3D printing meets injection molding. Find out why 3D printed injection molds exist and how you can make one.
To understand what a 3D printed injection mold is, let’s start with regular injection molding.
Injection molding is one of the most common manufacturing processes in the plastic industry. Essentially, molten plastic is injected into a mold cavity, it hardens as it cools, and then the mold is opened and the plastic pieces taken out.
Injection molding is primarily used in mass production because of its high upfront costs from design, tests, and tooling. Of course, the unit price drops dramatically the more parts that are produced, which is why it’s worth using injection molding for mass production.
Injection molds themselves are blocks with cavities that determine the shapes of the products being made. Molds are traditionally designed and produced via computer numerically controlled (CNC) milling machinery, which is quite expensive.
Since molds are usually made out of metals such as steel and aluminum, they’re very difficult to alter once produced. Therefore, 3D printing injection molds offers a cheap and flexible alternative.
Let’s have a look at how to actually print a 3D injection mold, some pros and cons, new developments in 3D printing injection molds, and finally some tips for printing on your own.
Note: Though 3D printing injection molds is within the reach of most hobbyist makers, actually using them may require more than the standard amount of effort and equipment. Of course, there’s always the possibility of using a professional 3D printing service. To find the best price and provider for your needs, check out Craftcloud, the 3D printing and price comparison service from All3DP.
3D printing injection molds is similar to how you print other 3D printed objects:
An example of a 3D printed injection mold, produced and used by the Athlone Institute of Technology, features in the image above. Their mold was designed to produce a 3D version of the college’s logo. The whole process took less than a day and the cost was negligible.
You can find more details on how to 3D print injection molds in our article 3D Printed Molds: A Simple DIY Guide.
Now that we’ve covered the basic process of how to 3D print injection molds, let’s have a look at what materials you can use.
Generally speaking, you’ll want something that has high strength and stiffness to withstand the pressure generated during injection. Also, it will need to have high temperature resistance.
Here are a few common materials used for 3D printed injection molds:
3D printing injection molds can be done with SLA, FDM, material jetting, and SLS. That said, since high dimensional accuracy and smooth surfaces are ideal for injection molds, SLA is the preferred 3D printing method to produce injection molds.
There is one thing you should know about the metal frames and their role in injection molds. The frames provide support against the pressure and heat generated during injection molding. Because metal frames can be used universally, it’s only the molds that need to be 3D printed, so altering designs is easy and flexible. However, in the case that the entire mold is 3D printed, more material and a longer printing time is required.
3D printing is a great option to produce injection molds, but it also has its drawbacks. Let’s go over the main advantages and disadvantages.
Now that we know about the pros and cons of 3D printing injection molds, let’s take a look at some of the most recent developments are in the field.
3D printed injection molds tend to degrade under high temperature and pressure. Improving surface integrity with a protective coating is a way to prevent heat degradation. Depositing a layer of metal, metal nitrates, ceramic, and oxides on the surface of 3D printed injection molds can enhance their heat and tear resistance.
Thermal conductivity is a measure of an object’s ability to conduct heat. Metals have better thermal conductivity than plastics. In other words, metals can be heated or cooled quicker than plastics.
Because 3D printed injection molds have a longer heating and cooling phase than those produced with CNC, they also have a longer cycle time. When fewer products can be produced in any given period, the production cost increases compared to traditional metallic molds.
To solve this issue, thermal conductive additives are included in mold materials to improve the injection process. For instance, boron nitride can be added to ABS and iron particles to epoxy resin.
Metal has better thermal conductivity than plastic, so why not 3D print metallic injection molds? With recent developments in metal 3D printing, this is now possible. That said, 3D printing metal is still far more expensive than with plastic, so upfront costs will still be high.
You can find more information about this process in our article on direct metal laser sintering (DMLS).
Before you start printing injection molds yourself, here are some helpful tips to consider:
(Lead image source: Rosti)
License: The text of "3D Printed Injection Mold: All You Need to Know" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.
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