3M automated process for door seal

3M recognised as the most innovative automotive supplier



The tape attached primary door seal is now being used in the hybrid vehicle of a German car manufacturer for the first time, providing weight savings of up to 3 kg.


The Center of Automotive Management (CAM) and Pricewaterhouse Coopers (PwC) auditing and consulting firm recognized the company 3M with the AutomotiveINNOVATIONS Award 2014 in the category “Car Body and Exterior.” With eight innovations between 2012 and 2013, the company could prevail against 34 other suppliers in this category. Recent innovations include thermoplastic polyurethane films, self-healing paints, lightweight materials and acoustic NVH insulations. We talked to Mr. Jochen Post, Regional Sales and Marketing Manager of 3M Automotive, to get a better insight into three recent major developments of the company: lightweight glass bubbles, “traffic light adhesive” and a complete new manufacturing process for door seal on body in cars.

Lightweight plastic parts with glass bubbles iM16K

The glass bubbles iM16K are polymer additives made from a water-resistant and chemically-stable soda-lime borosilicate glass. The bubbles are about 20 microns in size, have a density of 0.46 g/cc and can withstand an isostatic compressive strength of 1,100 bar. With such properties, these hollow glass microspheres can be used as a low density filler material for plastic and rubber parts produced in injection molding and extrusion. Depending on the material, the glass bubbles help to reduce weight of plastic parts by up to 30 percent. ABS, PE and PP are among the most common thermoplastic materials to be mixed with glass bubbles. In addition to weight reduction, the glass bubbles do also improve dimensional stability. This allows new part designs where, for instance, reinforcing struts my no longer be necessary. The glass bubbles also reduce shrinkage and sink marks during processing. Typical applications for the glass fillers are ranging from automotive and aerospace to construction products such as WPC (Wood Polymer Composites) and siding, contributing not only to reduce part weight, but also to improve dimensional stability and nailability.

“Traffic Light Adhesive”

The two-component structural adhesive 3M Scotch-Weld 7270 B/A, also called “traffic light adhesive”, offers quite unique properties for a viscoplastic hybrid adhesive by changing its colours. For the first time a colour indicator illustrates the curing progress by using the traffic light colours red, yellow and green. This visualization clearly defines the chemical process when joining materials, and thus prevents that bonded components are subject to premature loading. And it is easy to translate: red and white indicate that the components are fresh and ready for use. In the mixing nozzle the two components are mixed, the chemical reaction starts and leads to a colour change to yellow. Green gives the starting signal that handling strength is reached.

And there is another important feature of this structural adhesive: while the colour indicator clearly indicates the optimum mixing of the components and the structure of strength, an integrated shelf life indicator shows the usability of the product. If the expiration date is reached, the adhesive will turn blue. This technology of direct colour coupling is the basis for a safe and reliable bonding process for fiber composites and metals. With its large gap-filling properties, the adhesive also provides very good tensile shear and peel strength at high temperature.

Inventor of this adhesive is Dr. Adrian Jung. He experimented in the laboratory with dyes and examined their suitability for adhesives. A dye showed an unusual behavior: the colouring disappeared, but was also able to fully return. During the investigation of this phenomenon it was found that the mixture of certain dyes could be the basis for a traffic light adhesive. A. Jung pursued this project from the first idea in 2008 to the patenting and recent commercialization.

Tape attached primary door seal on body with heat-activated acrylic foam tape

The mechanically attached primary door seal on body is usually made of a rubber/thermoplastic profile with a steel or aluminum carrier, that is push-fit to the door flanges by hand. This carries the risk of damaging the surface of the painted car body. In addition, corrosion of the metal carrier can be an issue as well as leakage of water/ humidity. A tape attached version with heat-activated acrylic foam tape developed by 3M, in contrast, provides a continuous sealing line, does not need a metal core and provides a weight reduction of up to 50%, or 2.5-3 kg per passenger car. The tape attached primary door seal on body can be applied either manually or in an automated process. In general, the use of a robot is a well-known and proven process which is used for the attachment of taped door seals for several years. The automated process with robot and the use of taped endless rubber profiles offers lower costs and process benefits.

VIDEO: Door seal on body is applied in an automated process.

VIDEO: Door seal on body is applied in an automated process.

Another awarded innovation is the automatic cleaning of surfaces by means of a microfiber cloth. The cloth features an open, channel-like structure. The patented fiber combination of polyester and polyamide with a combination of hygroscopic and lipophilic properties is able to remove impurities even from sensitive surfaces such as paint or glass. The dirt moves inside of the channel and is therefore kept off the surface. Micro-scratches are avoided. The process also employs a robot and can be used as an upstream cleaning process, either wet or dry, to clean automotive surfaces from all kinds of impurities (for example as an upstream process prior to bonding of edge protection as mentioned above). Here a 600-700 meter long microfiber cloth is reeled off constantly from a roll and then coiled on another roll again. Between these two rolls a robot applies the permanently moving cloth to the surface which has to be cleaned. Both sides of the microfiber cloth can be used. The automatic cleaning process provides high process reliability and delivers the same results every time.

(based on an interview with Jochen Post, Regional Sales and Marketing Manager 3M Automotive)



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