Professional Tool Reviews for Pros
Stihl has plastic production facilities in the USA, Germany, and also China. We recently got a chance to visit the Stihl plastic production center in Germany while checking out new tools and products. If you ever wondered how injection molding works, our conversation and tour at the plant offered up a ground-level peek at how it’s done. 233 people currently work in the German plastics plant in Waiblingen in 3 shifts.
Stihl produces its own plastic parts to make products as lightweight and ergonomic as possible. Because many of their products utilize so many different materials, understanding the limitations and advantages of plastic lets them maximize its use in tools. In fact, almost all plastic parts such as battery covering hoods, hedge trimmer handles, and chainsaw housing parts are manufactured by Stihl itself.
Stihl uses mostly glass fiber reinforced plastics to give its parts more strength. These are similar to the type of plastic used in tool bodies. Given how injection molding works, to make lots of parts, you need lots of plastic. You also need the means to both store it and move it around the facility.
In the material storage room, we learned many sources of plastics converge to be stored and dried before use in production. One person per shift can run the entire room which supplies the factory with pellets (granulate). The glass-reinforced plastic pellets need to have the moisture removed via a drying installation. They also need to stay dry, so the room is dehumidified. This all works to ensure that the finished parts have no flow marks or bubbles.
Since there are 52 injection molded machines, vacuum pipelines feed each machine with the required granulate. The plastic source material comes in four colors: natural (for internal components), black, gray, and STIHL orange.
Looking up you can see that the entire facility is fed with these plastic pellets. Stihl says the injection molding machines process around 4,500 tons of plastic each year.
With the plastic injection molding machine receiving its “steady diet” of plastic, it can go to work. Most of the machines operate at up to 2,000 bars of pressure. That’s more than 29,000 pounds of force per square inch. Obviously, you need very high clamping pressure (as much as 800 tons or more) to hold the molds together as the plastic is injected and sets. As you’d expect, hydraulics come to the rescue here.
You also need precision. The molds used to make these parts are very precise—down to 1/100th of a millimeter. Here’s a quick overview of how injection molding works and the entire process:
The entire facility had a high amount of automation to move pieces around and reduce the amount of physical labor needed to produce the various plastic parts. We saw robots everywhere. They seemed most effective when moving materials out of the plastic injection molding machines.
One of the advantages of manufacturing plastic parts in-house is the ability to learn how to take advantage of certain process improvements.
For example, Stihl demonstrated a handle design whereby they “shoot” a pod through the middle of the mold to hollow it out. This process saves 40% of the weight without compromising the handle’s structural integrity. The process also ejects a significant amount of glass-reinforced plastic. Stihl happily recycles this as part of their workflow. The result is that the handles are made with 60% new material and 40% recycled material.
You might think a complex plastic injection molding process like this could lead to inconsistencies. Perhaps. To mitigate this, Stihl has several stages whereby finished pieces are weighed to the gram as part of a quality assurance step. This not only ensures that pieces are consistent and meet standards, but it also serves to flag problems with molds, machines, or other parts of the process that might need attention.
Since Stihl also produces many of their molds on their own, they maintain those molds so they last as long as possible (up to 1 million injections or more). As you can imagine, these are one of a kind and very expensive to replace or replicate. Checks and balances help keep everything working smoothly.
We loved our own process of learning how injection molding works. Partially, that led us to create this article in the first place. Hopefully, this piqued your interest as well and gave you some more appreciation for how much work goes into making that battery backpack, chainsaw, or power cutter. It certainly did for us.
For more information, please visit the Stihl website.
When he's not playing with the latest power tool, Clint DeBoer enjoys life as a husband, father, and avid reader—especially the Bible. He loves Jesus, has a degree in recording engineering, and has been involved in multimedia and/or online publishing in one form or another since 1992.
Clint’s career has covered nearly the entire realm of audio and video production. After graduating at the top of his class with an Associates Degree in Recording Engineering, he began working for the famed Soundelux studios in 1994, one of the largest post-production companies specializing in audio for feature films & television. Working on a myriad of feature films, Clint honed his skills as a dialogue editor, foley editor, and sound designer. Years later, he moved into the expanding area of video editing, where he served as the company’s senior AVID video editor for three years.
Working for such clients as Universal Pictures, Hollywood Pictures, Paramount Home Entertainment, NASA, Universal Studios, Planet Hollywood, SEGA, NASCAR, and others, Clint DeBoer dealt extensively with client management as well as film & video editing, color correction, and digital video & MPEG compression. He also carries several THX certifications (Technician I and II, THX Video), and is ISF Level II Certified.
After founding the CD Media, Inc. publishing company in 1996, he went on to help start or grow several successful online publications, including Audioholics (as Editor-in-Chief for 12 years), Audiogurus, and AV Gadgets. In 2008, Clint founded Pro Tool Reviews followed by the landscape and outdoor power equipment-focused OPE Reviews in 2017. He also heads up the Pro Tool Innovation Awards, an annual awards program honoring innovative tools and accessories across the trades.
Crediting God and his excellent staff for the success of what is now the largest power tool review publication in the industry, Clint DeBoer hopes to see continued growth for the company as it rapidly expands its reach. Pro Tool Reviews critically reviews hundreds of hand tools, power tools, and accessories each year to help inform users about the best and newest products in the industry. Reaching everyone from the construction industry professional and tradesman to the serious DIYer, Pro Tool Reviews helps tool consumers shop better, work smarter, and stay aware of what tools and products can help put them at the top of their game.
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Good morning You don’t say what particular plastic is used for the injection molding? Is it PP or HDPE ? Thanks alan
Thank you for that information, I work at a plastic manufacturing plant and we do mold injection, you gave me more insight on the process.
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