Investment Casting Purchasing Guidelines
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.
First, About Investment Casting Process
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.
Second: Choose the Investment Casting Foundry
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.
Third: Send Inquiry and Get Quotation
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.
Forth: Drawing
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
Fifth: Mold or Sample
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.
Sixth:Place investment casting order
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.