3D Printing for Short-Run Production of End-Use Parts

Conventional manufacturing technologies typically follow the rules of Economies of Scale. This means that the cost of manufacturing per part typically decreases as the number of parts produced increases. This is great when the volume of product sales is high. Parts can be popped-out every few seconds, day and night, and are quite accurate if the person who designed the part is familiar with Design For Manufacturability (DFM) of molded parts, and the machine parameters are correctly set.

However, what about lower-volume products? And what if I need to change my design?

Injection-mold tooling can be expensive

Many traditional manufacturing methods have a high cost of entry. For instance, our Facet Collar for the Chemex® coffee maker. Quotes for injection molding tooling and a modest estimated annual usage (EAU) exceeded $16,000, with a piece price of more than $4.00. Increasing the EAU reduced the piece price, but still faced high tooling cost and a large volume of parts and inventory.

We like to keep things lean, so we did not want to have so much inventory (and the storage space required to house it). We also did not want to deploy so much capital just to get started.

Injection-mold tooling is expensive to modify

Another potential issue with traditional injection molding tooling is the cost to make any design changes. The Facet Collar went through several iterations before we released it to the public. Sure, these iterations would have still been 3D printed even if our goal were to invest in the mold tooling… but if we need to make changes in the future, we’re not locked in by existing tool geometry.

Modifying the injection-mold tooling is a delicate process of cutting out the bad mold geometry, building up the cut surface with welding, cutting or Electrical Discharge Machining (EDM) the new material to conform to the changed design, and finish-polishing the mold cavities. After that, the tool has to be run-in again to fine tune the machine parameters. All of this is typically quite expensive- thousands of dollars- and takes skilled mold toolmakers days or weeks to complete.

Injection-mold tooling is not flexible, and takes time to manufacture or modify

With some notable rapid-tooling exceptions, such as those provided by Protolabs® or Xometry™, traditional injection mold tooling can take many weeks or even months to complete. After the tool is finished, the tool has to be run-in and the injection machine parameters fine-tuned. You then need to inspect the first-shots and approve the tooling. Then your first production run is manufactured. This could easily add weeks to your launch timeline, not including any possible dimensional or finish issues discovered in the first-shots.

Now, imagine that you need to make a design change a few months after you’ve started receiving production parts. The process listed above would need to be repeated… potentially pushing your launch date out farther, or running out of production parts.

How 3D printing can be great for short-run manufacturing

3D Printing can be valuable to companies with short or medium-run projects in several ways.

Reduce startup expenses

With the exception of some very high-end and specialized industrial 3D printers, such as Direct Metal Laser Sintering machines (Metal 3D printers), 3D printers do not typically have tooling or machine preparation requirements. Your cost is basically the cost of the actual print media (filament, resin, powder, etc.) and the relatively small overhead for operating the machine and postprocessing the prints.

Reduce lead times and time to market

Starting a 3D printing process is very fast. The startup time for the printer is typically… well, the time it takes to walk over and switch the printer on, and load the program into the machine. Say, 2 minutes.

Make live changes to your product

Because no fixturing is required to print your parts, the only things that need to be modified in the case of design changes are the 3D CAD model itself and the G-Code that runs the printer. The cost of doing this is minimal, and only takes a long as changing the 3D model and exporting a new program.

Challenges of 3D printing for short-run manufacturing

Of course, 3D Printing is not the perfect solution for every situation. Here are some things to consider.

The per-piece price and run time can be higher

Injection molding is incredibly fast. It can potentially yield multiple parts per second. 3D printing is relatively slow. Additionally, the piece price of a 3D printed part can be higher. Because of this, there is a break-even point where injection molding becomes more cost effective.

Economies of scale do not reduce costs

Part of the reason economies of scale work with injection-molded parts is that part of the initial tooling cost is amortized over the run of parts. Printing more parts on a 3D printer does not necessarily reduce the piece price. 3D printing does not have tooling cost, and the amount of material used and time taken simply multiplies by the number of parts produced. Therefore, the cost of the first part is the same as the 100th.

Specialty surface finishes are difficult to print

3D printers have come a long way in reliability, serviceability, speed, and surface finish. However, certain types of surface finishes cannot be readily and easily done on a printer. Post processing the part with different methods, such as epoxy coating for reflective surfaces, or media-blasting for uniformly matte finishes, can get around this problem. But, the additional post-processing can add to the piece price.

Consider leveraging 3D printing for your short-run manufacturing

In summary, injection-mold tooling is expensive, can take a while to manufacture, and isn’t very flexible. 3D printing can lower your startup expenses, reduce your time to market, and allow for design changes on the fly.

Find out today if your parts are good candidates for our small-to-medium batch manufacturing services!