Supporting > Additive Machining
Exploring 3D printing in metal
Vixen:
I have been following George's and Kvom's adventures into 3D metal printing with great interest. So rather than hi-jack either of their build logs, I have started a new topic.
Both George and Kvom have been successful in getting small parts printed directly in metal by Shapeways in the USA. George had some rockers and exhaust header parts printed in Stainless steel infused with bronze. Kvom had some small governor parts produced by lost wax casting from 3D printed wax. Both of these examples of 3D metal printing were small and intricate and would have been difficult (but not impossible) to produce by machining.
I enjoy exploring new technology especially if it could be applied to my large 1/3 scale Mercedes engine. A little research revealed there were similar 3D print bureaux in Europe who offered a similar service to Shapeways. Shipping and 20% import duty can be a killer for stuff made in the USA. At the moment, goods move tax free within Europe.
I produced a Solidworks model of the exhaust header for my Mercedes engine and e-mailed the file to three 3D print bureaux to compare prices. I contacted Shapeways, I-materialise and Sculpteo. All three responded with quotations in all available materials with the hour. Sculpteo, based in Paris, were slightly less expensive of the three. I ordered a hard plastic 3D print to prove the Solidworks model and confirm it would fit the space available on my engine.
This is the component I have used for all the cost comparisons. As you can see this exhaust header was considerably larger than the previously described parts. It consists of four flanges and four intersecting pipes each 11 mm in diameter. It would be difficult, but not impossible, to fabricate from tubes and silver solder. 3D metal printing offered a much easier alternative.
Sculpteo are slightly less expensive of the three firms contacted and offered to make one exhaust header in various materials for the following prices:
Laser printed rigid white plastic £12 dimensionally very accurate. This plastic is an ideal way to prove the 3D model and for trial fitting.
Laser sintered aluminium £122 dimensionally accurate
Laser sintered S316 stainless steel £252 dimensionally accurate
Laser sintered titanium £309 dimensionally accurate
Binder printed stainless steel infused with bronze £24 Dimensional errors up to 3 to 4 % Long thin items can bend and warp. The stainless steel powder is printed with a binder. then bronze powder is melted in a special furnace which infuses into the stainless steel.
Binder printed S316 stainless steel no price available as the exhaust header was too big for the printer
Lost Wax cast brass £171. Dimensional errors up to 4 % The lost wax model is laser printed, invested and cast, on site by Sculpteo. The dimensional accuracy can be improved by modifying the 3D model by a few %. Expensive trial and error. Limited to a 75 x 75 x 75 wax print envelope.
Lost Wax cast silver £207. Dimensional errors up to 4 % Intended for the jewelry trade. The lost wax model is laser printed, invested and cast, on site by Sculpteo. The dimensional accuracy can be improved by modifying the 3D model by a few %. Expensive trial and error. Limited to a 75 x 75 x 75 wax print envelope.
Lost Wax cast aluminium. Lost wax cast aluminium was on trial and is no longer offered.
Shipping was typically £15 per item
The stainless steel infused bronze price looked very attractive, the laser stuff was out of the question.
I ordered the rigid plastic test print, which arrived within five days. The print was perfect, all 16 bolt holes lined up perfectly with those on my engine, the surface texture resembled sand blasted metal, there were none of the contour lines we expect from DIY 3D printing. Everything looked good, perhaps too good to be true. I decided to contact the tech guys in Paris before I placed my order for 4 exhaust headers.
It was just as well I called them. They explained the stainless steel infused with bronze process. It appears the first stage is to 3D print fine stainless steel powder with a special adhesive binder. The stainless steel model resembles a sugar cube but is much more fragile. The SS model is transferred to an autoclave, where it is heated, under pressure and inert gas, together with some fine bronze powder. The bronze melts and infuses the stainless steel model by capillary action Must be similar to silver solder flashing into a joint when the correct temperature is reached.
Unfortunately larger items and long thin geometry items, such as my exhaust pipes, tend to shrink, twist and warp in an unpredictable manner during the infusion process. Small and compact items do not suffer so badly. The engineer said they would not guarantee dimensional errors to be less than 4% for my geometry and that the error was unpredictable, all four prints could be different. As you can understand my 3D project ended there. The best they could offer for steel infused with bronze was around 5 mm whereas I work to and want +/- 0.1 mm.
So this becomes a cautionary tale; it would seem that low price and high accuracy cannot be achieved for larger objects. The Laser sintered stainless or titanium processes may well give the necessary dimensional accuracy, but the price is prohibitive. I expect all the 3D print bureaux will achieve similar accuracy, if they are honest. They all use the same machinery and production processes. The sales desk promises the world but the engineers are more realistic and truthful.
Well that's my experience of 3D metal printing to-date, other may have better results. I would welcome your feed back and experiences. This looks to be as good a place as any to record our experiences.
Mike
Jasonb:
Mike, would be worth splitting the manifold drawing down the middle and getting a quote to lost wax cast each half in bronze which you could then silver solder together.
Vixen:
Jason,
That's one brilliant idea.
Another is to rotate the drawing through 45 degrees, then it will fit within the diagonals of the build box. The quotation system is automatic so does not consider rotating the model through different angles.
My worry is still dimensional accuracy. Lost wax is a four stage process all have shrinkage to cater for. Print the wax, invest it in plaster, burn out and finally pour the metal. Kvom achieved good accuracy but then the governor arm was very small.
I will pursue the lost wax idea with Sculpteo. At least they do talk and discuss. I will try to find out what dimensional accuracy they expect to achieve.
Mike
Ye-Ole Steam Dude:
Mike thanks for sharing in such an informative manner.
Thomas
Vixen:
Thomas
For £ pounds, you can read $ dollars or Euros. There value is close enough to give you a comparison of the different processes.
The various 3D print bureaux will give you a firm quotation based on your uploaded drawing within the hour.
Mike
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