Intermittent Cutting Tool for Ductile Material Strand Separation
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Solution Overview
Problem
Existing cutting apparatuses for plastic materials struggle with maintaining consistent cut quality and preventing material agglomeration at low throughput rates, leading to deformed pieces that interfere with processing and potential contamination due to thermal degradation of cutting tools.
Innovation Solution
A cutting apparatus with a nozzle having outlet openings separated by separator webs and a cutting tool driven to an intermittent rotational movement, allowing each knife to move from one separator web to the next, ensuring a clean cut independent of discharge rate and rotational speed, and preventing material contact with the cutting tool during discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the rotational speed of the cutting tool is reduced to maintain constant cut length at low throughput rates, then the cut length remains consistent, but the cutting speed falls below the lower limit value causing crushing-off or squeezing-off of the product piece
Solution Approach 1:
The cutting tool is driven to perform an intermittent rotational movement rather than continuous rotation. The cutting knives are moved from a first position behind a first separator web to a second position behind a second separator web, allowing the system to dynamically adjust the cutting cycle based on throughput requirements while maintaining optimal cutting speed and cut quality.
Solution Approach 2:
The cutting operation is performed periodically rather than continuously. The cutting tool rotates to the cutting position, performs the cut, then returns to the starting position and waits. This periodic action allows the cutting knife to operate at optimal speed during the cutting phase while avoiding the problem of continuously operating at reduced speeds.
2Productivity
If more cutting tools are added to increase productivity, then the cutting capacity increases, but the cutting speed is lowered further and material agglomeration occurs
Solution Approach 1:
The cutting tool is divided into multiple independent cutting knives arranged around the rotation axis. Each cutting knife is separated by separator webs, allowing each knife to independently cut material strands discharged through corresponding outlet openings. This segmentation enables parallel cutting operations without interfering with each other, maintaining high cutting speed while increasing productivity.
Solution Approach 2:
The cutting tools are arranged in a radial dimension around the rotation axis rather than being stacked linearly. This spatial arrangement in another dimension allows multiple cutting knives to operate simultaneously at the same radial position, increasing cutting capacity without reducing the cutting speed of individual knives.
3Productivity
If the cutting tool operates continuously to maintain high cutting speed, then cutting productivity is maximized, but material is pressed against the cutting tool surfaces causing thermal degradation and contamination
Solution Approach 1:
The cutting knife is extracted from the material flow path during the non-cutting portion of the cycle. By moving the cutting tool to a position behind the separator webs where it is not in contact with the discharged material, the system eliminates the harmful effect of material pressing against the cutting tool surfaces while maintaining high cutting productivity during the active cutting phase.
Solution Approach 2:
The cutting tool rapidly moves through the material discharge zone during the cutting phase and then skips to a safe position behind the separator webs. This rushing through minimizes the exposure time of the cutting tool to the material, reducing thermal degradation and contamination while maintaining high cutting speed during the brief cutting interval.
4Speed
If pneumatic drive units are used to enable fast cutting movements, then cutting speed is maintained, but the rated load-cycle change value limits the stop period between cutting operations
Solution Approach 1:
The pneumatic drive system is replaced with a motor-driven system that can more precisely control the rotational movement and stopping of the cutting tool. This substitution allows for longer stop periods between cutting operations, enabling the material to be fully discharged and the cutting tool to be properly positioned without rushing the stop, thereby eliminating the limitation imposed by pneumatic rated load-cycle change values.
Data Source
AI summary
A cutting apparatus for ductile materials comprises a nozzle having a number of outlet openings separated from each other by separator webs. Next to the nozzle, a rotating cutting tool is provided, having a plurality of cutting knives for cutting off the strands of material discharged through the outlet openings of the nozzle. Each separator web is at least as wide as a cutting knife. For performing a cutting operation, the cutting tool is intermittently rotated. Between two cutting operations, the cutting tool is stopped, whereby its knives remain in a rest position behind the separator webs. For the next cutting operation, the cutting tool is rotated by such an amount that its cutting knives move from a position behind a first separator web to the next adjacent separator web.