Die Casting vs Screw Machining

Precision metal components can be manufactured through die casting as well as screw machining. Both processes are able to produce parts with quick turnaround times, and exact tolerances. 

The decision to choose between die casting and screw machining often comes down to cost, efficiency as well as casting material. Here, we cover the benefits of both processes as well as reason to move from screw machining to die casting. 

What is die casting?

Die casting is an automated casting process where liquid or molten metal is pressed into a mold with high pressure and high filling speed. The liquid metal is allowed to cool and solidify. Once it hardens, the mold is opened and the casted part is ejected. 

Alloys with low melting points are usually used in die casting. The die casting process is very fast and suitable for producing large and complex components in a short amount of time. Two types of die casting that are commonly used is hot chamber die casting and cold chamber die casting

What is screw machining? 

In screw machining, precision finished parts are created using automated lathes and turning centres. The raw workpiece is rotated on the machine. Excess material is shaved off by the attached cutting tools at different angles and depths to achieve the desired shape and size. 

Screw machines can be used to manufacture close tolerance, metal, as well as plastic products. They are also often a top choice when it comes to creating threaded components. 

Benefits of screw machining

Screw machining offers two main benefits:

Screw machining allows steel alloys that cannot be die casted to be manufactured. Die cast molds are created with hardened steel in order to be able to function under high pressure and temperature that is essential in the die casting process. 

Metals with low melting points such as aluminium and zinc are used because they will not fuse with the mold. However, if a steel component is used, it would fuse with the mold. The end result would be a large block of useless compounded steel. 

Besides this, screw machining holds exact tolerances at a very low initial tooling cost. In fact, it is often thought that CNC machining has the tightest tolerances when it comes to manufacturing processes. As such, the initial investment for screw machining is much lower as compared to die casting. 

Benefits of die casting

Die casting is one of the most popular manufacturing techniques simply because it is economical and efficient. Die casted parts are used in many industries because of the following advantages that this process offers:

  • High speed production for high volume – Through die casting, complex shapes with close tolerances can be mass produced quickly. Little or no machining is required for die casted parts.High quality tooling ensures that the thousands of castings that are produced are identical. Multi-slide die casting machines can often deliver over 10,000 parts per hour. 
  • Dimensional accuracy and stability – Die casted parts are very durable and dimensionally accurate with close tolerances. 
  • Multiple finishing techniques – Die casted parts can be manufactured with smooth or textured finishes as according to the desired end product. They are also easily plated without difficulty. 
  • Strength and weight – Die casted parts are strong when compared to other injection moldings such as plastic. Thin wall castings are lightweight and strong.
  • Simple assembly – Integral fastening elements such as bosses and studs can be used to assemble die castings. 
  • Price – High speed production equals to lower overall cost per piece. Die casting tooling can also create internal and externally complex parts and thus, reduce the need of secondary operations such as sanding and polishing. Although the initial cost can be high, die casting can offer large overall savings. 

Why change from screw machining to die casting? 

If you are currently screw machining or deciding between die casting and screw machining, here are a few reasons as to why you should consider the die casting process for your project. 

  1. Die casting offers the capacity for parts that cannot be screw machined. With screw machining, there are only a limited number of shapes and sizes that can be machined from a bar or rubular stock that is roasted on an axis. 

Parts that include complex inner geometries and unique features are quite impossible to manufacture with screw machining. However, precision die casting allows you to produce parts with complicated interiors and exteriors. 

  1. Die casting holds exact tolerances, faster. One of the reasons many hesitate to convert from screw machining to die casting is the concern that die casting will not be able to hold as tight a tolerance compared to parts produced through screw machining. 

Tolerance for screw machined parts are indeed unmatched if it is done slowly. However, taking the time to create the desired parts so carefully will slow down the entire production process and drive up production costs. Many project required tolerances can be accommodated with die casting. 

For example, multi-slide die casting can produce precision parts with +/-0/02mm tolerances. 

Design parts can also be tweaked and lenient tolerance zones allowed for non critical parts to optimize production for quicker delivery times. 

  1. Die casting reduces scrap or raw material waste. Parts are produced by cutting away from a bar or tubular stock in screw machining. Manufactures who choose this process are paying for all the material, including the wasted metal that is being cut away. 

With the gating system on die cast machines, the die casting process produces minimal waste. This will further increase your overall earnings.  

Conclusion

While screw machining and die casting are both processes that can be used to produce precision parts, the advantages of die casting far outweighs that of screw machining. Die casting is ideal for high volume projects that need tight tolerances as well as fast delivery times. 

This article is a part of our comprehensive guide on “Die casting: Process, Equipment, Uses, and More

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