DIY Plastic Molding -- In-House Injection Molding using 3D Printed Molds

Mar 22, 2021

The use of DIY Plastic Molding

DIY plastic molding is omnipresent as a creating process. Most of the plastic products in the world get their formation by DIY plastic molding. The unique way of operating procedure fulfills the demand for large-scale manufacturing needs.

3D printed molds come up with an economic and time-saving solution. This technique is very useful in low-volume production. They enable engineers and designers to test mold designs in graceful creating methods. It makes it easy for the maker to modify them before making the copies. Hence, DIY plastic molding is a budget-friendly method when compared to a CNC machine.

DIY plastic molding

What do we need for DIY Plastic Molding?

When creating an arrangement for DIY plastic molding, one does require some funding. It needs the right type of instruments, for which time and money are necessary. This is, however, cheaper than the metal molds.

There are three parts of the mold that include the injection unit, the mold, and the clamp. The mechanism is as follows. It is designed under great observation to make the molding process easy. It’s manufactured plastic parts for industries ranging from aerospace to consumer electronics with short cycle times and low-cost parts.

It is one of the leading manufacturing processes for high-volume production, but to achieve that DIY injection molding uses sophisticated tools that can take months to make and cost hundreds of dollars. So, it is vital that design flaws correction takes place before making the actual molds.

For many years additive manufacturing also called 3D printing produces prototypes for the analysis of new product design. But, 3D printed prototypes could never meet the needs for full functionality. Production thermoplastics Poly jet addresses form and fit prototypes. The use of functional prototypes in end-use materials helps in the formation of fit 3D prints.

Apart from functional review 3D print, the DIY plastic injection molding is an alternative to machine soft tooling. Poly jet reduces mold-making time and cost by 50 to 70%. In the injection molding process, the plastic heats and injects into a tool that has a core and a cavity side.

3D Printed Plastic Mold 

Although they are not made of aluminum or steel, the process is the same using 3D printed plastic molds. The result is a hundred molded parts in thermoplastics such as polyethylene, polypropylene, polystyrene, ABS, nylon, and many others.

Since plastic molds behave a bit differently than metal ones, a few modifications are necessary. During mold design, minor adjustments made to draft angles and shut-offs can go a long way. The core and cavity prints on a poly jet 3D printer after some light sanding of the mold and then it is ready for the DIY plastic injection molding machine.

When molded parts remove manually they go for automated extraction. These fit an ejection system that uses pins that pass through the core to push apart from the mold and then mount the printed tool in a mold base. Now, it is ready to inject in the molded parts with a few adjustments to the machine settings to avoid damage.

The printed mold sets the barrel temperature and injection speed to the low ends the recommended range for the thermoplastic. Since plastic bolts don’t cool as fast as metal bolts; they increase the duration of the cooling cycle.

What do you need to make a start?

Formlab’s Form 3 is a desktop 3D printer with high-performance. It produces high-quality molds with rigid quality and a sleek finish. After DIY plastic molding, the SLA 3D printer is very useful for prototyping materials best for the 3D printers.

It is a highly glass-filled material that is a great recommendation for industrial use. The use of high-temperature resins has a high-temperature control. 3D printing can become a tool in DIY plastic molding.

The idea behind 3d printing is to make hard tools that are for long production runs. There is soft tooling which is usually made of aluminum but also uses CNC. That is good for a few thousand parts typically.

Thought behind DIY injection molding

Injection molding is the most common method for mass manufacturing plastic products. Examples include chairs, toys, disposable cutlery, and Lego bricks.

The birth of plastic injection molding

Injection molding creation solved the problem for billiards. In the nineteenth-century, billiard balls composed of ivory harvested from the tusks of African elephants. This devastated the elephant population, so a billiards manufacturer offered a ten-thousand-dollar prize for a replacement for ivory.

This spurred John Wesley Hyatt to develop one of the first plastics - celluloid - to create billiard boards. He patented an apparatus for molding products plastics from celluloid. This apparatus was the birth of plastic injection molding.

DIY plastic molding is Simple

Melt plastic, inject it into a mold, let it cool and, then pop out the plastic product. In reality, injection molding is an intricate and complex process. An injection molding machine has three main parts: the injection unit, the mold, and the clamp.

Plastic pellets in the hopper feed into the barrel of the injection unit. Inside the barrel, a screw transports the pellets forward. Heater bands wrapped around the barrel warm up the plastic pallets. Moreover, as the pallets move forward by the screw, they gradually melt and are entirely molten by the time they reach the front of the barrel.

Once enough molten plastic is in front of the screw, it rams forward like the plunger of a syringe. In a matter of seconds, the screw injects the molten plastic into the empty part of the mold called the cavity image. The plastic solidifies in under a minute, the mold opens and the parts eject. The mold then closes, and the process repeats.

All injection molded objects start with melting the plastic pellets, which are a few millimeters in diameter. They can mix with small amounts of pigment, called “colorant”, or with up to 15% recycled material, then fed into the injection molding machine.

Before the mid-twentieth century, injection molding machines used only external heating of the barrel to melt the plastic before a plunger injected the molten material. But, because plastic conducts heat poorly, the temperature was uneven in the plunger: either the middle was too cool and not fully melted or the outer regions were too hot and degraded the plastic. The solution was to reciprocate the screw. It regards as “the most important contribution that revolutionized the plastics industry in the twentieth century.”

Defects of injection molding

The following are some defects that may occur while DIY plastic injection molding. They include production lines, blemish marks, bends, air sacks, weld lines, and spots.

Pros of using an injection molding process

There are many pros that associate with plastic injection molding. They include fast production, low labor costs, manufacturing in large quantities, easy small production, competitive finishing time, and much more.

Cons of using an injection molding process

Some cons include the high Initial tooling can cost, molds can be expensive, designing before processing, and demand for a proper schedule which costs more money.


DIY injection moldings play a vital role in manufacturing particular types of parts with high accuracy of dimensions. We use this technique for obtaining our daily use products like; brushes, mug, buckets, mobile accessories, laptop covers, and parts, etc.

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