For this edition of Ask the Expert, we spoke with Dr. Denis Cormier, Earl W. Brinkman Professor of Industrial and Systems Engineering and AMPrint Center Director at the Rochester Institute of Technology. AMPrint collaborates with industry, government, and academic partners to develop the next generation of additive manufacturing (AM) and 3D printing (3DP) technologies, materials, and applications.
FuzeHub is partnering with AMPrint and NextCorps, the NYMEP Center for the Finger Lakes Region, on a Rapid Tooling Workshop that will introduce attendees to ways in which AM and 3DP can be used to quickly and inexpensively produce short-run tooling for a variety of manufacturing processes. This event is scheduled for July 23-24, 2025, at RIT. You’ll meet and learn from Dr. Cormier along with other AM/3DP experts. Learn more and register.
Additive manufacturing (AM) and 3D printing (3DP) are often used synonymously. Are they truly one and the same?
The ASTM F-42 committee develops standards pertaining to this industry. When that committee was formed (I was one of the dozen or so people who initially formed F-42), the very first meeting was dedicated to answering the question: “What do we call it?” We literally spent a day debating that question. 3D printing is the term that virtually everyone knows, so it’s convenient to use in general conversation. However, there is also a widespread perception that a “3D printer” is a toy that kids use to print trinkets. For that reason, the term “additive manufacturing” was adopted to differentiate a general-purpose term (i.e., 3DP) from industrial-grade processes capable of making functional end-use parts for commercial use.
In terms of speed, cost, and precision, how do AM/3DP techniques compare to traditional tooling techniques (e.g., CNC machining and die casting) for tooling?
That’s a tough question to answer, since it’s case-specific. CNC machining has gotten really fast. However, large thick slabs of tool steel or aluminum can get extremely pricey. In general, tooling made via AM processes is less expensive and can have significantly shorter lead times if the tool requires more than trivial machining. If the tool is extremely simple, however, then CNC machined aluminum is hard to beat.
For more complex shapes, rapid tooling is a great short-term solution. I say “short term” because rapid tooling made via AM processes generally have very limited lifespans. Depending on the process that’s used to print the tool, hand polishing to some extent is often required. Therefore, rapid tooling is suitable for low to (at most) medium production volumes. It is not at all suitable for mass production except for specialty cases, such as injection molding tools where geometrically complex conformal cooling channels are needed to achieve uniform cooling and/or to reduce cycle times.
Which AM/3DP materials are best for rapid tooling, and how do their properties (e.g., temperature resistance, wear, and surface finish) compare to conventional tooling materials?
Again, this depends a great deal on which type of tooling is being discussed. For plastic injection molding insert tools, some of the newer ceramic filled stereolithography (SLA) resins are being used with great success. Multi-piece hand molds with slides that are removed by hand after each injection cycle allow the molding of extremely complex parts in the exact same resin that the production application calls for. That process-material combination can produce strong and stiff parts with extremely smooth surfaces and fine details. The same goes for sand casting patterns.
I don’t have much direct experience with rapid tooling for sheet metal forming, but I’ve seen numerous instances where high performance engineering thermoplastics, such as Ultem or PEKK, have been successfully used. Those engineering thermoplastics have extremely high strength and toughness, and they can be coated to reduce sliding friction during forming.
Lastly, filament extrusion 3D printing processes can be used to make large scale, relatively low-cost tools for vacuum thermoforming and even carbon or fiberglass composite layup. Those tools don’t need to be particularly strong, so they can be printed with extremely sparse honeycomb infills to reduce the amount of material and printing time. If high temperature materials are chosen, such as Ultem or PEKK, then they should be able to withstand thermoforming or autoclaving temperatures without any trouble.
What are some key design considerations (e.g., geometry, draft angles, tolerances) to consider when determining whether a part is a candidate for rapid tooling?
AM prints one layer of material on top of another, so there will always be some degree of “stair stepping” surface roughness. Some processes, such as stereolithography, can print layers as thin as 50 microns (or about 0.002”). The surface roughness of those parts is minimal. Regardless of the printing process, tools used for injection molding, sand casting, thermoforming, and other processes generally must be quite smooth to release the part/pattern during manufacturing. So, the first rule is to print parts with the thinnest layers the machine can produce to reduce the amount of hand sanding needed after printing. Surfaces of printed tools often will be coated with release agents, but it’s still good practice to beef up draft angles to compensate for any bit of extra friction from those layer lines.
Tolerances are very process-specific. Typically, molded plastic parts don’t have the same tight tolerances that machined metal parts have. So, additively manufactured injection molds made via stereolithography generally will have acceptable tolerances. The same goes for sand casting patterns, sheet metal forming dies, and thermoforming tools. The one exception is if a metal additive manufacturing process is used to produce injection molding or die casting tools with conformal cooling channels. The tolerances and surface roughness of metal AM processes are nowhere near good enough, so finish machining and polishing of the printed aluminum or steel tool is needed.
Is there a return on investment (ROI) sweet spot, such as batch size or complexity, where rapid tooling with AM/3DP is most beneficial?
The answer to that question generally starts with batch size. For modestly sized parts (say within a 100x100x100mm cube), rapid tooling is usually worth considering for production volumes ranging from 10 to perhaps 5,000 parts. Printed tools for parts in that size range typically cost from as little as $100 to a few thousand dollars, depending on the size, material, and whether you print it yourself or outsource it. For tools that small, the lead time is typically 1-3 days. Using that price and lead time, you can already tell that a small part with trivial geometry will be faster and cheaper to CNC machine.
If the geometry is moderately or extremely complex (e.g., multiple slides in an injection molded part), then the time and money saved on hardened steel tooling will provide more than enough cost savings if only 10’s or low 1,000’s of parts are needed. As the size of the tool gets larger and larger, the question is more difficult to answer because there are relatively few AM processes that can produce extremely large tools in industrially relevant materials.
How easily can rapid tooling solutions be scaled up for small-to-medium scale production runs?
Fairly easily. That’s because the tools themselves are relatively inexpensive. For example, let’s say a complex 3D-printed injection mold tool set costs $500 and can produce 500 injection-molded parts before it degrades to the point of no longer being usable. A company can easily afford to print many sets of inexpensive tooling – especially if they do the printing in house. The one asterisk to that statement is that the cycle time per part can be longer due to the relatively low thermal conductivity of the additively manufactured tooling materials, and multi-piece hand molds require labor for someone to disassemble the mold (i.e., remove slides by hand) on each cycle. So, it’s a tradeoff.
A complex production tool might cost 10’s to 100’s of thousands of dollars and have a 1–3-month lead time. The rapid tooling option could cost a very small fraction of that and be available in 2-3 days; however, the cycle times will be longer, and production will require a little more labor. If the company only needs a few hundred or a few thousand parts, that’s a perfectly acceptable proposition. It can also be a low-cost bridge solution to mass production while a company waits for a production tool to arrive.
What quality control methods are used to ensure dimensional accuracy and surface finish before AM/3DP tooling is used?
The dimensional accuracy part was mostly addressed above. Namely, there typically will be some hand sanding to remove layer lines. Depending on the printing process, sealers may be applied to close pinholes in the printed part surface, and release agents may also be applied. Holes can be printed slightly undersized and then drilled or reamed, and printed threads may be chased by hand. The exception to this is when aluminum or steel tools are printed. That is normally done only when non-machining features such as conformal cooling channels inside the tool are needed. CNC finish machining and polishing will be needed for the contact surfaces of those molds, dies, or patterns.
To learn more about AM/3DP tooling, sign-up for the Rapid Tooling Workshop with AMPrint, FuzeHub and NextCorps and join us on July 23-24, 2025 at RIT.
To learn more about RIT’s AMPrint Center, watch this video.