What is the Process for Casting Design in Foundries?
Casting is the manufacturing process that foundries use when they are trying to create parts in specific desired shapes. Liquid material is poured into a mold which contains hollow cavities of the shape needed and then allowed to solidify.
Good metal casting design seeks to create the simplest mold possible to make the shape the foundry engineer is tasked to make. The engineer or designer chooses metals and casting methods that are best suited to the project needs. They then create a design based on their experience with the given materials and available methods in the foundry where they do their work.
The client that has ordered these cast parts will need to know how the cast metal object will behave when struck; how it might behave or stand up to different heat conditions and under stress. Will the part warp, crack, or deform over time? Answering these questions will help the engineer determine what kind of metal is best for each individual product.
Metal designs may also require a certain grade of finishing for aesthetic or mechanical reasons. The engineer who is creating the design must choose the right metals and casting method to meet these requirements and needs. He or she must then create a design that will meet those needs entirely. Knowing how certain metals behave when melted into liquid, how it will behave during the cooling process, and once it fully solidifies is important when creating a design. Knowing the answers to all the important questions will minimize problems on the production floor.
There are four main metal characteristics that affect the outcome of a casting design:
- Fluidity: This refers to the ease with which various metals will flow when they are in a molten state. The more fluid a metal is when liquid, the better it can capture small details within a mold.
- Pouring temperature: This refers to the temperature at which a given alloy can be poured; the hotter the metal, the more production challenges.
- Shrinkage: This refers to the contraction rate of molten metal as it cools once it has been melted into a liquid state. Liquid shrinkage describes the contraction rate when the metal first begins to cool, solidification shrinkage describes the point in time when the metal starts freezing from liquid to solid, and solid shrinkage is when the metal has set. These are important factors in predicting strains and defects that might occur during cooling. If parts of the design freeze much faster than others it can challenge the integrity of the casting.
- Slag or Dross formation: This describes the presence of non-metallic inclusions in a casting, and where they are acceptable (surface) or detrimental (sub-surface).
If an engineer has a deep understanding of all the factors above, and understands the relationship with the materials he or she has chosen and the methods that will be used to create the casting he or she has designed, they will help the staff of the foundry create high quality products.
It’s important to have a firm knowledge or the behaviors of each type of metal during the liquid and solid state and how they behave during cooling.
Metals with less fluidity may do better in molds that have less small detail. More brittle metals during cooling may be less suited to designs with sharp edges that are prone to chipping. Knowing melting temperatures can mean understanding how much monitoring of the product will be required by the foundry workers as they produce the products on the foundry floor. Steel has a high melting point therefore it requires a good deal more monitoring and precision throughout the casting process. Designers, engineers, and metalworkers all need to work together to create the best possible product and to keep production time and costs down for the customer and the foundries bottom line.
Product functionality is key. The end product needs to be of the highest possible quality and meet the needs of the end users. There are many expectations and requirements that must be met for any part being cast.
The other most important factor is the castability of the design. What will the costs associated with producing and machining that part be like?
Everyone in the foundry must communicate and work together to ensure the parts meet the standards that the foundry and the customer expect and to keep costs at a minimum for all concerned. Everyone should be included in the design conversation when a casting project comes in.
There’s can be a very high cost associated with having to go back and do the work all over again of the parts created are unacceptable.
Faircast Inc. Foundry has a highly qualified and extremely experienced engineers, designers, and staff members who will work together to make the products of parts you need. Our engineers will work closely with you during the casting design process which can save time and headaches for everyone. The earlier you get involved in the process the more likely it will be that time and costs will reflect the effort.
For all your metal casting needs, consider speaking with one of the Faircast Inc., engineers. We look forward to working with you.