Plastic injection molding is the most commonly used process in the factories as its demand in the market is quite high and is rapidly rising also with the each passing year. Because of its cheaper cost and fast manufacturing to gives the desired shaped results, it is very renowned among the people.
The manufacturing of an injection mold could possibly be the greatest expense a new product faces in the development cycle.The most common question we hear from designers and product engineers is, “How much will a plastic injection mold cost to make my product?”
Many factors play roles and directly affect the cost incurred to create an injection mold for your custom parts. In any case, a reliable injection molder should be able to provide an accurate estimate quickly from either a 3D CAD file, sketch or the general dimensions of your product.
The material cost is determined by the weight of material that is required and the unit price of that material. The weight of material is clearly a result of the part volume and material density; however, the part’s maximum wall thickness can also play a role. The weight of material that is required includes the material that fills the channels of the mold. The size of those channels, and hence the amount of material, is largely determined by the thickness of the part.
The production cost is primarily calculated from the hourly rate and the cycle time. The hourly rate is proportional to the size of the injection molding machine being used, so it is important to understand how the part design affects machine selection. Injection molding machines are typically referred to by the tonnage of the clamping force they provide. The required clamping force is determined by the projected area of the part and the pressure with which the material is injected. Therefore, a larger part will require a larger clamping force, and hence a more expensive machine. Also, certain materials that require high injection pressures may require higher tonnage machines. The size of the part must also comply with other machine specifications, such as clamp stroke, platen size, and shot capacity.
The cycle time can be broken down into the injection time, cooling time, and resetting time. By reducing any of these times, the production cost will be lowered. The injection time can be decreased by reducing the maximum wall thickness of the part and the part volume. The cooling time is also decreased for lower wall thicknesses, as they require less time to cool all the way through. Several thermodynamic properties of the material also affect the cooling time. Lastly, the resetting time depends on the machine size and the part size. A larger part will require larger motions from the machine to open, close, and eject the part, and a larger machine requires more time to perform these operations.
The tooling cost has two main components – the mold base and the machining of the cavities. The cost of the mold base is primarily controlled by the size of the part’s envelope. A larger part requires a larger, more expensive, mold base. The cost of machining the cavities is affected by nearly every aspect of the part’s geometry. The number of cavities you incorporate into your mold will directly correlate in molding costs. Fewer cavities require far less tooling work, so limiting the number of cavities in-turn will result in lower initial manufacturing costs to build your injection mold.
The quantity of parts also impacts the tooling cost. A larger production quantity will require a higher class mold that will not wear as quickly. The stronger mold material results in a higher mold base cost and more machining time.
One final consideration is the number of side-action directions, which can indirectly affect the cost. The additional cost for side-cores is determined by how many are used. However, the number of directions can restrict the number of cavities that can be included in the mold. For example, the mold for a part which requires 3 side-action directions can only contain 2 cavities. There is no direct cost added, but it is possible that the use of more cavities could provide further savings.