CH718768A2 - Method for the generation of predetermined breaking lines in oblong elements in thermoplastic polymers. - Google Patents

Abstract

The invention relates to a method for generating predetermined breaking lines in flat or sheet-like or oblong elements (1) in thermoplastic polymers such as polyester or the like and/or derivatives, said element (1) comprising at least two faces opposite sides and which are spaced apart by a predetermined thickness and which method provides for the execution of a pre-cut by means of a cutting tool in which said pre-cut takes place in such a way as to create a sharp slit while maintaining or generating a glassy phase of the material in the area of the thickness of material remaining beyond the pointed end of said pre-cut slot.

Description

- INTRODUCTION -

[0001] The invention refers to a method for generating pre-established breaking lines in oblong elements, or where at least one dimension is greater than the remaining ones, in thermoplastic polymers such as polyester or the like and/or derivatives.

[0002] The invention applies in particular, both to elements such as plates, panels or the like and to oblong elements, such as fibres, or ribbons or cables or the like.

[0003] Environmental policies at an international level are giving strong impulses to ecological transitions of production activities which generate less and less loads on the environment.

[0004] Plastics constitute a critical factor as regards pollution and the development trend points towards the replacement of materials that are difficult to recycle with recyclable materials, possibly to a large extent. The future regulations that will enter into force in the coming years will have as their object increasingly severe restrictions on the use of certain materials which are difficult to dispose of and which therefore represent a high ecological burden.

[0005] A technical field particularly interested, but not the only one, by these future developments is that of packaging. A sector with a high consumption of plastics due to the large amount of waste it generates. This is due both to the fact that the packaging pertains to mass products, and to the fact that the packaging has a very short life, i.e. the time it passes from leaving the production site to consumption by the end user.

[0006] A plastic material which has highly recyclable characteristics and which therefore lends itself very well to avoiding an excessive burden on the environment is made up of polyester or the like and/or derivatives. This material allows you to create containers and/or other types of packaging also for food use. Despite the undoubted qualities of mechanical resistance, formability, high transparency, compatibility with food products and high recyclability, this plastic material has some characteristics that make it not very adaptable to conditions in which it is necessary to provide pre-established separation lines between adjacent parts and between them connected of said plastic material, along which thanks to an action for example only manual and which requires little effort of force it is possible to carry out the separation.

[0007] This drawback makes the use of virgin and/or recycled polyester as an unattractive alternative material whenever the need to handle the product requires the presence of pre-established breaking or cutting lines and the separation along said lines by means of a purely manual action.

- STATE OF THE ART -

[0008] The separation behavior along pre-established breaking lines of products made of polyester or the like and/or derivatives also has drawbacks in the non-manual execution of these operations, since it is difficult to obtain a clear and well-defined separation line.

[0009] Several state of the art documents such as for example WO2011119639, WO20200055274, WO2O200055275 attempt to solve the problem by providing multilayer materials in which the layers are composed of polymers having different stoichiometric charge of polyester and loads to allow for the possibility of cracking by fractures or splits along sharp and clean lines of separation.

[0010] Other attempts such as EP3722217 and EP3566832 require a complex combination of different notches which make the process costly and complex.

[0011] Still others (EP3766799) claim, in combination with various notches, the need for thermal cooling treatments to stiffen the material with viscoelastic properties and therefore avoid its crushing during cutting.

[0012] The solutions currently in the state of the art are therefore not satisfactory and have various drawbacks. In the case of multi-material elements, the high rate of recyclability of polyester or similar and/or derivatives is lost, so the materials do not meet the future ecological standards that will be imposed on users. In relation to processes which provide for pre-cuts or combined areas of weakening, a first drawback is constituted by the high maintenance cost of the cutting tools which are more numerous than in the techniques used with other materials. A further drawback is linked to the complexity and therefore to the higher cost of the devices for performing the pre-cuts and therefore to the greater sensitivity of the machines to breakages and malfunctions. Furthermore, the processes claimed up to now are often energetically ineffective and do not take into account industrial problems such as the high degree of degradation of the cutting edges in the cutting of materials in thermoplastic polymers such as polyester or the like and/or derivatives and the consequent high maintenance of the plants. In all cases, the solutions do not provide dividing lines that are clean and sharp.

[0013] It is important to consider that a jagged parting line in a relatively stiff material can have greater cutting efficiency on soft materials and therefore can present a greater danger to users than a sharp and clean cut line that extends without spikes or ridges throughout the thickness of the material and along the length of the parting line.

[0014] There is therefore the need to provide working processes which allow to create pre-established breaking lines in flat or sheet-like elements in thermoplastic polymers such as polyester or the like and/or derivatives, thanks to which it is possible to separate two parts along said lines without the use of cutting tools.

[0015] A further object consists in carrying out working processes of the aforementioned type in which, thanks to the pre-established breaking lines between two parts in thermoplastic polymers such as polyester or the like and/or derivatives, it is possible to separate said parts from each other by means of an manual bending or mechanical stress thanks to a relative movement of the two parts to be separated.

[0016] A further problem that the invention aims to overcome is that of being able to create solutions for performing pre-cuts, i.e. incisions with a depth corresponding to a portion of an overall dimension of the thickness of the material, which allow effective separation of the parts of material divided by the pre-cut in subsequent times, even distant ones and which however allow the execution of the pre-cuts in the different conditions of the said thermoplastic materials determined by a previous processing and/or contextual to the execution of the pre-cut and/or determined by a storage condition of the pieces to be subjected to pre-cutting made of said thermoplastic materials.

[0017] Lastly, but no less important from an industrial and ecological point of view, it is necessary to find solutions which take into account the problems of maintenance of cutting tools by effectively compensating for the toughness and ductility of the material under certain environmental and stress conditions.

- SUMMARY OF THE INVENTION -

[0018] According to a first more general embodiment, a method for generating predetermined breaking lines in oblong or sheet-like elements in thermoplastic polymers, such as polyester or the like and/or derivatives, said element comprising at least two faces or surfaces between them opposite and which are spaced apart by a predetermined thickness, provides for the execution of a pre-cut by means of a cutting tool in which said pre-cut takes place in such a way as to create a sharp slit while maintaining or generating a glassy phase of the material in the area of the thickness of material remaining beyond the pointed end of said pre-cut slot.

[0019] The term pre-cut means a deep incision having dimensions corresponding to only part of the overall thickness between said two opposite surfaces.

[0020] In one embodiment, the cutting tool is configured in such a way as to be thin and with a cutting edge radius close to zero at the apex.

[0021] It should be noted that in the presence of a mechanical blade, the thickness of the blade tapers towards the apex with a constant inclination below a maximum of 20 degrees, preferably a maximum of a few degrees. The final blade imprint is further constricted by the relaxation of the spring tension after the blade is withdrawn from the slit. In the case of an ultrasonic actuation of the aforementioned blade, the final impression of the slit will be as close as possible to the negative of the cutting edge since the lateral compression of the plastic will be thermally relaxed during penetration due to the friction between the vibrating body and the substrate.

[0022] When it comes to cutting tools such as ultra-fast pulsed cold lasers, their focus is such that the energy front is as thin as possible, i.e. it has the smallest possible aperture (about one micron) in direction transverse to the extension of the cutting line. The material is removed by ablation without transmitting heat to the area surrounding the exposed one.

[0023] According to a characteristic, the aforementioned method provides for alternative combinations of steps: a first alternative which provides for an impulsive and essentially adiabatic actuation and penetration of the cutting tool into the material; a second alternative which provides for an actuation of the cutting tool in the direction of penetration of the same into the thickness of the material and optionally also in the direction of sliding along a predetermined cutting or incision line, and at the same time optionally a temperature difference between the temperature of the material and the temperature of the cutting tool; a third alternative provides for the execution of the cut by means of a rolling blade, i.e. a rotating circular blade which is made to advance along the path foreseen for the pre-established cutting or incision line, optionally providing for a temperature difference between the material temperature and the cutting tool temperature.

[0024] With reference to the first alternative, a first embodiment provides that the impulsive actuation of the knife which determines said adiabatic penetration into the material can be obtained with a single, ideally punctiform impulse of 1-10 Joules or alternatively with an ultrasonic vibration having a frequency between 20,000Hz and 50,000Hz, preferably around about 30,000Hz.

[0025] A variant embodiment of said first alternative provides for the pulse to be generated mechanically by means of a striking mass which strikes the blade of the cutting tool with the kinetic energy indicated above and for the duration of the pulse, generally under one millisecond .

[0026] Alternatively, instead of an impact mass, the adiabatic pulse penetration can be achieved by means of an ultrasonic cutting tool, which ultrasounds are controlled to emit cutting pulses with a frequency in the above-described range.

[0027] As regards the first alternative and the variants thereof, the term adiabatic penetration or adiabatic notch in the present description means a pulse penetration in which the pulse duration characteristics are such as to largely prevent a transformation and /or a transfer of energy from the cutting tool to the material underlying the cut and/or vice versa, which energy can be absorbed in the form of thermal energy by the material itself and/or by the cutting tool through a permanent deformation.

[0028] In this way, a transformation of the material due to the residual thickness below the bottom of the crack or notch is avoided, with which the material assumes characteristics of flexibility and elasticity which oppose breakage due to a relative oscillation along said pre-cut line of the two parts of material divided by said pre-cut line, assuming a behavior analogous to that of a film hinge.

[0029] With reference to the second alternative, the method provides for thermally treating a material area along the path along which an incision or a pre-cut slit is provided.

[0030] According to a variant embodiment, the material has a higher temperature, at least along the line along which the incision is followed, this temperature being chosen depending on the material so as to facilitate the penetration of the blade of the cutting tool into the material itself avoiding structural modifications of the material due to crushing or compression of the same by the cutting tool.

[0031] According to a further executive variant which can be provided alternatively or in combination with the previous one, provision is made for cooling the tempering of the cutting tool with respect to the material, so as to increase the resistance of the cutting tool to wear and in particular to limit the loss of sharpness of the cutting edge.

[0032] According to one embodiment, the temperature of the material and/or of the cutting tool is such as to allow the vitreous phases to be preserved, and to create a sharp crack subsequently and/or simultaneously with said heat treatment thanks to the intervention of a sharp element.

[0033] According to an embodiment, the two alternatives described above can also be applied in combination with each other whereby the method for generating predetermined breaking lines in oblong, flat or sheet-like elements in thermoplastic polymers such as polyester or the like and/ or derivatives, the said element comprising at least two faces opposite each other and which are spaced apart by a predetermined thickness, envisages the following steps: defining a path of said predetermined breaking line along at least part of the extension of said faces; the execution of an incision or notch from at least one of said faces and along said path which incision is made with a depth corresponding to part of the overall thickness of said element, i.e. to part of the distance between said two faces ; and in which the incision for the pre-cut can be obtained through different methods of penetration into the material (guillotine or knife) and with different types of load (progressive or impulsive) depending on the simplicity of application or the choice of material to be cut ; at least during the incision, carry out a temperature control of the cutting tool and/or of the material at least along said incision or said notch, i.e. at least along the side walls of said notch and along the bridge of the material of the thick part of the element in which there is no engraving or carving; the temperature control consists in maintaining a temperature difference between the cutting body of the cutting tool and the substrate, since the glass transition temperature of the constituent polymer must be between those of the two elements;

[0034] According to one embodiment, said temperature difference can be obtained through thermal conditioning of one or both elements prior to contact and etching.

[0035] According to one characteristic, a step of thermal stabilization by cooling can be carried out after the execution of the notch in order to faithfully preserve the topography created and/or to bring the cutting edge back to the pre-established working temperature.

[0036] The aforesaid thermal stabilization step can be provided in combination with both of the alternatives described above and/or with the third alternative which provides for the combination of the aforesaid alternatives.

[0037] As regards the thermal conditioning, various embodiments of the method are possible.

[0038] In a first embodiment, the temperature control takes place by heating to a temperature below the glass transition temperature, prior to performing the etching or notching and/or while performing the etching or of the notch, at least a part of the material, at least along the path along which the notch or incision is performed and for a certain width astride said path and a certain depth, preferably the entire thickness of the material.

[0039] One embodiment may provide, in combination or alternatively, for cooling at least the cutting edge of the blade of the cutting tool and/or the entire blade to a temperature much lower than the glass transition temperature of the polymer constituting the substrate.

[0040] Advantageously, the cutting edge of the blade can become more resistant following the cooling of the blade thus implying less wear of the cutting body and consequently a longer life time, this results in reduced maintenance of the device capable of putting this into practice cutting principle.

[0041] Equally advantageously, the material at a temperature close to or higher than the glass transition temperature reduces its hardness and facilitates the penetration and/or sliding of the cutting edge during the execution of the carving or engraving. This phenomenon further reduces the wear of the cutting edge as well as the necessary force and the consequent pressure on the tool, this results in a further saving of energy and possibly in lighter and cheaper machinery.

[0042] The temperature of the blade, possibly altered by the contact with the substrate during engraving, can be re-established following the engraving step in combination or parallel to the thermal stabilization process of the substrate.

[0043] According to yet another embodiment, the incision or carving can be performed using, as an alternative to a knife, ultra-fast lasers for cold ablation.

[0044] An embodiment can provide that the blade or at least the cutting edge are under the influence of heating units (by contact, induction or convection) during the whole step of performing the engraving or notching.

[0045] This embodiment can be provided in combination with a thermal conditioning step of the material itself before carrying out the etching or notching step or during the execution of said etching or notching step if the substrate is at a temperature higher than the glass transition temperature of the constituent polymer.

[0046] According to this embodiment, the hot cutting edge brings the substrate into contact during carving or etching in the rubbery or molten phase. This mechanism generates a self-lubricating effect on the cut, reducing friction and consequently the wear of the cutting unit. The material in the rubbery or molten phase (in any case above the glass transition temperature) reduces its hardness and facilitates the penetration and/or sliding of the cutting edge during the execution of the carving or engraving. This phenomenon further reduces the wear of the cutting edge as well as the necessary force and the consequent pressure on the tool, which results in a further saving of energy and possibly in lighter and cheaper machinery.

[0047] These attentions guarantee greater ease of penetration and/or sliding of the blade and/or better conservation of the same, resulting in reduced maintenance of the engraving systems and in less energy expenditure due to the lower force required and, if strategically positioned in the material manufacturing process, it also guarantees thermal optimization compared to other apparently similar processes.

[0048] According to a further embodiment, the cutting edge is made from a thin blade with a sectional shape such that the radius at the apex tends to zero.

[0049] To accentuate the sharp apex effect of the cut, the incision can be performed using an impulsive load to facilitate the creation of a crack which germinates from the base of the notch in the direction of the face opposite to that of the notch.

[0050] According to the embodiment which provides for an impulsive load, the stress mode also makes it possible to increase the apparent stiffness of the material following its viscoelastic behavior to deformation, all without acting on the temperature of the material, thus allowing a mechanically adiabatic cut.

[0051] The invention also provides a method for breaking assisted by pre-established breaking lines, incisions or notches of an oblong or plate-shaped element made of thermoplastic polymers such as polyester or the like and/or derivatives and which element comprises at least two mutually facing faces opposite and which are spaced apart by a predetermined thickness, which method provides for the creation along the path of a predetermined breaking line of an incision or notch according to the pitches of one of the aforementioned embodiments of the method for generating breaking lines predetermined in flat or sheet-like elements or in oblong elements in thermoplastic polymers such as polyester or the like and/or derivatives or any combination or sub-combination of said embodiments of said method for generating predetermined breaking lines in oblong, flat or sheets in thermoplastic polymers such as polyester or the like and/or derivatives and in combination with these steps, the step of flexing the two parts of said element separated by said pre-established breaking line, around a bending axis coinciding with said line and in the direction of mutual approach of the surfaces of said two parts corresponding to the face opposite to that from which the engraving or carving was made.

- UNDERLYING MECHANISMS-

[0052] In summary, the present assisted breaking process along pre-established breaking lines provides for the creation of a notch in the thickness of the material, which notch has a partial depth with respect to the overall thickness and which notch is made according to one of the embodiments or of the variants described above, the bending of the flat or plate-shaped element on the side opposite to said notch causing the sudden relaxation of the elastic energy and the progressive propagation of the fracture from the bottom of the notch through the body, along the thickness of said element unaffected by the notch until the next surface.

[0053] This single-degree-of-freedom bending causes propagating cracking of the material bridge corresponding to the part of the thickness of the element which has not been crossed by the notch or incision, which cracking takes place according to characteristics typical of the cracking of materials with glassy characteristics. Cracking is a split that extends predictably and without tearing along the pre-established breaking line defined by the incision or notch, so that the edge of the two parts along said line remains clean and homogeneous throughout the thickness of the material without form even jagged cusps or apexes which can form cutting edges capable of cutting softer materials.

[0054] As regards the scientific mechanisms underlying the effectiveness of the aforementioned method, the proprietor assumes the following: Polymers are materials generally endowed with high tenacity and a ductile behavior which favors the formation of zones of plastic deformation (Irwin ). Plastic deformation can induce yield stress (a form of local crystallization) in the studied structure and is concentrated around the crack apex. Conversely, brittle materials such as mineral glass tend to crack due to fracture mechanics (Griffith) without creating a plastic dissipation zone.

[0055] The energy necessary to cause the propagation of the cracks therefore depends on two factors, the elastic energy of a body under tension which tries to make its surface grow, called surface energy (or tension), and the energy dissipated thermally in the deformation of the area adjacent to the crack, the latter offers resistance to propagation.

[0056] Figure 1 shows an example of a fracture mode that applies to the present method.

[0057] In a situation similar to that in the figure, the crack will tend to open if the applied force results in normal tension, i.e. perpendicular to the surface of the crack, for example in the case of planar tension or convex bending with respect to the 'carving. The thickness of the bridge of material not affected by the shear must be thick enough to guarantee a high moment of inertia of the section and not to confuse the neutral line of flexure with the ends of the bridge, so as to allow local stress concentration and the accumulation of elastic energy which will be suddenly released during the fracture.

[0058] The determining factors for cracking are therefore the shape of the notch, i.e. a radius at the tip tending to zero which offers the maximum concentration of stress, and the toughness of the material, i.e. the ability to withstand deformation.

[0059] While cutting mineral glass by cracking is common practice due to the purely brittle behavior of ceramics, as far as polymers are concerned, the inability to break depends almost exclusively on their plastic behaviour. For this reason, some so-called rigid plastics can respond to cracking similar to glass, while others, such as thermoplastic polymers, can show a yield strength and dissipate the elastic energy in deformation, crystallization and consequent heating of the element under stress.

[0060] It has been found experimentally that, by way of example for polyester and/or derivatives, the thermoplastic nature of PET does not unconditionally lend itself to assisted cracking, i.e. following a simple pre-cut and which instead requires a particular how to perform the pre-cut incision.

[0061] One of these methods precisely provides for the aforementioned impulsive adiabatic penetration possibly with a subsequent step of thermal conditioning to compensate for any heating of the material and/or of the cutting tool; a second method envisages a tempering difference between the cutting edge and the material, a third method envisages a combination of the two aforementioned methods, in which the thermal conditioning of the material and/or the cutting tool is foreseen to preserve the local glassy phases for the purpose of reduce the toughness and embrittle the material in the notch area.

[0062] In case of cracking induced by heat treatment such as a pulsed laser with long pulses or a continuously operated laser, the heat-affected zone around the cut tends to reduce the stress concentration in the vicinity thereof. Furthermore, the totally thermal treatment induces a local microstructuration, for example smoothing of the fault tip by coalescence, a morphology which is not suitable for crack propagation.

[0063] The temperature of the material during processing is therefore irrelevant, if the adequate precautions are taken as indicated in the illustrated embodiments, as long as the topography achieved through the notch or incision is preserved up to failure and that this occurs when the area of crack propagation is in a brittle stage, i.e. below the vitrification temperature and without crystalline phases. The preservation of the morphology can therefore be enforced through a cooling thermal stabilization step as soon as possible after carving.

[0064] Following other experimental findings, the influence of the cutting method on the fractureability of the engraved element was ascertained. Different modes of penetration of the cutting element into the plastic material are possible. The kinematics of the cut can be essentially of three types (or a combination of the three types): normal to the surface (guillotine), translated on the surface (knife) and translated on the surface (wheel). The dynamics of the cut can also vary from slow continuous or progressive to rapid and impulsive. While the difference in cutting "squeezing" or "slipping" or "rolling" is in the common sensitivity, the behavior of viscoelastic materials in reaction to different stress dynamics is instead surprising. In fact, while in purely elastic materials, such as glass, the material never undergoes deformation and fractures when the stress exceeds its elastic limit, thermoplastic polymers in the glass phase ("cold") are elastic but tend to yield when exceeds the elastic limit to obtain permanent deformation. The rheological behavior of viscoelastic materials appears as a property derived from thermoplasticity and adds a dependence of stiffness not only on temperature but also on stress dynamics. Microscopically, polymers need an adaptation time to move the polymer chains under stress and rearrange them to relax the tensions, if time is not left, one can run into an overload of the single chains which begin to tear even with little stretching of the material. Another consequence of the viscoelastic effect is creep: according to this phenomenon, a body under load tends to relax its stress following the reorganization of the order of the molecules to dissipate the tension or compression, this can induce permanent deformations in the long term even with moderate loads compared to the nominal elastic limit of the material. The consequence is that the harmonic (vibrational) response to stress is non-linear and strongly depends on the amplitude and frequency of mechanical excitation thus resulting in a non-adiabatic hysteresis loop due to the innate absorption of the system. The material therefore behaves purely elastically (or mechanically adiabatically) for high excitation frequencies and/or small amplitudes. To resolve the question of the type of load to be used to exploit an adiabatic response, the stress must have a frequency spectrum rich in the high frequencies. A Dirac delta (or impulse) (mathematical model for an impulsive load) is a discontinuous and non-harmonic function which by definition has a "white" spectrum, i.e. an "infinite band", as its Fourier transform. In other words, to compose an impulse it is necessary to add up all the excitation frequencies resulting in a theoretically immediate or punctiform excitation, without ripple except in the impulsive harmonic response of the stimulated material, a high-frequency and evanescent shock wave which can germinate cracks from stress concentration zones. By extension, this relative and dynamic behavior of the components involved in the cut can be obtained alternatively through a cyclic and rapid stress as through the effect of a cutting element provided with an ultrasonic actuator acting on one or two axes resting on the plane of penetration of the blade.

[0065] This dependence on the load speed means that the cutting system can benefit from an impulsive load to drastically increase the apparent stiffness of the material, without needing to alter its temperature and indeed allowing it to show a stiff and brittle behavior even in a material in the rubbery phase, above the glass transition temperature. Therefore, a sudden stress does not cause the cutting area to deform vertically under the load of the cutting edge but allows a clear cut of the polymer chains and therefore a clean cut. In case it is in the glass phase (below the glass transition temperature), this impulsive load can germinate a crack from the bottom of the notch bringing the crack angle even closer to zero.

[0066] The invention takes into consideration industrial problems of optimization of maintenance neglected by analogous solutions for the facilitated breaking of thermoplastic polymers. These considerations have direct benefits from an economic, energy and logistical point of view, influential parameters in the industry and adjuvants to the ecological balance of a processing site.

[0067] Synergistically, the strategic positioning of this invention within a processing line can take advantage of the thermal conditioning inherent in the methods preceding or following the line to avoid one or more phases of active conditioning, prior to or subsequent to carving or etching. A particular positioning in the processing line can therefore further reduce the ecological footprint of the plant and simplify its implementation.

[0068] The tribological effect of self-lubrication of the cut can only be obtained if at least one of the bodies in contact is above the glass transition temperature of the polymer since thermoplastic materials are by nature ductile in the rubbery or molten phase since the viscosity drops with temperature. In this thermal situation, the polymer chains gain mobility and align the cut ends in the direction of the blade's sliding direction, creating a surface suitable for sliding (smoother and with a reduced coefficient of sliding friction). If the polymer at the interface with the cutting edge is in this phase, the relative friction coefficient drops since the adjacent area, extremely ductile due to the greater mobility of the polymer chains, behaves like a lubricating gel and, in case of a sufficiently rapid action the bodies come into elastohydrodynamic or even hydrodynamic contact for high speeds and temperatures. Furthermore, as the elastic modulus decreases, the lateral pressure reacting to the penetration of the cutting edge into the substrate is reduced. Consequently, as the friction force depends on the coefficient of friction and on the force normal to the contact surface, the resistance to penetration and sliding decreases.

[0069] The self-lubricating effect is therefore more effective for a "knife" notch or incision with sliding movement or with a rotating knife while the apparent hardening and "cracking" effect is more evident in a "guillotine" cut “, that is, an impulsive carving or incision.

[0070] The invention also relates to a system for implementing the method according to one or more of the preceding embodiments and variants.

[0071] According to a first embodiment, said system can comprise: a cutting tool with a cutting edge, which cutting tool is movable for a predetermined stroke in a direction perpendicular to the cutting edge towards the surface of a piece in which to generate by penetration partially a notch and which cutting tool is driven by a striking body which is accelerated in the direction of penetration against said cutting tool and which transfers the kinetic energy by impact against said cutting tool in an impulsive manner; a return mechanism of the tool and/or hammer in the retracted position with respect to the surface of said piece.

[0072] According to a second embodiment, said system can comprise: a unit for thermal conditioning of a workpiece at least along an area of material coinciding with a predetermined path of execution of a notch or an incision which extends for part of the thickness of said piece and/or a thermal conditioning unit of a cutting member; the said cutting element being movable in the direction of penetration into the said workpiece and/or in the direction of sliding along a path defined by the incision to be made for the execution of the said incision or of the said incision starting from a face of the said element and with said extension in depth corresponding to a part of the overall thickness of the material; a unit of measurement and precise regulation of the temperature or temperatures of the material of the workpiece and/or of said cutting blade at a temperature below or above the glass transition temperature of said material.

[0073] According to one embodiment it is possible to provide a stabilizing station with a said cooling unit downstream of a material engraving and/or carving station made according to one of the above two variants.

[0074] According to a further embodiment it is possible to provide, alternatively or in combination, a stabilization station for the material integrated with the engraving and/or carving unit and/or with the supporting and abutment counterpart, since the stabilization by cooling of the material performed following the execution of the engraving or carving.

[0075] The invention relates to further improvements which are the subject of the dependent claims.

- DESCRIPTION OF THE DRAWINGS AND ADVANCED EXECUTIVE FORMS-

[0076] The characteristics of the invention and the advantages will emerge in greater detail from the following description of some non-limiting embodiments illustrated in the attached drawings in which: Figure 1 schematically shows an example of notching and stressing of the two parts separated by the notching for their separation by notch-assisted fracture. Figure 2 shows in an enlarged image a notch which extends for part of the overall thickness of a flat or sheet-like element, starting from one face of said flat or sheet-like element. Figures 3 to 7 schematically show the steps of an embodiment of the method according to the present invention. FIG. 8 schematically shows an embodiment of a plant for implementing the method according to an example of the method of the present invention. Figure 9 schematically shows an embodiment in which the cutting tool performs a combined movement of penetration into the thickness of the material for a predetermined depth and a translation along the path of the pre-cut line.

[0077] Figure 10 schematically shows an embodiment in which the cutting tool makes the notch for a depth corresponding to part of the thickness by means of an adiabatic impulsive penetration of the tool, according to a guillotine path and in which the actuation of the impulsive cutting tool is indicated by a schematic example of an impulse transmitted to the same tool as in the case of a blade or a knife and/or from the same to the material as in the case of an ultrasonic cutting tool.

[0078] What is illustrated in the figures constitutes only an example of the method according to the present invention which has no limiting purpose with respect to the more general technical concept object of the claims.

[0079] In the present description and in the claims the term notch is used as a synonym for the term incision and slot.

[0080] Figure 3 shows a flat or sheet-like element which is made of a thermoplastic polymer such as polyester or the like and/or derivatives.

[0081] The term flat or sheet-like means an element having at least two mutually opposite faces, the extension of which is greater than the distance of said two faces, which distance is defined as thickness in the present description and in the claims.

[0082] Alternatively, the term plate may also include oblong elements also having a substantially rounded or cylindrical or polygonal section.

[0083] The element 1 therefore has a thickness D and two opposite faces 101, 201 which are spaced apart to the extent of said thickness D.

[0084] Number 2 shows a virtual line along which element 1 must be separated into two parts 1.1 and 1.2, respectively.

[0085] According to an embodiment of the method of the present invention and as shown schematically in Figure 2, the process provides for subjecting the element 1 to a first cooling step at a temperature well below the glass transition temperature of the constituent polymer .

[0086] Reference 3 shows a cooling device which operates for example on the basis of conveying a flow of cold gas or air 103 at least against a zone 301 of the element 1 coinciding with the virtual line 2 separating the two parts 1.1 and 1.2 among them.

[0087] In relation to the solution indicated in figure 4, the depth and extension of the zone 103 can vary with respect to what is illustrated. The cooling unit can also be different and not operate by conveying cold gas to the zone 301, but for example the cooling can be obtained by thermal conduction through direct contact between a cooling body and the element 3 or in other ways. Such cooling preferably takes place during and/or immediately after cutting in order to stabilize the material in which the incision has been made.

[0088] Furthermore, as will be seen below, the step of cooling to a temperature below the glass transition temperature of the constituent polymer, at least of the zone 301 which contains the virtual line 2 which traces the path of the predetermined breaking line can also be omitted and performed at the same time as the incision execution step along the trace defined by virtual line 2.

[0089] This possibility is made evident in figure 5 in which the cooling unit 3 by conveying a flow 103 of cold gas or air is illustrated with broken lines.

[0090] Figure 5 shows schematically the execution step of the incision using a punch or a cutting tool of which only the area of the cutting edge of the blade is shown, which is indicated with 4.

[0091] Figure 5 shows explicitly, albeit schematically, an embodiment in which said blade or at least said cutting edge of blade 4 are subjected to cooling to a working temperature which is also abundantly below the temperature of glass transition of the constituent polymer. A cooling unit 5, such as a cryogenic unit, is in thermal contact with the blade 4 which is thus maintained at a working temperature which is lower by the predetermined extent than the glass transition temperature of the constituent polymer and ideal for the conservation of the blades.

[0092] The cooling action of the blade 4 can take place in a step upstream of the execution of the cut in the element 1 or this cooling action can continue even during the execution of the cut or alternatively the cooling can have place only during the execution of the cut.

[0093] In figure 5, the action of performing the notch is schematically represented by the arrow I.

[0094] Figure 6 shows the condition of the element 1 after the incision has been made along the virtual line 2 and in the area 301 of the element 1. This area has been subjected to cooling according to one or more of the previous variants which provide alternatively or in combination a cooling step of the element 1 and in particular of the area 301 before performing the notch and/or a cooling step during the notch of the element 1 which can take place directly by means of a unit 3 of cooling which acts thermally directly on the element or alternatively or in combination indirectly by cooling the cutting unit, i.e. the blade. The notch is illustrated schematically and dimensionally not realistic for illustrative purposes only and is indicated by the reference number 7.

[0095] Depending on the variant with which the temperature of the material is cooled and therefore controlled so that it always remains decidedly and abundantly below the glass transition temperature of the constituent polymer, the temperature to which the element must be cooled directly and the temperature to which the cutting tool must be cooled must be such as to prevent the thermal energy generated during the cut from heating even only locally part of the material of the bridge of material of the remaining thickness not affected by the cut and that in figure 2 it is identified with D2.

[0096] In this way, the thermal energy generated by the incision action is largely compensated by preventing it from reaching values above the glass transition temperature of the constituent polymer and inducing microstructural modifications by coalescence and/or in the area close to the incision or local crystallization making it plastically ductile.

[0097] Thanks to this condition, the separation of the two parts 1.1 and 1.2 of the element 1 along the track 2 of the notch 7 can simply take place by angular displacement of the two parts 1.1 and 1.2 against each other in the approach direction of the semi-surfaces opposite to the one in which the notch 7 has been made as indicated by the arrows S in figures 6 and 7.

[0098] The notch performed according to one or more of the variants described above allows for the generation of a pre-established breaking line, which assists the separation by means of cracking or fracture of the material also along the part of the thickness which was not affected by the notch itself (see part identified with D2 in figure 2). The separation surface indicated by 8 in figure 7 and along which the breakage or fracture of the material takes place assumes a continuous, clear-cut and non-jagged shape without indentations or cutting cusps.

[0099] In relation to the depth of the notch D1 with reference to the overall thickness D of the element 1, this depth can vary between about 10 and 90% of the overall thickness and compatibly with the functional needs required for the element 1, i.e. with the conditions to which it is desired to allow the two parts 1.1 and 1.2 of the element 1 to be effectively connected until the bending step is exercised around the pre-established breaking line defined by the notch 7 and at the force conditions necessary to carry out this operation bending around the pre-established breaking line, i.e. the notch or incision.

[0100] Note that the force with which the blade is pushed against the material varies according to the overall thickness of the material and/or the desired depth of cut, the width of the element to be broken, the quality of the cutting edge used as well as the temperature conditions and stress of the material. For relatively thin slabs, ie below a centimetre, in particular one or two millimetres, the energy applied to exert this push can be of the order of a few joules, at most a few tens of joules.

[0101] The penetration force or driving energy of the cutting tool can easily and quickly be determined empirically by experiment in the setting steps of the pre-cutting system.

[0102] The embodiment illustrated above and the various variants described refer to the use of a blade to perform the incision. Temperature control takes place by pre-cooling the substrate and/or by cooling the cutting blade.

[0103] A possible alternative embodiment provides, instead of using an incision blade, the use of an ultra-fast laser of the femto-second type for cold ablation. Also in this case, before carrying out the incision and/or also during said execution by means of said cold laser, it is possible to provide a cooling step of the material of the element 1 and in particular of the area 301 in which it will or is notch 7 is made according to one or more of the variants described above.

[0104] A cold laser which has proved to be functional for carrying out the method according to the invention is for example the laser device known as SATSUMA and marketed by Amplitude.

[0105] Figure 8 shows schematically and by way of non-limiting example a system or plant for carrying out the steps of the method according to one of the embodiments of the present description.

[0106] The figures are to be considered as iconic symbols of operating units which substantially show the layout of the system and its correspondence with the sequence of method steps, as well as the essential functionalities of the operating units.

[0107] A conveyor 800 transports an element 1 from one processing station to the next. A first processing station consists of the temperature control station of the element 1 or at least of said area 301. This station is indicated as a pre-cooling station and is indicated with 801. The station comprises a thermal conditioning unit 811 of the element 1 which, operating according to one or more different heat generation and transfer methods, maintains the temperature of said element 1 at a predetermined working temperature. In particular, said temperature is lower than the glass transition temperature of the polymer constituting the substrate to be etched.

[0108] A subsequent station 802 provides the engraving or notching unit which can be made according to one of the variants described above. In combination with the notching unit indicated by 812, said station 802 may comprise a temperature control unit which is intended to control the temperature of the cutting tool and/or also a temperature control unit which is intended to further control the temperature of the material at least in the area 301. The temperature control unit or units are shown with a broken line and are indicated with 813 whether both are present or only one of the two alternatives is present.

[0109] When for example an ultra-fast laser is used in place of a cutting blade, the blade temperature control unit is not required and is replaced in an equivalent manner as regards the technical effect of keeping the temperature of the blade controlled. material, the laser setup parameters that affect heat dissipation in the cutting zone, and the light-matter interaction regime that must remain in adiabatic ablation of the substrate in zone 301.

[0110] According to a variant it is possible that the station 801 is not provided and that only the station 802 is provided in one or more of the variants described for the same.

[0111] In the example of figure 8, the illustrated system also comprises automatic means for the separation of the two parts 1.1 and 1.2 of the element 1. Although these means indicated in stations 803 and 804 are illustrated online, this solution is only optional, the preferred solution being that of providing said automatic means in a separate device which is used at different times from the moment of execution of the pre-established breaking line in stations 801 and/or 802.

[0112] Obviously the separation steps performed in the stations 803 and 804 can and are normally performed also by means of a manual action by human persons.

[0113] The operating units of the various stations 801, 802, 803, 804 are controlled by a central control unit 805 which operates on the basis of a control software 806. The control software processes the data obtained from sensors 807, in particular by the temperature sensors as regards the temperature control units of the substrate and/or of the cutting blades and/or of the cold laser, to generate the command signals of said individual operating units. An 808 data acquisition unit receives signals from the 807 sensors and supplies them to the 805 control unit.

[0114] The control software 806 comprises the coding of the instructions and settings necessary for the execution of the method steps according to one or more of the embodiments and embodiments described above.

[0115] Figure 9 schematically shows a variant embodiment in which, in the presence of a difference in tempering between the knife and the material, both pre-existing and induced by conditioning one or the other part, as shown with the dashed elements 3, 103 and 5, the cutting tool 4 performs both the movement in the direction of penetration, i.e. perpendicular to the cutting edge, and a sliding movement along the path provided for the notch 2.

[0116] Figure 10 instead shows the execution of the notch with partial depth of the thickness exerted by means of an adiabatic impulsive penetration of the cutting tool into the material. Since various embodiments of a cutting system of this type are possible, mechanical, by means of ultrasound, electromagnetic and others, this type of actuation of the cutting tool is shown generalized by means of a blade 4 and a mechanism for applying an impulsive motion of the same blade 4 showing the energy impulse transmitted to the blade in a graph.

[0117] This pulse is of the order, from 2 to 20N*s, between 1 and 10J of kinetic energy and a duration of 0.1-0.5ms.

[0118] A mechanical actuation system can provide an actuation by gravity with a return controlled by a motor or elastic elements.

[0119] An alternative may provide for a mechanically driven striking mass along a stroke towards and against the blade and backwards.

[0120] An electromagnetic alternative can provide a striking mass whose stroke in the direction of impact against the blade and backwards is controlled by an electromagnet, similarly for example to electromagnetically actuated dental hammers.

[0121] An ultrasonic alternative can take advantage of the pulsed penetration effect which essentially consists in the rapid repetition of minor pulses addressable in a vertical or parallel direction to the surface at a frequency between 20kHz and 40kHz and a power between 20W and 100W.

- EXPERIMENTAL EXAMPLES -

[0122] The method according to the present invention has been tested in some simple experiments as in the following examples:

EXAMPLE 1

[0123] A PET sheet was subjected to the execution of the three notches by means of a cutter each with a different pressure exerted on the blade, i.e. light, medium and strong as in the previous example and by means of a combined drive in the direction of penetration and sliding of the blade .

[0124] Before carrying out the carving, the blade of the cutter was cooled each time by means of a cold gas at a temperature close to 0°C in order to generate the temperature difference between the blade and the material. The carving was done immediately before the blade warmed up.

[0125] The three samples with the three different types of notches were manipulated by bending as for the samples described above. In all three cases, upon reaching an angle of the order of magnitude of approximately 90°, the two parts separated by fracturing the material bridge in the thickness area not affected by the notch. The separation was clear for all three samples and the fracture front on both sides of the plate was a clear surface without roughness, indentations or other deformations. The force and/or inclination required was inversely proportional to the depth of cut, the blade in its ideal conservation condition.

EXAMPLE 2

[0126] The same type of slab was subjected to the execution of the three notches by means of a cutter each with a different pressure exerted on the blade, ie light, medium and strong as in the previous example.

[0127] In this example, the area where the incision was to be made was subjected to cooling by exposure to an expanding gas. The temperature of the material along the area intended to be engraved was approximately 0°C. Immediately after cooling, the incision was made.

[0128] The engraving was performed immediately after cooling to avoid heating of the material.

[0129] The three samples with the three different types of notches were manipulated by bending as for the samples described above. In all three cases, upon reaching an angle of the order of magnitude of approximately 90°, the two parts separated by fracturing the material bridge in the thickness area not affected by the notch. The separation was clear for all three samples and the fracture front on both sides of the plate was a clear surface without roughness, indentations or other deformations.

EXAMPLE 3

[0130] The same type of slab was subjected to the execution of the three notches by means of a cutter each with a different pressure exerted on the blade, ie light, medium and strong as in the previous example.

[0131] In this example, the area where the incision was to be made was subjected to heating by exposure to a gas flow heated by a resistance. The temperature of the material along the area intended to be engraved was such as to soften the material. Immediately after heating, the incision was made.

[0132] Furthermore, each time the blade of the cutter was cooled with a similar treatment and at a temperature of about 0°C.

[0133] The etching was performed immediately after heating the material and cooling it to avoid heating the blade by contact with the substrate. The plate material was cooled below its glass transition temperature following etching to fix and preserve the resulting morphology. The cut thus performed required considerably less effort to penetrate and/or translate into the material, the blade will be kept even longer. The cut is particularly clean, the incision is almost invisible.

Example 4

[0134] The same slab was subjected to etching by adiabatic impulsive penetration of the tool.

[0135] A blade was placed on the surface of the material with its cutting edge resting against said surface. A vertically guided hammer mass was dropped from various heights against the side of the blade opposite the cutting edge.

[0136] Trials established a height value from which to drop the striking mass such that the slab was not sheared completely, i.e. such that the blade penetrated only part of the thickness of the slab.

[0137] Between incisions were made at different heights lower than the maximum limit height beyond which a complete shearing of the material was obtained.

[0138] Three samples were obtained each with a notch of different depth. The three different types of carving were manipulated by bending as for the specimens described above. In all three cases, upon reaching an angle of the order of magnitude decidedly smaller than 90°, the two parts separated by fracturing the material bridge in the thickness area not affected by the notch. The separation was clean with a dry fracture which for all three samples presented a fracture front on both sides of the plate consisting of a clean surface without roughness, indentations or other deformations.

[0139] The same experiment was carried out by combining a preventive thermal conditioning of the knife and/or of the material in order to generate a temperature difference between them and the ease of breaking along the notch was verified similarly to what was described above for the other experiments. Also in this case, the separation was clear with a dry fracture which for all three samples presented a fracture front on both sides of the plate which was constituted by a clear surface without roughness, indentations or other deformations. The ease of breaking is not determined by the thermal conditioning of the material before and during cutting. The height of the striking mass has been reduced to obtain a behavior similar to the mode without heat treatments, the purpose of the preventive or contemporary conditioning is to reduce the effort required to engrave and reduce tool maintenance.

[0140] In a further experimental test, for the execution of a notch with partial depth with respect to the overall thickness of about 2mm of a slab and with a length of the notch of about 2.5cm, the partial notch was made by impulsive penetration with an energy of about 0.2 to 0.6 Joule. Subsequently, the folding of the two parts separated by the notch in the opposite direction to the side on which the notch is made made it possible to obtain a clean and decisive break whose edges are smooth and free of serrations or other surface irregularities.

[0141] In the schematic figures, the incision execution mode using a blade is shown only for the impulse execution variant, in which the incision is generated with a movement of the knife only in the direction of penetration and for an execution variant in which the knife slides along a pre-established path which defines the position of the notch. An initial piercing action is followed by translation of the blade along said path, maintaining the piercing position.

[0142] An alternative not shown provides for the blade to be in the form of a rotating disk which has a cutting edge along its peripheral edge. The notch takes place by initial penetration in the pre-established thickness of the material and then translation along the path that defines the position of the notch, during which translation, the circular blade rotates on itself, always bringing a new part of the cutting edge to incise the material.

[0143] In this case, the cooling of the blade can take place during the making of the notch by means of one of the alternatives described above and in which the part of the cutting edge which has not yet cut into the material is suitably cooled to increase its resistance and duration .

[0144] This concept also applies when, as an alternative to the variant which provides for cooling of the blade, the variant which provides for heating of the blade is used. In this case, it is possible that only the part of the cutting edge which still has to engrave the material, immediately before the incision, is heated to the working temperature.

Claims (17)

1. Method for the generation of pre-established breaking lines in flat or sheet-like or oblong elements in thermoplastic polymers such as polyester or the like and/or derivatives, said element comprising at least two mutually opposite faces which are spaced apart by a pre-established thickness and the which method provides for the execution of a pre-cut by means of a cutting tool in which said pre-cut takes place in such a way as to create a sharp slit while maintaining or generating a glassy phase of the material in the area of the thickness of material remaining beyond the sharp end of said pre-cut slot. 2. Method for generating predetermined breaking lines in flat or plate-like elements in thermoplastic polymers such as polyester or the like and/or derivatives according to claim 1, the said providing for alternative combinations of steps according to: a first alternative which provides for an impulsive and essentially adiabatic actuation and penetration of the cutting tool into the material; a second alternative which provides for an actuation of the cutting tool in the direction of penetration of the same into the thickness of the material and optionally also in the direction of sliding along a predetermined cutting line, and at the same time a temperature difference between the temperature of the material and the temperature of the cutting tool; a third alternative provides for the execution of the cut by means of a rolling blade, i.e. a rotating circular blade which is made to advance along the path foreseen for the pre-established cutting or incision line, optionally providing for a temperature difference between the material temperature and the cutting tool temperature. 3. Method according to claim 2, wherein the impulsive actuation of the knife which determines said adiabatic penetration into the material, takes place with impulses having a duration of less than one millisecond and an energy comprised between 0.1 and 10J per cm of cut or alternatively with a cyclical repetition of the effort at a frequency between 20kHz and 50kHz, preferably around about 30kHz. The method according to claims 2 or 3, wherein the impulse drive is generated mechanically and/or electromechanically and/or electromagnetically by actuation of a striking mass which strikes the blade of the cutting tool for the duration of the impulse and with a pre-set and pre-set energy or adiabatic impulsive penetration is achieved by means of an ultrasonic cutting tool. The method according to one or more of the preceding claims, wherein the method provides the step of thermally treating an area of material along the path along which a pre-cutting incision or slot is provided. 6. Method according to one or more of the preceding claims, wherein the tempering of the cutting tool with respect to the material is cooled, so as to increase the resistance of the cutting tool to wear and in particular to limit the loss of sharpening of the cutting edge and/or to bring the material to a higher temperature than the temperature of the cutting tool, at least along the line along which the notch is followed, this temperature being chosen depending on the material so as to facilitate penetration of the blade of the cutting tool in the material itself, avoiding structural modifications of the material due to crushing or compression of the same by the cutting tool and consequent possible inaccuracies on the effective depth of the incision. 7. Method according to one or more of the preceding claims, wherein the temperature of the material and/or of the cutting tool is such as to allow the vitreous phases of said material to be preserved, and subsequently and/or simultaneously with said heat treatment to be created sharp slot thanks to the intervention of the cutting tool. 8. Method according to one or more of the preceding claims characterized in that it provides a combination of the alternatives according to claim 2 and in which the following steps are provided: – the definition of a path of said pre-established breaking line along at least part of the extension of said faces; – the execution of an incision or notch on at least one of the said faces and along the said path which incision is made with a depth corresponding to part of the overall thickness of the said element; and – the incision for making the pre-cut being obtained by guillotine or sliding or rolling penetration into the material and with a progressive, constant or impulsive load; – at least during the incision, carry out a temperature control of the cutting tool and/or of the material at least along said incision or said notch, i.e. at least along the side walls of said notch and/or along the bridge of the material of the thick part of the element in which there is no engraving or carving, which temperature control consists in maintaining a temperature difference between the cutting tool and the material which includes the glass transition temperature of the polymer constituting the substrate. 9. Method according to one or more of the preceding claims in which the temperature control takes place according to one or more of the following combinations: by cooling and/or heating during and/or after the execution of the engraving or carving, at least a part of the material, at least along the path along which the engraving or engraving is performed and for a certain extent in width a straddling said path and a certain depth, preferably the entire thickness of the element, at a temperature below the glass transition temperature; cooling and/or heating at least the cutting edge of the cutting tool blade and/or the entire blade to a temperature below the glass transition temperature. 10. Method according to one or more of the preceding claims, wherein the incision is performed by means of a guillotine or knife blade or by ultra-fast lasers or by ultrasound. 11. Method according to one or more of the preceding claims wherein a thermal conditioning step is provided, preferably for cooling the material and/or the cutting tool, at the end of the execution of the incision to fix the morphology of the cut. 12. Method for assisted breaking by pre-established breaking lines, incisions or notches of a flat or sheet-like or oblong element in thermoplastic polymers such as polyester or the like and/or derivatives and which element comprises at least two opposite faces which are spaced apart from a pre-established thickness, which method provides for the creation along the path of a pre-established breaking line of an incision or notch according to the steps of one of the aforementioned embodiments of the method for generating pre-established breaking lines in flat or slab-shaped or oblong shapes in thermoplastic polymers such as polyester or the like and/or derivatives according to one or more of claims 1 to 11, comprising in combination with these steps, the step of bending the two parts of said element separated by said pre-established breaking line, around to a folding axis coinciding with said line and in the direction of mutual approach of the semi-surfaces d said two parts corresponding to the face opposite to that from which the incision or carving was made. 13. System for implementing the method according to one or more of the preceding claims 1 to 12, wherein said system comprises: a cutting tool with a cutting edge, which cutting tool is movable for a predetermined stroke in the direction perpendicular to the cutting edge towards the surface of a workpiece in which a notch is generated by partial penetration and which cutting tool is driven by an impact body which is accelerated in the direction of penetration against said cutting tool and which transfers kinetic energy by impact against said cutting tool in an impulsive manner; a return mechanism of the tool and/or hammer in the retracted position with respect to the surface of said piece. 14. System for implementing the method according to one or more of the preceding claims 1 to 12, wherein said system comprises: a cutting member movable in the direction of penetration into said workpiece and/or in the direction of sliding along a path defined by the longitudinal extension path of the incision to be made for the execution of said incision or of said incision starting from a face of said element and with said depth extension corresponding to a part of the overall thickness of the material. 15. System for implementing the method according to one or more of the preceding claims 1 to 12, wherein said system comprises: a unit for thermal conditioning of a workpiece at least along an area of material coinciding with a predetermined path of execution of a notch or an incision which extends for part of the thickness of said piece and/or a thermal conditioning unit of a cutting member; a unit of measurement and precise regulation of the temperature or temperatures of the material of the workpiece and/or of said cutting blade at a temperature below or above the glass transition temperature of said material. 16. System according to one or more of claims 13 to 15, characterized in that it comprises, alternatively or in combination, a material stabilization cooling station integrated with the cutting tool and/or with the supporting and abutment counterpart, being the stabilization by cooling of the material performed at the same time and/or following the execution of the incision or carving. 17. System according to one or more of claims 13 to 16, wherein the optional cooling of at least the blade or only the cutting edge area takes place during or after the execution of the incision or carving, a cryogenic unit in thermal contact being provided with said blade and/or at least with said cutting edge region, which cryogenic unit can be activated before and/or during and/or after actuation of the cutting unit to perform the incision or notch.