File Preparation

My shape’s exterior look is based on Jakub Lattenberg’s easter bunny 3D model (Easter Bunny, Sheep and Chicken by jll8 – Thingiverse).  However, this model is solid on the inside, so it can’t be considered an impossible shape. Other 3D subtractive processing method can produce this solid shape without the need of using 3D printing. So I import the STL file into Blender to modify it further.

In Blender, I first hollow out the bunny’s body using an ovel shape and the Boolean-Difference modifier. Then I snap fitted a rod into the center of the hollow space. To further fill the void, I added  a 3D 8-Bit heart model done by MakerBot from Thingiverse (8-Bit Heart by MakerBot – Thingiverse) to the center of that pole. Finally, I combined all shapes and exported the modified STL file for 3D printing.

FDM Method

When preparing the model in Bambu Studio, generating support was the main challenge I faced since all other setting was left at default of the OEDK 0.2mm Standard preset. In my first print, I only added support to the feet and tail of the bunny and not to the ears as I saw their angle is around 45 degrees, around the threshold. Another reason why I didn’t add support to the ears in the beginning is the software will add “ghost” supports to the inside of my structure that gives no support to the ears. They only comes up when select to generate support on the ears above a certain height.

However, the first print proved that the ears requires at least some support for it to stick firmly onto the body. The printed bunny was earless and a long segment of extruded filament was found near it, proving the base of the ear detached soon after printing before subsequent layers can be printed. This is likely caused by the small contact area of the ears, so the adhesion is inadequate event when the overhang angle is not that big. I also noticed that the grating on the body is too dense to see the internal structures so I went back to Blender to open a small hole on the back to allow better visualization.

I sent the g-code to multiple printers so they can print with different colored PLA simultaneously. When I went to retrieve the product, I noticed something strange: only the one that was printed using white PLA had a obvious defect. Part of the lower wall appeared to be printed at the wrong coordinate causing the surrounding area to warp.

I thought this was perhaps the printer malfunctioning so I go to the printer that printed the red bunny and ask it to print again but this time in white PLA. This guaranteed the printer was properly functioning and was using the same g-code. I also was checking the printer more frequently. Unfortunately the issue reappeared and I stopped the printing. I didn’t catch the exact moment when the failure occurred but this shows the error is reoccurring and probably associated with some corrupted g-code or bug during file preparation.

For the successful pieces, I used a flush cutter to clip away any hanging residues from the supports. Lightly sanded the surface using high grit sandpapers as excess sanding seems to take away the color of the material.

SLA Method

Printing using the SLA method was a little challenging for my model because it’s hollowed with internal structures. The structure is suspended and upside-down during the printing process so it’s impossible to print without any supports regardless what orientation I used, the PreForm software wouldn’t allow me to print bellow the support threshold.

When I started to clean up the supports on the cured product, I began to realize the model with a hole on the back doesn’t print well using SLA from an aesthetic point of view. The hole was meant to get a better visual of the internal structure but now is shows all the support filaments on the inside that couldn’t be cleaned out.

In the end, I decided to print the first version without the hole on the back. This way the supports snaps off more easily and the internal supports are hidden by the outside shell. Because I used the clear resin, the outline internal structure can still be vaguely see when putting against a light source.

The supports were removed using wire cutter. I tried to remove all the stubs left on the surface but some were too short and too thick to be removed by clipping. So I used sandpapers to remove them. Unfortunately, sanding left scratch marks on the surface that effect the transparency of the material. Even after cleaning the area with alcohol, where the sandpaper touched still looked a bit more misty than the surrounding. Because of this, I rounded the bumps as much as possible but the surface still feel a little rough when touched.

Cost Analysis

Cost Type	Cost	Price	Source	Quantity	Total
Materials	PLA Filament 1.75mm, 1kg (2.2lbs) Spool- White	$21.99/ spool	Amazon	11.36/1000	0.25
	PLA Filament 1.75mm, 1kg (2.2lbs) Spool- Blue	$21.99/ spool	Amazon	11.36/1000	0.25
	PLA Filament 1.75mm, 1kg (2.2lbs) Spool- Yellow	$21.99/ spool	Amazon	11.36/1000	0.25
	PLA Filament 1.75mm, 1kg (2.2lbs) Spool- Red	$21.99/ spool	Amazon	11.36/1000	0.25
	Clear Resin Cartridge v4, 1L	$149/ unit	Formlabs	28.4/1000	4.23
	Vending Machine Capsules 2″	$100/ 2000 cts	American Carnival Mart	5	0.25
	Isopropyl Alcohol 99%, 4qt	$33/ unit	Alliance Chemical	1/151	0.22
Labor	3D Printing Technician	$25 /hr	ZipRecruiter	0.75 hr	18.75
Overhead	SLA 3D Printer Operation Cost	$0.342/hr	LinkIn	7 hr	2.39
	FDM 3D Printer Operation Cost	$7/hr	ZONGHENG3D	7.5 hr	52.5
	Quality Control	$37 /hr	ZipRecruiter	0.5 hr	18.5
Design	3D Modeling Artist	$39/hr	ZipRecruiter	0.75 hr	21
Misc. (Scrap)	PLA Filament 1.75mm, 1kg (2.2lbs) Spool- White	$21.99/ spool	Amazon	11.36/1000	0.25
	Clear Resin Cartridge v4, 1L	$149/ unit	Formlabs	14.2/1000	2.12
Sum					121.21