Assorted problems with 3D printing PLA molds

I am 3D printing a block mold - rubber will be poured into it to make a case mold for beer. bottles. It is an amazing process but there are still issues to deal with:
-Stringing (top left). This usually happens when the nozzle is running too hot. This new batch of filament needs a slightly lower temperature, so I adjusted from 215 to 207.
-Size constraints: This is too big to print as one mold so it has to be done in multiple sections (two mains, two end-caps). Pieces fit precisely and can be glued or taped.
-Experience shows where glue, tape or special brackets (e.g. corners lower left) are needed.
-Special tools must be made (lower left is a clip-insertion tool).
-Corner lifting: Happens mid-print (the large thin pads on the lower right are to prevent that).
-Pressure bowing: The stabilizer bars spanning the two mid-pieces (lower left) and the triangular lip (upper right) keep that edge straight despite pressure from the liquid rubber inside.

Related Pictures

The bottle is more important than the beer!

What is depicted here doesn't happen with ceramic beer bottles. They do the talking. They talk about how we should be manufacturing our own stuff locally. They remind us that we make beer here so we should also make the bottles. They tell us we should take pride in things we can manufacture ourselves. That we should use local raw materials rather than importing them. Glass bottles are just a container, ceramic bottles elevate beer, they bring sustainability and style to beer drinking. Ceramic bottles bring local craftsmen to your beer experience - potters can make them. Ordinary glass will always be just ordinary glass, but ceramic bottles bring a world of aesthetic possibilities to this basic part of our culture.

3D printing case vs block molds for ceramics

Left are case molds, they are made by 3D printing the positive profile on a backplate (with holes for natches). These are secured into slotted rails. Right is a block mold, it is made by 3D printing the profile of a working mold with integrated rails. This one is printed vertically in four pieces. It is held together and straight with printed brackets. We pour rubber into these to make case molds. Each method has advantages and issues.
-Case: Faster to print. Easier to draw. Joins cast as easily removed bumps on the working molds. This is only suitable for prototyping, making one working mold.
-Block: Much more attention is needed in printing, there are more issues with orientation of print, infill, support, multi-piecing, fit and seam-filling. 3D drawing of these is more difficult. And block molds are bigger because they are molds of molds. They also need to be more precise to merit the cost of the rubber.

Infill and support issues with 3D PLA prints

Top: The left one has a rectilinear fill, the right a square grid fill. Notice the fill on the left has buckled part way up - this piece is too tall for that type. While the grid fill on the right is far more stable, it is not as easily removed (although it can stay in place here).
Middle: The piece on the right printed in half the time because the only fill needed is at the bottom. The fill is rectilinear and easily removed - it affects the smoothness of the surfaces but they are not a finished ones so it does not matter. However that method is risky, notice the failed print on the lower right - upward pull of the flat section pulled it away. This happened twice more so I chalked up the one success to luck.
Bottom: Took about 16 hours. Like others, the grid support that printed out past the edge - that part has to be cut away with a sharp blade knife to enable mating with the other pieces.

Links

Typecodes	3D printing problems 3D printing for mold making in ceramics requires determination and skill. And a memory for the many problematic techniques.
Glossary	3D Printer Standard 3D printers (not clay 3D printers) are incredibly useful in ceramic production and design, bringing difficult processes within reach of potters and hobbyists.

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