With advances in CNC machining and EDM technology over past few decades, moldmakers can produce molds with higher tolerances in less time. While this method is optimized to meet everyday needs, opportunities for new methods such as additive manufacturing in mold making industry continue to grow.

 

Although many moldmakers have heard of additive manufacturing (Additive Manufacturing AM, also known as 3D printing), there are many barriers to using additive manufacturing, such as cost-effectiveness issues. With so many technologies and options available, value of additive manufacturing is often blurred. After all, with additive manufacturing, everything can be done from printing an entire mold or insert (usually using powder bed fusion, PBF or photopolymerization) to local repair of mold surface or hardfacing (usually using directed energy deposition/directed energy deposition) deposition, DED) for various mold making needs. However, in mold making process, these applications ultimately translate into improvements in time, primarily in project cycle times, production cycle times, and mold life.
There are many additive manufacturing technologies mentioned above, but no single technology can achieve all benefits that additive manufacturing technology claims. Therefore, matching application required by mold company with the best additive technology is the key to successful use of this technology. Graph below shows how various additive manufacturing technologies relate to their areas of benefit.

 

If companies are concerned about shortening mold lead time, they can focus on reducing photopolymerization, material injection and material extrusion, which can be used to produce molds with shorter cycle times than traditional mold manufacturing.
The first reason for shortening mold lead time is that this type of additive manufacturing allows mold manufacturers to shorten lead time for supply of mold blanks due to use of uniform raw materials. Just like a steel plant, whether it is producing steel plates or ingots, raw material is iron ore. Versatility of raw materials in each additive manufacturing process means that each size mold (or part) can use one size and specification of raw materials, which is easy to stock.
The second reason is that programming and operating 3D printers is simpler and faster than using traditional subtractive manufacturing processes such as CAM/CNC, resulting in shorter cycle times.
Finally, geometrical freedom that additive manufacturing technology can provide can eliminate some of EDM process, thereby reducing number of manufacturing steps. In the case of verification molds, inserts printed with polymers, especially filled polymers, will become more practical and widespread. Typically, polymer proof molds are used in "printed" state and require no further processing.

While design rules for mold surfaces (including draft, venting, etc.) have been perfected as a science over past few decades, the way mold temperatures are controlled is being re-evaluated, in part due to additive manufacturing techniques. Additive manufacturing facilitates two different approaches to shortening injection cycle times through temperature control: (1) changing shape of cooling channels; and (2) improving heat transfer in multi-material molds.
The first method stems from conformal waterways printed using PBF. Conformal waterways follow shape of molding surface more closely, thus resulting in a more uniform temperature throughout mold. This has been shown to reduce cycle times by at least 15-30%. For an injection molding plant, cycle time is money, cycle time savings can accumulate quickly and become a powerful motivator for investing in molds that conform to waterways.
The second method is to use multiple materials in mold, just like with DED. For example, molds can be made using thermally conductive materials such as bronze and harder materials on mold surface.

DED can add high-performance materials to mold surface, using additional material on the edges of mold or other critical surfaces that are prone to wear and damage to improve wear resistance of mold. This eliminates need to use expensive materials to make a complete set of molds, and also allows mold to last longer than ordinary mold steel. Using this method, life of mold can usually be extended by 1 to 3 times.
In addition, in DED and PBF additive manufacturing processes, printed molten metal usually has a finer grain structure and higher hardness, which also results in a higher life than molds made by these methods.
In addition to increasing life of mold, DED technology can also repair and remanufacture mold to add additional life to mold. In hardfacing and remanufacturing, traditional machining techniques are often difficult to use to repair molds.
Almost all current metal 3D printing technologies still rely on machining to complete surface finish. However, advent of "hybrid machines" that combine additive manufacturing techniques, including PBF, binder jetting, material extrusion and fusion with machining techniques, has brought dawn of a machine-free machine. Such mixing machines can save significant machining time for some mold making processes.

Additive manufacturing technology offers several new options to enhance technical capabilities of traditional moldmakers. However, in order to assess their utility, it is necessary for moldmakers to be very specific about pros and cons of each technology, choose technology that best suits their needs in order to obtain a better return on investment.