Integrating vision into a manual assembly process
Clear Vision Systems (CVS), manufactured by Kautex Textron CVS Ltd are designed to keep vehicle headlamps or the cameras and sensors used in Advanced Driver Assistance Systems clean from dirt, dust, frost, snow, and pollution. They are manufactured at Kautex plants in the UK, USA, China and the Czech Republic. Specialist water tubing assemblies used in these systems are constructed completely by hand.
At the UK plant based in South Wales, around 200 different variants are manufactured with some 12,000,000 tubing assemblies produced each year. They comprise numerous components, including the tubing, nozzle, clips, coloured tapes, foam pads, t-pieces etc.
Example water tube assembly showing nozzles, clips, and coloured tape.
Workbench showing the assembly fixture with tubing inserted and the operator touch screen. The camera and bar light are mounted together above the bench.
Addressing the issues
Kautex is a top 100 Tier 1 supplier to global automotive OEMs, so quality is of paramount importance. Quality defect analysis indicated that many of the defects associated with manual assembly could be identified using industrial vision. Each variant requires a dedicated manufacturing fixture which can be used on any of 80 assembly workbenches.
- Once the tubing is locked into the fixture, operators assemble the product from printed assembly documentation which include written instructions, diagrams and pictures.
- On completion, the assembly is visually inspected and compressed air is forced through the tube to ensure that there are no blockages.
- When testing is passed, the completed part is released and production data is sent to the company’s OEE system.
While it was clear that adding a vision system could identify defects, the company’s Advanced Manufacturing Team realised that a much more complete solution was to fully integrate the vision system as part of the assembly process in order to:
- Utilise the manufacturing SQL database
- Ensure that only appropriately trained operators can work on a particular assembly
- Ensure that the correct fixture is being used for a batch
- Provide complete traceability for individual assemblies
- Provide the flexibility to adapt the system for any new or modified variants
- Reduce the amount of paperwork involved in the assembly process
This improves the efficiency of the assembly process and reduces costs associated with waste and rejected product.
The vision solution
The vision solution was developed by STEMMER IMAGING in conjunction with Envisage Systems Ltd, a systems integrator with whom they had worked closely previously and who took the lead on this project.
A 5 Mpixel Genie Nano GigE Vision colour camera equipped with a 1” format, 12 mm focal length lens is mounted above a workbench. This provides a 1.3 metre field of view.
Bar lights from Smart Vision Lights provide the illumination, overcoming any effects from ambient light coming through skylights in the assembly area.
A GEVA-300 compact vision processor, running Sherlock machine vision software provides local image evaluation before images are transferred to the central server via Ethernet. It can also accommodate additional cameras and so is upwardly scalable.
The system uses standard measurement and inspection tools from Sherlock, for identifying the presence of the correct coloured tape in the correct position, measurements on foam pads and clips etc.
The camera, vision processor and software are all Teledyne DALSA products. Envisage also designed a bespoke operator interface for the software. STEMMER IMAGING supplied all of the imaging components used as well as providing places for Kautex personnel on a training course for the Sherlock software.
Demonstration systems were also made available for proof of process through the early parts of the project. Twenty of the 80 workbenches were fitted with a vision system, all connected to the company’s central server via Ethernet.
The new system in action
For any particular batch, the appropriate assembly fixture is plugged into any workbench. The operator logs in via a touch screen using their unique ID. Scanning the production label barcode reads the assembly part number and checks via the database that the operator ID has the required assembly training. It also displays the number of parts to be assembled.
A unique identifier prevents initiation of the same batch if the label is accidentally scanned again. The vision inspection file for the part is also loaded. The barcode on the fixture is scanned to check that this is the correct one for use. The system then initiates a quality check for the vision system which involves an inspection of a known good part and known bad part. All production data from the database, including instructions, diagrams, pictures etc., can be displayed on the screen without the need for printing.
Image from the vision system indicating a failed inspection for 2 foam pads. The red box highlights a partially assembled pad and the green box shows a correctly assembled pad.
Once assembly is complete, the operator initiates inspection. If the part passes, an image is stored and the part is released from the fixture. If it fails, the image is displayed with red boxes highlighting all incorrect areas, which can be reworked then inspected again. The part is not released until it has completely passed the inspection.
If the part cannot be reworked, a line leader can enter a code to release the part. All actions are recorded on the central server, together with every image produced during inspection, providing a full audit trail for every single part.
Making a difference
The introduction of the new system has resulted in:
- 100% reduction in all targeted defects now measured by vision since the introduction of the system
- 87% reduction in the total number of defects from the hose production section as a whole
- Approximately 70% reduction in the amount of paperwork being printed
- 100% traceability of every single assembly including images
- The system being adopted as a Kautex standard
- The system being used for all new projects
- Plans to introduce the system into the US plant
The flexibility offered by the system effectively future proofs it for use with new variants. It can readily accommodate an additional camera if larger assemblies are introduced and any inspection can be set up using the sophisticated range of measurement tools available.