Prototyping or mass production of plastic parts: what are the differences between plastic injection and plastic machining?

 Prototyping or mass production of plastic parts: what are the differences between plastic injection and plastic machining?

In this article you will find a comparison of two plastics processes: plastic injection and plastic machining. Indeed, among their differences lies a certain complementarity that we detail below.

Plastic injection and machining: two plastics processing skills

Plastics processing is the sector that brings together all the professions that transform plastic materials into everyday objects.

Today, discover two plastics processes, with their differences and advantages. They are used to shape objects that we find in our daily lives: we present to you plastic machining and plastic injection. In some cases, they make it possible to manufacture the same parts but in different ways and in different quantities (prototyping or series).

Both totally different and complementary, here are some examples of objects which can be made by one or the other:

Mechanical parts,

Plastic boxes,

Skins, _

Hoods, _

Complex parts with angles

Plastic injection

The plastic injection process

Plastic injection consists of making objects from molten plastic injected under pressure into a mould. The plastic being in the form of granules, an endless screw transports the granules from the hopper to the injection nozzle through a heating system, passing from a solid state to a viscous state, before cooling and hardening in the mold.

It is also possible to use certain soft raw materials such as rubber or silicone, which will make it possible to produce flexible injected parts.

Injection molding is commonly used forth manufacture of products such as containers (packaging), water bottles or cell phone cases. These everyday consumer items are most often molded by plastic injection.

Why do manufacturers use injection molding to manufacture their parts?

Manufacturers use injection molding because the process is relatively quick and can generate a large number of identical parts.

Injection manufacturing is particularly suitable for mass production and very large series production: more than 1000 parts at once. It still takes between 2 and 6 months to design and manufacture the mold, depending on the complexity of the part to be molded. Then, mass production is extremely fast (several parts per minute) and will depend on the number of parts to be manufactured.

In summary: the advantages and disadvantages of plastic injection

+ Particularly suitable for very large production series: +1000 parts

+ Guarantees the regularity of parts with little loss

+ Large economies of scale possible on very large series

– Not suitable for the manufacture of prototypes or small series : very expensive

– The cost of manufacturing the mold needs to be made profitable

– The time required for its manufacture upstream of production

-The impossibility of making modifications to the mold between two series, otherwise it must be redone.

The process of plastic machining

The process of plastic machining consists of removing material by numerically controlled ( CNC ) milling from a cutting plan on flat plastic plates (2D). The use of CNC numerical control makes it possible to give high precision machining and mass production.

Machining is the first step in shaping the boxes and covers, which will then be folded and glued to be finalized: this is the plastic sheet metal process, complementary to plastic machining to shape 3D parts.

Why do manufacturers resort to plastic machining for the manufacture of their parts?

Machining is particularly suitable for the manufacture of single parts: it is the flagship process for the creation of made-to-measure parts.

Indeed, the fact that there is no need for a mold allows several advantages in this sense:

We can afford to produce individually with a controlled cost: the cost of the mold less.

You may wish to manufacture your part(s) quickly (2 weeks max): since there is no need to plan the mold manufacturing time.

You can request modifications to your part(s) between two productions: since it is a digital plan, it is not frozen in time, unlike a mold that is difficult to modify. A flexibility appreciated by manufacturers of electronic boxes, especially when your electronic component subcontractor changes its elements or even when you change supplier, and you have to modify the final product (box or covering).

Machining has another advantage that can be considered as an associated service: it is re-machining. Always positioned on a made-to-measure offer, re-machining is a possibility of manufacturing at a lower cost to customize a standard part: we come to make the holes, counter bores and impressions desired to customize the part or the plastic case to your image. .

In summary: the advantages and disadvantages of plastic machining

+ Particularly suitable for one-off manufacturing and the making of prototypes at the start of a project, for example.

Suitable for small and medium series. Economical process: no mold costs.

Reactive process: count 2 weeks max for the manufacture of a “standard” part + the possibility of making modifications to the plan between two productions.

Machining and re-machining are two services that enable the manufacture of custom- made plastic parts.

– The technique of machining by material removal makes shavings and therefore waste material. It can be recovered and upgraded through the ” up cycling ” process. – Can be time-consuming for very large series (more than 1000 pieces)

The links between injection molding and plastic machining

The main relationship between injection and machining is when the flexibility of machining is put at the service of the industrialization of injection:

You want to launch mass production of a product that does not is not yet completely finished or developed: the design by machining and plastic sheet metal allows the production of prototypes at a controlled cost.

In addition, the flexibility of the machining technology allows you to make a multitude of test versions before validating a final prototype.

This final prototype can then be used as a reference part (control part) for mass production.

Interdependent processes:

The molds used in plastic injection, whether metal or plastic, are machined.

The shavings remaining after machining can be used in an up cycling process: they can be remitted, put on a plate or molded.

Both competitive and complementary, these plastic processing activities are not reserved for Asian countries: France is recognized for its know-how in CNC mass manufacturing, make manufacturer’s work for the manufacture of your custom-made plastic parts, in prototype or series there is a choice on our territory.


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