It is important for injection moulders and product manufacturers to work within their budgets while still getting products to market in a timely manner. The design process is a major step for both the manufacturers and the injection moulders, and it can have a huge impact on the final outcome of the project. Including plastic mould injectors in the design process at an early stage can help to improve cost effectiveness, efficiency and the timeliness of the project.
There are a few common elements that are part of the design step in the manufacturing process.
Design starts with Drafting.
Draft angles enable the cooled and finished part of the product to be ejected from the mould easier. If friction can be minimised as the part is released from the mould, that can reduce damage to the part and wear on the mould. Draft angles are calculated very carefully to ensure that there is little pull on the product or the mould during release.
Wall Thickness is another important factor.
If the wall thickness is uniform, then that helps to minimise cosmetic defects and ensures that the moulded parts are structurally strong. Most resins will have a wall thickness of between .04 and .150, but it is important to work with a skilled and experienced injection moulder to ensure that the thickness specifications are correct for the material you want to use. If you want to ensure that your product doesn’t warp or have sink, then you should be very careful about wall thickness.
Strengthen the walls with Ribs.
Most injection moulded products will use ribs to reinforce the item’s walls without the need for greater wall thickness. If you have a very complex part, then you can decrease the mould flow length with some decent rib design. Ribs are usually about 2/3 the thickness of the walls or less. If wider ribs are used, then there can be some sinking problems to deal with later.
The Gate Location is vital.
The part of the mould where the plastic material will flow into the mould part cavity is the gate. Some parts are made using multiple gates, and these can help determine the polymer molecule orientation. The location of the gates affects how the part will decrease in size as it cools, so it is vital to ensuring that your part will function properly.
The location of the Ejector Pin can help apply proper force.
To assist with ejection from the mould, an ejector pin will be used, and its location will be crucial during the early stages of the manufacturing process. If the ejector pin isn’t placed properly, then your product can have some unwanted marks. How thick your product walls are and the texture of the sidewalls helps to determine the optimal position for the ejector pin.
Sink Areas must be assessed.
Sometimes, the material in the thicker parts of the product, like the bosses or the ribs, will shrink greater than the adjacent wall will. This is due to the cooling effect that increases for thinner parts of the products than for thicker parts. The different cooling rates can leave what is commonly referred to as a sink mark.
Sink marks can be avoided by using the right materials and performing the necessary tooling. There are a lot of ways that an experienced injection moulding specialist can avoid sink areas.
It is important that the manufacturer work closely with an injection moulder to ensure that the product comes out like it should. If you are facing challenges with your plastic design process, then you should consider hiring an experienced injection moulder for the job.