Thursday, October 15, 2020

Coasters, anyone?

I Needed Some Coasters, So...

The coasters are orange, the bottom of the box is yellow, and the top is pink, all at least a little fluorescent. 

I printed some coasters and a storage box for them using TPU filament. I think they came out alright.

These coasters are all 100 mm in diameter and 2.88 mm high (I printed in 0.24 mm layers) and the box holds a stack of six of them.  Each coaster has a different pattern. The patterns and the lip around the edge of each coaster are designed to trap condensation that dribbles off your cold glass so it doesn't end up on your furniture. I kept the patterns shallow in Z. If the patterns get too deep it starts to become a problem keeping them clean.

The box's lid fits loosely so it's easy to remove. You can put it under the bottom of the box if you turn it upside down. The rounded corners have enough space to use a finger to lift the coasters out of the box, one at a time.

Being printed in TPU, the coasters are great for hot and cold drinks, but I would not set a pot right off the stove on them. I tried washing them on the top rack in a dishwasher and they came out looking like they just came off the printer- perfect, but who knows? Maybe they'll show some wear after multiple cycles.


I used TPU because I like the way it looks, especially when it fluoresces. The photo shows the result of four printing sessions split among three colors. The first two sessions were to print three coasters at a time, one more session to print the box bottom, and finally one to print the box lid. 

Another reason to use TPU was because I liked the idea of the surface being a little soft.  Setting a glass or cup down on a soft surface will sound and feel different from setting it down on a hard surface. I have a granite counter top, and setting a glass or cup down on it always makes me feel like I'm going damage either the glass/cup or the counter top.

I printed at 240C- a bit higher than the recommended temperature range for TPU, but the plastic really flows at that temperature, yields a super shiny finish, and the interlayer adhesion is amazing. I get almost no hairs on the prints. They seem to be leakproof. Of course, with use they will probably start to look bad because spills will inevitably find tiny gaps between lines in the print that can't be properly cleaned out. It's no big deal - I have a 3D printer, so I'll just replace them with another set before they start to look bad.

Print speed was 40 mm/sec, no cooling fan, 45C PEI bed.

It should be easy to print these in as many colors as there are pieces (8 in total). You can do all sorts of crazy stuff, if your printer can produce multicolor prints.

You don't have to print with TPU if you don't want to. PC, ABS, PETG, or PLA, will work too, but you might have to be careful about putting hot drinks on PLA.

The box lid is printed with the top side down on the bed. My printer's PEI bed has scratches that transfer to the print, so the top cover doesn't look as perfect as the sides and everything else. I think printing on glass would be a good idea, at least for the top cover. 

It's easy to change the shape and size of the prints by scaling them when you slice the files to print. If you think they aren't deep enough just scale them in Z for the (any) depth you want. If you want larger or smaller or oval coasters (??), just scale the X and Y axes appropriately after you put them on the plater in the slicer.

I printed with concentric infill for the top and bottom layers and they came out with some interesting patterns.

Finally, clean the nozzle thoroughly just before the print starts, while it's at print temperature.  That will help prevent getting little blobs of charred plastic embedded in the print. Avoiding over extrusion helps, too.

STL files are here.

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