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Mirror tester reflects success

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ANDREW Engineering never thought much about car side mirrors before this project which, when you think about it, are quite involved. To start with, there are two types per car: left hand (LH) and right hand (RH).

In a RHD car, the glass in the RH mirror will be flat, while in the LH it will be curved.

For a LHD car, this will be opposite. Curved glass always has writing on it (for example “Objects Are Closer Than They Appear”). This will be in English for Australian cars, but for export cars it may be Arabic or Chinese. Almost all mirrors these days are electric in operation, but prestige model mirrors introduce more options and complexity, including body-matched paint, heated glass, glass position “memory” and blinkers.

With modern car making practices, such as “just in time”, and the fact that car makers make several types of cars, in any order, on the same production line, mirror assembly manufacturers must make sure they deliver not only fully functional mirrors but mirrors with the right paint colour, glass type, text and options.

Late in 2004, Australia’s only car side mirror manufacturer approached Andrew Engineering with a requirement to test and inspect their completed side mirror assemblies. Some of their requirements included:

• Checking the glass tilt angles and glass curvature.

• Checking the presence and language of text printed on the glass.

• Detecting small black gaskets, studs and screws.

• Checking the colour of the painted exterior.

Other requirements included the need to test four mirror types in the same machine, which was to be as small as possible. The client also wanted the flexibility to add more tests or mirrors in the future.

Andrew Engineering came up with a machine featuring a single colour machine vision system and a two axis CNC system: axis 1 is the component turntable, while axis 2 is the camera arm.

By controlling the positions of the two axes, practically every feature of the part to be tested/inspected can be “seen” by the camera.

An automatic front door prevents ambient light from affecting the tests, and the machine load height can be adjusted to the operators’ preferred working height.

The machine can handle numerous product variants via simple change-over nests and program selection from the custom operator interface.

At delivery, Andrew Engineering’s first machine catered for four mirror types (left and right hand for two vehicle types), with over 30 possible build variants.

Some of the tests/inspections completed by the machine include tracking the electrically-operated glass tilting mechanism, determining the presence and language of the text printed on the glass, the detection of small black gaskets, the detection of studs and screws, and checking the colour of the painted exterior.

The glass-tracking feature confirms minimum tilt angles in all four directions (up, down, in, out), and then returns the glass to its centre (shipping) position. Speed of travel is also measured with the camera, while current draw is monitored electrically.

Stand-out features

ANDREW Engineering sees its product as being innovative because it uses a single, moveable camera to inspect multiple features on a part. This inherent flexibility allows the user to easily test multiple variants in the same machine.

Being able to control the relative position of the camera and the component makes previously difficult inspections relatively easy and totally reliable.

Andrew Engineering has given its customer the ability to add/modify/delete tests and inspections, and to edit the test sequence, etc. The vision system and motion controller integrate seamlessly through a user-friendly, attractive and flexible operator interface.

While inspecting mirror assemblies with vision systems is not especially unique, Andrew Engineering claims a significant advance over the existing method, which usually involved having dedicated machines for each mirror type, and using multiple cameras to “see” all the required features on a given mirror.

This method is not flexible and, as vision systems are one of the major costs, this format is relatively expensive.

Whereto from here?

ANDREW Engineering sees many future applications of its technology.

Firstly, the company has now built two more testers similar to the first, and is looking at a fourth.

When the fourth one is completed, all mirrors fitted to Australian-made cars will have been put through one of Andrew Engineering’s testers.

Secondly, Andrew Engineering is developing a “cut-down” version of the machine, designed for testing simpler, all-black mirrors. The target market for this machine is the huge mirror manufacturing industry developing in China, where the company intends to demonstrate the machine later this year.

At the same time, Andrew Engineering is also developing a robot-based system for applications requiring the dexterity of a 6-axis robot. While the company believes it can make lower cost and smaller machines using two or three custom-configured axes, having a robot system “ready to go” should be a real advantage when Andrew Engineering comes across difficult applications.

Finally, the company believes that its system is suitable for inspecting other complex automotive sub-assemblies, and is already in discussions with manufacturers of door trims, fuel tanks, brake callipers and seat frames.

Andrew Engineering’s software would be identical in each case, and the company would simply configure the machine mechanics to best suit the application. For example, the door trim inspection machine may have simple X–Y linear axes, while the seat frame machine may have one rotary and one linear axis.

Larger, more complex products, such as plastic fuel tank assemblies, are more suited to a robot-based system.

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