On the Use of 3D Printers in Lean Manufacturing

3D printing is a hot, new manufacturing technique. Its advantages are the ability to create nearly any shape, and to do so without any customized tools. In this blog post, I would like to show and inspire you how you can use 3D printing in lean manufacturing to make your production system even more efficient!

Introduction to 3D printing

3D printing, or additive manufacturing, is a revolutionary technology that builds three-dimensional objects layer by layer from a digital design. Unlike traditional subtractive methods that remove material, 3D printing adds material only where needed, significantly reducing waste. It works by slicing a digital model into thin cross-sections, then a printer deposits or fuses material according to these layers until the object is complete. This process allows for the creation of complex geometries and customized products.

I have occasionally written in the past about 3D printing, since it is such a cool technique (e.g., my 2013 visit to the Euromold exhibit or my 2024 visit to Stratasys). However, in this post my focus is on how to use 3D printing for lean manufacturing.

3D printed parts are already used in commercial products, albeit usually more for custom make-to-order products or small quantities. Another main use is for prototyping and testing. Sometimes they directly print the product. Even if it is not good enough for final use, it is quite helpful for prototyping. Alternatively, you can print the tool to make the product! For example, the blow mold here can make products using the final material. While it may not last as long as a steel or aluminum mold, it is good enough for testing and prototyping.

Where I’ve Seen 3D Printing

In my shop floor visits, I see more and more 3D printing machines and 3D printed objects, not necessarily as part of the product, but as tools that help to MAKE the product. One recent example was during my visit to the BMW plant in Dingolfing, where I had the chance to do a deep dive into the shop floor. The car plants of BMW are excellent, and are the only plants in Europe where I feel like I am in a Toyota plant. Everybody is busy but not stressed, and the share of value-added time is extremely high, comparable to Toyota (see here for a comparison of the value add of car plants). I will probably write a few more articles connected to BMW Dingolfing. I also noticed 3D printed parts at Mercedes plants, and I assume 3D printing is becoming more frequent in industry in general.

Anyway, back to 3D printing. Every segment of the assembly line had their own 3D printer. The section leaders and the group leaders were frequently using them to print parts. While the printers were not running 24/7, they saw good use.

Example Application of 3D Printed Tool

There were quite a few 3D printed parts on the shop floor. Of course, there were also some use for fun, like a 3D printed spoiler attached to a tool cart. But, there were also real uses to improve efficiency.

One great example was in the assembly of the roof. The roof is glued on. In preparation for the gluing process, it is necessary to clean the parts of the roof where the glue will go. The worker had to rub over the path for the glue with a round cleaning tool twice. The illustration below on the left shows a sketch of the roof, and in gray the path the worker had to rub over using the cleaning tool. Especially the triangular part was tricky, as the worker had to stay close to the path. Deviating from the path would not only result in an inferior cleaning, but there was also the possibility that the worker would bump the cleaning tool into other parts of the roof (e.g., a rubber part [not shown]), which could be damaged.

Hence, the worker had to exercise great care to ensure good quality. This entire process was greatly simplified with the use of a 3D printed frame as shown in the upper image on the right and the render below. This frame is put into position using a reference point (a edge or notch, not shown). The worker can now simply move the tool along the frame without any risk of deviating from the path or damaging other parts of the roof. This significantly increased efficiency and also improved quality.

These tools were created by the group leaders of the section on their own initiative. BMW in general (and also Toyota) have the majority of their improvements done by front-line operators and their direct supervisors, rather than faraway engineers with limited time.

On a side note, this station also used projection of work instructions directly on the surface of the work piece (the roof). Th projector assisted by projecting arrows where the worker should start, how often, and in which direction. This projection was updated automatically as the worker completed segments of the cleaning path. Already followed arrows disappeared, and new ones popped up. Overall, this reduced the risk of forgetting a segment or an iteration.

On Technology and Cost

There are many different 3D printing techniques available. At the top end is anything involving lasers, like selective laser sintering or selective laser melting. However, with a cost of hundreds of thousands of dollars, they are not cheap. The powder used also makes it a potential mess. Hence, this is not suitable for the shop floor, either financially or from a cleaning and health point of view. Stereolithography is also messy, as is binder jetting.

The technique of choice for 3D printing on the shop floor is fused deposition modeling (DFM, also known as fused filament fabrication, FFF), where a plastic filament is heated and extruded layer by layer to create the part. These machines are easy to use, clean, and safe. And… they are also not that expensive. Consumer-grade machines can start as low as USD $100. However, their performance is not quite sufficient for industrial use. But industrial grade fused deposition modeling machines are only a few thousand dollars. This is not a lot for industry, and being able to put a fused deposition modeling machine on the shop floor should be financially feasible for most companies.

Our Own Use of 3D Printed Aids for Trainings

I even use 3D printed parts for my own lean training. My partner and I created a small assembly line out of individual modules that puts a ball forward at a preset time. We use this to simulate small production systems, demonstrating (shifting) bottlenecks and teaching different ways to run a production line. Our 3D printer has helped us a lot with the physical part of these trainings.

Overall, there is much potential for 3D printed tools and aides in manufacturing operations to improve quality and productivity and hence also cost. Now, go out, print something that helps the shop floor, and organize your industry!

PS: Many thanks to Thorsten Ahrens for showing me his excellent shop floor at BMW group Dingolfing! BMW is one of the very few car makers that comes close to Toyota in terms of lean manufacturing (the other one is Nissan).