Precision inspection for white goods

Precision inspection for white goods

Precision inspection for white goods

Prettl
Appliance Systems Deutschland GmbH (PAS) is using In-Sight vision
systems from Cognex to guarantee quality in their production process.
Every control panel manufactured at their plant must first be put
through its paces in an intricate production process as they are
destined for the world’s white goods industry. Not an easy task
considering the reflective surfaces, variety of colorus and multiple
features needing to be fully inspected. In-Sight vision systems proved
up to the challenge.

In-Sight meets the colourful challenge posed by white goods

Prettl
is one of the world’s leading suppliers of system control panels and
cables for white goods. They develop state-of-the-art control panels
for washing machines and driers. The front control panels for high-end
washing machines manufactured by Prettl are masterpieces beautiful,
multifunctional and reliable. With stylish curves, and glossy finishes,
they come in many different colours. Equipped with a wide range of
variable functions, the company’s control panels are ideal for any type
of application; coloureds, whites or delicate fabrics.  Quick wash
cycles, gentle wash cycles and spin-drying at any speed are also
standard features.

Two companies who have been implementing
projects in tandem for many years were charged with creating the
inspection station and developing and assembling the production plant:
Weber Konstruktion Maschinenbau GmbH, Aschaffenburg (Germany), and
Weber Systemtechnik, Wetzlar, who is a member of the specialist global
Cognex partner integrator network (PSI) in Germany.

The challenge - accurate inspection of multiple positions and colours

The
project team decided to use Cognex In-Sight technology on this project
because it has already proven itself in many other large projects
previously carried out together by the two companies. “It was essential
that the quality inspection system be able to cope with the
multifaceted and high-quality design of the Prettl control panels”,
says Alexander Kobras, managing director (technical) of Weber
Konstruktion. “The control panel is bent into shape and the lettering
is then applied but the critical point is that the controls, the LED
indicators and the lettering can all be positioned differently on
different product variants and, above all, there is a wide range of
product colours, which makes an intelligent inspection station with
reliable camera technology essential,” continues Kobras, an expert in
the field of production technology.

This was made possible by the
use of a six-axis robot arm which holds the control panel and moves it
into all of the checking positions required by the camera. “In-Sight
not only checks that the various features are present and positioned
correctly, it also checks their quality,” says Thorsten Rauber, head of
the measurement and checking systems division of Weber Systemtechnik.
The inspection criteria include the position of the features, their
completeness and the quality of aspects such as the pad printing. There
can be occasional problems with lettering that is not complete, is
smeared or is applied twice.

A vision solution for multiple inspection scenarios: reflective surfaces and colours
The inspection system, consisting of Cognex In-Sight technology and the
user interface of the flexible inspection software from Weber
Systemtechnik, can easily adapt to a wide variety of colour and
brightness contrasts. The surface finish of the control panels ranges
from black, white, red and blue through to silver and many other
high-lustre finishes, which sometimes cause strong reflections. One of
the specifications for the development of the inspection station was
that the checking process should be performed as quickly and easily as
possible without the need for extensive training of staff. “Inspection
of all of these different scenarios with just one hardware
configuration, one camera and one source of illumination was one of the
main challenges,” says Thorsten Rauber.

The
vision system also needs to be capable of detecting any surface damage
present, such as paint scratches, which was a real challenge for the
Weber team due to the wide variety of possible surface damage.

Complete product traceability included!
In addition and depending on the model and customer requirements, the
system can read a barcode and a data matrix code and this product data
can then be used for internal process-related tasks such as ensuring
maximum traceability of production results.
The functions of the control panel are simulated by means of electrical
communication between the vision system and the circuit boards of the
control panel and the LEDs are activated so that a visual check can be
performed. When a defect is recorded by the In-Sight system, the system
stores the picture with the associated data on the internal database. A
worker can then access the picture and the data and decide on the next
steps to take even before he or she takes a look at the individual
item. This saves time and speeds up working processes.

In-Sight
demonstrates its strengths impressively. Both Alexander Kobras and
Thorsten Rauber appreciate the development efforts made by Cognex. In
particular, the algorithms work much better than those of competitor
systems. Real-time process control, high-speed image processing, highly
precise object localisation and easy operation without programming
expertise have made the control station created by Weber Konstruktion
and Weber Systemtechnik a trusty assistant of PAS.