Have you ever wondered how to print in 3D? I have! With my last project, I was able to learn how to 3D print an impossible object in both PLA and resin! I used a chainmail from https://www.thingiverse.com/thing:42850.

Here is how the gumbballs look,

Process

It took me a while to decide on a figure that I wanted to do for this homework. I tried some initial printing with a few and changed my mind several times. Choosing the piece was my first challenge! I first tried a skateboard but besides printing very ugly, the wheels came off so it was not impossible anymore. I also tried a skeleton with was so delicate at that scale that it broke (looking back I could have probably used it with some improvements I learnt later, but at that moment it did not look like an option). I also tried a klein bottle but I realized that I wanted something that could move so I then decided to do a chainmail and to stick with this one; no more reconsidering it. Before printing anything, however, I measured the gumball with some calipers to get an idea of how big the figure should be: 1.9795in in height with the cap on and 1.9165in as the largest diameter on the transparent part. 

I did one piece with the Form 3 SLA resin printer from Formlabs and the other four with FDM PLA printers from Prusa.

SLA Resin printing:

While I started printing with the FDM machines, I ended up finishing the resin piece first. This process involved using PreForm to modify the file and add supports: I autogenerated supports, aligned the long axis of the piece parallel to the front, and sent the file to the printer. Then I printed the file. My first resin printing failed and with how long this printer takes, this was a bit disappointing. But I changed the file a bit, not knowing how much it would help. I changed it such that the figure was still tilted but more horizontal, and this time it worked! Once printed, I cleaned the resin piece in the alcohol bath. I then removed the supports and tried separating the rings. I run into the issue that the rings were joined together a bit, so I had to use a cutter to cut through the joints, following the shape; ideally this should not be done. I then pushed each ring against each other to break the remaining small joint. The piece broke in about three spots and one ring came off, which was not great, but it worked better than I had imagined. I then cured the piece in the UV light to strengthen it. Both cleaning and curing took 15 minutes each. While I am happy that the shape works, I am not sure if the rings that broke will eventually come off; it probably depends on how much the UV light strengthened the material.

FDM PLA printing

Surprisingly, PLA printing gave me more headaches than resin.

I downloaded the file as an stl. file and uploaded it into 3DPrinterOS. Then I scaled it and moved using ‘Layout’ which created a gcode. file wen saving. Then, I sliced it with the recommended layer height, wall thickness and infill density, and then sent it to print. For some weird reason, I assumed that the file that I downloaded came with the other settings that it needed to print correctly, such as raft, orientation and supports. So, when I printed it, I was having a lot of trouble removing the supports. Basically, I spent a long time thinking that removing them was the issue and I tried being super careful. I tried increasing the size a bit and modifying the given settings for infill/wall thickness/layer height, but I still had trouble because the problem was with the supports, and I broke some pieces anyways. I was considering giving up and simply submitting what I had, but then I got some help from my classmates who where also working on the homework at that moment (not going to name people just in case). They heard about my problem and suggested some things like placing the figure horizontal to decrease supports. It might seem simple but I was so focused on working on removing the supports that I had not noticed that I should change everything else from the file to make it work! Then someone was like “but your file can be printed without supports…”. And so, I realized even more that I had not been looking in the right spot! It turned out that the person who submitted the file explicitly wrote that it could be done without supports, and I just had not realized that I could remove this setting from the program. It now might seem obvious, but for the first time printing and using the program, this was key for the success of the print. I reprinted the files, using brim instead of raft (I also had not realized that this could be changed in the program) and they turned out way better. There’s still improvements that can be done, like that it can be seen where the brim was removed, but it worked! Also, because I had tried to increase the file size more and then forgot to change it back, the PLA pieces turned out larger than the resin piece. I did not do any post-processing to these pieces other than removing the brim and separating the rings.

Some pieces broken when trying to remove the supports:

      

End result:

Difference in size:

Cost Calculation

Due to time constrains, I will simplify the cost calculation and only make an estimate for the parts that I submitted (not any failures).

Labor time:

• I estimate about 810 minutes and $14/hour for this job
• 810  min * $14/ 60 min = $189

Cost from printing:

• The FDM printer gives a cost for each piece that you print. However, I fogot to take a picture of the last piece that I printed. Despite this, it was all in the cent amounts, so I will be adding $1 more to the cost, which is most likely over the price. I will also assume that the prices that the machine gives are for printing, even though they might just include material.
• As for the resin printer, the good piece took a bit over 3 hours to print. I took note of the grams of filament that the FDM printer would use for the four pieces (55.85 g). Even though this was not the final settings that I sent to print, it was a close file, so I will be using an estimated 14 g (55.85/4 = 16.9625g) of material per piece. Assuming that the same material was used for resin [1] (the piece was smaller but it had supports), and with a price of $45 per kg [1], this results in: 14g * $45/1000g = $0.63. 
• This cost is an estimate as it makes some assumptions and it does not include electricity at least for sure for the resin estimate, but it is probably a fine estimate.

Total cost: $189 + $1 + $0.63 = $190.63 which is about $191

References: 

[1] https://3dprinterly.com/how-much-does-3d-printing-cost/