Selection of aluminum casting process
Selection of aluminum casting process
(OP)
Hi,
I have some very basic questions and will appreciate any and all help. We're tooling up for production of a new product we've developed. The product can be seen at (www.tailboats.com)
There are three of four major aluminum parts that should probably be made using some form of casting technology. The largest part runs approx 12" x 3" x 6". Fatigue resistance, corrosion resistance and tensile strength are primary considerations. The parts will require some finish machining operations after casting and will then be powder coated.
We'll be ordering the parts in batches of less than 50 parts each.
I'm not clear on the relative technical and cost benefits between the various casting processs...eg. permanent mold, investment casting and die casting.
What casting processes should we be considering first? What kind of tooling and production costs should we expect...order-of-magnitude? Do you have any recommendations as to who we might contact?
Thank you for your help.
Best regards,
Tom
I have some very basic questions and will appreciate any and all help. We're tooling up for production of a new product we've developed. The product can be seen at (www.tailboats.com)
There are three of four major aluminum parts that should probably be made using some form of casting technology. The largest part runs approx 12" x 3" x 6". Fatigue resistance, corrosion resistance and tensile strength are primary considerations. The parts will require some finish machining operations after casting and will then be powder coated.
We'll be ordering the parts in batches of less than 50 parts each.
I'm not clear on the relative technical and cost benefits between the various casting processs...eg. permanent mold, investment casting and die casting.
What casting processes should we be considering first? What kind of tooling and production costs should we expect...order-of-magnitude? Do you have any recommendations as to who we might contact?
Thank you for your help.
Best regards,
Tom





RE: Selection of aluminum casting process
Investment casting creates a wax pattern of the part, the part is attached to a sprue and then coated with refractory
several times until the shell is strong enough to support itself and the molten metal. The shell is de-waxed and sintered/preheated and the metal is poured into the shell. Extremely tight tolerances can be achieved using investment casting and all the machining would probably be eliminated.
I would think you would not use aluminum for this part due to corrosion. I would think you would be looking at stainless.
For your first runs of parts I would probably try to make the parts weldments or machine from solid. Prove out the design and see how the market for the product is deveoping and then go to castings.
Hope this helps
Bill
RE: Selection of aluminum casting process
RE: Selection of aluminum casting process
RE: Selection of aluminum casting process
Thank you all so much for your input.
The tooling costs for sand casting are less than I anticipated. However, a concern I have with sand casting is surface finish and fatigue. One of the parts is subject to +/-5 ksi fully-reversing alternating stress per FEA. In your experience, will this be a problem for a sand casting?
The lost foam process sounds interesting.
Powder coated aluminum should be fine for a marine environment. I will take a close look at Almag 35.
We may be able to go for larger quantities.
We've already built and tested a full-scale prototype, so are satisfied with the overall kinematics. The parts for the prototype were all milled from standard aluminum sections. Now we need to redesign all the parts for the selected manufacturing processes.
Best regards,
Tom
RE: Selection of aluminum casting process
It always turns out to be 356-T6.
;---
Lost foam is particularly good at difficult parts, where it would be impossible to remove the pattern from the mold. The patterns aren't removed in the usual way; they're consumable, so you have to tool up to make them in quantity. Your parts look simple enough to do with reusable wood patterns in classical sand molds.
;---
Until your volumes go way up, you should seriously consider hogging the parts from thick bar or plate. If you can make them with a relatively small number of relatively large diameter tools, a CNC mill can achieve astonishing metal removal rates, and the mill's owner can offer competitive pricing. Also, 'billet' parts have a certain snob appeal to the gearheads who might buy your boats.
Don't even try to start with flimsy rolled sections; they'll move away from the cutter and 'sing' even at low feed rates. If you've got the spindle speed and feedrates high enough, milling is almost silent, the chips hit the ceiling, and they leave a mark...
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Selection of aluminum casting process
The parts are currently milled from billet. This approach is too expensive, even at high metal removal rates.
My primary reason for evaluating various casting technologies is to slash parts manufacturing cost by at least a factor of 3. With die-casting, I can achieve a 15:1 cost reduction on the larger parts...but die-casting is a bit of a wild card in terms of fatigue strength, or at least it presently appears so. So I'm focusing on other casting technologies.
Agreed...356-T6 looks to be the best all around casting alloy for these parts. The LF process is intriguing.
Best regards,
Tom
RE: Selection of aluminum casting process
RE: Selection of aluminum casting process
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Selection of aluminum casting process
An attraction of LF is that there may be more flexibility on section thickness than with die casting.
If you can recommend any foundries who've mastered the lost foam technique, I'd be most grateful.
Mike, I'm not sure what you mean by "For the same money it would cost you to start up die casting, you could start up with plastic foam". Are you suggesting the tooling cost for LF is comparable to that of die casting?
Many thanks,
Tom
RE: Selection of aluminum casting process
For each process mentioned, you have to sink a die. The die doesn't know what you're going to do with it.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Selection of aluminum casting process
Is it possible that investment casting (lost wax) may offer the best economy for the short run size in that a scaled-up (for shrinkage) model of the part could be used as a pattern and then some or all machining may be eliminated?
RE: Selection of aluminum casting process
Tooling cost is an area that seems to offer a fair bit of flexibility...bridge tooling, permanent tooling, rapid tooling. I'd have thought that a tool for foam or plastic might be made from aluminum or some type of SLA/SLS material, kirksite, etc. Whereas a die for molten aluminum would require cast iron or steel...though Laserform might also work here.
My budget is limited (whose isn't? ;)) and for current needs I'd be satisfied with a tool life of 1,000's of pieces, not 100,000's. By the time we sell 1,000's of units, tool cost will no longer be a major issue.
Sooo many options. Many foundries seem to have a vested interest in the traditional tooing technologies and tooling suppliers. These might work if I were Ford or GM, but I need to economize aggressively....which means becoming familiar enough with all the options to be able to start excluding them from further consideration.
Best regards,
Tom
RE: Selection of aluminum casting process
mcguire this partly answers your question, wherein all the advantages of investment casting is offered without the need for large investments.
RE: Selection of aluminum casting process
Other resins require more pressure, or are abrasive and/or corrosive.
I wouldn't count on lost wax getting you close enough to net shape to eliminate machining. I assume you're talking about machining bearing surfaces of the moving parts. Because the product is human- powered, there's not a lot of power to waste, and excesive friction or loose fits will cause perceived quality problems.
;--
Will you ever have the volume to pay for hard tooling? Frankly, I think not; you've got a niche product there. I'd be inclined to go with the sand casting for now, and as time permits, produce interchangeable part _designs_ optimized for the different processes that have been suggested here. Do conjectural designs for different production volumes, and get quotes on them, just in case Sharper Image or Wal-Mart calls.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Selection of aluminum casting process
RE: Selection of aluminum casting process
Mike H...we're planning on secondary machining for the critical bores. The bores hold rolling element bearings or bushings. The only concern is fit.
Best regards,
Tom
RE: Selection of aluminum casting process
http://www.tpicast.com/about.asp
RE: Selection of aluminum casting process
Thank you.
I just got back from the Pacific Design & Mfg show in Anaheim. Spoke with the folks at Harmony/TPI who are working up a quote for us. Interesting process. Tooling costs look reasonable for smaller quantities. Surface finish is pretty decent too.
The rubber plaster mold process also looks interesting. Came away with a lot of new insights and options.
Best regards,
Tom
RE: Selection of aluminum casting process
http://www.portshellmolding.com/home.htm
As a matter of interest.
http://site.cubictechnologies.com/3d/PAGE27.HTM
RE: Selection of aluminum casting process
I would strongly vole for the investment casting for a batch of 1000 pcs as the costs involved in the tooling and the production are less. Also this would be the best for little after machining operations (good Surface finish).
RE: Selection of aluminum casting process
Thank you. You are a storehouse of knowledge. I will contact the folks at Port Shell Molding and Cubic.
The metal spray mold-making process of Cubic is of particular interest. I've been looking for a mold-making technology for injection molded parts that could significantly reduce tooling costs, which is a major hurdle for the introduction of any new product. Their metal spray process looks like a possibility. Simpler than SLA/SLS.
The Port Shell molding process may also suit a couple of our parts particularly well.
Best regards,
Tom
RE: Selection of aluminum casting process
We have not ruled out investment casting as a possibility. The product has several parts, and it is likely we will employ a number of different casting and molding processes.
Functionality and cost are the main drivers. If there's a lower cost process or material that provides the required functionality, we'll go with it.
One downside of all this is that there are so many different options to choose from, yet there is not very much info on the relative costs for each option. This necessitates a lot of budgetary quoting.
I suppose it would be helpful if there were vendors who could provide competitive bids for supplying all the parts per processes of their own recommendation. We would provide specs, design drawings and applied loads for each part detailing features required for functionality. The vendor would select a manufacturing process for each part and refine each part design for manufacturability (shelling, ribbing, etc). The manufacturing of each part may be vendor in-house or outsourced. In this manner, we could more effectively draw on the accumulated expertise of those who are more intimately familiar with the various technologies. The vendor proposing the lowest cost, technically compliant "package" would get the job. Is such an approach common in the casting and injection molding industry? I suppose a strategic alliance of some sort could accomplish the same.
Best regards,
Tom
RE: Selection of aluminum casting process
As your batch quantities are rather small , the process of manufacturing not defined and the technical delivery condition not in place large units having the expertise and means might shy away from quoting. The smaller ones would be keen to supply but will need all the technical inputs from you. I suppose this must have been your experience.
Most often the foundries adopt the safe and mean path by asking the customer to define all the parameters and freeze the drawing. There is also the big question of product liability in the event of a failure.(Many unpleasant issues will arise!!)
This problem to some extent can be handled by independent consultants and designers who have their network around the industry. Academics may not be successful in this aspect.
RE: Selection of aluminum casting process
Sounds like sand would be best, there are precision sand guys, a356 is probably the best. Let me know if you need some names of good foundries. we could even get you several quotes. Send me a drawing