What is injection molding:
Injection molding is a manufacturing process for mass production of parts.It is most commonly used for mass production of the same parts, usually on a scale of tens of thousands or even millions of times.
Why injection molding is used:
The main advantage of injection molding is its ability to concentrate production.Once the machines and molds are ready, the price per unit of product during production is very low.As more parts are produced, prices will fall sharply.Other advantages include:
Injection molding produces a lower rejection rate than traditional manufacturing processes, such as machining, and can reduce a large proportion of the original blank or sheet.It may be slightly higher for additive manufacturing processes with relatively lower rejection rates for 3D printing.Waste plastic in injection molding production usually comes from: sprue, sprue location and any spill from the cavity of the part
The runner is simply the channel through which molten plastic is poured from the nozzle of the injection molding machine to the gate of the entire injection mold.It is separated from the mold itself.The runner is a channel system connected to the gate that directs molten plastic into the cavity of the mold.After the injection mold is filled (typically only a few seconds), the entire molten plastic cools, leaving solid plastic in the runner, gate, cavity itself, and possibly a little overflow on the edge of the part (if the seal is poor).
Thermoplastic materials are materials that can be recycled.Crush gate/runner spout and any scrap parts.These recycled materials are then added proportionally to the new raw material.(Some of the plastic's properties can be degraded as it is molded over and over again.)Recycled materials are used for low quality components that do not require high performance characteristics.
Injection molding is a highly repeatable process.That is, the second part of production will be exactly the same as the first part.This provides good control over product consistency and component reliability in mass production.What are the disadvantages of injection molding:
Because of design, testing, and tooling requirements, the upfront costs can be very high.If you are going to mass produce parts, you need to make sure they are designed correctly the first time.The correct design includes:
Design and then specification the prototype of the part itself
Initial prototype development can be done on a 3D printer, often using different materials (such as ABS plastic)
Design injection molds for initial production
Injection moulds are usually developed in the production of 300-1000 injection product samples.
Inspect and improve any details of the injection mold prior to mass production in the injection mold manufacturing facility.
Potential negative effects of injection molding include:
Two main disadvantages of injection molding are the high cost of tools and the long lead time required.The mold itself is a project and only a phase of the entire injection molding process.Before injection molding is produced, the parts must first be designed and prototyped (perhaps via CNC or 3D printing), and then the molds must be designed and made to produce the parts in duplicate.After the above two stages are completed and a large number of test adjustments are made, the parts can be molded by injection.The process of debugging molds before mass production takes time and money.Especially for multi - cavity mold forming parts.For example, you want to inject a new shampoo bottle cap.The hat might have threads to attach it to the bottle, hinges, buttons, and maybe some wrapping.A single cavity mold for the component can be manufactured first to ensure that all features are made as required.After commissioning, a new set of moulds can be made, forming up to 16 LIDS at a time.They first tested the mold with a single cavity, so they found any problems and did not need to modify each cavity 16 times.
Because tools are usually made of steel (a very hard material) or aluminum, they are difficult to change.If plastic is to be added to parts, the mold cavity can be made larger by cutting steel or aluminum.But if you want to reduce plastic, you need to reduce the size of the tool cavity by adding aluminum or metal.This is very difficult and in many cases may mean scrapping the mold completely (or a part of it) and starting over.
Injection molding requires uniform wall thickness.Generally, the thickness of the whole wall is about 2-3 mm.Maintaining a uniform wall thickness is important to prevent defects such as dents that should result from inconsistencies in the cooling process.A good rule of thumb is to keep the wall thickness less than or equal to 4 millimeters.The thicker the product wall is, the more materials are used, and the longer the molding cycle is, the higher the cost of each component is.On the contrary, if the wall thickness is more than 1mm or so, you may encounter problems when filling the mold (resulting in a lack of material or short shot).Designers can compensate by using materials with a higher melt flow index, such as nylon.
In general, injection molding is not recommended for large parts.This is due to the size limitations of the injection molding machine and the mold itself.Although injection machines exist for making very large parts (a 1000-ton injection machine, for example, is about the size of a train carriage), it is very expensive.For this reason, larger parts than common injection molding machines are usually multi-piece.
Large moulds require experienced design to avoid increasing project costs.
Note for injection molding:
Before you attempt to produce parts by injection molding, consider the following:
Upfront costs: Substantial initial investment is required to prepare for injection product production.It's best to know this key point in advance.
To determine the number of parts to be produced, injection molding is the most cost-effective method of manufacturing
Determine the number of parts that are expected to benefit from the investment (consider the costs of design, testing, production, assembly, marketing, and distribution, as well as the expected price points for sales).
Part design: Simplifying product geometry early on and minimizing the number of parts will pay dividends.
Tool design: In advance in the mold design process to take into account the production process may appear defects.Consider gate locations and run simulation analyses using mold flow software such as Solidworks Plastics.
Cycle time: Minimize cycle time.Use sophisticated tools.Small changes can make a big difference, and reducing your cycle time by just a few seconds can save you a lot of money when you produce millions of parts.
Assembly: Design your parts to minimize assembly.Injection molding is done in Southeast Asia mainly because of the cost advantage of assembling simple parts in the injection molding process.If the assembly process can be optimized in the process, it will save a lot of labor costs.
Injection molding is a great technology for mass production.At this stage of production, 3D printing is more affordable and flexible for products in the early stages of design.