Can I make a Cinderella costume for Halloween? #
I want to be Cinderella for Halloween, and a key component of Cinderella’s costume is her glass slippers. Glass blowing shoes seems too out of my level right now, and glass shoes do not seem fun to wear, so I will be printing them out of clear PVB.
Why PVB? It’s a relatively easy filament to print, but it also comes in clear! And PVB also happens to be soluble in Isopropyl Alcohol (IPA), which makes it great for post processing and smoothing layer lines. This means you can print and then smooth the layer lines, resulting in some pretty convincing “glass” objects.
Here is an example of a clear PVB print from r/3Dprinting:
For our group assignment, we will be running some callibration test prints to see the tolerances on overhand and clearances. We will be using this stl file:
Printing a shoe to fit my actual foot will be large and time-consuming, so I will be borrowing a friend’s Ratrig V-Core 3.1, with 400 mm^3 build volume for this project. (The Ratrig’s name is Remy, after Remy from Ratatouille)
Before we run Remy, we want to do some callibration tests, one of which being the pressure advance callibration. Ratrig uses Klipper, an open-source firmware for 3D printing, which comes with great documentation!
Pressure advance is an important callibration test that allows the extruder to provide even pressure to the filament, even when going at different speeds and angles with different corners.
We will be printing the pressure advance cube, which has increasing pressure on each layer so we can find the best settings. Here is a great page on Klipper’s documentation with the stl and instructions on printing the pressure advance calibration cube:
Settings:
- Vase mode
- 1 perimeter
- Coarse layer height, (around 75% of nozzle diameter)
GCODE for the pressure advance callibration: (this was typed directly into the Klipper interface)
TUNING_TOWER COMMAND=SET_PRESSURE_ADVANCE PARAMETER=ADVANCE START=0 FACTOR=.005
To actually MAKE my shoe, I considered a few approaches:
- Measure around my foot in a “high-heel” position and CAD a shoe based on the measurements.
- Scan my foot and CAD a shoe around it
- Scan my existing pair of high heels and edit the CAD file based on the scan
I decided that measuring or individually scanning my foot would not be a good idea, because I could be putting my feet in slightly different slopes and orientations which could result in different shoes. Also scanning my foot in CBA would be weird. I decided to scan a pair of heels that already fit me, because they were identical, so I could easily CAD around them and get matching shoes.
Scanning and CADing #
For scanning, I will be using the Creality Ferret, which can scan up to a 2x2x2 m^3 object, which will be sufficient for the heels. I placed the heel on a rotating platform and kept the Ferret stationary while slowly rotating the platform.
The ferret did relatively well, but it had a lot of trouble capturing the heel part of the shoe, most likely because the heel was made of a black, reflective material.
To solve this, I taped around the heel with normal scotch tape to cover the reflective surface, and it worked like a charm!
Here is the final scan after taping the heel:
After importing the scanned mesh to Fusion however, I realized there were many issues with the scan. There were lots of holes and gaps, so I used “erase and fill” under the mesh functions. This took a long time to run but resulted in a much better mesh.
Upon closer inspection, however, I realized there were random meshes made in places where there was supposed to be space (such as the gap for my toes).
So I decided to CAD the rest of the shoe myself. I used Fusion and CADed around the 3D scan of the shoe, starting with the shape and contour of the sole:
Then I built the toebox and heel based on measurements of my foot and the heel on the shoe:
Printing #
I wanted the shoe to look as clear as possible, and after some research, I found that using a larger nozzle diameter, and therefore larger layer lines, the object would come out more clear after post processing.
I decided to use a 1 mm nozzle. The only issue was, I didn’t have one that fit Remy, so I took a 0.4 mm nozzle and drilled it out with a 0.040 inch steel drill (which is technically 1.01 mm, but this discrepancy was adjusted in the print settings)
I used PrusaSlicer for generating GCode for my object.
I had to play around a lot with different print settings because I ran into first layer adhesion issues, as printing with such a large nozzle for PVB can be challenging. Some settings I changed:
- Turn fan down to 10% for first layer
- Use kapton tape on print bed for better surface
- Print first layer SLOWLY - 15 mm / s
- Print rest of layers slowly, 30 mm / s (this was because the extruder had trouble keeping up feeding filament through the big nozzle)
- Change extrusion parameters to be in percentages (in terms of nozzle diameter)
Slicing #
With thick layer lines providing more structural stability for the shoe, I turned down the infill to 15%, but I used modifier boxes around the heel portion and edited the infill for the heel to be 40%. This ensures that the heel (where a lot of my weight when wearing the shoe is distributed) is strong.
Disaster Strikes! #
Although the first few layers of hte Remy’s nozzle exploded during the print and stopped! The hotend broke as well, which was a shame since the first few layers looked really nice and clear.
The nozzle flailing off also somehow knocked the PVB spool to the ground? After some digging, I realized this was not an uncommon issue for the RatRig printer. The nozzle exploding could have also been a result of printing the large filament diameter with the (questionably) machined nozzle, and also printing a trickier filament. The pressure build up could have resulted in the nozzle popping off.
I printed one shoe on a Bambu X1 due to time reasons, and used a 0.4 nozzle. The layers did not come out as clear as I would have liked, but the PVB still created a cool iridescent effect, similar to Silk PLA.
Post-processing was also tricky. I used IPA and originally dipped the shoe into a tray with IPA, but I later found that this ended up very sticky and messy, so I used a brush to paint on IPA instead. This worked much better and ensured more even coverage.
I also broke the shoe in half when I wore it oops. I joined it back together using IPA and superglue.
Reflections: #
- Be careful when printing large layers, especially with unfamiliar filament!
- If you really want something super clear, try resin. Otherwise use PVB with one perimeter in vase mode.
- Use a bath or a soft brush for post processing PVB.
- Add more infill in thin areas such as the sile thick areas like the heel do support more weight, but are less prone to shearing and bending forces.
- Do not get your fingerprints all over a sticky PVB surface that has been treated with IPA
- PVB for clear printing is probably best suited for vase mode, with only one layer and no infill.
Overall, this was a fun experiment. I will definitely try printing with PVB again soon, but with a 0.8 mm nozzle that I will buy and NOT machine by myself. I would like to try printing a clear vase that can be washed with IPA on both sides for an extra smooth, transparent effect.
Notes for future PVB settings:
- 50% speed factor
- 215 C nozzle temperature
- 60 C
- Fan at 30%
- -0.3 mm offset