing.

Printing Done!#

Exactly 4 hours and 4 minutes later the printing was ready.

The main thing we choose this test geometry, was that it comes with it’s own Assessment Protocol

Assessment#

1. Dimensional Accuracy#

I am measuring the x and y dimensions of the stack:

Target	Measured X	X Error	Measured Y	Y Error
25	24.8	0.2	24.8	0.2
20	19.7	0.3	19.8	0.2
15	14.9	0.1	14.9	0.1
10	10.0	0	10.0	0
5	5.0	0	4.9	0.1

Avg Error X: 0.12mmm
Avg Error Y: 0.12mmm
Avg (Avg Error X, Avg Error Y): 0.12mmm
Diff (Avg Error X, Avg Error Y): 0mmm

According to the guidelines:

0.00 - 0.10mm: 5 points
0.11 - 0.20mm: 4
0.21 - 0.30mm: 3
0.31 - 0.40mm: 2
greater than 0.40mm: 1

2. Fine Flow Control#

Spines less than 30mm: 0
Spines greated than 30mmm, but strings: 2.5
Spines greated than 30mmm, no strings: 5

Spines 40mm long - fully printed!, but lot’s of stings: 2.5

3. Fine Negative Features#

How many pins can be removed from holes, using only finger pressures, no tools? All can be removed: 5

4. Overhangs#

Dropped loops everywhere: 1
15, 20, 30 differ from 45: 2
15, 20 differ from 45: 3
15 differ from 45: 4

5. Bridging#

More than 3 contacts within the bridges: 1
3 contacts: 2
2 contacts: 3
1 contact: 4
No contact: 5

6. XY Resonance#

I marked the side of the object with a marker, so I could know which picture is X and which is Y. I was surprised how porous the print was! The liquid of the marker really dispersed!

Visually inspecting the ringing feature, for both X and Y:

If ringing more that three hash marks: 0
No ringing: 2.5

7. Z-axis alignment#

Is there a registrations effect with a period equal to the leadscrew? If so, 0, otherwise 2.5.

No, no registrations: Score 2.5

Summary of the Assessment#

Check	Points
Dimensional accuracy	4
Negative feature resolution	2.5
Positive feature resolution	5
Overhang	3
Bridging	3
XY ringing	2.5
Z-axis alignment	2.5
Total for Prusa Mini:	22.5

Highest Possible: 30
Prusa i3 MK3: 22.5 (same as our Prusa Mini!)
Makerbot Replicator 2: 18

(But we don’t know Slicing Parameters and Printing Times for these)

Conclusion#

First time doing 3D Printing, very impressed with the results - and ease of use of the Prusa Mini. Mini+ just came out, would be nice to get one.