I have access to a 3D printer. It just prints plastic (ABS, PLA, PETG, …), so it won’t work for rocket engines, but If you need a part, let me know.
Is it connected to a PC, so all you need is a 3D file?
Details down to 1mm dia are sustainable (don’t fall apart under their own weight)
That suggests it is really weak, since 1mm thick injection moulded ABS is really strong. OTOH there are many applications where one can work with thicker sections…
Peter wrote:
That suggests it is really weak, since 1mm thick injection moulded ABS is really strong.
The problem with 3D printing of delicate parts is that the plastic must be molten/liquid when it comes out of the extruder. There is a delicate balance between letting it cool down slowly enough so that it can bond with the layer underneath – otherwise the layers will just come apart later – and cooling it sufficiently fast (usually with fan with adjustable speed next to the extrusion nozzle) that it will not lose it’s shape. Once solidified, parts from 3D printed ABS and injection moulded ABS should not be much different in strength.
Software-wise, 3D printing (speaking at amateur level – I guess rocket engine parts made from Inconel require different stuff) is a two-stage process: First you have to create your 3D model using a design tool (like the above mentioned Solidworks if you can afford it (I can’t…)). The most common file format for 3D printing generated from that is “.stl” (STereoLithography or Standard Tessellation Language). The second stage is the “Slicer” which computes the layers of molten plastic from the .stl file. This must know all the parameters of your printer and the type of plastic used for printing and will either generate a set of coordinates for standalone printers which can print off SD cards or USB sticks, or directly feed coordinates to a connected printer. Whether or not a part will come out well almost entirely depends on the “Slicer” used. The good ones will adjust printing speed, cooling fan speed, extrusion speed, automatic generation of support parts for overhanging bits of the model (which later will have to be cut away manually) etc. in an optimal way. If you print at home, the “Slicer” and it’s operating parameters will be your major concern. If you get your parts printed from a printshop you need not worry about that.
Another very smart open source 3D modeling tool is OpenSCAD ( http://www.openscad.org/ ). It has a text interface only which is easy to use for an engineer or IT person used to programming languages. It is ideal for designing small parts from known measurements. However the gallery on their home page shows some examples of very complex designs as well.
We have a 3D printer at work. I have never played with it myself, but the parts are of surprisingly high quality. We made a turbine drink mixing machine with it, where the mixing of the drink (Gin and Tonic) was made by the printer 
Thinking about it, that is the only “working” part ever made by it. It is used to make small scale models to customers and to explain things to customers and so on (much easier with a 3D physical object).
Peter wrote:
That suggests it is really weak, since 1mm thick injection moulded ABS is really strong. OTOH there are many applications where one can work with thicker sections…
Yes, that’s right. This is because it’s approaching the granularity of the nylon powder that’s being fused in the sintering process. The minimum resolution is 0.75mm, although shallow details (in legends for instance) work down to about .4mm wide at .3mm high.
But as soon as the material ‘bulks up’, in a wall 1.5mm thick for instance, it takes on the characteristics of moulded nylon. I suspect this is because the volume and thermal properties allow complete fusing of the powder. I suspect the metal sintering has similar properties, though the parts are so expensive I’ve not tested any to destruction (yet!).
Does anybody offer a service where they will use 3d printed plastic parts as a pattern for burnout casting?
Silversmiths use the technique make replicas of almost anything that will burn.
Shapeways offer 3D wax printing for the lost wax process. Fearsomely expensive though especially as you need a 3D part for every piece. The wax melts out, not burning, since this would contaminate the piece.
There’s much discussion of burnout of PLA or other plastic parts for iron or brass casting, but no successful results that I’m aware of so far. There are 3D foam patterns for burnout, but these are CNC, not 3D printed.
Titanium printed structural parts for the 787 – now FAA certified
http://www.cbc.ca/beta/news/business/boeing-dreamliner-printed-titanium-parts-1.4065636
I don’t understand how printing is cheaper than other processes, unless the number of identical items is very low.
Probably because titanium alloys are extremely difficult to forge right, and since they are quite expensive any machining drives costs up.
Titanium can be diecast, to seemingly very tight tolerances.
However this level of printing needs some really exotic equipment, not accessible to any normal person.
