blog 
Die Casting vs. Screw Machining
Choosing the right process for your metal component
If you’re considering screw machining or die casting for your next part, your project probably requires exact tolerances, quick turnaround times, and is high in production volume. These characteristics make a part a viable candidate for each process.
Although precision metal components are achievable through both production processes, the choice often comes down to efficiency and cost—which production process will add more value to your project? In this blog, we’ll cover the different benefits of screw machining and die casting and what you stand to gain by converting your precision component from screw machining to die casting.
Benefits of screw machining
When it comes to screw machining, there are two main benefits.
The first is the screw machining allows you to manufacture steel alloys that cannot be die cast. Die cast tools are made of hardened steel to withstand the high pressure and heat of the die casting process. Since aluminum and zinc have significantly lower melt temperatures than steel, the metals don’t fuse with the steel tool. Attempting to die cast a steel component, on the other hand, would yield one large block of compounded steel.
The second benefit is that screw machining holds exact tolerances at a lower initial tooling expense. CNC machining of any kind is sometimes thought to hold the tightest tolerances of any manufacturing process.
While it is true that machining produces tight tolerances and precise parts, Dynacast engineers argue that die casting can produce parts of nearly equal precision and increased complexity at a lower part price, faster. And when efficiency and cost are factors in your decision, the benefits of die casting will outweigh the benefits of screw machining every time.
Benefits of die casting
The benefits of die casting are largely associated with production speed and part price savings.
Dynacast’s multi-slide machines can be designed with multiple cavities and enable our engineers to cast extremely complex parts, quickly. Our multi-slide die casting machines cycle at speeds of up to 75 cycles per minute, delivering 4,500 shots per hour. In a two-cavity tool, this means 9,000 parts per hour.
A faster cycle time contributes to lowered overall cost per piece. Additionally, die cast tools ensure unmatched complexity of internal and external geometries, so there are fewer secondary operations associated with die casting. With multi-slide die casting, you can cast complex geometries that would otherwise need to be manufactured from two or more pieces and assembled using any other processes.
While screw machining offers a lower up-front tooling cost, die casting more than makes up for that in the overall part price savings. On an ideal part (one that is small, high volume, and can be cast in zinc), the tool is paid back in full somewhere between 10-14 months of production. Every part made after that is an earning towards your bottom line.
Do you want to know if your current chosen alloy can be converted into a zinc alloy with similar properties? Consult our interactive metal selector tool, or ask one of our engineers.
What do you gain from converting from screw machining to die casting?
So maybe you’re currently screw machining your precision metal component. While this effectively produces a complex part, our engineers recognize the drawbacks of screw machining as compared to die casting. In addition to offering higher efficiency at a lower overall piece part price, die casting also offers greater design freedom, exacting tolerances, and material waste reduction.
Open capacity for parts that can’t be screw machined
One of the biggest advantages of converting to die casting from screw machining is that die casting allows you to produce shapes that are impossible to achieve with screw machining. When utilizing screw machining as a manufacturing process, you are limited to parts that can be machined from bar or tubular stock on a rotating axis. Parts that require complex inner geometries or dissimilar features are virtually impossible to screw machine.
Exact tolerances, faster
When converting to die casting, design engineers are often concerned that die casting won’t be able to hold as tight a tolerance as screw machined parts. Generally speaking, if you screw machine slow enough, the tolerances are unmatched. With that said, taking the time to do so slows down the entire production process, and often, the tolerance that a project requires can be accommodated by multi-slide die casting.
The concessions for tight tolerances, while there may be some, are not great. Multi-slide die casting produces precision components with tolerances of +/-0.02mm. And with Dynacast, design engineers are able to work together with customers to tweak the design of the part for optimal manufacturability, delivering faster cycle times and increased part performance.
Reduce scrap/raw material waste
Finally, converting from screw machining to die casting drastically cuts down on wasted material.
Screw machining works by cutting away from a solid piece of metal, or tubular stock. That means, as the customer, you’re paying for all the raw material that goes into the tubular stock, not just the material in the final part. You’re paying for the wasted metal that hits the floor.
In contrast, in a four-cavity die casting tool, the gating system only produces waste roughly the size of the tab of a pen cap. By utilizing die casting, you’re cutting down on waste and additional cost while improving your overall yield.
Die casting is an ideal match for high volume projects that require tight tolerances and speedy delivery. Want to learn how to design for optimal manufacturability in die casting? Download our free design guide to learn more.
