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Selection of aluminum casting process
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(Mechanical)
(OP)
19 Oct 04 00:11Hi,
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
(Industrial)
19 Oct 04 02:36Tooling costs are going to be the deciding factor on what process you use. Typically in short run parts a wood pattern is made and parts are cast using green sand or no-bake sand. Tooling cost $-$ depending on the complexity of the part. Aluminum patterns will increase the tooling cost to $-$. Permanent mold casting is the next level of tooling but size control and repeatability is excellent. Injection molding is the next step. Tooling cost escalate in each process. Permanent mold and injection molding only work for the light metals, aluminum and zinc and magnesium.
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
(Mechanical)
19 Oct 04 11:36For this type of run it would have to be sand casting id say.
(Materials)
19 Oct 04 22:21For a short run of 50 pieces per batch, sand casting is advisable. Machining the sample out of a block may probably be good if it is difficult to find a foundry to process small batches.
(Mechanical)
(OP)
6 Jan 05 21:08Gentlemen,
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
(Mechanical)
7 Jan 05 00:03Most aluminum founders will put on a big song and dance number about helping you choose from the thousands of alloys that are available. They will then scientifically arrive at the best alloy and temper choice for your particular application.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
(Mechanical)
(OP)
7 Jan 05 00:24Mike,
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
(Materials)
7 Jan 05 08:09Tom--Lost foam is a great casting process for making near net shape castings.BUT--you really need to find a foundry that knows this process. The key is controlling the characteristics of the foam pattern, such as density and moisture content.Also control of the pattern wash coating.Most foundries don't have the expertise to do this, and you end up with lap type defects in the castings.Another problem with lost foam is that you can't control the thermal gradients during solidification, as the process does not lend itself to the placement of chills. 356-T6 is a good alloy for sand castings and if you need higher mech properties you can upgrade to A356-T6, or even 357-T6, which is basically a jazzed-up 356.
(Mechanical)
7 Jan 05 21:10For the same money it would cost you to start up die casting, you could start up with plastic foam.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
(Mechanical)
(OP)
7 Jan 05 23:41Swall/Mike,
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
(Mechanical)
8 Jan 05 12:42I'd expect the tooling costs to be similar.For each process mentioned, you have to sink a die. The die doesn't know what you're going to do with it.
Want more information on oem stainless steel lost wax casting supplier? Feel free to contact us.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
(Materials)
8 Jan 05 12:49Casting experts
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?
(Mechanical)
(OP)
8 Jan 05 12:59Mike,
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
(Materials)
9 Jan 05 00:02You can consider using ceramic molds and cores . this would be true to cast and reproducibity is good. Wooden or metal patterns can be used. This technology is being offered for around US$ by a company in US. It is pretty straight and simple. I too have been considering using this for making thin walled impellers.
mcguire this partly answers your question, wherein all the advantages of investment casting is offered without the need for large investments.
(Mechanical)
9 Jan 05 01:11Tools for rigd polyurethane foam can be made from soft materials. I wouldn't use RPU in an outdoor application.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
(Materials)
10 Jan 05 13:26Tom--ten years ago when I was involved with a couple of lost foam aluminum projects, the captive foundries of the automotive OEM's were the ones with the necessary expertise. Also, the outboard motor manufacturers had it as well. With job shop foundries, it was hit or miss. (My experience was that it was mostly miss).I'm sure the job shop foundry lost foam situation is better today, but off hand, I don't know of any that I could recommend. The more I look at your needs and volumes, the more I agree with the other posters that sand casting is best suited to your needs.Sand casting is very versatile and you can do any aluminum casting alloy with it.
(Mechanical)
(OP)
11 Jan 05 12:06Thank you all for the input. I believe I'm leaning towards sand casting, rubber-plaster mold and similar low-tooling cost processes. The savings should still be substantial w.r.t. machining from billet and allow us to meet our cost target.
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
(Materials)
11 Jan 05 14:47May not be applicable but very interesting.
(Mechanical)
(OP)
12 Jan 05 01:33Unclesyd,
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
(Materials)
12 Jan 05 09:33From the windmills of my mind here is another process that might be viable. I shouldn&#;t tell you that I first worked on this process in .As a matter of interest.
(Mechanical)
12 Jan 05 11:42Hello all,
I would strongly vole for the investment casting for a batch of 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).
(Mechanical)
(OP)
12 Jan 05 16:26Unclesyd,
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
(Mechanical)
(OP)
12 Jan 05 19:16Cancsco,
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
(Materials)
12 Jan 05 22:25 Mcguiness,
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.
(Materials)
25 Jan 05 16:47We work with alot of aluminum casting guys of all types.
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
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We look for long-term partnerships with our clients and suppliers to achieve the greatest efficiency and quality. However, Investment casting Purchasing is a very professional job. So how to purchase investment castings is also becoming a professional work. Besides the application product knowledge, the related technical knowledge of investment casting is required. And they can fully communicate with foundry engineers. Here we list out some main points of purchasing guidelines of precision investment castings.
The casting buyer should learn the design knowledge of the investment casting process. That is helpful for the next purchasing job. One of the most features of investment casting is the flexibility of the structure design. The structure of the parts should follow the requirements of investment casting. It needs easy to mold release, shell making, filling, and cleaning, and also try to achieve uniform wall thickness. This will benefit for establishing a good temperature distribution and the solidification order, avoiding shrinkage cavity caused by local overheating. At design details, the designer should design appropriate casting around corners, to help the filling, cooling, and deoxidization. Especially in new product design, if engineers are familiar with the casting process and take part in it. That will make casting design and material selection more reasonable, easy to guarantee the casting quality, and can reduce the cost of investment castings.
At present, there are two kinds of different production processes of investment casting. One is the water glass casting process. It is a kind of paraffin and stearic acid pattern material with water glass shell technology. The other is the silica sol casting process. It is with high-quality medium temperature pattern material, the whole silicon sol shell, and medium frequency induction melting quick pouring process. The cost of the water glass casting process is low. But the size accuracy and surface roughness are relatively poor. It is mainly used to produce carbon steel and low alloy steel castings. And it is difficult to produce a high level of investment casting. However, the silica sol casting process can produce parts with high dimensional accuracy and good surface quality. It can reach or even exceed the international level of investment castings. So, casting purchasers must understand the foundry production technology and detection methods. Then to determine if the foundry can achieve expected quality requirements for investment castings.
Also need to know the production scale and management level about the foundry. That ensures on-time delivery of bulk orders for qualified castings. To get high-quality investment castings, it will need joint efforts and close collaboration of both sides (supplier & purchaser). Buyers need to spend a certain amount of time developing suppliers before purchasing castings. Except to choose a reliable investment casting supplier, communication between the purchaser and foundry is very important before the design of investment castings.
Therefore, purchasers and suppliers should focus on establishing long-term and mutually beneficial cooperation and a good interactive relationship. If the contention is available, visit the foundry on site is the best way to know it. We are pleased that if the clients come to us.
After confirming the foundry, you can send an inquiry to them. When sending an inquiry to an investment casting foundry, it is better with details of material and technical quality requirements. Such as the required machining sections, locating datum, heat treatment, surface treatment, packaging requirement, inspection, and test items and the inspection report, etc. The quantity of order and the place of delivery will be provided. It is better to provide the weight of castings to help the foundry quotation. The delivery cycle and payment terms are also important factors to be considered. It should be stated at the time of inquiry or quotation. Requirements about the casting quality should be economic, applicable, and reasonable, on the premise of meet the use function, higher requirements will increase the difficulty of manufacturing, may also affect the production cost and price. This is not good for both purchaser and foundry.
Investment casting Parts drawing is the main basis of quotation and production. Its information can help to avoid misunderstanding. Before sending an inquiry to an investment casting producer, a confirmation by clients is needed. The basic details of the drawing can show the part name, material, tolerance, surface roughness, critical dimensions, permitting the residual gate height, processing base, processing surface, and the machined surface, change content, inspection requirements, heat treatment, and surface treatment requirements, etc.
We suggest casting purchasers to map casting and finished machining drawing separately. When the customer has a requirement on internal gate location, parting surface, and the plunger position, will specify the location of the position or not allowed to set in the drawing. For irregularly shaped complex castings, the 3D drawing should be provided, which will be better for a foundry to correctly understand drawings and make casting mold.
And we can also provide a drawing design service if the client has difficulty on drawing design
Based on the design and price agreement, we can start making mold or samples.
Production of investment casting starts from the mold design and manufacturing, mold production cost is generally listed in the quotation separately. It is a one-time cost and should be paid by the purchaser in advance. Surely, mold ownership generally belongs to the purchaser, can be preserved and used by the foundry. Both sides should reach an agreement at the start dealing with the mold. If process need, when foundries need to modify the original drawing design, they should map casting or separately write amendments to a purchaser for confirmation, then to make the mold.
After the mold is ready, the foundry needs to provide samples to the purchaser first to check the size, assembly, or do the necessary testing. Only after passing testing of the sample, can the buyer start mass production. Sometimes it is not very convenient to modify some sizes, for those out-of-tolerance dimensions that will not affect use function, customers can directly use and don&#;t require to modify the mold. In this case, it is better to ask a customer to modify the drawing tolerance according to actual samples. or to write a note when confirming the sample. That can avoid dispute when mass production in the future.
After checking the drawing or sample, when the design is modified, a proper mold fixing fee will be charged. So before making the mold, the purchasing party shall review the drawings and keep good communication with the manufacturer. Sample material generally should be consistent with drawings requirements. When there is difficult to make a sample in required material, the foundry should negotiate with the buyer in advance. After getting an agreement with the customer, the foundry can use another kind of material with a similar or same shrinkage rate. But the sample will be only used to check the size and geometry shape. Again when mass production, drawing material will be applied. When the mold is transferred from a foundry to another foundry, due to the use of different wax materials, shell materials, and technological conditions. It may cause a change in the shrinkage rate.
It is necessary to reconfirm the sample before bulk production.
After confirming the mold making and samples. The mass production order can be placed to investment casting foundry. In producing, the purchasing can keep following the order update. To ask the supplier to provide the lasted news or test record in producing. For first-time cooperation, If need, the purchasing company can send a third inspection party to make the following. After the order was finished, it can be delivered as a requirement.
As an investment casting foundry and supplier from China, frank communication and mutual cooperativeness are thereby our business principle. With qualified products supplying, We would like to offer the best price and after-sales service. To ensure the customer gets the most benefits from our deal and cooperation.
For more oem precision lost wax investment casting manufacturersinformation, please contact us. We will provide professional answers.