I am writing on behalf of a renown sculptor based in New York City who is internationally recognized for doing large scale and technically complex works. We will be building a series of standing figurative sculptures using digital replication technology. The figures will be approximately 64â€ tall.
We are now seeking firms that would have the technical capabilities and interest in working on milling for this project. Our challenge is that typically firms that would be capable of this project would generally not be doing â€œsculpturalâ€ fabrication. I would like to ask if anyone may have any recommendations for firms that would be able and interested in working with us on our projects.
We are interested in exploring having the 64â€ figures directly milled in aluminum or bronze using the best milling technology available. We would like to be able to produce the highest definition rendering and also be sure that it is dimensionally correct. We are very well known for the high quality of craftsmanship our artworks, thus the quality of this sculpture is of utmost importance. We are very experienced in high quality metal working and have projects underway in some of the worlds’ top foundries and fabricators. We understand very well the cost and difficult of this project. We have a completed a high resolution scan and polygon model (over 800mgs!) and are beginning to engineer the manufacturing data and explore other RM methods for producing the metal using stereolithographic patterns and patternless casting techniques.
I would appreciate any comments or leads you may have.
It’s a little hard to comment without some representative pics, but I’ll make some general points. 64" is easily within the build envelope of a large 5 axis milling machine. However, your geometry might have other factors that make one piece milling difficult or impossible- undercuts, deep pockets, etc. In those cases, you might have to split it up into several pieces, then weld them together, which is probably not ideal. Also, sourcing (and transporting) such a large block of aluminum will be difficult and expensive, especially when most of the metal will be turned into waste.
Investment casting from stereolithography sounds like it might be better. You would probably have to do the pattern in 2 or 3 pieces and bond them together (which is much easier than welding a large finished piece). The other good thing about using STL is that your geometry will come out exactly as you designed- there is no scope for interpretation, tool marks, etc. In addition, your investment casting foundry will almost certainly have experience working with STL patterns, and they also obviously know about casting sculptural art.
You could machine polystyrene blocks either in one go using a 5 axis machine, or in a series of smaller blocks.
Then sand cast the aluminium. Lost polystyrene casting. The cast aluminium would need a fair amount of finishing however.
Why not start looking in a part of the country that can make your objects to your design needs. Ohio, Illinois Wisconsin, Or Indiana still might have a few foundaries is you are casting the figures. Thomases Register is a good start.
General note, Casting is done in small batch or not in the US.
generally, 64" is quite easy
64" (±.100) easy but takes care
64" (±.01) tougher but well within standard CNC
64" (± .001) starts to get more expensive.
64" (±.0001) you can do it but is generally outside the boundaries of standard machining. add grinding to the mix.
The human eye has a boundary. most people never know 1/2 degree out of level and 1/16" per foot for many constructed items.
do you have tolerance stack up issues? or can you get away with 1/32" here and there?
I am using Mastercam 9.0 to make milling geometry easier without too much M & G Code.
Mastercam can take many imported items but cannot change imported geometry that easy.
There are lots of investment casting foundries left in the US, mostly casting bronze sculptures. That part is easy. I know of a couple here in Denver, and it’s not exactly a hotbed of old-school industry.
And I can’t imagine tolerances are that critical on something like this. +/- .050 ought to be fine, and any sloppy ass machine in the world should hold that.
mfgquote.com is also a good place to start to find shops interested in taking the work and getting quotes. I have found some great machinists that way.
We are definately researching casting SLA. We already have relationships with art foundries who do this as well as mill foam and stone. However, I want to explore milling metal in order to weigh the alternatives. Optimally we are looking for a “direct to metal” method.
When I mention tolerances, our quality issues are more with very fine detail and getting surfaces as smooth as possible without mill lines. I will check MFGquote, thank you, but I am mostly coming to you guys for a shop recommendation.
In practice I have seen this at three locations.
Structural aircraft parts, particularily Boeing landing gear struts. They and similar parts started from an immense forging which was then mounted onto a tremendous multi-axis gantry mill, then other mills for finer localized machining. The parts were individually sandblasted or peened in a sealed blast chamber, producing the most gorgeous finish I’ve ever seen on a metal part. It looked like shallow velvet with dichromic abberations.
Machine tool manufacturer: an even bigger mill to mill the big mills’ parts, follwed by grinding on a gantry grinder, followed by hand scraping the parts to ultimate finish, which were gorgeous.
A company that made small house sized steel and concrete casks for storage of spent nuclear fuel. .
I know the last two will take on custom work.