Ever stricter specifications for the acceptance of components, particularly
in the automotive industry, have increased the pressure for 100% quality
verification of all manufacturing processes over the last few years. Screw
thread inspection is no exception.
Until recently, common practice for thread detection has been the use
of Eddy Current probes, lasers, proximity sensors or a vision system.
These systems were successful to some degree but today's quality-conscious
end customers need to know more than just the presence of a thread.
ORLIN Technologies can now offer a solution that automates the tried
and tested thread gauge method of screw thread quality inspection, based
on the LAR series of linear / rotary moving coil (voice coil) actuators
from SMAC.
Features
Automatically checks for:
Minor diameter out of spec
Major diameter out of spec
Pitch diameter out of spec
Pitch
Foreign objects (e.g. broken tap, swarf etc)
Double tapped thread
Thread depth
Missing threads
Cylindericity
The
system can be used with blind or through holes, internal or external threads.
It is easily incorporated into a production environment to give definitive
pass/fail checks of thread quality at high speed and low cost. It has
been designed for long life and minimal maintenance, meaning complete
reliability even under 24/7 operation.
SPC data acquisition for process control means that tool wear becomes
apparent sooner, increasing quality of all of your parts. All of this
translates to higher throughput, lower costs and increased customer confidence.
To view a video of a typical thread checking application, click
here
Case study
To overcome the limitations of other systems, a major automotive manufacturer
has recently chosen an automated thread checking solution developed
by SMAC for 100% quality inspection of tapped threads in a casting
The requirement
. The manufacturer's requirement included automatic checking for:
Thread depth
Number of threads
Faults such as crossed thread, no thread
Oversize / undersized thread indicating worn or damaged tap
Other requirements were:
High throughput
Objective measurement data output for each part for quality control
Reliability - 24/7 operation
Cost effective solution
The solution
The traditional method for checking threads would have been by hand with
a screw plug gauge. This process is labour intensive, subject to human
error and relies on a skilled workforce. The SMAC solution takes this
well proven manual technique and automates it allowing it to be integrated
into a modern production environment.
A conventional thread gauge is mounted on a linear / rotary actuator
(in this case an LAR55-100-75FS). All of SMAC's LAR series actuators have
high resolution linear and rotary encoders for precise position measurement
of angle and distance. This data is monitored by the controller and compared
to pass/fail parameters to identify and reject faulty parts. It can also
be interpreted and fed back to a database for a complete Quality Control
history.
To carry out the checking procedure, SMAC's unique softland
routine is employed to find the part, landing with a controlled, low force
so as not to damage the gauge. While maintaining a low contact force,
the actuator then rotates anticlockwise until the thread gauge drops into
the thread (indicated by a sharp change in linear position). It then rotates
clockwise at a pre-determined torque, driving the gauge into the thread
(an over-torque situation indicates a fault such as crossed thread, insufficient
thread depth or excessive debris).
Other checks that can be carried out include measuring linear motion
during one rotation of the rotary axis confirming the pitch of the thread
and a push-pull test with the rotary axis held stationary giving the play
in the thread.
When combined with SMAC's controllers, the actuator is fully programmable
in position, velocity, acceleration and force, and therefore can carry
out a comprehensive, qualitative check of a screw thread in just a few
seconds. Part changeover is achieved simply and easily by selecting a
different program (either memory-resident or downloaded via RS232) and
if necessary, changing the thread gauge.
We also have an Applications Book containing 60 application examples
available for download here.
The
system can be used with blind or through holes, internal or external threads.
It is easily incorporated into a production environment to give definitive
pass/fail checks of thread quality at high speed and low cost. It has
been designed for long life and minimal maintenance, meaning complete
reliability even under 24/7 operation.
