When designing a part in zinc, to help deliver the flow of molten zinc a critical component is gate design with zinc castings. Welcome back to our two-part series on understanding gates in zinc die casting.
Determine The Gate Size
Our design engineering team use PQ². We match up the part, the mold with the machine with the PQ² process.
Including looking at dry shot parameters, how fast you can move the plunger.
We put it onto a graph, to determine what gate size give us the best quality fill.
Depending on the quality necessary for a plated, painted part or a mechanical finish.
Typically, the gate location and the size of the gate will determine the size of the machine. Machine size will determine how good of a quality part we get.
Now, for a lower quality surface finish, the part does not require a chrome plated part. Allowing us to consider going with more cavities in the die. The more cavities you put in a die, the lower the quality of the part or finish you will receive out of the part.
You are sacrificing some quality of the part when you add more and more cavities to your tool. We like to just run the dies as fast as we can and with as few cavities as possible.
As well as the use of large tonnage machines to get better quality parts.
Machine Selection Factors in Gate Design with Zinc Castings
To get better quality parts we use large tonnage machines.
However, when part price takes a higher priority than quality, we design the casting with multiple cavities.
Using multiple cavities for the casting, provides a reduction of cost. Our design engineers provide the best quality mechanical finish or paint finish they can achieve with multiple cavity castings.
However, it is sometimes difficult to obtain a cast with this design for paint finish and plate finish.
Cost Factors in Gate Location
Another factor to consider with a quality part is part geometry and wall thicknesses. We use different styles of overflow to make sure that the gasses, once we pull them out of the casting, don’t reenter the casting. Jim, Senior Engineer, uses that example, illustrating how the geometry of a part can trap air during the fill.
Jim continues with a lot of times the customer has restrictions on what they’re calling decorative surfaces.
They will not want a gate location in a certain area. That adds a lot of complications then perhaps with the geometry of the part.
When we are unable to put a gate where it needs to be, the part will need to go through a machining operation. This secondary machining may be a buff operation, trying to eliminate the gate presence as much as possible.
The gate location can play a part in determine cost of the casting. Added machining operation will increase the cost of the casting.
Flow Simulations
The flow simulation helps verify the gate design with zinc castings. Our engineers are able to try different types of processes to use when designing a casting.
Using flow simulation allows us to get radical with our designs. Jim recalls, a large casting they designed with help of flow simulation. The casting was a foot for the underneath component of a table.
Jim said, “I went with a bizarre what we call caliber gates, where we have two tangential gates approaching each other.”
All the flow comes in the middle and collides when using the two tangential gates.
Two gates caused the molten zinc to come in the center. The flow simulation showed the zinc start filling the cavity and pushed the air out of the casting that way.
Typically, when you collide flow, it does not have a good outcome. However, with flow simulation they were able to try it. The simulated parts looked good; leading us to build the tool that way. This is a radical concept, to fill it in the center and have the flow keep building and push the air out.
In Conclusion
Gate design with zinc castings is critical for part design. Our engineers, backed by advanced flow simulations, demonstrate the innovative approach we take in pushing the boundaries of design. Adjusting the approach to the gates in different geometries to get the desired flow effect through the gate area.
The Deco Advantage
Michele Duwe
Michele Duwe is the Sales and Marketing Manager with Deco Products. She has eight plus years as a digital marketing manager and over a decade of sales and marketing experience.
