Easy Detection of Pre-treatments and Improved Traceability

Robust and reliable adhesive bonding processes are required to prevent part failure and damage. Report about DIN 2304 from IFAM tells that most failures of adhesive bonding are linked to deviation from process guidelines or insufficient process control. In comparison to the actual cost of the adhesive, costs of damages can come at significant multipliers. 

Bonding of materials involves a sequence of operations, all of which need strict control and complete procedural documentation. Sika constantly tries to help customers improve their processes. With the implementation of DIN 6701 for the Rail manufacturing market and its sub-suppliers as well as the introduction of DIN 2304 for the general manufacturing industry the topic of safer and controllable processes became even more important. We at Sika, go a step further by providing users of Sika products with piece of mind in better in-process control for surface preparation steps and product traceability tools.

automated Glass bonding on a  truck in a factory
Application of a pretreatment on a bus windscreen

Enhanced in-process Control

Substrates must be cleaned, activated or primed in order to achieve an unpolluted surface prior to the application of a sealant or adhesive. Most cleaners and activators are clear as water in their aspect. Hence, it is not easy to tell if the product is applied or not. The same can apply for black primers when applied on ceramic coatings or very dark colored surfaces like paint or plastics. The difficult detection can cause a lot of uncertainties or lead to big safety concerns in case of a forgotten pre-treatment step in a manual process or even worse, in case of a malfunction of an automated process. It can lead to over proportional workload when such a mistake is identified since numerous parts must be checked.

Sika has developed a series of pre-treatment products, which can be easy detected with UV light. Luminescence properties can be used to assist with application verification. Thus, it will improve process safety and lowering risks for rework or damage. The product portfolio consists of cleaner/activators and a black primer.

Portfolio Overview

Description Product  
Glass activator Sika®Aktivator-110 LUM  
Metal activator and general activator for STP products Sika®Aktivator-205 LUM  
Paint activator  Sika®Aktivator-306 LUM  
Multi-purpose primer Sika®Primer-207  

Detection of the Pre-treatment

In manual sealing and bonding processes, the pre-treatments containing a luminescent dye can be detected using a simple UV torch that provides the required wavelength of 320nm – 420nm. Using a vision system to automatically verify coverage and location of luminescent pre-treatments reducing scrap, improving quality, reducing rework and eliminating manual inspection. The vision system can detect location, coverage, breaks or gaps, reduced width, and diagonal breaks. The system works on all colors and is fully adjustable to meet each customer’s specifications. These systems are highly customized to part design and manufacturing requirements. Sikas System Engineering Department can provide guidance for system integrators.

Luminescent Effect

Application Quality

Depending on the product and surface quality, the application quality can be checked besides of an existing or potentially non-existing application. The pre-treatment is fluorescing under UV light as seen with the naked eye.

Visual detection of pre-treatment  by eye
Image: Visual detection by eye
Detection of pre-treatment with Cognex IN sight camera
Image: Detection with Cognex IN-Sight camera

Luminescent pre-treatments can help to improve process quality thanks to easy detection. The systems are applicable for manual processes as well as for automated bonding system lines. They allow early warning of missing or wrong applications during in-process control. With that, scrap reduction or lower number of deficient products, improved quality and reduced rework can be achieved.

Enhanced Traceability Equals Enhanced Control

The DIN 6701 and DIN 2304 require proper traceability of all products used during adhesive bonding processes. Thus, to ensure a high level of quality and less risk of mistakes. Best practice for good traceability of products used in bonding processes has been established already before the DIN 6701 was introduced. Applicators had to document various information on a control sheet such as:
Products used for surface preparation
Products used for bonding
Batch number of products used
Expiry date of products used

bonding of interior console with Sikaflex-521 UV

The applicators confirmed confirming with their signature each process step in accordance to the bonding instructions. This system was a common approach at large glass replacement companies and rail vehicle producers. Nowadays, product traceability has been formalized within various norms.

Sika follows Automotive OEM requirements and has supported enhanced traceability. The EAN13 and EAN128 are printed on the packaging and for glass replacement companies and rail customers stickers with batch number and expiry date are provided. In order to simply the traceability even further, Sika has implemented the Data Matrix Code (DMC). The DMC is coded in accordance with the industry standard and can be read by most industrial solutions. Optical identification is the key to digitization and transparency. It ensures complete traceability of products. The DMC provides various information such as:
Product name
Sika article code
Batch number
Expiry date