Cutting uncured rubber sheet and slabs cleanly and accurately around the clock - the rotary shear cutter.

For many years, cutting uncured rubber slabs or sheet to length cleanly and accurately has been a problem in the rubber industry. Several types of cutters have been used with varying degrees of success. Guillotines, pinch-off type cutters, paper cutters and hand cutting with a knife have been the most prominent choices.

Each of these approaches has certain problems Guillotine cutters are typically slow because the product must be stopped while each cut is made. They are inaccurate, require continual adjustment for a clean cut and require frequent blade resharpening. Most guillotines are used in off-line installations.

Pinch-off type cutters, while faster than a guillotine, require frequent adjustment to ensure a clean cut, and are generally limited to thinner sections. Cut length adjustment is over a limited range beyond which the product will jam or the cut length will become inaccurate. They are most frequently used in on-line installations.

Paper cutters are generally limited to thinner sections or soft materials, require the product to be stopped while the cut occurs and require frequent blade adjustment to maintain clean cuts. These are primarily used for off-line installations. Harder and thicker products are less likely to be cut cleanly because of the forcing apart of the blades.

Hand cutting is still found in a few installations. This is tedious, inconsistent, dangerous and only useful for small batches off-line.

As production requirements have changed, including the need for faster production rates, reduced scrap and more accurate production parameters, the old cutting methods can no longer provide the results needed.

A rotary shear cutter provides the means to increased productivity. It can cut in line with a mill, calender or sheet extrusion process at line speeds of 100 FPM or faster, and do so accurately and with increased reliability.

The rotary shear cutter is a ruggedly designed and constructed machine that is capable of making clean cuts on uncured rubber sheet and slabs up to 70 inches wide. Whether the rubber is thin or as much as one inch thick, the shear can produce clean, accurate cuts with a minimum of maintenance.

What makes this possible is the design of the cutterhead and stationary blade assembly. The heavy cutter head and its rectangular cross-section blade are configured to make a scissors-like cut against an identical stationary blade. This arrangement will cut a single sheet of newspaper cleanly across its full width. This cutting action provides clean cuts on thin sections, thick slabs, soft materials, hard or tough materials, and even on rubber sheet on a plastic or paper liner.

The rectangular cutting blades can be turned end for end and turned over using all four edges as a cutting edge. The scissors-like cutting action tends to lengthen the time between resharpening. Products that are heavily loaded with fillers that are abrasive will shorten the time between sharpening somewhat. Sharpening of the blades is done on a surface grinder. No jigs or special sharpening angles are required, further reducing the cost of maintenance.

The cutter head is driven by an AC flux vector drive through a heavy-duty gear reducer and HTD timing belt drive system. A digital controller with encoder feedback provides control of cutter RPM in continuous operating mode to within 0.01% of set speed.

For slow cut rates and/or long cut lengths, a single revolution clutch/brake with integral flywheel driven by an AC motor provides the cutting action. A digital length counter with an encoder allows the operator to set cut lengths in 0.010" increments. Each single revolution cut is made at the rate of 200 RPM and takes about 300 msec.

An integral feed conveyor and hugger belt assembly guides the product to the cut point. An integral discharge conveyor carries cut pieces away from the cut point. These conveyors are driven by a DC or AC flux vector drive system. A freestanding ultrasonic loop control system can be used to maintain a loop of product between the cutter feed conveyor and the upstream process.

This machine is designed to operate in 24 x 7 operations, such as custom rubber and masterbatch mixing lines, calender lines, sheet extrusion lines and other continuous processes. It is also accurate enough to produce cut preforms for compression molds and transfer press pot loads. It is a huge advance from the methods of cutting rubber sheet and slabs previously used.