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In 3D printing, also known as additive manufacturing, material strength is defined in different ways: tensile strength, impact resistance, chemical resistance, UV resistance, and temperature resistance.
A material’s strength is one of its mechanical properties. The mechanical properties of a material determine its behavior under applied loads. Material strength refers to the maximum stress it can be put under before it fails.
Strength is measured in megapascals (MPa). One MPa equals one million pascals (Pa). A pascal – the standard unit used to quantify internal pressure — is one newton (N) of force per square meter. A newton is the International System of Units (SI) derived unit of force.
This article will introduce you to the standard ways in which the strength of materials used in 3D printing is measured, how strength is defined and what materials exhibit mechanical properties that translate into strength.
You will also learn the differences between HP’s high-performance nylon PA11 and PA12 materials and how they’ve enabled groundbreaking solutions in real world applications.
Standard definitions of material strength used in 3D printing
Tensile strength
Tensile strength, also known as elastic strength, refers to a material’s stiffness and is the maximum amount of stress it can tolerate before becoming deformed by stretching or breaks.
For the purposes of 3D printing, calculating the tensile strength of a material will indicate how far a model can be loaded before it fails.
Poly Ether Etherketone (PEEK), carbon fiber filaments, and polycarbonate are strong filaments commonly used for load-bearing applications.
Elongation
Elongation refers to a material’s ductility. In materials science, ductility is the extent to which a material can be deformed plastically when put under tensile stress before it fails.
Image of flexible spring printed with HP 3D HR TPA enabled by Evonik. Post-processed with AMT PostPro chemical vapor smoothing.
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High ductility means a material will be able to be stretched or elongated into, for example, a thin wire shape without breaking. Gold, platinum, silver, and iron all have high ductility.
Low ductility means a material will fracture if it’s deformed under a heavy load. Tungsten and steel containing high carbon have low ductility.
Hardness
The Rockwell scale, divided into nine sub-scales ranging from A to K, is a commonly used method for measuring and reporting the hardness of materials used in machining. Using the Rockwell scale, the last letter denotes hardness. 3D printing materials are usually HRC or HRB.
For polymers such as PC, we use the durometer scale, which measures rubber material hardness in numbers. The harder the material, the higher the number.
Impact resistance
Impact resistance refers to a material’s ability to withstand impact without fracturing or breaking. The higher a material’s impact strength, the less likelihood there is of it breaking or fracturing when subjected to sudden stress.
Image of headrest printed with BASF Ultrasint® TPU01.
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Polycarbonate, nylon, and Poly Ether Etherketone (PEEK), flexible filaments typically used for safety equipment, safety boxes, tool housings, and eyeglasses, can all bear sudden high loads before they fracture or fail.
Chemical resistance
Chemical resistance is particularly important when you’re making 3D printed parts in a process that requires chemicals and you’re working in a chemically harsh environment.
For example, if you’re making 3D printed parts that need to be cleaned and sterilized or fluid systems such as the fluid reservoir in a car that must be resistant to the chemicals flowing through them, they would need to be chemically resistant.
Nylon and Polycarbonate are most widely used for printing 3D objects in such conditions because they possess excellent chemical resistance. Acrylonitrile Butadiene Styrene (ABS) is also resistant to certain chemicals.
UV resistance
Being exposed to sunlight can weaken a material’s bonds and cause a part to fail. If you’re making 3D printed parts that will be exposed to sunlight, you will need a 3D printer filament with high UV resistance.
ABS, Acrylic Styrene Acrylonitrile (ASA), and Nylon are the materials most commonly used for parts with an outdoor purpose.
Temperature resistance
When you’re making parts that need to function in high temperatures, it’s essential to use a material that doesn’t soften.
Nylon, PEEK, and Polycarbonate filaments are more heat resistant than other filaments but need to be 3D printed at higher temperatures than other materials. You must make sure that your 3D printer's hot end — where the filament moves out onto the construction plate — can handle these temperatures.
Heat Deflection Temperature
Heat Deflection Temperature (HDT) is the temperature at which a material starts to deform when put under a specific load.
Commonly used 3D printing materials and their strength
When material strength is an important factor in your 3D printing process, you will choose the material you use by calculating the strength needed and your cost structure.
Polycarbonate (PC) delivers high tensile strength along with high impact and heat resistance. It’s widely seen as one of the strongest 3D printing filaments.
PC can be a little complicated to 3D print with because it requires a relatively high extrusion and build plate temperature.
Acrylonitrile Butadiene Styrene (ABS) and Polylactic Acid (PLA) are among the most common thermoplastics used in 3D printing.
PLA is typically used by hobbyists rather than ABS, as it is stronger and stiffer, but less heat resistant. ABS is well-suited for prototyping, as it’s weaker and less rigid but also tougher and lighter. ABS is also resistant to certain chemicals.
Nylon, or polyamide (PLA), offers high impact resistance and is tough and semi-flexible. It's abrasion resistant and good for printing durable parts. HP nylon PA11 and PA12 are used with HP’s Multi Jet Fusion (MJF) technology.
PEEK and carbon fiber filaments are strong filaments commonly used for load-bearing applications.
The strongest materials are mostly used in industrial 3D printing applications — tools, jigs, fixtures, and components in industrial machinery and equipment used in manufacturing and production lines.
Introducing nylon PA11 and PA12
PA11 and PA12 are types of nylon that differ from each other considerably simply because they possess one different carbon atom.
PA11 is a bioplastic polyamide powder made from renewable resources derived from vegetable/castor oil and is only manufactured by one company. PA12 is synthetic, made from petroleum materials and made by several different manufacturers.
PA11 and PA12 are commonly used in powder-bed fusion processes such as HP Multi Jet Fusion (MJF).
HP nylon PA11 vs PA12
Within the HP 3D printing materials portfolio:
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- HP 3D High Reusability PA 127 is ideal for producing strong, low-cost quality parts. It’s a robust thermoplastic that produces high-density parts with balanced property profiles and strong structures and provides good chemical resistance to oils, greases, aliphatic hydrocarbons, and alkalis.
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- HP 3D High Reusability PA 118 is perfect for producing strong, ductile functional parts. It enables excellent chemical resistance and enhanced elongation-at-break and offers impact resistance and ductility for prostheses, insoles, sports goods, snap fits, living hinges, and more.
PA11 and PA12 applications and case studies
GoProto and Ropes Edge: protecting life-supporting ropes from damage on sharp edges with PA12
The product Ropes Edge wanted to bring to market needed to be able to support the weight of a human body. It could not fail.
Solutions provider and member of the HP Digital Manufacturing Network, GoProto recognized right away that HP Multi Jet Fusion technology would be the best solution. It would help deliver low-volume production of a device with complex geometries and an extremely high level of durability.
GoProto also knew that HP 3D High Reusability PA 12 offered the strength Ropes Edge needed.
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Using HP 3D High Reusability PA 12 and HP Multi Jet Fusion technology, GoProto and Ropes Edge perfected the design and produced a revolutionary life-supporting device, named the Vortex.
Read the story of the Vortex case study and watch the video about how Ropes Edge and GoProto teamed up.
Dustram produces strong, rugged tile-removal equipment with PA12
DustRam LLC makes dust-free tile removal equipment for the contracting and flooring industry. It wanted to design and build tougher, more effective equipment while reducing costs and production time and staying ahead of the competition.
Discovering HP’s Multi Jet Fusion (MJF) technology, DustRam realized it could increase productivity by four times (to 1/10 of the time) and at about 50% to 75% of the cost.
Working with MJF and HP’s 3D High Reusability PA 12, DustRam was able to cut time, weight, and costs for some of their 3D printed products while increasing strength and durability.
As Jack King, DustRam President explains, “Most people wouldn’t believe this nylon can withstand this kind of heavy-duty work, but we actually have replaceable noses that are still in use one year later.”
Read the full DustRam HP MJF and PA12 case study and watch the video.
Using PA11, Bowman International disrupts bearings industry with high-performance parts
Bowman International is a leading manufacturer and supplier of plain bearings in the United Kingdom and throughout Europe.
Using HP 3D High Reusability PA 11 material allowed Bowman to 3D print parts that feature enhanced elongation at break — critical when assembled - show improved performance and require less maintenance and fewer spare parts. Parts are also easier to assemble and cheaper to manufacture.
By 3D printing bearing cages with HP MJF technology, Bowman can take the entire bearings load capacity to 30, 40 or even 50% higher. This extends the life of a traditional split bearing by 3 to 5 times.
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The newly designed split roller bearing now features 3D printed bearing cages that increase the radial load capacities by 70% and increase the axial load by 1,000%. 3D printed seals offer better wear properties and enhanced ease of use.
Read the Bowman case study and watch the video.
HP Jet Fusion industrial printers and materials compatibility
Explore the HP 3D printing materials portfolio and discover which are the most effective when combined with our Jet Fusion industrial 3D printers.
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Footnotes and disclaimers
- Data courtesy of OT4 Orthopädietechnik GmbH
- Data courtesy of GoProto Inc.
- Data courtesy of BASF
- Data courtesy of Skorpion Engineering
- Data courtesy of Ropes Edge and GoProto
- Data courtesy of Bowman
- HP Jet Fusion 3D Printing Solutions using HP 3D High Reusability PA 12 provide up to 80% powder reusability ratio, producing functional parts batch after batch. For testing, material is aged in real printing conditions and powder is tracked by generations (worst case for reusability). Parts are then made from each generation and tested for mechanical properties and accuracy.
- HP Jet Fusion 3D Printing Solutions using HP 3D High Reusability PA 11 provide up to 70% powder reusability ratio, producing functional parts batch after batch. For testing, material is aged in real printing conditions and powder is tracked by generations (worst case for reusability). Parts are then made from each generation and tested for mechanical properties and accuracy.