Material properties for the development of innovative products.

The study of material properties in the product design cycle is one of the main headaches in prototyping laboratories. Additive manufacturing technologies add a lot of value to the speed of prototype manufacturing, but leave the study of material properties necessary for the manufacture of the final product in the dark.

The product innovation cycleis made up of stages that are inviolable. Among them are: product design, prototype manufacturing and industrialization of the final product.

The design process allows defining the functionality of parts and mechanisms. The best product design programs allow assigning material to the parts to calculate the expected mechanical resistance. In this process, prototypes can be made with inexpensive materials to validate geometries and the viability of the design.

In the prototype, the goal is to demonstrate the functionality of the product through a physical product. Prototypes are made using rapid manufacturing methods and it is desirable to use materials with chemical and physical properties similar to those required in the final product.

The industrialization of products determines manufacturing costs and, therefore, the product margin. The material properties must allow for the key functions of the product. For example: food-grade materials, biocompatible materials, hypoallergenic materials, recycled plastics, which must also be compatible with mass production methods.

Methods and Characteristics of Materials for Design Prototypes

3D Printing with FDM: Simple chemical and physical properties materials are used. For example, it is not necessary to use biocompatible materials to manufacture a medical product prototype. The goal is to validate the functionality and fit of the parts.

Common Materials for Design Prototypes. 3D Printing Prototypes.

PLA (Polylactic Acid)

Heat Resistance: 60-65°C
Print Agility: 5 (Very easy)
Deformation Temperature: 60-65°C
Mechanical Properties: 50-60 MPa
Chemical Properties: Biodegradable, low resistance to chemicals.

ABS (Acrylonitrile Butadiene Styrene)

Heat Resistance: 100-110°C
Print Agility: 3 (Moderate)
Deformation Temperature: 95-105°C
Mechanical Properties: 40-50 MPa
Chemical Properties: Resistant to chemicals, moderate resistance to solvents.

PETG (Polyethylene Terephthalate Glycol-modified)

Heat Resistance: 70-80°C
Print Agility: 4 (Easy)
Deformation Temperature: 70-80°C
Mechanical Strength: 45-55 MPa
Chemical Properties: Resistant to chemicals and moisture.

TPU (Thermoplastic Polyurethane)

Heat Resistance: 80-90°C
Print Agility: 3 (Moderate)
Deformation Temperature: 80-90°C
Mechanical Properties: 30-40 MPa (Flexible)
Chemical Properties: High resistance to oils, fats, and abrasion.

Nylon (Polyamide)

Heat Resistance: 120-130°C
Print Agility: 2 (Difficult)
Deformation Temperature: 110-130°C
Mechanical Strength: 70-80 MPa
Chemical Properties: Excellent chemical and mechanical resistance.

C (Polycarbonate)

Heat Resistance: 140-150°C
Print Agility: 2 (Difficult)
Deformation Temperature: 130-150°C
Mechanical Strength: 60-70 MPa
Chemical Properties: High chemical and thermal resistance.

ASA (Acrylonitrile Styrene Acrylate)

Heat Resistance: 100-105°C
Print Agility: 3 (Moderate)
Deformation Temperature: 95-105°C
Mechanical Strength: 40-50 MPa
Chemical Properties: Resistant to UV rays and weathering.

Carbon Fiber Composites

Heat Resistance: Depends on the base material (70-150°C)
Print Agility: 2-3 (Depends on the base)
Deformation Temperature: Similar to the base material
Mechanical Strength: >70 MPa (Enhanced by reinforcement)
Chemical Properties: Depends on the base material; improves resistance and rigidity.

FDM is a useful method for model making and prototyping. It is recommended to use inexpensive materials for models, as it is not necessary to validate geometries and shapes with materials with special chemical properties or materials with unique chemical properties.

3D Printing Material Prices

PLA (Polylactic Acid): $15 – $40
ABS (Acrylonitrile Butadiene Styrene): $20 – $55
PETG (Glycol-Modified Polyethylene Terephthalate): $20 – $40
TPU (Thermoplastic Polyurethane): $30 – $80
Nylon (Polyamide): $40 – $100
PC (Polycarbonate): $60 – $120
Composites (e.g., with carbon fiber): $70 – $150

Material Characteristics for Design Models and Prototyping with SLA.

Standard Resin

Approximate Price: $50 – $100 per liter
Mechanical Properties: Moderate rigidity, brittle under load.
Heat Resistance: ~50°C
Applications: Visual prototypes, conceptual models.

Resina Flexible

Approximate Price: $80 – $120 per liter
Mechanical Properties: Elasticity, supports repetitive deformations.
Heat Resistance: ~60°C
Applications: Prototypes of joints, flexible parts or shock absorbers.

High Strength Resin

Approximate Price: $100 – $150 per liter
Mechanical Properties: High impact resistance, durable.
Heat Resistance: ~75°C
Applications: Functional parts, intensive mechanical tests.

Resina Transparente

Approximate Price: $70 – $120 per liter
Mechanical Properties: Moderate rigidity, brittle under load.
Heat Resistance: ~50°C
Applications: Optical components, decorative parts.

High Temperature Resin

Approximate Price: $150 – $250 per liter
Mechanical Properties: Rigid, withstands high temperatures.
Heat Resistance: ~200°C
Applications: Molds, parts subjected to extreme heat.

Dental Resin/Biomedical Materials

Approximate Price: $200 – $300 per liter
Mechanical Properties: Biocompatibility, sterilizable.
Heat Resistance: ~70°C
Applications: Dental prosthetics, medical applications.

Resina Fundible

Approximate Price: $100 – $180 per liter
Mechanical Properties: Moderate rigidity, burns without leaving residue.
Heat Resistance: ~50°C
Applications: Casting of jewelry and metal parts.

Material: Technical Resin

Approximate Price: $100 – $200 per liter
Mechanical Properties: Resistance to impacts, bending and fatigue.
Heat Resistance: ~100°C
Applications: Intensive use functional parts.

Just like in the case of rapid product manufacturing with FDM, in the case of 3D printing with SLA, it is essential to use the cheapest photosensitive resins for the manufacturing of parts and visual models. On the other hand, the use of technical resins, with complex chemical and physical characteristics, is a very suitable alternative for the manufacturing of functional prototypes.

Prototype manufacturing methods. Material compatibility.

With models, basic geometric validations are sought. It is not necessary to choose materials with special properties to meet specific functions. In contrast, functional prototypes aim to demonstrate the full functionality of a product. For this reason, the use of special materials and manufacturing methods is justified to achieve visually decent results, as well as high resistance mechanical properties.

Vacuum Molding: Master mold fabrication to obtain parts and pieces of prototypes. Materials like Polyurethane and Silicone are used. To fabricate these molds, shapes are typically obtained through 3D printing, followed by negative impressions using vacuum techniques that allow the creation of the master molds. This procedure is very useful for prototype pre-series as well as for merging materials in complex areas of the prototype.

CNC Machining: A cutting procedure using computerized machines, it is possible to manufacture parts and prototypes with complex materials, such as: Aluminum, steel, ABS, and Polyacetal. It is a very expensive procedure and materials, therefore, it is reserved for high-precision prototypes.

Resin Casting Molding: To use materials with special chemical properties, in the case of parts with complex geometries, it is common and recommended to use handcrafted molding to achieve casting with resins. This technique allows taking advantage of the wide availability of materials in photosensitive resins. For example, with these types of methods, we work on prototypes that require food-grade, parts with hypoallergenic properties, as well as prototype parts that require some degree of biocompatibility.

Compatibility and Transition of Manufacturing Methods: From Prototype to Industrialization

The disconnect between prototype manufacturing methods and industrial methods that enable mass production poses a real challenge. Failing to anticipate these connections rigorously in prototyping can represent an additional challenge in the industrialization process.

Next, we have prepared a brief summary of compatibility between prototyping methods and methods used in industrial factories, relating this coherence to the materials that have optimal properties for use in these processes.

Prototyping Method	Compatible Industrial Process	Compatible Industrial Material
3D printing (FDM)	Injection molding	PP, PE, PC-ABS, Nylon 6, Nylon 12
3D printing (SLA)	Injection molding, precision casting	Polycarbonate, PMMA, Nylon, Metals
Vacuum Molds	Injection molding (with metal or plastic molds)	Polypropylene, Polyethylene, PVC
CNC machining	CNC production, casting or extrusion	Aluminum alloys, Stainless steels
Hand Casting (Resins)	Injection molding or thermosetting casting	Thermosetting as industrial epoxy

Chemical properties of materials useful for manufacturing special products.

Materials have chemical and physical properties that make them suitable or not for certain types of innovative products. The choice of material types is closely related to the functional requirements of each product, and these unique properties must be anticipated from the study of suitable materials in the basic engineering project, even if models and prototypes are made that do not meet these characteristics.

The functional requirements of a product define the "What" of a product, not the "How". When we talk about functional requirements of an invention, we refer to the list of functions that the product must absolutely fulfill, not the methods or complex techniques that enable achieving those objectives.

Once the functional requirements are defined, it is key to identify which materials are associated with each part and piece of the product and what the properties of the suitable materials are according to those requirements.

According to our experience in more than 300 prototypes manufactured, we have encountered special characteristics in the product design and prototyping process that have led us to this brief summary about: common materials in the prototyping process to address needs such as: manufacturing food-grade parts, manufacturing heat-resistant plastic parts, manufacturing medical prototypes or hospitality machine prototypes that required certain biocompatibility levels, manufacturing toy prototypes and sexual toys with hypoallergenic properties and biocompatible properties, or prototypes that would undergo specific certifications, where the chemical properties of the materials are crucial.

Prototyping Materials	Food-Grade Materials	Resistencia Alta al Calor	Biocompatibilidad	Regulaciones/Requisitos
PLA, ABS, PETG, TPU, Nylon, PC	PETG, PP, PE	PC, Nylon, ABS	Nylon, TPU (certified)	FDA certifications (for food or medical use)
Standard, Technical, and High-Temperature Resins	PMMA and Polycarbonate (with Certification)	High temperature resins	Biomedical and dental resins	ISO 10993 for biocompatibility
Poliuretano, Silicona	Food-Grade Silicone	Thermosetting silicone	Medical silicone	Food or medical grade depending on application
Aluminum, Steel, ABS, and Polyacetal:	Food-Grade Aluminum	High resistance steels, Aluminum	Anodized aluminum, Surgical steels	ISO certifications for industrial precision
Epoxy Resins and Polyurethane:	Not recommended	Thermosetting epoxy	Biocompatible epoxy	Chemical and thermal safety regulations

Products that require materials with special properties.

It is easy to identify from the basic engineering project the parts and pieces of a product that must be manufactured with materials with special properties. Below are some examples that we have worked on Let's Prototype and that have represented a great challenge in terms of decisions about ideal materials for each stage.

1. Transform single-use plastic products into reusable products.

There are several arguments to consider why it is a priority to replace single-use plastic products with products that have multiple use cycles. Among them, the following stand out:

Companies need to demonstrate their commitment to the environment.
The use of single-use plastics will incur very significant taxes.
Economic aid and subsidies are reserved for products made with environmentally responsible materials.

For example, in the healthcare sector, many plastic products cannot be reused because they cannot withstand the temperatures and conditions generated inside an autoclave machine for sterilization. These conditions expose them to steam and temperatures exceeding 130°C, which requires the use of plastics with heat-resistant properties.

In the same way, we have manufactured robot prototypes for restaurants and industrial kitchens, which required the design and production of parts and components with food-grade requirements. Additionally, they needed to be cleaned in machines, dishwashers, and other similar equipment that, as a common denominator, operate at high temperatures. Prototyping parts with these characteristics has driven the growth of Let’s Prototype as a design company, conducting parallel studies of suitable materials with appropriate properties for each project.

2. Products with special mechanical resistance and compatible prototyping methods.

Sectors such as prosthetic design and manufacturing, industrial tool prototype manufacturing, and parts for the aerospace industry are some examples of industries that frequently require the development of innovative prototypes with maximum resistance characteristics from the early stages of development.

Functional prototypes that require materials with high mechanical strength properties are compatible with prototyping methods and materials such as:

3D printing (FDM)

Prototyping Material: Nylon.

Industrial Compatible Material: Nylon 6, Nylon 12.
Key Mechanical Properties: High mechanical and chemical resistance.

Prototyping Material: TPU.

Industrial Compatible Material: Thermoplastic elastomers (industrial TPU).
Key Mechanical Properties: Elasticity, abrasion resistance, and tensile strength.

3D printing (SLA)

Prototyping Material: Technical resins.

Industrial Compatible Material: Polycarbonate, PMMA, Nylon.
Key Mechanical Properties: High rigidity and impact resistance.

CNC machining

Prototyping Material: Aluminum.

Industrial Compatible Material: Aluminum alloys (6061, 7075).
Key Mechanical Properties: Lightweight and structural strength.

Prototyping Material: Steels.

Industrial Compatible Material: High-strength steels (AISI 4140, AISI 1045).
Key Mechanical Properties: Extreme hardness and resistance to cyclic loads.

Vacuum Molds

Prototyping Material: Polyurethane.

Industrial Compatible Material: Thermoplastics such as PP, PE, PVC.
Key Mechanical Properties: Resistance to deformation and continuous use.

Hand Casting

Prototyping Material: Thermosetting epoxy.

Industrial Compatible Material: Industrial thermosetting epoxies.
Key Mechanical Properties: Heat resistance and high hardness.

3. The need for materials with biocompatible properties to create products.

Most innovative medical products require the use of materials with biocompatible properties from the very first stage.

Biocompatible Materials: When we talk about materials with biocompatible properties, we refer to materials whose chemical properties comply with regulations that ensure the safety of these surfaces. Biocompatible materials are composed of chemical properties that minimize the body's rejection. These materials have three fundamental characteristics:

Chemical Inertia: Refers to their ability to avoid the use of toxic elements in their composition.
Stability: Refers to the biological stability in the composition of materials, allowing this characteristic to prevent corrosion.
Compatibility: Refers to the property of integrating with or accurately mimicking natural tissues.

Of course, the medical sector and innovation companies in the healthcare sector are highly demanding of this type of materials. The truth is that there have been significant advancements in the democratization of biocompatible materials for industrial manufacturing processes. There are also important advancements in biocompatible materials for prototypes, compatible with the usual methods used in the design and validation stages of innovative products for the healthcare sector.

Biocompatible Materials Available for Prototyping.

Biocompatible Polymers

Nylon (Polyamide):

Composition: Repetition of amide groups (-CONH-) in its structure.
Usage: Temporary implants, medical devices.

TPU (Thermoplastic Polyurethane):

Composition: Urethane groups (-NHCOO-) in an elastomer structure.
Usage: Flexible prostheses, catheters, skin-contact devices.

PEEK (Polyether Ether Ketone):

Composition: Aromatic polymer with ether and ketone bonds.
Usage: Permanent implants, orthopedic components.

Silicone:

Composition: Polysiloxane polymers (-Si-O-Si-) with methyl or vinyl groups.
Usage: Prostheses, catheters, medical devices for tissue contact.

Biocompatible Metals Useful for the Development of Medical Products.

Titanium (Ti):

Composition: Pure metal or in alloys with aluminum and vanadium (Ti-6Al-4V).
Usage: Bone implants, dental implants, and pacemakers.

Stainless Steel (316L):

Composition: Alloy of iron (Fe), nickel (Ni), chromium (Cr), and molybdenum (Mo).
Usage: Surgical instruments, temporary implants.

Cobalt-Chromium Alloys (Co-Cr):

Composition: Mixture of cobalt, chromium, and traces of molybdenum.
Usage: Joint prostheses, vascular stents.

Resins and Adhesives with Biocompatible Properties for Medical Product Design and Prototyping.

Epoxy Resins:

Composition: Epoxide groups (-C(O)C(O)-) with biocompatible hardeners.
Usage: Custom prostheses, temporary medical components.

Photopolymer Resins (SLA):

Composition: Acrylates or methacrylates activated by UV light.
Usage: Dental prostheses, aligners.

Need to Manufacture Food-Grade Parts for the Prototype.

Materials with food-grade properties are those that, when in contact with food, do not transfer toxic substances or alter the properties of the food. Regulations in both the United States and Europe are becoming increasingly strict regarding the materials that can be used for food handling.

As with biocompatible materials, food-grade materials often deform at high temperatures, making them very common in industrial processes, such as steel molding. However, the options for materials with food-grade compatible properties are much more limited for manufacturing using prototyping methods.

Below is a summary of commonly used food-grade materials in the prototyping process:

Impresión 3D por FDM con materiales compatibles con grado alimentario.PETG (Polietileno Tereftalato Modificado con Glicol): Se trata de uno de los materiales más comunes en la impresión 3D y por tanto en procesos de fabricación de maquetas de inventos y prototipos funcionales. Entre sus propiedades destaca la resistencia a la humedad y la estabilidad química, propiedades que garantizan su seguridad al interactuar con alimentos. En nuestro estudio de diseño de productos, lo usamos con frecuencia para prototipos de envases reutilizables así como prototipos de utensilios para la cocina. Un detalle importante, es que no todos los PETG tienen propiedades compatibles con el uso alimentario, es recomendable siempre solicitar este certificado al proveedor del material.

PLA (Polylactic Acid): PLA is another of the most commonly used materials in 3D printing. Its affordable price makes it suitable for early prototypes in the design of innovative products. Among its properties, its biodegradability stands out, which adds a relevant aspect in terms of sustainability. Our industrial design team uses PLA to manufacture prototypes of disposable utensils and sustainable packaging. An important limitation to note is that PLA deforms at low temperatures and is not highly heat-resistant. Therefore, it is not recommended for prototypes that will interact with very hot foods.

Nylon (Polyamide) Food-Grade: The use of Nylon in 3D printing is not as common as PETG and PLA. This difference is related to the characteristics of 3D printers available on the market. Product development companies often have professional 3D printers that can work at higher temperatures, allowing for the use of Nylon to manufacture prototypes and parts requiring higher mechanical strength, better chemical properties, and, above all, higher thermal resistance.

Use of Vacuum Molds for Working with Food-Grade Materials.

As you may know, in the prototype creation process, the use of vacuum molds, built from parts that can be obtained through 3D printing, is very common. These molds do not withstand heat as well, much less than industrial molds. However, to obtain prototype parts that meet the necessary properties for food-grade certification, they are more than sufficient.

In our industrial design laboratory in Madrid, we use this method to create prototypes that require seals, rollers, or any part that interacts with food.

In combination with the vacuum mold manufacturing method, we use materials such as:

Food-Grade Silicone: In addition to the chemical properties that ensure its stability in contact with food, it provides flexibility and resistance to high temperatures. The results of these food-grade prototyped parts are very similar to those you know as baking molds.

Food-Grade Polyurethane: Polyurethane perfectly meets the necessary properties for use in this cold mold system for manufacturing parts and prototypes. In addition to having great stability in its chemical properties, it stands out for its mechanical and thermal resistance. For example, we have frequently used it for manufacturing parts that interact with food in machine prototypes that require food-grade materials. Sushi machine prototypes, orange juice machine prototypes with a self-cleaning system, burger-making machine prototypes are some practical examples where we have used this manufacturing method in combination with Polyurethane.

Use of Photopolymer Resins Compatible with 3D Printing and Food-Grade: Photopolymer resins or photosensitive resins are commonly used for 3D printing of parts with the SLA method. Through exposure to light, parts are formed that, due to the chemical properties of these materials, maintain their compatibility with food-grade standards once cured. It is true that the use of these resins for parts requiring certifications is still very limited.