One of the challenges in testing wire harnesses is
maintaining control of the testing process. Typically, the testing process is
not fully automated. Operators connect an untested harness to the test fixture,
and remove a tested unit from the test fixture. After a wire harness has been
tested, it must be categorized as having passed or failed, and the operator
must appropriately segregate the failed ones from the good ones. At times, an
operator may fail to properly segregate a failed unit, causing significant
problems downstream. Another potential problem occurs when an operator fails to
wait until the test is completed and removes a partially tested unit from the
test fixture. Selecting the wrong test program is also a potential problem. Also See 3D wiring harness routing services.
Manufacturers who have several options available to them to
control the testing process to minimize the possibility of intermingling
defective units with good ones. These methods include:
• Activating a fixture clamp when the harness has passed all
tests
• Printing a label only when the harness has passed all
tests
• Sounding an alarm if the operator removes the harness
before the test is completed
• Ensuring that the operator cannot alter the test program
The following is a brief explanation of each approach.
Activating a fixture clamp:
Many high-volume manufacturers use fixture clamps to prevent
the operator from removing the wire harness before the tester has verified that
all tests have passed. In this scenario, a defective harness can only be
removed from the fixture through intervention of a supervisor or other
authorized personnel. This results in improved quality control.
A fixture clamp is a device that provides a means of locking
a wire harness connector in place while the wire harness is being tested. Most
fixture clamp designs use a mechanical locking device that engages when a
connector is inserted into a holder. When all tests have passed, an electric
solenoid is used to release the connector at the end of the test. It is best to
use fixture clamps that are closed and held by a mechanical latch and are
opened by activation of an electrical solenoid. This ensures that the clamp
will remain closed even if the power is disconnected.
It is important for the tester to be able to activate the
solenoid via a control port. Here is a description of the operational scenario
involving the use of a fixture clamp controlled by the tester:
• When the operator inserts the wire harness connector into
the fixture block, the connector becomes mechanically locked in place.
• When the wire harness passes all tests, the tester
activates the solenoid which releases the harness connector.
• If the wire harness is defective, and cannot be repaired,
a supervisor or other authorized person can use a security override procedure
that releases the fixture clamp, allowing the defective wire harness to be
removed from the fixture.
Printing a Label:
Some wire harness testers can be programmed to interface to
a label printer, causing a product label to be printed when a wire harness
passes all tests. This is a superior method to using pre-printed labels. Using
the tester to print a label when a wire harness passes all tests ensures that
only good products receive labels. This assurance does not exist when using
pre-printed labels. Using the tester to print labels also allows for dynamic
data to be part of the label information, such as the current date and time,
operator ID, and tester ID. When only good wire harnesses get labels, it
simplifies the process of segregating good product from bad.
Sounding an Alarm:
Some wire harness testers may be programmed to enter into an
alarm mode when a wire harness is removed from the test fixture before the
tester has completed testing. While in the alarm mode, the tester would do the
following:
• Stop testing
• Sound an audible alarm
• Display a message indicating early removal of the harness
• Require activation of a security override by a supervisor
or other authorized personnel to de-activate the alarm
Once testing has begun, if the wire harness is removed
before testing is completed the tester enters the alarm mode. The alarm mode
aborts the test, sounds a continuous alarm, and displays a message indicating
that the wire harness was removed before testing was completed. This behavior
continues until an authorized person activates a security override procedure.
It is important that the alarm mode cannot be cleared by cycling power on the
tester.
Ensuring that the operator cannot alter the test program
To prevent problems associated with running the wrong test
program, the tester must have the capability to lockout unauthorized personnel
from selecting the test program. This ensures that once the proper test program
has been selected, the operator cannot alter the selection.
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