rapid prototyping or injection molding

 

Is 3D Printing the End of Injection Molding?

Some analysts of the manufacturing industry insist that the rise of 3D printing is the demise of injection molding. It is true that there are cases where 3D printing is preferred over injections molding, but the reports about the end of injection molding are essentially made by people with a vested interest and are untrue or exaggerated.

Plastic injection molding is in no danger of fading anytime soon and will continue to hold a great deal of the market share when it comes to creating plastic parts. Despite the recent advances in 3D printing technology, more than 80% of plastic parts manufactured today are injection molded.

When asked “which technique should I use to manufacture my parts?” any serious specialist would say, “It totally depends.” It depends on variables like material type, cost, quality, and quantity of course.

Quantity

According to most specialists in the field of plastic engineering, currently 3D printing makes sense for most manufacturing orders of quantities less than 50 units. For small quantities, additive techniques have a clear edge over injection molding, because the setup cost and time is nearly zero and no special preparation of tools is necessary.

But for mass production orders, injection molding is the clear winner; especially considering the long production time necessary for 3D printing compared to injection molding.

There is an emerging trend of combining 3D printing and injection molding for limited mass productions. In this so-called hybrid method, the mold tooling inserts are 3D printed and then the parts are injection molded. In cases where production is limited, 3D printed inserts can be used as test molds for production in very limited quantities. 3D printed molds won’t endure more than just 60 to 180 pieces.

Recent studies show that 3D printed tooling inserts still have some problems with both polymer inserts as well as metal inserts.

 

Quality

The inability to create parts with the same properties as traditional injection molded parts is one of the key limitations of 3D printing techniques. Admittedly, the number of raw materials available for 3D printing is constantly increasing, but, compared to the wide spectrum of materials that can be injection molded, materials for 3D printing are still scarce. It’s acceptable to 3D print a prototype with nearly the identical material to evaluate its shape, but if the material is not the same as the production material then there is no way to test the physical characteristics of the produced parts.

Another issue that 3D printers still can’t solve is the surface finish. As good as the 3D printer may be, the surface finish it produces is still no match for the smooth surfaces achievable with polished steel injection molds.

Last but not least in the list of shortcomings of additive methods compared to injection molding is the issue of tolerance. Over the past few years, 3D printers have improved their ability to hold tighter part tolerances and this trend is expected to continue in the near future. But the quality of today’s 3D printed parts is far less than those achieved by injection molding.

 

Costs

If the quality issues of 3D printing don’t disqualify it as a viable option for the manufacturing process, then cost is the clincher. The costs of 3D printed parts in comparison with injection molded can be calculated in a tight equation with the quantity being produced. In a nutshell, 3D printing is only economically feasible when dealing with a very small number of parts for an on-demand manufacturing order or in rapid prototyping. Otherwise, injection molding is by far the cheaper way to produce the same, or better, quality.

At the end of the day, when it comes to choosing between 3D printing and injection molding, you have first to decide about the quantity and quality you need, and the cost you are willing to pay.

 

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