Process for making an object from plastic material and apparatus therefor
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Solution Overview
Problem
Existing processes for creating multi-colored plastic objects with reliefs require complex and expensive molds, increasing production costs and limiting design flexibility.
Innovation Solution
A process involving the use of exposure reliefs with hollows and sealing edges in a two-step molding technique, where the second plastic material fills passage channels between reliefs without entering the hollows, allowing for the creation of objects with ornamental patterns without complex undercuts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If complex undercuts and movement systems are used in molds to create reliefs on the outer surface of multi-colored plastic objects, then the outer surface can have reliefs or bas-reliefs, but the cost of the moulding equipment and therefore the cost of the product increases
Solution Approach 1:
The mold is divided into two separate casts: a first cast that creates the base structure with recesses, and a second cast that forms the relief features. This segmentation allows each cast to be simpler in design while collectively achieving the complex relief effect on the final product surface.
Solution Approach 2:
The first cast is performed first to create the base portion with recesses that will later receive the second plastic material. This preliminary structuring enables the second cast to simply fill in the relief areas without requiring complex undercut mechanisms, as the relief geometry is pre-established by the first cast's recess patterns.
2Shape
If complex undercuts and movement systems are used in molds to create reliefs on the outer surface of multi-colored plastic objects, then the outer surface can have reliefs or bas-reliefs, but the cost of the product increases
Solution Approach 1:
The manufacturing process is segmented into two sequential molding operations using two separate casts. The first cast produces the base structure, and the second cast adds the relief features. This segmentation eliminates the need for expensive complex undercut mechanisms in a single mold, thereby reducing manufacturing costs while achieving the desired relief surface.
Solution Approach 2:
The relief pattern is created by forming complementary recesses in the first cast, which then serve as negative molds for the second plastic material. This copying approach allows the relief geometry to be replicated without requiring the second cast to directly form complex positive relief features, simplifying the molding process and reducing costs.
3Manufacturing precision
If the second plastic material fully invades the concave area space to take the smooth shape of the half-mould surface, then the outer surface is substantially smooth, but reliefs or bas-reliefs cannot be obtained
Solution Approach 1:
The second plastic material is selectively placed only in specific recess areas of the first cast rather than filling all concave spaces. This local quality approach ensures that relief features are created only where intended, while other areas maintain smooth surfaces, allowing both smoothness and relief features to coexist on the final product.
Solution Approach 2:
The second plastic material is injected in a controlled manner to partially fill only the recess areas that correspond to desired relief features, rather than completely filling all available concave spaces. This partial action enables precise control over where reliefs appear on the surface, creating the desired patterned relief effect while maintaining smoothness in non-relief areas.
Data Source
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AI summary
The present invention relates to a process for making an object from plastic material (10), comprising the following operations: moulding at least one insert (11), injecting a first plastic material (A) into a first moulding cast, such first cast being configured so that the at least one insert (11 ) comprises a base (12) from which exposure reliefs (13) extend, intended to be visible when the object made of plastic material (10) is finished, between the exposure reliefs (13) passage channels (14) being defined for a second plastic material (B) in a subsequent overmoulding operation; positioning the insert (11) in a second moulding cast, so that the insert (11) is positioned with the base (12) pressed against a first surface (17) of a first half-mould (18) of the second cast, and with the exposure reliefs (13) pressed against an opposite second surface (19) of a second half-mould (20); overmoulding a second plastic material (B) on a part of the insert (11), injecting the second plastic material (B) into the second cast, so that the second plastic material (B) injected fills the second cast passing through the passage channels (14) defined between the exposure reliefs (13) of the insert, covering the base (12) and being interposed between the exposure reliefs (13).