Web Cutting Apparatus with Draw Roller Tension Control
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Solution Overview
Problem
Conventional web cutting systems are inefficient for cutting continuously moving webs of materials with high elongation tendencies and low friction coefficients, such as woven plastic fabrics, as they struggle to maintain adequate tension and achieve precise cuts at high speeds.
Innovation Solution
A web cutting apparatus featuring a transport table and a movable knife guided along an orbit, which allows for precise and efficient cutting of continuously moving woven plastic webs by maintaining optimal web tension and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional knife arrangements are used to cut woven plastic webs, then cutting action can be achieved, but web tension is insufficient causing excessive elongation and imprecise cuts
Solution Approach 1:
A draw roller assembly is introduced as an intermediary device between the knife and the web. The draw roller rotates faster than the web feed rate, creating a speed differential that generates sufficient web tension during the cutting stroke. This mediator enables the knife to cut precisely without directly relying on web tension from the feed mechanism alone.
Solution Approach 2:
The system changes the speed parameter by operating the draw roller at a higher rotational speed than the web feed rate. This parameter change creates the necessary tension condition during cutting while allowing the web to be handled at low tension during non-cutting operations to prevent elongation.
2Manufacturing precision
If web tension is increased to improve cutting action, then cutting precision improves, but web elongation increases causing excessive knife travel
Solution Approach 1:
The draw roller operates periodically - rotating at high speed only during the cutting stroke to generate tension, then slowing to match web feed rate during non-cutting periods. This periodic action allows precise cuts when needed while preventing continuous web elongation that would cause excessive knife travel.
Solution Approach 2:
The system dynamically adjusts the draw roller speed - faster than web feed during cutting, and equal to web feed during transport. This dynamic speed adjustment enables the system to optimize both cutting precision and web elongation control at different operational phases.
3Productivity
If cross cutting method is implemented for high speed cutting, then throughput increases, but maintaining web tension and cut accuracy becomes difficult
Solution Approach 1:
The draw roller assembly serves as a mediator that actively manages web tension during high-speed cross cutting. By controlling the draw roller speed differential, the system maintains adequate web tension even at high throughput rates, ensuring cut accuracy is preserved despite increased productivity demands.
4Productivity
If knife speed is increased to match high web speed for high throughput, then productivity improves, but power consumption and maintenance increase
Solution Approach 1:
The knife motion is dynamically controlled - moving at high speed only during the brief cutting stroke, then returning at lower speed during non-cutting periods. This dynamic motion profile allows the system to maintain high throughput while reducing average power consumption and wear, as the high-speed phase is limited to when actually needed for cutting.
Data Source
Figure 1
Figure 1A
Figure 2
AI summary
An apparatus and a method for cutting a moving web (2) of woven sheet material is disclosed. The key components of the apparatus are a pre-draw roller assembly (9) and post-draw roller assembly (11); a cross cutter apparatus (7), mounted at an angle between said roller assemblies (9, 11), and having a moveable knife assembly (38); a system of pneumatic cylinders (16, 17, 18, and 19) that operate a first tension rollers assembly (13) and second tension roller assembly (14) respectively mounted corresponding to said pre-draw assembly (9) and post-draw assembly (11) that help hold down said moving fabric securely and under tension; and a cross cutter apparatus (7) having a movable knife assembly (38) in between of the rollers (9, 11), and a set of pulleys (28, 29) that make possible the movement of the knife assembly on a cutting platform (8), whereby the continuous web (2) is cut into the web cut pieces (15).