Thermoplastic joining process Hot Riveting
bdtronic has introduced advanced heat stake, or hot riveting, technology with both a hot air (Hot Jet) and Hot Stamp methods. Our approach is to control all important variables such as temperature, force and distance. This ensures consistent hot riveting strength and results.
The bdtronic BHS hot riveting technology is cost-efficient and environmentally friendly. This hot staking machine technology is a clean, reliable and economical solution for your joining process. A single head heats up a thermoplastic dome, forms a rivet and instantly cools down to achieve a maximum strong joint.
Our BHS hot riveting systems come with active dynamic temperature regulation even in the smallest process temperature windows. Our heat staking technology can handle all types of thermoplastic materials, including the most difficult engineering resins with glass filters.
To learn more about our heat staking technology, or to see if bdtronic can add value to your automation process, please fill out our easy to use form today here.
BHS Hot Air®
BHS HOT AIR® two-step technology means that two modules in two stations carry out the heating and hot riveting process simultaneously. This reduces the cycle time significantly. Products with up to twelve rivet pins can be processed.
Benefits BHS HOT AIR®
- Cycle time reduction
- Higher pin tolerances
- No Flash
- Gap filling
BHS HOT STAMP®
BHS HOT JET®
Process control of Heat Staking Machines
Joining of materials is a major focus of product development processes and production solutions due to the steady rise in consumption of plastic materials. More materials are being developed to meet requirements such as energy and cost efficiency, resource protection and lightweight design, though their processing often poses challenges. The number of mixed material assemblies is rising, with the result that joining processes like gluing and hot riveting are gaining in popularity. This trend demands innovative, cost-efficient and optimal solutions for hybrid assemblies, in other words for joining different materials such as plastic to metal, or to composite materials such as FR-4.
In the automotive industry, in electronics production as well as medical technology, the focus is on meeting extremely stringent quality and cleanliness requirements. The products are exposed to high loads throughout their life, and must therefore perform their function reliably. This requires exceptional precision and reproducibility in manufacturing. In addition, the aim must be to achieve the best possible process result within the shortest possible time. This means that processes must be developed which are compatible with the individual properties of the materials, but also generate fewer costs.
This is why more and more companies are turning to hot riveting.
What is hot riveting?
Hot riveting is an efficient joining method in which two materials are permanently joined at specific points by a form-closing process. This process is also known as heat staking or hot forming. It is important that at least one of the materials is a thermoplastic, which melts through application of energy and can be shaped with a tool. The type of heat applied falls under the categories of conduction (hot stamping), convection (hot air method), radiation and friction. bdtronic only uses conduction and convection-type methods. The advantage of these methods is that they produce no contaminating swarf or dust. The process also prevents damage to electronic components and advanced thermoplastics, creates very strong joints every time, and protects decorative surfaces.
What sets it apart from other technologies:
What are the benefits of the hot riveting process?
No additional consumables such as screws are required. The joining element is already part of the plastic part created by injection moulding in the form of one or more rivet pins or plastic domes, which reduces costs and logistics. Hot riveting is a clean process as no swarf is produced by friction. As only one of the two materials to be joined must be a thermoplastic, a vast range of material combinations can be joined.
What is hot riveting used for?
Alongside mixed material combinations, the hot riveting process also enables plastic-plastic joining. Openings such as exhaust vents can be closed, or components such as lenses can be securely fastened by a type of flanging process. Hot riveting provides the option of creating structural joints through high rivet strength, and ensuring gap filling as well as zero play.
What are the main applications?
Typical applications include permanent mounting of PCBs in and on housing or of covers to housings, temporary or permanent fastening of lead frames or microelectronic components as transport protection. From control units in the vehicle, to sensors for driver assistant systems, locking systems, vehicle interior trim, on front lights and rear lights, in the engine, in media carriers, in oil, through to battery production, the automotive industry uses hot riveting in a variety of different ways. bdtronic hot riveting technology is even in use from brown and white goods, and even in the plumbing industry.
How is hot riveting performed?
Various hot riveting machine solutions cover a whole range of different production environments. From manual machines for single part processing to fully-automated series production, the machine portfolio meets all the customer’s requirements. They can be specially tailored and modified according to requirements. Hot riveting systems feature exceptional reliability and precision. Control software which is Windows-based makes the process easy and more adaptable for machine operators. Key factors include temperature control, which ensures dynamically and within milliseconds that the process runs like clockwork every time and also guarantees precision.
What is required of a riveted joint?
The final riveting result can be defined quite specifically. In general, good joint strength goes hand in hand with longer process and cycle times. However, high strength and short cycle times are often required at the same time due to the large quantities, so these requirements may clash. To address this, a design guideline has been drafted which aims to create a compromise between maximum strength and minimum cycle time. The process is then created in consultation with the customer who specifies the riveted joint requirements.
The external appearance of a riveted joint says nothing about its actual strength. The quality of a riveted joint must be tested and measured by lab tests using series production samples. bdtronic today has ten application laboratories worldwide, in which process simulations and sample production can be carried out under close-to-production conditions.
Which systems are available?
BHS HOT STAMP®
The BHS HOT STAMP® process is a hot stamp riveting process. The riveting head is fitted with a stamp which can be replaced quickly. The stamp can be individually selected and easily replaced for any rivet geometry. The rivet pin can be quickly and securely brought to the optimal melting temperature and formed by precise and quick temperature control, which is based on continuous temperature measurement directly at the contact point between stamp and rivet pin, also known as the plastic dome. Therefore, highly-filled, thermally-resistant semi-crystalline thermoplastics, high-performance polymers or engineering plastics can be reliably processed. A cylinder integrated in the riveting head carries out the stroke or displacement movement, the pressure of which can be adjusted. A position sensor monitors the position of the riveting head, and therefore the presence of a rivet pin and the end position. Safe and hair-free removal of the riveting head from the riveted joint is guaranteed by an integrated air cooling system. The process is variable and can be carried out individually, product and requirement-specific.
The process flow for BHS HOT STAMP® is as follows:
The stamp is first heated. As soon as it has reached the process temperature, it is moved onto the pin at the default pressure, and melts the material until it reaches the end position and has formed a rivet. Finally, it is actively cooled, the stamp is removed and moved again to the home position. As heating, melting, shaping, cooling and removal steps are carried out using one tool, this process is also known as a “single-step process”.
BHS HOT JET®
BHS HOT JET® is a hot air riveting process, and is also a “single-step process”. The riveting head is fitted with a nozzle-sleeve combination. Inside the nozzle there is a stamp, which is easy and quick to change. Nozzle and stamp can be selected specific to the product. The rivet pin is heated until malleable by a consistent hot air flow, in which the air temperature is selected according to the material, and a precision process is guaranteed by temperature measurement and control. The precise temperature setting and the continuous and monitored hot air flow also combine here to produce the ideal joint. BHS HOT JET® is particularly suited to high-strength joints.
BHS HOT JET® process flow:
The air flow is first heated to a regulated temperature. The nozzle is then fitted flush to the join material, and the rivet pin steadily heated. The section of the component on the outside remains unaffected by the heat. The rivet pin is formed by the stamp inside. The rivet hub and end position are monitored. After forming, all this is actively cooled and the stamp removed hair-free.
Hot riveting is the ideal method of permanently joining two materials, where at least one of these is a thermoplastic. It produces a solid, reliable joint which is pleasing on the eye. This method also saves costs and produces consistently excellent Quality.