What is Custom injection molding?

The first question that comes to mind on hearing the term Custom injection molding is what is Custom injection molding? Custom injection molding refers to the making of plastic parts for specific applications i.e. customizing the components as per the customer’s requirements.

Injection molding of Custom Plastic Parts

Injection molding is a process in which plastic pellets are melted and injected under high pressure into a mold cavity. The molded parts are then ejected, and the process repeated. The finished products can then be used as is, or as a component of other products. To do so requires an injection molding machine and tooling (often called a mold or maxnext GmbH Nürnberg die). The molding machine consists of a clamping unit to open and close the mold automatically, and an injection unit to heat and inject the material into the closed mold. Injection molding utilizes very high pressures and typically the machine is hydraulic or, increasingly, electric. Tooling for production injection molding applications must be able to survive under high pressure and is made from steel or aluminum. The potential high cost of tooling often drives the economics of a plastic molding application. Injection molding is an effective way to make custom parts.

The process broken down

There are three main components in the injection molding process. The injection apparatus itself which melts and then transmits the plastic, the mold, which is custom designed, and clamping to provide controlled pressure. The mold is a specially designed tool with a base and one or more cavities that will eventually be filled with resin. The injection unit melts the plastic granules and then injects them into the mold by either a reciprocating screw or a ram injector. The reciprocating screw offers the ability to inject smaller amounts of resin in the total shots, which is better for producing smaller parts. After injection, the mold is cooled constantly until the resin reaches a temperature that allows it to solidify.

Complications with Injection Molding

Injection molding complications are few and can be easily avoided by paying close attention to the design of the mold, the process itself and caring for your equipment. Parts can be burned or scorched when the temperature is too high, which is sometimes caused by the length of the cycle time which may be too long. This causes the resin to overheat. Warping of parts happens when there is an uneven surface temperature for the molds. Surface imperfections (commonly known as bubbles) happen when the melt temperature is too high, which causes the resin to break down and produce gas. This can also be caused by moisture in the resin. Another complication is incomplete cavity filling, which occurs when there isn’t enough resin released into the mold or if the injection speed is too slow, which results in the resin freezing.

Running a Custom Injection Molding Business

Custom molding business is a competitive business and to survive you should find your niche market. Most custom molders in business today have found a niche. Through experience, the molder became good at molding a particular type of part or at molding a particular kind of material, or in working in a specific segment of the marketplace. In other words, he acquired an expertise and stuck with it.

Injection Mold Prototypes

Injection mold prototypes fulfill a number of needs in the plastic injection molding process. Inventors, industrial designers, manufacturers and others are constantly seeking ways to develop new products in a short time span.

Who needs prototype injection molds?

Perhaps it is the need for speed that drives you to having an injection mold prototype built. You might want to beat the competition to the marketplace and don’t have time for a hardened production tool.

You might also need to see how various components of an assembly actually fit and function; an injection mold prototype is perfect.

You can quickly and relatively inexpensively have an injection mold maker build a prototype. Most prototypes last a lot longer than they are guaranteed to, so you might even get some short production out of the deal!

What types of injection mold prototypes are there?

You can get a prototype built out of aluminum, pre-hardened steel or even non-metallic composites. Each has their advantage and special features. Aluminum is the most common material used in prototypes because it is very easy to machine, yet is able to withstand the injection molding process.

There are several mold grades of aluminum commonly used, such as Alcoa’s QC-10. This is a remarkable material in that it is relatively hard, able to be machined in great detail, and is 4 times more conductive than steel. This conductivity can help reduce cycle times in molding.

Aluminum, such as QC-10 can be CNC machined, WEDM’d, sinker EDM’d and highly polished. About the only thing it cannot do is last as long as steel. A bit more care must be taken when working with it as well, due to the fact that it is still aluminum, not steel!

Another common choice for injection mold prototypes is pre-hardened steel, such as P-20 or PX-5. These, and others steels, are widely used if a higher production is required, or there are fine details that exceed the ability of the aluminum to be machined.

These steels are also fairly easy to machine, especially PX-5. This steel is harder than P-20, but easier to machine and polishes better as well. There are two other pre-hardened steels that are often used: NAK-55 and NAK-80. These steels are excellent, especially when there is a need for polishing. Many prototype injection molds have produced far more high quality parts than expected, and the quality of the material is a major reason.

How long does it take to get a prototype injection mold?

Naturally this depends on your pocketbook! It is not uncommon to get a quality prototype in 1-4 weeks. Of course, the more maxnext GmbH Nürnberg complicated you design, the longer it will take. Most injection mold makers can deliver very quickly, especially for a premium.

What are some tips to succeed with prototypes?

Work with the injection mold designer and injection mold maker to make your part as easy to produce as possible. This will speed things up dramatically and reduce your expense. Undercuts, side actions, lifters and such add to the cost exponentially. Often it is possible to achieve the desired part without having necessarily all the features that the final product might contain.