Page 42 - MetalForming April 2011

Switch (normally- closed)
Press controls or die protection PLC should initiate E-Stop command whenever circuit opens
Pierced hole
OK
Pierced hole
MISSING
Strip
Pass line/ die level
Pierced hole
OK
Extruded hole
OK
Pierced hole
MISSING
Extrusion
MISSING
Tooling Technology
Sensoring
for
In-Die Tapping
...to check for the presence of a pretapped hole as well as sufficient tap penetration, even in the event of tap wear.
BY L. RAY OSBORNE
All commercially available in-die tapping (IDT) sys- tems employ some sort of spring-loaded misfeed- protection system, intended to protect the tap and, most importantly, the tapping device itself, in the event of a:
• No-hole condition due to a short feed of the strip material;
• No-hole condition due to a broken or missing pierce punch; or
• Undersized hole due to a broken or missing extrusion punch.
Although misfeed-protection systems are included in commercial IDT designs as failsafe, protective mechanisms, it’s wise for metalformers to employ some method to ensure the successful production of a pretapped hole with every press cycle.
Ray Osborne, a mechanical engineer with Anchor Danly Co. (www.anchordanly.com), recently authored an article titled, The Art and Science of In-Die Tapping, published in the Sep- tember 2010 issue of MetalForming.
Fig. 1 and 2—The most rudimentary sensor configuration used in conjunction with IDT, a hot-pilot system checks for the actual presence of a pretapped hole before it reaches the IDT station. Stampers typically locate this assembly within the lower die, with the pilot punch pointing upward.
40 MetalForming/April 2011
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