The Faema Compact has a water shut-off valve on the front, and the knob is prone to breakage.
I designed a 3D printable replacement part, available here:

http://www.thingiverse.com/thing:238148

If anyone here needs one for their machine, let me know!

THAT is quite kewl, congratulations. What kind of work goes into designing a knob like that? Had you made it out of wood or metal, then I would have a good idea, but 3-D printing? None.

-phillip

Is the end result of 3d printing a strong enough material?

I've held a 3D printed part that was super thin and delicate, and then a very robust hard plastic part. I think it just depends on the design and the polymer that is used. I'm sure a plastic knob would be no problem.

What a great technology! The applications are endless.

Parts.

Negatives & positives for casting.

Very cool stuff!

phillip canuck wrote:THAT is quite kewl, congratulations. What kind of work goes into designing a knob like that? Had you made it out of wood or metal, then I would have a good idea, but 3-D printing? None.

The first step is modeling the geometry of the part. This involves measuring the original part to get accurate dimensions, then building up the model. I used an open source program called OpenSCAD which uses a text language to describe how the object is composed of primitive 3-D objects, such as cubes (rectangular cuboids, actually), cylinders, spheres, extrusion of 2D shapes, meshes, etc, which can be joined through union, intersection, and differences. I then exported the model as an "STL" file, which defines the surface of the object in terms of a mesh of triangles. The STL model only defines the outside skin of the object.

The STL is then opened in a "slicer" program, because most 3D printers build up layer by layer (as if the object were sliced horizontally, each layer is a "slice"). This program generates the commands for the 3D printer to create the object. It determines the exact motions of the motors on the printer, which can lead to a good print or a poor one. The slicer also determines

• Skin Thickness
• Infill
• Support material

Each slice is typically printed as a border defining the edge of the part, which is then filled in. A thicker skin may involve multiple loops to define the border edge, or simply a dense linear extrusion near the edge, typically at 45 degree angles to the build plate, with each layer alternating by 90 degrees.

The infill defines how dense the inside is printed - 100% infill means that the part is completely solid, while 0% infill is completely hollow. The slicer settings determine how the infill is drawn, for example linear strips of filament, or hexagonal shapes (leading to a honeycomb structure inside), etc.

Support material may be needed if there are sharp overhangs - the slicer adds structure that is not part of the original part to allow the overhang a surface to be printed on. It does not lay the overhanging structure directly on the support so that it does not bond strongly. After printing, the support structure can be (usually) easily removed.

Once the part is printed, it will have obvious lines/jaggies - the printer has a raw vertical resolution defined by the extrusion diameter, though there are tricks that can smooth things out somewhat; horizontal resolution is considerably better. Finishing can range from using the part as is, to sanding it smooth, painting, polishing, etc. The plastic material I used, PLA, is food-safe, though the additives for color and physical properties may make it less so. ABS printed parts can be finished in a bath of acetone vapor, which melts the surface layer, smoothing the part, at the cost of definition of fine detail.


You can read the OpenSCAD source which can be downloaded from the thingiverse link above. You can also see pictures of the printed object there.

sonnyhad wrote:Is the end result of 3d printing a strong enough material?

Yes. To some extent it depends upon the design and slicer settings, as well as the material chosen. For this application, the knob should be strong enough. And if it breaks, I can just print another

Allon, that's a great explanation - thank you!

-phillip