Author Topic: Exploring 3D printing in metal  (Read 4900 times)

Online Vixen

  • Full Member
  • ****
  • Posts: 999
  • Hampshire UK
Exploring 3D printing in metal
« on: August 23, 2017, 08:25:53 PM »
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
« Last Edit: October 30, 2017, 03:58:15 PM by Vixen »
It is the journey that matters, not the destination

Offline Jasonb

  • Full Member
  • *****
  • Posts: 6112
  • Surrey, UK
Re: Exploring 3D printing in metal
« Reply #1 on: August 23, 2017, 08:54:36 PM »
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.

Online Vixen

  • Full Member
  • ****
  • Posts: 999
  • Hampshire UK
Re: Exploring 3D printing in metal
« Reply #2 on: August 23, 2017, 09:08:10 PM »
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
« Last Edit: August 23, 2017, 09:39:59 PM by Vixen »
It is the journey that matters, not the destination

Online Ye-Ole Steam Dude

  • Full Member
  • ****
  • Posts: 1050
  • Deep East Texas on Sam Rayburn Lake
    • Shop Crafted
Re: Exploring 3D printing in metal
« Reply #3 on: August 23, 2017, 09:44:53 PM »

Mike thanks for sharing in such an informative manner.

Thomas

Online Vixen

  • Full Member
  • ****
  • Posts: 999
  • Hampshire UK
Re: Exploring 3D printing in metal
« Reply #4 on: August 23, 2017, 09:55:22 PM »
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
« Last Edit: August 23, 2017, 10:20:01 PM by Vixen »
It is the journey that matters, not the destination

Offline crueby

  • Full Member
  • *****
  • Posts: 7478
  • Rochester NY
Re: Exploring 3D printing in metal
« Reply #5 on: August 23, 2017, 10:36:45 PM »
Excellent information - thanks! It will be interesting to see how the pricing and material choices evolve over time, this is still a young industry.

For Shapeways, I thought that they also had a printing location in Europe to cut the postage to that part of the world?

I've never tried  contacting foundries to get one-offs made from my own patterns, for those who have, how do these prices compare? I wonder how different the pricing would be to get the pattern printed in plastic or wax, then take them to another foundry?  Seems like someone like Jo-The-Casting-Hoarder would know...   :thinking:

Online Vixen

  • Full Member
  • ****
  • Posts: 999
  • Hampshire UK
Re: Exploring 3D printing in metal
« Reply #6 on: August 23, 2017, 10:46:37 PM »
I am going to follow up Jason brilliant idea of casting two halves and silver soldering them together

When I get the 3D model cut in half, I will upload it to Sculpteo and obtain quotations for a 3D printed wax and also for an investment cast bronze half header.

I will add that information to the data base for all to see.

Not sure if Shapeways use a different name in Europe.

Mike
It is the journey that matters, not the destination

Offline jadge

  • Full Member
  • ****
  • Posts: 314
  • Cambridge, UK
Re: Exploring 3D printing in metal
« Reply #7 on: August 23, 2017, 10:49:53 PM »
I've examined some parts printed by the stainless steel infused with bronze method. The printing was done in Europe, but I can't remember which country. I don't recall there being huge tolerance issues. But the engineer who ordered the parts was confused as to why his nice shiny stainless steel part had tarnished to a mottled bronze finish over a few weeks.

This is definitely an area to keep an eye on. The company that had the parts made make gas sensors. One issue with the sintered parts is that they are not guarenteed to be gas tight; which may, or may not, be a problem.

Andrew

Online gbritnell

  • Full Member
  • ****
  • Posts: 1832
Re: Exploring 3D printing in metal
« Reply #8 on: August 24, 2017, 02:58:19 AM »
As I had mentioned when I got my cast parts back from Shapeway, they were done in stainless, they are very hard. They can be touched with a file but just barely so machining can be done with carbide tooling but tapping small holes could be an issue. I would think that brass or bronze would be the better alternative, cost not withstanding.
gbritnell
Talent unshared is talent wasted.

Offline Jasonb

  • Full Member
  • *****
  • Posts: 6112
  • Surrey, UK
Re: Exploring 3D printing in metal
« Reply #9 on: August 24, 2017, 07:43:16 AM »
Mike regarding accuracy it may be worth thinking of your part as a "casting" when you draw it and leave some thickness on the flanges so they can be machined flat by you and also drill the holes yourself. Not a problem machining the wax and cast items.

Another option would be to just get the two halves of the pipework printed and while soldering them up solder on your own flanges. These could be cut and drilled on your CNC leaving them joined by tabs etc so they are all held in position for soldering to keep then where you want them and then separate after soldering.

Out of interest what is the wall thickness of the pipes? Maybe even draw in some tabs/pins & sockets to line things up for soldering like you get on plastic model kits. They could be external which would allow them to be filed off after soldering to keep a clean bore.

Interesting to see the cost of the aluminium parts, I was thinking of having some bearing brackets done but not at that price, would be better to get PLA and burn it out of a sans mould.

Offline ChuckKey

  • Full Member
  • ****
  • Posts: 47
Re: Exploring 3D printing in metal
« Reply #10 on: August 24, 2017, 09:26:31 AM »
Might it be possible to get a core for the manifold printed in, or coated with, a conductive material, and produce a manifold by electroplating? ISTR an impressive article in Model Engineer many years ago in which someone did this. They coated the core with https://en.wikipedia.org/wiki/Aquadag.

Offline Jasonb

  • Full Member
  • *****
  • Posts: 6112
  • Surrey, UK
Re: Exploring 3D printing in metal
« Reply #11 on: August 24, 2017, 09:38:05 AM »
Shapeways have a place in the Netherlands and judging by what jobs they have vacancies for looks like where stuff is printed

https://www.shapeways.com/jobs

Online steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 9652
  • Central Massachusetts, USA
Re: Exploring 3D printing in metal
« Reply #12 on: August 24, 2017, 11:31:52 AM »
Nice write up Mike!   


Lot's to consider there!

DLS is pretty damn accurate in titanium, and I've used those parts before in a Med device prototype.    Amazing properties as well!...

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Chipswitheverything

  • Full Member
  • ****
  • Posts: 256
Re: Exploring 3D printing in metal
« Reply #13 on: August 24, 2017, 12:10:10 PM »
Just to say thank you to Mike, Jason and others for explaining aspects of this remarkable and interesting technology and how it can contribute to practical model engineering. Though I'm not personally likely to get involved, it's good to be updated about the scope of these new possibilities.    Dave

Online Vixen

  • Full Member
  • ****
  • Posts: 999
  • Hampshire UK
Re: Exploring 3D printing in metal
« Reply #14 on: August 24, 2017, 12:33:12 PM »
Thanks for all your advice and feedback.

I have considered several alternatives for fabricating the Mercedes exhaust headers. I can silver solder copper pipes and elbows in a jig. I already have 12 mm and 10 mm copper elbows and the thin wall copper tube. I have also considered electroforming the bannana bunch pipework in copper and silver soldering that to the flanges. Gathos sell a complete elecrtoforming kit for 75 which contains the chemical bath, the chemicals, sacrificial anodes and the conductive paint.

There are many options but I am trying to keep this thread clean as the knowledge base for 3D metal printing.

We know there are a number of 3D print bureaux who specialise in 3D metal printing. They all use similar processes and all operate through the internet. Their price structures are similar.

The SS infused bronze metal printing is affordable, about double the cost of a plastic print. However, it is important to be aware of it's limitations.  (see below)

Most offer printed wax and also full lost wax casting in brass or bronze. This process is size limited to a 3" (75 mm cube). I am still awaiting price indications of these processes to add to the knowledge base. I would expect the price to be mid way between SS infused Bronze and fully sintered.

The highest dimensional accuracy comes from laser sintered metal printing (aluminium, stainless steel, titanium etc) Unfortunately the cost is astronomical.

By far the most attractive process is the SS infused bronze material. What do we know about this material? George reports it is extremely hard, therefore post finishing will be difficult, requiring carbide tooling etc. This suggests the 3D print should be as near to the finished article as possible.

The tech guys inform me that shrinkage and warping may be an issue, depending on the size and geometry of the object. A long tubular manifold with four unsupported flanges is a particularly poor geometry for SS infused bronze printing. Joining the four flanges with tabs would help.

The predicted errors are 2% for parts below 3" (75 mm), and 3% for parts above 3" and pro rata for larger sizes. That seems to imply that small objects like rocker arms etc should be fine but larger objects may need further design consideration. For instance I can cut my Mercedes manifold in half and add a bridge piece between the two flanges. This will stiffen the object and get me into the smaller error band.

The recommended minimum wall thickness for SS infused bronze is about 1/16" (1.5 mm)

This is a fast evolving market and the 3D printers are all striving for higher and higher quality. How long can we afford to wait?

Mike


« Last Edit: August 24, 2017, 01:05:55 PM by Vixen »
It is the journey that matters, not the destination