Special Machines: Plastic Welding and Joining Equipment

TQC have developed a range of equipment using different welding and joining technologies for plastics.  This equipment ranges from simple fixtures to complex fully automatic assembly cells.

The techniques used for joining 2 plastics (or a plastic and non plastic material) are many but here is a list of the more common requests TQC has had in the past:

Plastic fusion.  This is where the two plastics use their native material to make the bond between the 2 parts.  The techniques include:

  • Hot plate welding done on thermoplastic parts.  This is where a heated plate is placed between the 2 parts, pressure is applied to each part forcing contact with the hot surface to heat up the bond area.  Once the parts are at the optimum temperature, the parts are separated, the hot plate removed and then the parts are pressed together.  This action takes place as quickly as possible to ensure that the plastic is still molten.
  • Friction welding.  There are 3 main types of friction welding; spin welding, vibration welding and sonic welding. This is where one part is kept motionless and the other part is moved to create a molten layer between the 2 parts.  One result of these techniques that cases problems with subsequent leak testing is that small hair of material can sometimes be produced, you may have to consider extra filtration between the leak test instrument and the assembly during the leak test.  Friction Welding can also be used on metal parts and TQC has some experience of Friction Welding large steel pipes used in sub sea engineering applications.
  • Heat staking.  This is similar to hot plate welding and comes in 2 forms; one is where pillars on one part go through mating holes in the other effectively riveting the 2 parts together, heat is used to peen over the pillars onto the mating part; a second technique is to push heated pins through both surfaces to locally melt both parts effectively stitch welding them together.
  • Laser welding.  Laser welding can be used to weld certain plastic materials and plastic to metal.  However, this technique has to have tight control of the material specifications and of the laser power to be successful.  As with any laser heating technology, the production of fumes also includes fume extraction.

Adhesive dispensing: the trick here is to find an adhesive that will give you the bond strength between the two parts to be joined; and most importantly be able to cure the glue.  Adhesives are dispensed as a liquid, however in the case of hot melt adhesives they have to be heated to liquefy.  The adhesives can also be as a single part adhesive, or as 2 part adhesives.  To add more complication, some surfaces may need to be primed beforehand (with subsequent curing) to achieve the required bond strength.  There are an array of dispensing systems; pneumatic pump based, gear pump based etc.  With respect to curing the adhesive, you must make sure that you have an adhesive that can cure within a suitable time for your production process.  Can has to be taken about the time to bond strength, do you have to hold the 2 parts together for a prolonged time or does sufficient bond strength form within a relatively short time allowing the fixturing to release the assembly?  Sometimes the curing time can be shortened by using a UV source to cure the adhesive quickly.

Gasket materials.  In certain applications the use of a flexible gasket may be required to seal 2 surfaces.  This may be because of slight movement between the two parts is expected e.g. bonding glass and metal.  Again the gasket material can be single or 2 parts but mostly they are single part materials.  Again, one may have to prime surfaces before applying the gasket.  Typically, a gasket makes a continuous bead to seal round a through connection between the 2 parts; this can be simple to apply if the part of the gasket is circular or square.  However, in the case of more complex 2D and 3D seal paths an operator or a robot system may be used to apply the adhesive.  Usually, with controlled dispensing rates and accurately controlled motion of the nozzle, a more consistent application of the adhesive can be achieved with a robot or mechanism that an operator.

TQC has considerable experience with a variety of plastic welding and joining techniques and their integration into machine systems.  TQC has worked closely with a number of the adhesive manufacturers to select the correct adhesives for a particular application. If you have a requirement for joining 2 parts together within a machine system contact TQC to discuss your requirements.

To find out more about how we can help you with your special machine and plastic welding and joining requirements:

We build all machines in-house, applying our 25+ years experience in specialised test and automated handling machines to the engineering projects we undertake. We offer customer support, backup and service call-out for all projects, whatever the size.

Get in touch with us to discuss your requirements and we will be happy to offer our professional advice and visit you at your site.

TQC Ltd, Hooton Street, Carlton Road, Nottingham, NG3 2NJ, United Kingdom
Tel: +44 (0)115 9503561   |   Fax: +44 (0)115 9484642   |   E-mail: sales@tqc.co.uk