If you’ve ever tried to use fasteners for plastic materials, then you know the importance of this post. If you haven’t, then you will learn a little something about the process and things to consider before beginning your project.
Below, we have compiled a list of five things to know about fastening in plastic materials.
- “Flexural Modulus.” What is it?
Also known as “bending modulus,” it is the ratio of stress to strain in flexural deformation, or the tendency for a material to bend. In other words, it’s a ratio that tells you the flexibility of the plastic, and how it responds to the application of threaded fasteners.
The lower the flexural modulus, the more the material will flow and form threads.
- Fillers and Reinforcements. How are they used?
Fillers and fiberglass reinforcements can affect at least one property of a thermoplastic, which means it can increase the strength and resistance of the plastic. They can also decrease shrinkage and increase the stiffness of the material.
- Fastening in plastic materials: pros and cons
Pros: Using thread forming fasteners in materials comprised of plastic have a low “fastener cost” and a large supply base.
Cons: In contrast, there can be a high “fastening cost” using screws and inserts, with added inventory and handling of issues. There is also an expected longer cycle time of molding or insert driving.
- “Thermal expansion”
Plastic materials are prone to changing shape with added heat; this is only a problem if the materials have dissimilar expansion rates and if the temperature change is significant. Plastic expands with heat quicker than steel does, resulting in a gap which can form under the head of the fastener.
- Guidelines to consider
If you can, try to test fasteners in the application before committing to hard tooling. In addition, consider the ratio of drive-to-strip in the actual design. Lastly, keep drive gun speeds reduced in a 300-700 RPM range.
Bossard Proven Productivity is full of tips and tricks to bring our customers the best results possible. For more information about our fasteners or production, contact us anytime at ProvenProductivity@bossard.com.
Fastening in Plastic Materials by Bossard