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EP-4737097-A1 - PROCESSING METHOD

EP4737097A1EP 4737097 A1EP4737097 A1EP 4737097A1EP-4737097-A1

Abstract

Method for processing a semi-finished product (2) by hot forming, to produce a manufactured article (1), the semi-finished product (2) being made of a polymeric material having a degradation temperature and a minimum processing temperature for hot forming; comprising a surface (2a), defining the portion of the semi-finished product that is in contact with the outside, and a core (2b) defining the internal portion of the semi-finished product (2) at a greater distance from the surface (2a), the method comprising: a heating phase of the semi-finished product (2) up to a maximum temperature; a forming phase, subsequent to the heating phase, wherein the semi-finished product (2) undergoes forming to produce an intermediate product; a cooling phase wherein the intermediate product is transformed into the manufactured article (1), the heating phase comprises: a first heating sub-phase, wherein the heating power has a substantially constant first value from the start of the heating up to a first predetermined temperature of the surface (2a) of the semi-finished product (2); and a second heating sub-phase subsequent to the first heating sub-phase, wherein the heating power has a substantially constant second value, which is lower and between 5% and 40% of the first value; at the end of the heating phase: the temperature of the surface (2a) is equal to the maximum temperature; the maximum temperature being lower than the degradation temperature of the material of the semi-finished product (2); the temperature of the core (2b) is higher than said minimum processing temperature of the material; the temperature gradient between the surface (2a) and the core (2b) is lower than the difference between the maximum temperature and the minimum processing temperature.

Inventors

  • ALDINIO-COLBACHINI, Daciano
  • SCHIAVO, Fabio

Assignees

  • Solera-Thermoform Group SpA

Dates

Publication Date
20260506
Application Date
20251027

Claims (11)

  1. Method for processing a semi-finished product (2) by hot forming, to produce a manufactured article (1), - said semi-finished product (2): - being made of a polymeric material having a degradation temperature and a minimum processing temperature for hot forming; - comprising a surface (2a), defining the portion of the semi-finished product that is in contact with the outside, and a core (2b) defining the internal portion of said semi-finished product (2) at a greater distance from said surface (2a), said method comprising: - a heating phase of said semi-finished product (2) up to a maximum temperature; - a forming phase, subsequent to said heating phase, wherein said semi-finished product (2) undergoes forming to produce an intermediate product; - a cooling phase wherein said intermediate product is transformed into said manufactured article (1), and characterized in that: - said heating phase comprises: - a first heating sub-phase, wherein the heating power has a substantially constant first value from the start of said heating up to a first predetermined temperature of said surface (2a) of said semi-finished product (2); and - a second heating sub-phase subsequent to said first heating sub-phase, wherein said heating power has a substantially constant second value, which is lower and between 5% and 40% of said first value; - at the end of said heating phase: - the temperature of said surface (2a) is equal to said maximum temperature; - said maximum temperature being lower than said degradation temperature of the material of said semi-finished product (2); - the temperature of said core (2b) is higher than said minimum processing temperature of said material; - the temperature gradient between said surface (2a) and said core (2b) is lower than the difference between said maximum temperature and said minimum processing temperature.
  2. Method according to Claim 1, wherein the ratio between said second value and said first value is between 25% and 35%.
  3. Method according to any one of the preceding claims, wherein in said heating phase, said heating power varies with constant average powers in said sub-phases.
  4. Method according to the preceding claim, wherein in said heating phase, said heating power varies sinusoidally or in a wave train fashion with constant average powers in said sub-phases.
  5. Method according to any one of the preceding claims, wherein said first predetermined temperature is a phase transition temperature of said polymeric material.
  6. Method according to any one of the preceding claims, wherein said first heating sub-phase and said second heating sub-phase are substantially consecutive.
  7. Method according to any one of the preceding claims, wherein said semi-finished product (2) is made of thermoplastic polymeric material.
  8. Method according to any one of the preceding claims, wherein said semi-finished product (2) is a sheet.
  9. Method according to the preceding claim, wherein said sheet has a thickness between 1 mm and 10 mm.
  10. Method according to any one of the preceding claims, wherein said hot forming is vacuum thermoforming.
  11. Method according to any one of Claims 1-4, 6-10, wherein said first predetermined temperature has a value corresponding to a predetermined percentage of said maximum temperature.

Description

The present invention relates to a processing method of the type specified in the preamble to the first claim. The object of the present invention is a processing method which finds application in the field of material processing and primarily, but not exclusively, in the field of polymeric material processing. Currently, processing techniques for semi-finished products that allow for the making of manufactured articles are known. In detail, these processing techniques may include molding methods. In these techniques, the material can be inserted into a mold and undergoes to a deformation process that allows the material to acquire the desired shape of the mold. These techniques can be hot or cold, depending on the values of the process temperatures. For example, a hot molding process is the injection molding, wherein the material, typically polymeric, is melted and injected into the mold until its internal cavity is filled, then cooled and extracted from the mold. Another molding technique is under vacuum thermoforming, wherein a sheet of polymeric material is laid on the mold by means of a vacuum. The sheet is heated by heating elements (typically lamps) and rendered malleable so that it can be deformed. The vacuum created within the mold draws the sheet towards the mold and deforms it so that it adheres to the mold until it takes the shape thereof. At the end of the forming, the manufactured article thus obtained then undergoes a controlled cooling and is extracted from the mold. The known techniques described include some significant drawbacks. In particular, they can result in the alteration of the material being processed if it is operated under suboptimal conditions, leading to a deterioration in the quality of the final product obtained. In this situation, the technical task underlying this invention is to devise a processing method capable of substantially overcoming at least part of the aforementioned drawbacks. Within said technical task, an important purpose of the invention is to obtain a processing method that can make the processing method more efficient. Another important purpose of the invention is to create a processing method that allows to prevent alterations in the material to be processed. The technical task and the specified aims are achieved by a processing method as claimed in the annexed claim 1. Preferred technical solutions are highlighted in the dependent claims. The characteristics and advantages of the invention are clarified below by the detailed description of preferred embodiments of the invention, with reference to the accompanying figures, in which: Fig. 1 shows a semi-finished product subjected to the processing method according to the invention; andFig. 2 illustrates a product made by the processing method according to the invention. In this document, measurements, values, shapes, and geometric references (such as perpendicularity and parallelism), when associated with words like "approximately" or other similar terms such as "about" or "substantially", are to be understood as subject to measurement errors or inaccuracies due to production and/or manufacturing errors and, above all, subject to a slight deviation from the value, measurement, shape, or geometric reference to which it is associated. For example, such terms, if associated with a value, preferably indicate a deviation not exceeding 10% of the value itself. Moreover, when used, terms like "first", "second", "upper", "lower", "main", and "secondary" do not necessarily identify an order, priority of relation, or relative position but may simply be used to more clearly distinguish between different components. Unless otherwise specified, as apparent from the following description, terms such as "processing", "computing", "determination", "computation", or similar refer to the action and/or processes of a computer or similar electronic computation device that manipulates and/or transforms data represented as physical quantities, such as electronic magnitudes of records of a computing system and/or memories into other data similarly represented as physical quantities within computer systems, records, or other storage, transmission, or information display devices. The measurements and data reported in this text are to be considered, unless otherwise indicated, as performed in International Standard Atmosphere ICAO (ISO 2533:1975). With reference to the figures, the article made by means of the processing method according to the invention is globally indicated with the number 1. It can be an article that can be used, for example, for the assembly of automotive parts. Alternatively, it may be a food storage product, such as food trays. The article 1 may be a manufactured article intended for use as a commodity. The method according to the invention is a processing method for a semi-finished product 2. In particular, it can be a processing method by hot forming, to produce a manufactured article 1. In detail, the proc