OEM engineers and die cast engineers consider several factors when addressing the elements involved in metal die casting design. One critical element in this process is the geometry of the die cast part and how it relates to the placement of the parting lines.
What is a Parting Line?
An engineer within a die cast company knows that die casting dies must be constructed in at least two parts. When the die is placed within the die cast machine, the two plates come together to form the two halves of the part, whether in aluminum, magnesium, or zinc alloys being used.
Around the perimeter of the part, a visible line will run precisely where the two dies would meet. This line is called the parting line. This line determines which half is the “cover” die and which will be the “ejector” die. It also determines how the rest of the part will be designed with additional processes.
Why is the Parting Line Important?
The parting line determines the overall design of the part in conjunction with the following considerations:
Cost Efficiency
- Reduction of flash formation
- Elimination/reduction of trimming, hand filing, or additional flash removal processing.
- Elimination/reduction of machining.
Engineering Requirements
- Influence tolerances are to be held in the area of the casting. Tolerance standards must follow NADCA guidelines.
- Influences draft angles, wall thickness, and geometry considerations.
- Influences metal flow and casting integrity.
Cosmetic Appearance
- Designating a parting line to “flow” with the contours of the design will optimize the overall aesthetics of the die casting part.
Cosmetic Surface Finishes vs. No Surface Finishes
Surface finishes for die casting component design should be discussed in the pre-planning phase of the part’s engineering. This discussion is critical because the location of the parting line, the gate, overflows, and vents should accommodate and not blemish the part’s surface finish.
1) If cosmetic surface requirements are not a priority, the die casting component will be designed so that the die halves utilize the most advantageous casting conditions and cost-efficiency.
2) If cosmetic surface requirements are a priority, the die cast engineer will work with you to incorporate design practices and additional processes to meet your needs efficiently.
Who makes the final decision on the Parting Line Location?
When working with a metal die casting design, the die casting engineer should be the final decision maker on the location of the parting line. Because the OEM designer may not be familiar with its importance, the die casting engineer should discuss the options available.
