Annular Knife Cutting Unit for Thermoforming Witness Formation
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Solution Overview
Problem
Thermoforming machines face challenges in producing high-quality products due to visible and tactile defects caused by attachment portions or 'witnesses' left on thermoformed objects, which are difficult and costly to restore, affecting productivity and adaptability to different materials.
Innovation Solution
An in-mold cutting unit with annular knife elements, counter-cutting elements, and removably housed witness-forming inserts that allow for precise and adaptable cutting, enabling quick separation and restoration without visible marks, and easy adaptation to various materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If incisions are made directly on the sharp edge of the male mold or female countermold to generate witnesses, then the thermoformed objects can be separated from the residual web, but the sharp edges undergo configuration alteration after grinding, requiring difficult and costly restoration operations
Solution Approach 1:
The cutting device is divided into separate components: a male cutting element with a sharp edge and a female cutting element with a counter-edge. The witnesses are formed by the interaction of these separate elements rather than by incisions on the mold edges themselves, allowing the mold edges to remain intact and reusable without restoration.
Solution Approach 2:
The witness formation function is extracted from the mold edges and transferred to dedicated cutting elements. The male and female cutting elements are removable components that can be replaced independently, separating the witness formation function from the permanent mold structure and eliminating the need for restoration operations on the mold edges.
2Reliability
If the sharp edges of the male mold are restored by grinding after multiple cuts, then the cutting function is maintained, but the restoration operation requires special machine tools and causes machine downtime of several days
Solution Approach 1:
The male and female cutting elements are designed as disposable or replaceable components that can be easily removed and replaced when worn. This eliminates the need for time-consuming grinding restoration operations on the permanent mold edges, allowing quick replacement of cutting elements and minimizing machine downtime to maintain cutting function.
3Ease of operation
If incisions are made on the mold edges to create witnesses, then separation of thermoformed objects is achieved, but the configuration of the sharp edges changes after grinding, affecting adaptability to different materials
Solution Approach 1:
The cutting elements are designed with adjustable parameters such as the angle and depth of the counter-edge on the female cutting element. This allows the cutting device to be dynamically adjusted to accommodate different thermoformable materials with varying physical characteristics, maintaining adaptability while achieving effective separation through the witness formation mechanism.
Data Source
AI summary
The present disclosure relates to an in-mold cutting unit for a thermoforming machine having at least one mold element (4), at least one counter-mold element (5) intended to cooperate, in use, with a respective mold element (4), and actuation means intended to command the relative movement of the mold (4) and countermold (5) elements; the cutting unit comprising at least one annular knife element (60) having a sharp edge (61), and at least one counter-cutting element (7) for each knife element (60), defining a sharp counter-edge portion (71), and the in-mold cutting unit comprising at least one witness-forming insert (8) removably housable in a respective reception seat (S) at the at least one annular knife element (60) or the at least one counter-cutting element (7), and delimiting at least one recess or incision (89) thereon, during use very close to the sharp edge (61) of the annular knife element (60) or to the sharp counter-edge portion (71) for the formation of a respective witness (T) between a thermoformed object (TO) and residual web (2a).