How do inline cutters best process edge trim?
We're doing a series of blog posts about how an inline cutter system (cutter/fan trim removal system) efficiently conveys, processes and removes continuous edge trim and waste filament. Part 2 discusses trim and filament pick-up lines. Part 3 explores inline cutters.
The inline cutter’s function in a continuous edge trim and waste-filaments removal system is to cut the continuous low-bulk-density, hard-to-handle trim or filaments into short, easily conveyed and handled, relatively high-bulk-density cut pieces.
It is located between the pick up lines and the material handling fan.
The cutting action takes place between a bed knife and two or six rotating fly knives.
The cutting clearance between the bed and fly knives and the uniformity of this clearance across the width of the cutter are the factors that determine whether the trim or filament can be satisfactorily cut, and if so, the time, for any given wear rate, that it will continue to be satisfactorily cut. The material can only be cut properly when the cutting clearance is less than the material thickness. When the knives are worn down so that the cutting clearance is equal or greater than the material thickness, they must be re-sharpened and adjusted to the original cutting clearance.
It is advantageous to use a cutter that can be accurately set to the smallest possible clearance. A small clearance provides the versatility of cutting all materials down to the very thinnest size. The smaller the starting clearance the longer will be the operating time before the knives will wear to the point they will no longer cut.
Assume a cutting clearance of 1 1/4 mil is required to cut 1 1/4 mil thick polyethylene. A cutter that can be set to 1/4 mil will have a 1 mil wear life before the critical 1 1/4 mil clearance is reached. A cutter that can only be set to 1 mil minimum will have only a 1/4 mil wear life before the critical 1 1/4 mil clearance is reached.
Advantages of Precision AirConvey's Inline Cutters
PAC's in-line cutters for cutter/fan systems effectively cut even the thinnest web or the finest filament and provide maximum knife life before re-sharpening.
Cutters with a rotating shaft in the cutting chamber should be avoided, as these are a major source of shaft wraps and cutter jamming — key problems with filaments and fibrous or stringy trims. PAC’s exclusive design has the rotating shaft outside of the cutting chamber to completely eliminate the shaft wrap problem.
The cutter rotor should be designed for minimum pneumatic pressure drop across the cutter to reduce the energy cost of operating the system. PAC’s exclusive design has rotor side members located outside of the cutting chamber and an open rotor to insure both the free passage of the cut material through the cutting chamber and minimum pressure drop under all operating conditions.
Cut length is determined by dividing the trim or filament velocity by the number of cuts/minute. For example, PAC's standard cutters have two rotating knives and one bed knife. When driven at a nominal 1,750 RPM, they make 3,500 cuts/minute. Using this cutter with the trim from a web processed at 400 feet/minute will produce cut pieces that are 1.37 inches long, because (400×12)/3,500=1.37.
PAC’s cutters are regularly available with a wider-than-usual 300 to 3,500 RPM range. A simple, trouble-free, direct drive is used and speeds can be readily matched to most requirements. Other drive speeds can be supplied for special applications. A six-blade version of the cutter is also available.
Part 4 explores conveying lines.