Sensing Presence of Micro-slugs in
Three-part Dies
The Signature
Technologies
SA-2000 “SAM”
module, and Signature
Technologies “SamView™” software
package can be used to monitor the minute differences in die-closure space
such as that produced by slugs pulled and left in the die space. Adding
SPCview enhances the user interface. This method has been used very
successfully in semiconductor leadframe manufacturing at high press speeds!
Slugging
is a common problem in dies where cutting operations are performed.
Separated pieces can “pull back” into the die space, and cause marking or
malformations in the finished part. Several
different methods have been attempted to detect slugging. The following method has been proven effective in 3-part dies
EVEN
WHEN the slug embeds into the work piece.
The system works by
measuring the strain in the movable stripper plate. When a slug is present, the stripper plate will contact EARLY
in the stroke, and “wrap itself” around the slug as shown in the
exaggerated view to the left.
This will cause an anomalous strain indication at a point
in the stroke where normally nothing is occurring.
Even if the slug embeds, the initial force signature will still be
present, and signal the existence of the slug.
SAMview
software screen displays as shown below. Fault point is automatically
detected and alarm/event logged. Use of SPCview software can provide
charting of the start point and be tied to text messaging to the operator in
order to simplify the interface if desired.
This
method will NOT work on two-part dies, which have fixed strippers,
but is very effective in 3-part dies that either control the stripper to have
slight clearance on material thickness, or actually contact the material.
The system is self - adjusting unlike proximity type stripper position
sensors.
Multiple sensors can be used if multiple assembly operations
are performed simultaneously. The
SAM™ module can handle
inputs in groups of 8 up to 56 total points.
If desired, Signature
Technologies can provide controls to adjust the forming station(s)
dynamically based on the dimensional measurements.
Signature
Technologies
can supply a wide variety of solutions to various manufacturing process
problems dealing with measurement, verification of properties, tool condition,
and machine health. We can also
“close the loop” by performing process adjustments in response to specific
variations in force, location, or shape of the work piece, as well as more
simple controls which can track and reject specific parts which don’t meet
specific quality criteria.
For a .pdf file copy of this bulletin please click here.
