Tag: material selection

Information on choosing a material for custom manufactured parts.

Choosing the Right Plastic for Your Part

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Blue Plastic bottle (top view) and cap

Plastic Selection Tips for Machining

For low-volume and close tolerance applications, machining of plastics can be a cost-effective and reliable method for your projects. It is typically simpler to machine and less expensive than metal. Highly engineered plastics perform quite well under a variety of conditions, while inexpensive lower-performance versions are available for projects with less stringent requirements.

The typical engineered part requires three characteristics to function. Your search for plastics that will supply all three will come up with a list of potential materials. The information below lists the most common characteristics any engineer will need to consider when looking for a plastic that will function as required. The suggested materials serve as a starting point, and are not comprehensive.

Some plastics are available with fillers that will change the properties of the plastic to suit your needs without having to upgrade materials. However, these fillers, such as glass, may also reduce machinability.

choosing plastic for machining parts infographic

Biocompatible

For medical devices. These plastics are able to come into contact with the human body without causing problems. Include a USP class VI designation (Biological Reactivity Testing), also regulated by ISO 10993 (Biological Evaluation of Medical Devices).

Biocompatible Plastics:

  • Radel

  • UHMW

  • Polycarbonate

  • PEEK

Chemical Resistance

Plastics in general have a wide variety of chemical resistance. Though some seem almost universally resistant, others are highly sensitive and crack when exposed to almost any chemical. Before choosing a plastic, consult a good reference guide to learn about specific interactions with chemicals.

High Chemical Resistance Plastics:

  • UHMW

  • Teflon

  • PEEK

  • CTFE

Low Chemical Resistance Plastics:

  • Acrylic

  • ABS

  • Noryl

  • Polysulfone

Clearness

Stock plastic begins clear but machining generally changes them from translucent to opaque. If clearness is a requirement, polishing is necessary. Polishing methods include buffing, direct machine polish, flame polish and vapor polish.

Clear Plastics:

  • Acrylic

  • Polycarbonate

  • Clear PVC

  • Polysulfone

  • Ultem

Cost

When choosing material for your project, consider the machining and finishing costs in addition to the price of the raw material. Though usually more inexpensive than metals, higher performance engineered plastics cost more.

Inexpensive Plastics:

  • Delrin

  • UHMW

  • Polypropylene

  • HDPE

Expensive Plastics:

  • PEEK

  • Vespel

  • PPS

  • Radel

  • HDPE

Dimensional Stability

Unlike metals, machined plastics have less structural stability. They tend to absorb water and expand when exposed to heat. More stable plastics have low water absorption and a low CTFE.

Dimensionally Stable Plastics:

  • Ultem

  • PEEK

  • PPS

  • PET

Less Dimensionally Stable Plastics:

  • Nylon

  • UHMW

  • HDPE

  • LDPE

FDA

Plastics that come into contact with food, especially packaging, require approval for use by the Food and Drug Administration.

FDA Approved Plastics:

  • Delrin

  • PET

  • Polycarbonate

  • PEEK

Limiting PV

For bearing applications, plastics need a combination of pressure and velocity to give it the thermal and structural ability to withstand rotational wear.

High Limiting PV Plastics:

  • PEEK

  • Nylatron

  • Delrin AF

  • Torlon 4301

Low Limiting PV Plastics:

  • UHMW

  • PBT

  • PET

  • Nylon

Steam Sterilization

Most biocompatible plastics will hold up to this process of using steam to sterilize material prior to first use.

Plastics Compatible With Steam Sterilization:

  • Radel

  • Ultem

  • PEEK

  • Teflon

Strength

For structural applications, two types of loading strength (measured in psi) are important to consider when choosing a plastic. Tensile strength, the most widely measured, indicates the amount of pressure required to pull a sample apart from the ends, as well as the amount of stretching before the break. In compression strength tests, the opposite is tested. Samples are pressed and the amount of force necessary to break them is measured.

High Strength Plastics:

  • Ultem

  • Peek

  • PPS

  • Nylon

  • Delrin

Low Strength Plastics:

  • Teflon

  • UHMW

  • LDPE

  • HDPE

  • Polypropylene

Temperature Resistance

Two types of temperature resistance are important to machined plastic parts: the optimal air temperature, or the amount of heat deflection if under a load.

High Temperature Resistance:

  • PTFE

  • PEEK

  • Ultem

  • Torlon

  • PPS

Low Temperature Resistance:

  • Acrylic

  • UHMW

  • ABS

  • PVC

Toughness/Impact resistance

This index measures the ability of a plastic to endure a blow or sudden impact. This is not the same as continual pressure or load. Some plastics can withstand an impact but will not do well under a constant load.

High Impact Resistance Plastics:

  • Nylon

  • Polycarbonate

  • UHMW

  • PEEK

Low Impact Resistance Plastics:

  • PET

  • Acrylic

  • Noryl

  • Polysulfone

UV Resistance

Outdoor applications require a resistance to UV light. Without it, material will age and become brittle. Black plastics usually have some resistance because of color.

High UV Resistance Plastics:

  • Ultem

  • Polycarbonate (UV stabilized only)

  • PBT

Low UV Resistance:

  • Polycarbonate (FDA)

  • Nylon

  • Acetal

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The Least You Need to Know About Aluminum for Machining

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cast aluminum part machined

Alum 6061

Aluminum 6061 is one of the most widely used alloy materials in machining due to its price, strength and versatility. Though Aluminum 2024 has a higher strength to weight ratio, it is not as corrosion resistant.

The ability of aluminum 6061 to withstand corrosion makes it economical because it doesn’t require finishing. Once exposed to the atmosphere, it develops a thin protective layer that protects it from surface rust.

The combination of corrosion resistance and low weight make it an economical material to use in short production runs because parts can be created faster. In addition, it is chemical resistant and easy to machine.

Parts that require multiple processes, such as machining and then welding, benefit from Aluminum 6061 because in addition to being easy to machine it is also weldable.

Aluminum 6061 Tempers

There are a variety of tempers for 6061 aluminum alloy, including:

  • 6061-F:

    No special treatment

  • 6061-O:

    Annealed, good for forming

  • 6061-T1:

    Cooled and naturally aged

  • 6061-T4, 6061-T4511:

    Heat-treated and naturally aged

  • 6061-T51:

    Cooled and artificially aged

  • 6061-T6, 6061-T6511:

    Heat-treated and artifically aged, most common alloy used in a variety of applications

  • special tempers: 

    varies

Aluminum 6061 Composition

Aluminum 6061 is composed of the following elements by percentage of weight:

  • Magnesium (0.8-1.2)
  • Silicon (0.4-0.8)
  • Iron (Max 0.7)
  • Copper (0.15-0.4)
  • Zinc (Max 0.25)
  • Titanium (Max 0.15)
  • Manganese (Max 0.15)
  • Chromium (0.04-0.35)
  • Other (0.05)
  • Aluminum (balance)

aluminum 6061 infographic: tempers, common forms, composition, applications

Aluminum 6061 Characteristics

Alloy Temper Formability Machinability Corrosion Resistant Weldability (Arc with Inert Gas) Brazeability Anodizing Response
6061 O Very High Poor Very Good Excellent Excellent N/A
6061 T1, T4, T4511 High Fair Very Good Excellent Excellent Very Good
6061 T6, T6511 Low Good Very Good Excellent Excellent Excellent

Aluminum 6061 Applications

  • aircraft wings and fuselages, not as strong as Alum 2024 but more corrosion resistant
  • boats
  • automotive parts
  • flashlights
  • cans
  • tactical flashlights
  • SCUBA tanks made after 1965
  • bicycle frames and parts (T6)
  • fly fishing reels (T6)
  • firearms (T6)
  • RC aircraft (T6)
  • welding
  • extrusions
  • forgings

For More Information About Aluminum

Fun facts from Chemicool

The Aluminum Association

Aluminium International Today

 

How to Choose Material for Your Custom Manufactured Part

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small round metal part manufactured

Advances in science have made a huge impact on product design and production. One important area of consideration for any product is the material or materials you choose to construct it with.

With a vast amount of materials available, how do you know which one is right for your product?

Several variables come into play, including:

  • machinability
  • price
  • availability
  • strength
  • delivery time

If your final product requires a combination of processes and assembly, things can get even trickier.

While we can’t make your decision for you, here’s a simple process to help you systematically choose the correct material for your application needs.

material selection process for manufacturing

Design Requirements

Before investigating your material options, you must first look to the design. The following key considerations will develop the criteria for your material:

  • Government regulations
  • Performance
  • Size, shape and weight
  • Cost
  • Manufacturing and assembly (machinability, etc.)
  • Intellectual property
  • Industry standards
  • Reliability

While all the above considerations may not apply to your project, collect data on as many of them as possible. More requirements will help narrow down the final material selection.

Create Material Criteria

All the requirements identified in the previous step will create criteria for your desired material. For example, it will need to support a certain amount of weight, which in turn becomes the load bearing criteria. Any material that cannot support this is immediately eliminated from your possible choices.

Come Up With a Potential Materials List

The first thing you can do with your criteria is rule out any material that doesn’t meet every requirement. You are then left with the materials that can do the job. Create a list, but don’t proceed any further.

Evaluate Potential Materials

You need to right material for the job, but exceeding requirements isn’t necessary. In lean manufacturing, using higher grade materials than necessary is considered overprocessing, one of the eight major wastes.

Some data may not be available, and you may have to go through testing to ensure that it will work for your application. It may even be necessary to create a prototype out of more than one material to be sure.

Make Final Selection

Once you’ve found materials that meet your requirements, choose the one that does the job at the lowest cost. This is not just cost of materials, but also cost of production. Some materials that are designed to be machinable will be harder to form or weld. All this needs to be considered, especially if you are assembling a part that uses multiple manufacturing processes.

Have a Project in Mind?

If you are currently working on a project, or have questions about the right material for your part, upload your file on our quote page. We’ll be happy to answer any questions you have.