3D-Printed Plastic Molds versus Conventional Aluminum Tooling

Jack Lie CNC machining expert

Specialize in CNC Milling, CNC Turning, 3D Printing, Urethane Casting, and Sheet Metal Fabrication Services.

Industrial 3D printing has an overwhelming impact on different industries from diverse perspectives. The quick availability of rapid prototypes, parts with usually not manufacturable or expensive designs, and material advancements have also become possible with industrial 3D printing. Apart from that, industrial 3D printing is also being used for the manufacturing of plastic injection molds. However, it is not suitable; why? We will explain it here in this article.

The proponents claim that using industrial 3D printing to manufacture plastic molds saves 90% of the time, reduces the cost by 70%, and facilitates applications under light loads. But it is still essential to understand the disadvantages of making plastic molds using industrial 3D printing machines compared to conventionally machined aluminum molds. So, here are the reasons based on which manufacturing of plastic molds using 3D printing is not considered a good option:

1. Quality of the Mold

When a plastic mold is manufactured using a 3D printer, the quality of the mold might not be impressive. The industrial 3D printer uses layers to form a complete mold, exhibiting a stair-step effect on the wall or angled surface. At the same time, the molds are sure to be drilled or reamed for holes and tapped or milled for threaded features. These secondary operations add in the time the mold. However, the quality of the mold should remain uncompromised.

2. Size of the Mold

The permissible volume of the mold using an industrial 3D printer is around ten cubic inches, close to the size of a grapefruit. Inarguably, modern additive machines have better capability and capacity to form molds. However, these advanced machines are way behind the EDM equipment and machining centers. The reason is that they can conveniently manufacture molds up to the size of 59 cubic inches, which is about six times larger than the capacity of an industrial 3D printer.

3. Exposure to Excessive Heat

The molds used in the injection molding have to face excessive heat to allow the material to flow appropriately. Usually, the temperature for steel and aluminum molds remains around 260°C, particularly when preparing high-temperature plastics. Conversely, it is impossible to meet such a high temperature for the molds of stereolithography and similar 3D printing methods. It is because these processes involve photoreactive resins cured by UV light. These plastic molds instantly break down when exposed to this much heat for an extended period.

The 3D-printed plastic molds become ineffective before they complete their 100 shots of soft plastic material such as styrene and polyethylene. But glass-filled polycarbonates and other tough thermoplastics might show some resistance. Subsequently, we can say that the plastic molds made up of industrial 3D printing are not suitable to face heat in the injection molding process.

4. Comparison of Costs

The cost has always been a point of discussion regarding preferring from the conventional manufacturing of aluminum molds or manufacturing using an industrial 3D printer. Usually, the industrial 3D-printed plastic molds are considered lower in cost, which is a wrong perception. For instance, the making of plastic mold using a 3D printer is costing $1000. It will touch the figure of $20,000 if manufactured using a conventional aluminum mold-making method.

But is it worthwhile? Of course, it is not because the mold made up of the 3D printer will not offer its services more than 50 to 100 times. The investor would need another mold to maintain the speed of production. So, the investor will have to incur an investment of $1000 more. While it is important to know here that the cost estimation of 3D-printed mold may not include labor cost.

On the other hand, the aluminum mold produced using conventional methods might cost you $15,000. Still, this investment is enough to cover production-consumption for a considerable time, as such molds can support 10,000 production cycles. Likewise, with the conventional manufacturing of aluminum molds, investors have a better ability to choose customization options.

5. Design of the Mold

Amid other complexities, the mold’s design is of significant importance, which often remains compromised with 3D printers. Nonetheless, molds made up of the conventional mold-making processes offer colossal convenience when adding such a technical feature to the mold’s design. Commonly, the molds made up of 3D printers consume plastic material, which is reluctant to achieve the following targets for the mold, and conventionally prepared aluminum molds readily possess these abilities. Some of the notable instances are given below:

  • The exact placement and quantity of ejector pins are harder to achieve with 3D printers.
  • Draft angles should be expanded to 5 degrees or more, extraordinarily surpassing that of most aluminum tooling necessities.
  • Point gates and tunnels must be avoided in case of 3D-printed plastic molds.
  • For plastic tooling, fan, sprue, and tab gates should increase three times their original size. 
  • Polymer flow through the 3D-printed plastic mold should be situated similarly to 3D print lines to stay away from sticking and enhancing filling at reduced injection pressures.

Consequently, the simple design of plastic molds may work with the 3D printer. Nevertheless, complex design molds are far away from the domain of these printers.

Possible Advantages of Mold Making Using Industrial 3D Printer

Hand in hand, despite being a failure for large volume productions, plastic molds made up of 3D printers still have some advantages. These advantages include: 

  • If a low quantity of elementary molds is required with a large drafted angle, an industrial 3D printer is perfect for making the plastic mold. 
  • If your tool-and-die team is confident that they can glorify all the features needed in the mold and is acquainted with the mold’s design rules, you can go ahead. Otherwise, you might waste your time and money. 
  • Suppose you have enough resources, labor, and machines to process/assemble the plastic mold. In that case, you can work on it, but it might not remain economical.