Archive for November 2012

Rotary vs V Blade Wire Stripping.

Wire stripping is a mechanical insulation separation process which can be performed by various methods.  Two of the most common methods are Rotary Blade and V Blade. This article will outline these two methods, the advantages and drawbacks.

Rotary Blade.

A wire stripper with a rotary blade has one or two blades centered around an opening that the wire is pushed through.  A wire guide sized to  the wire OD ensures the wire does not rotate in an oblong fashion and cause damage to the inner conductors.  The blades are adjusted to match the ID of the wire without nicking the inner conductors.  During processing, the blades close around the wire and rotate to slit the jacket. A number of revolutions may be required to separate the insulation slug from the wire.  This depends on the thickness and insulation type.

The rotary blades provide a very clean shoulder on the insulation.  The rotary action of the blades also twists the stands of single conductor stranded wire, which helps in the insertion of the wire to a terminal block or PC board hole prior to wave soldering.  Non concentric wire can be problematic and cause less than desirable results in nicked strands or jagged separation of the insulation. Below is the operation of the Carpenter 72C which shows the action of the rotary blade to strip wire.

V Blade.

The V blade configuration provides good quality wire stripping of a large range of wire cross sections. This blade style is used on bench top single process wire strippers, automated cut/strip machines and fully automated work centers such as the Schaefer Megomat Primo XLT.  Adjusting a V blade wire stripper is fast and changeover to a different wire takes only a few seconds.  The angle of a V blade is typically 90 degrees.  This angle is generally accepted as the best providing optimum overall results on a wide rage of wire sizes.  Narrow entry angles such as 30 or 60 degree are also used but would be deployed on specific applications. The V blade strips the wire at four points and not the whole surface as a rotary blade does.  Special configurations like the Lakes patented Uni-V blade adds a secondary angle which provides more contact to the blade.

Other V blade configurations are full radius and tangent radius V.  The blade illustrated above is full radius blade for a Carpenter Compu-Strip 97A.  This blade is sized for a specific wire cross section.  Adjacent wire sizes cannot be stripped with a radius V blade.

The illustration above shows the Tangent radius (Lakes Precision TA-V).  The entry angle lines meet the arc at a tangent point. This type of blade, when closed, presents a diamond shaped edge profile.Advantages: By adjusting cutter head shut height, ( if insulation material and wall thickness allow), you can process
adjacent wire sizes with the same blade, or you could compensate for off-center wire extrusions.

The video below illustrates the operation of a 90 degree V blade in a Carpenter 77E heavy duty wire stripper.

The V blade profile with its variations can process a large variety of wire sizes and insulation types.  The four point contact on the 90 degree V blade provides a lesser quality shoulder than the rotary but can be offset by the use of a full or tangent radius V blade.

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