Custom design of packaging through advanced 2 technologies : case of study applied to apples 3

In the context of food packaging design, customization enhances the value of a product 10 by meeting the needs of the consumer. Personalization is also linked to adaptation. This makes it 11 possible to improve the properties of the packaging from various points of view: functional, 12 aesthetic, economic and ecological. Currently the functional and formal properties of packaging are 13 not investigated among themselves, however the study of both properties are the basis for creating 14 a new concept of personalized and sustainable product. In accordance with this approach, the 15 conceptual design procedure of packaging with personalized and adapted geometries based on the 16 digitization of fresh food is proposed in this work. This study is based on the application of 17 advanced technologies for the design and development of food packaging, in this case apples, in 18 order to improve the quality of the packaging. The results obtained show that it is possible to use 19 advanced technologies in the early stages of product design in order to obtain competitive products 20 adapted to new emerging needs. 21


Introduction
The challenges demanded by the European Union in the food packaging industry raise new objectives among which are the sustainability of raw materials and minimization of waste, reduction of energy consumption during the production process, minimization of environmental impact, recyclability of packaging and littering reduction [1,2].This combined with the fact that during the last decade the demand for healthy and fresh products, especially fruits and vegetables, is gradually growing, in a context where eating and consumption habits are constantly changing due to the lifestyle in society, makes other specific needs appear in the packaging of food by the consumer, mainly related to the design and adaptability of packaging [3].Among these needs, others are added such as providing more nutritional information on the packaging, greater food security and less risk to health [4][5][6].Thus, there are studies that place the packaging of the fresh product as the second reason for choosing a product where factors such as comfort, appearance, transparency and texture must be considered [4].
Thermoplastic polymers comply or can comply with all of these conditions, which is why they have been chosen by manufacturers of different products as materials for their packaging [7].
Polyethylene terephthalate (PET) is a polymer whose properties include its mechanical resistance to both impact and chemical products, its transparency, its lightness, the reduced demand for energy in its manufacture and transport, its mouldability and its recyclability [8].In addition, it is the most recycled plastic in the world and the European Food Safety Authority has corroborated that PET does not contain bisphenol-A (BPA), phthalates or dioxins [2].However, they have been identified as one of the main causes of global environmental degradation and this problem is expected to increase due to increased demand from developing or re-industrializing countries around the world [9,10].For example, from the perspective of a country in constant development and consumption of different raw materials, China accounted for 24% of PET plastic demand in 2016, and it is critical to understand the consumption needs of this type of market when examining the prospects for global PET volume growth [11].
In fact, the clear trend towards increasing the consumption of food that needs packaging carries with the constant development of materials and techniques that improve the performance of this service [12].In short, it can be distinguished several aspects [13]: the improvement of the production times, the reduction of the material and the improvement of its aesthetic and functional properties.
Thus, the fresh food packaging industry is interested in developing efficient and innovative solutions to ensure the quality of the products taking into account their sustainability and environmental sustainability [11].For this reason, the design evaluation in the development of sustainable products should include aspects related to the design, manufacture and use of the packaging [14,15].
In this context, the packaging design process implies consideration of aspects associated with cost, appearance, usability, manufacturing, sustainability, standards or competitiveness [14].It should be added that the manufacturing process selected for a product is directly related to the aspects mentioned above, and in the case of food packaging one of most commonly used is thermoforming process [16].
Typically, previous research on the packaging design process in thermoforming, focus on studying the moulds and materials used in the process [9,[17][18][19].Also, recent research implements functions for the intelligent packaging development, through which sensitive labels control the condition of the food [20].These initiatives are aimed at improving food health and getting more freshness of food, achieving in this way a better preservation of it [3].
On the other hand, the packaging sector demands customized solutions in terms of shapes, sizes and colours, so that the packaging is unique [21].In turn, it is intended to pursue product differentiation by means of sustainable products and new designs [22].In such a way, it is also possible to respond demographic changes and consumption habits [23][24][25].
Thus, according to [26], a packaging can be personalised in reference to the non-generic, making a difference as to design, brand and/or size, among others.Stated differently, a container can be designed specifically for that type of product.On the other hand, it can be understood that an adapted packaging is the one that adapts itself to the inner shape and size of the product [26].
However, despite the needs that were determined in previous research and after having analysed the fresh food packaging which are currently commercialised on the market, it is observed that the majority of them are standard and just a few includes customization in terms of forms [27].
In addition, in these cases there is no adaptation to specific sizes according to calibres.
According to the reasoning presented, this research studies of the personalization and adaptation in packaging design, through a case of study with apples, on the protection of the product in order to provide designers with a tool for the packaging 4.0 generation.This is linked to the sustainability of both the interior of the product and the material expense.The main objective of this study is to validate the use of advanced technologies as part of the unconventional design of packaging, increasing the sustainability and functionality of these products.A packaging can be understood as personalized to the non-generic, being able to differentiate in terms of design, brand and / or size among others, that is to say, a packaging designed specifically for that type of product.

Tools and materials used to obtain the customized packaging
To carry out the experimental development, the apple has been used as the target product because its size facilitates the obtaining of measurements, studying the adaptation to packaging depending on two different calibres: category I and category II, according to [28].For the development of the experimental, a total of 20 apples were used, 10 units of each calibre were used to carry out the design adapted from the computer-aided design (CAD) concept, which were digitised by means of 3D digitalisation [29], Figure 1.To this end, 8 image captures were obtained for each unit needed to create the three-dimensional model, Figure 2. The David® SLS-1 3D scanner was used, according to [30].These scanned elements have as their main purpose the creation of adapted geometries through the generation of curves based on the scanned elements.
(a) (b)  Thus, the development of the concepts was carried out through the CAD software, Solidworks®.
As a result, the development of packaging design was simplified in time and has allowed to generate more complex and personalized forms to the food.
On the other hand, the evaluation of the design proposals was validated through the generation of reliable prototypes.The mould design and The Standard Triangle Language (STL) file of the mould are generated by Solidworks® and, then, is parameterized using software for 3D printing, Simplify.
A Gcode file is generated for printing it in a FDM machine, BQ Witbox that use a diameter filament of 1.75 mm.And, the PET sheet of 500 micrometers thick is thermoformed to generate the prototype with Formech compac mini using the FDM mould, Figure 3.  Also, several functional measures of each natural product were evaluated to analyse the differences between them, also using Solidworks® software.These dimensions were selected according to the parameters established for the calibres: the largest diameter, dm, and the maximum height, H.According to this, two measurements were collected for each of the dimensions studied: L01 and L02 for dm and L03 and L04 for H, Figure 5.It should be noted that L01/L02 were made in the two directions of maximum diameter of the fruit and L03/L04 in the two highest heights recorded.
This has obtained the variation in the measurement between pieces of fruit.One of the objectives of digitizing these elements, in spite of the normal variations of a natural product, is to define the range of measures that present representative variations to be taken into account in the design of the packaging.As a result, comparative tables were obtained and the dimensional range was defined, which will serve to obtain the adaptation parameters on the design of the packaging, which is the object of study.
Once the concept was generated, the design was developed in Solidworks® using the 10 scanned elements as a means of generating the construction curves.In accordance with this, the set of lines and tangent arcs have been defined, which together form the design of the idea previously conceptualized.Likewise, the numerical relations between the different container geometries were defined, using as relation parameters the maximum height, H and the maximum diameter, dm, of the container.
Then, when the final design was developed in Solidworks®, the relationship equations, defined above, were introduced in order to evaluate the degree of adaptability through this type of digital tools.Then, the variable measures of the packaging were defined to carry out the adaptation to the two categories of size of apple studied, according to [28].
Finally, the adaptability range of the design created for this practical case was established and, in addition, the degree of adaptation of the dimensions obtained with each of the digitalized units for the two calibres studied was evaluated.Figure 6 shows an example of the results obtained.

Virtual evaluation of digital elements
As described above, the study was conducted for two types of calibres, according to [28].As seen, the size refers to the predominant size within the packaging, and is defined according to the maximum equatorial diameter [31].Thus, the apple samples were scanned to generate a parametric model of each one to make the measurements according to the methodology.The data obtained from the samples studied are detailed in Figure 7.
From the results obtained from the study of the morphology of apples it is determined that the dominant geometry in the plant has a slightly oval shape, therefore we can speak of major axis, L01, and minor axis, L02, to name the maximum dimensions of the digitalized samples, seen in the plant.
It is worth mentioning again that L01 and L2 correspond to the average dimensions for the width of the apple, on the other hand L03 and L04 are the height measurements collected on the digitized elements.In an initial analysis of the results it is observed that calibre 1, Figure 7  From the graphs it can be seen that for calibre 1, parameter L01 has intervals between 83 mm and 85.5 mm while L02 varies between 80.2 mm and 83.75 mm, Figure 4.8 a).This shows the disparity of measurement for apples of the same calibre, intrinsically affecting their standardisation for subsequent parameterisation.
As regards the height of the apple, parameters L03 and L04, the aim is to obtain as a result the maximum height per calibre.In this case, the results obtained with greater value are L03 with a dimensional interval between 77.7 mm and 88.16 mm.
As for size 2, Figure 8 b), the category of fruit has worse quality and the measurement intervals tend to increase according to standard [28], 5% for calibre 1 and 10% for calibre 2. As for the measurement results, because parameter L01 is predominant from the point of view of package design, a measurement range between 69.4 mm and 75.9 mm is observed.The maximum height L03 varies between 56 mm and 68.5 mm.
On the other hand, Figure 8 shows the mean data for the four parameters with the measurement dispersion.In both cases, the measurements show a greater dispersion in the parameters L03 and L04 which corresponds to the height of the apples, being slightly higher for the apples of calibre 2. As for the measure of greater influence for the design of the package, L01, it is precisely the apple of calibre 1 that exhibits greater homogeneity.Analysing the data presented so far, it can be deduced that the size of the package of a calibre can be included in a dimension that encompasses all sizes of apple inside a category, included the difference between all the fruits of the same type and calibre.Therefore, the variations in the samples that affect the design of the packaging are the maximum width and height obtained from grouping the digital models.
For calibre 1, 85 mm as the maximum measurement within the calibre established according to the standard and tolerance of 5% [28], a maximum diameter of 86.7 mm was obtained for virtual measurements, Figure 9 a).On the other hand, for size 2, with a nominal size of 73 mm and a permitted tolerance of 5% according to [28], 78 mm has been obtained, Figure 9 b).These dimensions served as a starting point for the dimensional study of the container although these dimensions could be reduced due to the irregular geometries.Although all apples are included in the same diameter, the plant shape is slightly oval, as discussed in previous paragraphs.Thus, the linear dimension on the plant in one of the faces is lower with respect to its perpendicular, L02 and L01 respectively.According to this, a dimensional relationship, dr, was established for the diameter, according to equation 1: Thus, from the data obtained in the 20 case studies corresponding to calibres 1 and 2, a dimensional relationship was established between both distances of 0.97 and 0.98 respectively.This It is important to bear in mind that these dimensions were studied at an experimental level.The aim is to propose a method in which, using scanned elements, designs can be generated; to this end, a coefficient has been proposed that can be applied to the dimension of a given calibre.
Analysing the dimensional results of the three-dimensional models of the scanned apples and the measurements according to the norm, it was detected that a relief coefficient, Cd, can be defined for the design of a packaging, which in this case study was established at 1.06.This coefficient was determined from the observation of the maximum dimensions per calibre, according to the norm, and the virtual dimensions studied.This coefficient will make it possible to ensure that the size of the containers is adapted to all geometries included within a calibre.
Then, if for calibre 1 the maximum diameter allowed, including tolerances, is 89.25 mm and the maximum diameter that appears as a measure of nominal calibre is 85 mm.It can be defined that the coefficient could be between 1.05 and 1.06.However, because of the differences naturally present in fresh foods, 1.06 has been considered to be used to ensure proper functioning.Thus, the validation of this coefficient was carried out by implementing this coefficient in the development of the adaptation of calibre 2.
Therefore, the calculation of container dimensions can be done according to the following equation: Where Cm is the maximum size and dm the width of the packaging.
Then, for calibre 1 the dimension of dm corresponds to 90 mm, obtained from the multiplication of Cd and cm of 85 mm, and for calibre 2 of 77.4 mm, from cm of 73 mm.These data were validated during the parametric design, which is explained in the following section.
With respect to the height of the packaging, a ratio has been established with respect to dm of 1.05 for calibre 1 and for calibre 2 the ratio of measurements is 1.10.Due to the fact that the standard does not specify heights per calibre, this ratio was determined from the measurements made on the samples studied.The ratios were then determined from the subtraction of the maximum length and maximum height obtained virtually from the apples.Thus, in the parametric design, when this measurement relationship is related to dm, the same relief coefficient is implicitly included, Cd.

Parameterization of the conceptual proposal
Once the design of the packaging was carried out, a series of parameters were obtained that have given rise to the creation of equations that parameterise the package All of them based on two variables, the maximum height of the container, H, and the maximum width, dm.Thus, Figure 10 a) shows a diagram of the variables that affect the sizing of the container.
From the initial geometry extracted from the concept design of the apple, it was parameterized according to a series of equations described below.Figure 10 b) shows a diagram with the dimensions that affect the mould when thermoforming the designed package.Thus, the equations that affect the overall dimension of the packaging correspond to: dn=dm*0.97, Where Hb is the height of the bottom half of the designed packaging and Ht is the height of the top half.In the same way the dimensions in plant of the container are given by the greater width, dm, and the smaller width, dn.In this case study, an oval geometry has been created.
On the other hand, as mentioned above, the design created in this study consists of a series of arches that are tangentially joined, in plan and profile, and a flat surface at the ends with a circular shape.Then, the curves that define these geometries, Figure 10, were also able to be related by means of equations from the CAD design initially created.Thus, the relationship between H and the slightly oval curved geometry that makes up the package design in the profile view is given by the equations: Rt=H*0.18, ( 7) dt=dm*0.45, ( 9) These equations define the radius of curvature of the upper part, Rt, and lower, Rp.In addition, the adaptation of the dimension of the flat part, so that the packaging can be easily supported, is given by the diameter in both halves of the container, db and dt, and was related to the parameter dm.On the other hand, the radius Rp is the parameter that encompasses the overall geometry of the container in plant, and the construction of the shape was constructed by sweeping through the vertical curves given by Rb and Rt.
The rest of the tangent arcs that make up the packaging design are automatically adapted from the curves generated with the above equations.Then, the generated equations were introduced in the parametric design software.The benefit of the parametric design of a packaging is the customization of their geometry according to the need of adaptation of the product to be contained.In addition, the design can be evaluated in real time by means of the digitized fruit samples.
As a result, all construction operations such as rounds, sketches, etc. were related.The number of operations obtained was a total of 12 for each of the parts of the container.As was commented, these equations and variables serve to modify the geometry of an object quickly.
For the lower part, a relationship has been defined between the curves that make up the container and therefore the mould, according to the equations defined in the previous section.These equations were related to the sketches made in the parametric design program.In the same way, the equations of the upper part have been parameterized.
In short, by modifying one of the measures, the packaging is automatically adapted.This is one of the first steps for the generation adapted to a specific packaging design in the context of industry 4.0.
Another result obtained in this case study is the maximum and minimum ratio of measures between H and dm, obtaining a range of adaptation measures.The maximum ratio of dm to H is 1.Once the packaging was parameterized, a series of configurations were established in the Solidworks® software to evaluate the appropriate sizes for each of the samples studied and with which the theoretically established Cd has been validated.The configurations allow the packaging to adapt automatically to the measures established, making it easier to adapt to calibres and measures according to specific needs.

Evaluation of results
In order to analyse the viability of the coefficient obtained, Cd, using the 3D scanned fruit models, the correct arrangement of the apple was evaluated with respect to the dimensions of the packaging.Then, after analysing the dimensions with the configurations of the packaging, it was observed that the Cd corresponds adequately, although the optimum height for each sample varies.
Bearing this in mind, it can be concluded that, depending on the design needs in the same calibre, several containers with different H could be established.This may be possible thanks to new technologies such as additive manufacturing, which allows low-cost moulds to be made in order to optimise the maximum performance of the container.However, if the design requirements allow it with this methodology it is possible to establish an optimal design that encompasses all food units of the same topology.
On the other hand, if you want to generate a custom packaging for a unit is also possible.This example could have multiple applications that can be extended to other types of products and food.
Thus, the final dimensions, which were adapted to the size obtained according to the Cd calculated in the measurement part, correspond for calibre 1 with the ratio of dm of 89.3 mm and H of 85 mm.Although, as was mentioned, some of the samples studied could modify the height for the use of the dimensions having a range between 80 mm and 85 mm Similarly, for calibre 2 the ratio of dm and H are 75 mm and 70 mm, respectively, and having a range of H between 67 mm and 70 mm.
For more information see Appendix A.
Then, in accordance with the reasoning that was carried out; the results obtained for the two calibres studied were validated by means of a physical prototype.The FDM moulds created for the two calibres are shown in Figure 12.As stated above, the design was validated using the physical prototypes and 20 apples for each calibre studied, Figure 13.These apples were selected taking into account shapes and size variations, and different breeds were included in the units studied.For more information see Appendix B. Once the results were analysed, it can be said that the final solution obtained is positive as all the units of the same calibre correspond to the dimensions of the packaging.However, according to the studies in the parametric program, it can be seen that in several of the cases studied the dimensions are not adjusted in their entirety, causing parts of the packaging to be empty.This is not a functional problem for the design because these variations are given by the wide range of measurements that are included within a calibre.Specifically, these dimensional deviations are accentuated in calibre 2, which is a smaller calibre and comprises a larger range of measurements.
In the case of calibre 1, which belongs to category I according to [28], lower dimensional deviations are observed.However, the morphological inequalities between the different apple varieties are increasing.
Means then that in this situation, personalisation and adaptation could be increased by reducing the spectrum of fruit types that can be introduced in the same type of packaging.Therefore, depending on the type of product to be packed, adaptation and personalization can be considered with a greater degree of accuracy.

Discussion
The main idea of reverse engineering is to synthesize a fruit model so that they can be used and measured as part of the design process.The studies carried out show that it is possible to generate personalized designs and they can also be adapted according to the specifications required by a specific product.Digitization and flexible designs make it easier to customize and test concepts in real time to help design teams make decisions in less time and with greater reliability [32].
Then, the introduction of scanned elements in the design process facilitates the adaptation of the size and shape of the packaging to the type of fruit contained, allowing only the quantity of plastic material necessary for its sale and transport to be used.In this way, the product is optimised, which means a reduction in environmental and economic impact.This fact is relevant because currently thousands of tons of plastic and food are discarded daily [11], and great efforts are made to mitigate this impact, generating stricter and stricter regulations in the withdrawal and recycling of food packaging [33].The high number of packaging manufactured daily means that a small reduction in each container has a great influence on the environment.This working methodology promotes the reduction of material that is so necessary in a strategic sector such as the food sector.
As noted above, much of the food waste is produced by using containers with large amounts of food that end up deteriorating in homes [34].Thus, the possibility offered by this methodology for the realization of custom packaging by type of fruit and category can lead to the reduction of food waste due to the possibility of reducing the amount of product inside and by improving the preservation of specific properties of each food [35].
The application of digital elements in the design process were validated as part of the creation of a method that includes advanced technologies in its procedure, as was researched in other fields of engineering [36,37].In the study two main parameters were selected that relate to the functional measures for the containers, the maximum height and width, to adapt a packaging to a given calibre.
However, the geometry of a fresh food is irregular so they made four measurements at the top and bottom to calculate the height.The same was done for the width.It should be added that these measurements have been carried out to analyse the dimensions of the product studied at laboratory level.The main objective of this work was to evaluate the direct application of the scanned models for the generation of personalized packages for a range of measures established within a calibre.
This study proposed a 3D scanning scheme for fresh food to support custom packaging design [30].Then, the three-dimensional model of the fruits approximates the real geometry.Thus, the application of 3D fruits facilitates the realization of personalized and adapted designs, as well as the evaluation in real time of design proposals.On the other hand, the parametric design of the package according to the two parameters studied, maximum height and width, gives rise to the possibility of generating packages adapted to the dimensions and needs of the food according to its established range of measures.In short, the result was the creation of a packaging, fully defined by equations, which is capable of adapting to the measurements in a given range.
Based on these results, the computational design is aimed at the parameterization of designs to favour customization by means of optimal configurations according to the design variables and favouring the adaptation of the design to the specific need [38,39].Along these lines, it can be stated that computer programs facilitate the realization of personalized and flexible designs to adapt to needs by means of the parameterization and digitalization of elements [40][41][42].Product customization then also serves as an engine to improve sustainability throughout the product life cycle [43].Custom design enhances product design by meeting the specific needs of users, according to [44].
Furthermore, according to new trends and competitiveness, the design and development of packaging needs solutions that streamline the working procedure.In this context, based on the approaches made on the customization of packaging, there is also a latent need for quick and flexible solutions.Specifically, the process of manufacturing moulds by conventional methods usually delays the validation time of the final prototype of the product, so that designers cannot make changes or explore alternatives quickly and reliably [45].Faced with this situation, an alternative is the application of additive manufacturing techniques that can provide design teams with a fast and economical tool that can thus be used from the early stages of product design.
In accordance with the reasoning that was carried out, throughout this work it was possible to prove that it is possible to make reliable prototypes using economic moulds built by additive manufacturing.The similarity of the prototypes generated thanks to 3D printing and thermoforming technologies evidences the possibility of creating prototypes that provide greater reliability in a simple way.Then, the evaluation by means of these prototypes provides a reliable tool for the validation of the mentioned designs.In short, it was proven that it is possible to thermoform geometries with different shapes.Therefore, it is possible to obtain products with better performance and therefore competitive.This can also affect the life cycle of the product because from the point of view of social, economic and environmental impact there is a significant improvement.
Finally, this work presents several future lines of action, the most important of which is the advanced study of new packaging designs by means of topological optimisation and the extension of the study of virtual environments for early evaluation.

Conclusions
The following conclusions can be drawn from the research work carried out in this study: It is possible to digitize fresh food by means of 3D scanning techniques, obtaining reliable digital elements that can be used in advanced technologies.In this sense, it was possible to define a procedure for the reverse engineering of different types of food, detailing the specific parameters according to size and finish.
It was possible to use the digitized fruits during the conceptual phase in the packaging design process.Thus, custom designs were developed using these elements as a reference during computeraided design, thus validating the proposed methodology.In addition, the evaluation of the ideas generated was also favoured by the possibility of checking dimensions in real time using these digital products.On the other hand, the adaptation according to the specifications required by a specific product is also improved.Therefore, it can be said that the application of 3D fruits facilitates the development of customized and adapted designs.
It is possible to completely parameterize the geometry of the package to create custom designs and, in turn, automatically adaptable.In short, the creation of a packaging, fully defined by equations, is able to adapt to measurements in a given range.The parameterized design was made possible by means of the virtual evaluation of digitized fruits.
Table B2.Images from the validation study with prototype of the custom packaging for Calibre 2.

Figure 1 .
Figure 1.a) Scanning procedure using the SLS-1 David V5 scanner, b) Visualization of the apple trough the software.

Figure 2 .
Figure 2. Example of capture of the image, which the 3D scanner performs, of an apple of calibre 1.

Figure 3 .
Figure 3. Generation of prototypes in thermoforming with moulds created by FDM.

Figure 4 .
Figure 4. General procedure used to obtain the final package

Figure 6 .
Figure 6.Example of the result of the adaptation parameters with respect to the digitized product.

Figure 9 .
Figure 9. Overlap of the 10 apple units to establish a common diameter based on the sample: a) larger size 1: b) size 2 with dimensions between 63 and 73 mm.
.preprints.org) | NOT PEER-REVIEWED | Posted: 3 January 2019 Preprints (www.preprints.org)| NOT PEER-REVIEWED | Posted: 3 January 2019 doi:10.20944/preprints201901.0008.v18 of 18 relationship was used for the design and parameterization of the packaging by CAD, giving rise to a final geometry of non-cylindrical container.

Figure 10 .
Figure 10.Dimensions of the container and the mould: a) Plan of the variables that affect the container and therefore the upper and lower mould; b) Dimensions of the moulds, on the left upper half and on the right lower half.

Figure 11 .
Figure 11.Example of maximum and minimum ratio between dm and H for H equal to 85 mm: a) Maximum ratio being dm=137 mm; b) Minimum ratio being dm= 20 mm.

Figure 12 .
Figure 12.Parts, inferior and superior, of the mould to generate the physical prototypes: a) Moulds for calibre 1; b) moulds for calibre 2.

Figure 13 .
Figure 13.Images of the evaluation carried out with the prototype and commercial fruits.