The Difference Between Jigs and Fixtures

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Jigs or fixtures? The two terms are easy to confuse. You’ll often find them paired together and despite sharing similar functions, the two are not interchangeable. Let’s learn the subtle differences between these manufacturing tools by examining how they are used to improve manufacturing quality, reduce production costs, and automate work.

Jigs Improve Manual Work
You might know the term “jig” from your weekend fishing hobby, but it has a different meaning within the engineer’s lexicon. For our purposes, a jig holds the position of a tool in order to perform a manufacturing task. It’s often a custom part that ensures accuracy and repeatability when drilling and tapping holes.

Shops may use different types of jigs for various tasks inside manufacturing equipment.

Drill bushings are a common jig application. They help guide a drill through a workpiece in order to maintain accurate positioning and angle. Not only does it lead to higher quality work, but a drill bushing can also increase manufacturing speed.

Fixtures for Automated Manufacturing Processes
How does a fixture differ from a jig? Rather than guiding a manufacturing tool, fixtures hold a workpiece in a secure position, orientation, or location. A prime example, and one were familiar with at Proto Labs, is the fixture in which a block of raw material is clamped into inside a CNC machine. The vice on your workbench is also a fixture. Continue reading

Optical Liquid Silicone Rubber: A New Fixture in Molding

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Proto Labs offers many manufacturing processes and materials for prototype and production parts. But one process has a material that separates itself from the rest, optical liquid silicone rubber (OLSR). OLSR is an advanced material that has many properties that make it a preferred material choice over polycarbonate (PC) and acrylic (PMMA) for lighting and optical parts. Here are a few of the benefits that OLSR offers:

prototype lenses molded in liquid silicone rubber

Prototype lenses molded in liquid silicone rubber.

Light Transmission
Light transmission is lost as light passes through a material. PC, PMMA, and even glass will have light loss with glass retaining up to 95 percent, PMMA around 93 percent, and PC between 88 to 90 percent. When your product requires a clear PC or PMMA part, you can improve on light transmission using OLSR, which retains up to 94 percent light transmission.

How about the refractive index? OLSR has a low refractive index of 1.42 when compared to PC and PMMA, which are at 1.58 and 1.49 respectively.

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Still another advantage is the non-yellowing factor. Thermoplastics without additives are not UV resistant, which means the parts could yellow and degrade over long exposures to lights and sunlight. OLSR is non-yellowing so it’s great for outdoor fixtures exposed to harsh environments.

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5 Common Rapid CNC Machining Questions

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Most are familiar with machining, but what makes it unique at Proto Labs? These are a few of the most common questions we receive about our rapid CNC machining service. These answers will help you optimize your design for CNC machining and determine how it can improve your product development efforts.

CNC-Machining-Block-Plastic

CNC machining is a subtractive manufacturing process that mills away at a block of solid plastic or metal.

1. What is unique about Proto Labs’ CNC machining process?
In order to efficiently machine low quantities as fast as possible, we do things a bit differently compared to a traditional machine shop. When you upload a 3D CAD file to protolabs.com, our proprietary software analyses the design, creates a quote, and generates the CNC toolpaths. By automating the front-end of the manufacturing process, we can machine a part in as fast as one day.

2. How does the quoting process work?
Once you upload your 3D CAD model to our website, the software calculates the price—not a budgetary estimate—to machine your design. Within a few hours, you’ll receive an email with an interactive quote. Here, you can select different materials and quantities and receive real-time price updates. The quote even contains a 3D-view of your machined part, which will highlight any differences between the machined part and the original 3D CAD model. See a ProtoQuote preview here. Continue reading

Design Complex Components with Insert Molding

Low-volume injection molding isn’t limited to just simple parts. At Proto Labs, we have the ability to manufacture complicated parts using side-actions, hand-loaded inserts, overmolding, and have now started beta testing our insert molding process.

Instead of a mold that produces a final part using two separate shots like overmolding, insert molding generally consists of a preformed part—often metal—that is loaded into a mold, where it is then overmolded with plastic to create a part with improved functional or mechanical properties.

A threaded insert is placed atop a mold core where plastic is molded over it to form the final component.

Threaded Inserts
One way insert molding is leveraged is with threaded inserts, which reinforce the mechanical properties of plastic parts’ ability to be fastened together, especially over repeated assembly. Self-tapping screws work well with softer plastics, but they can become easily worn and/or cross threaded, and fail to perform well, which results in damaged parts that need to be replaced.

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Overmolding: Chemical and Mechanical Bonding

Learn more about overmolding in our free webinar we’re hosting with RTP Company on Tuesday, Nov. 15 at 1 p.m. CT. REGISTER TODAY!

Overmolding is not a new manufacturing technology, but there is still some confusion about how to design for the two-part process. One of the largest areas to consider? Bonding. A number of materials can be used to overmold components together, but without a chemical bond or mechanical interlock, some overmolded parts won’t stand the test of time.

Chemical Bonding
This bonding process involves two chemically compatible materials that are molded together to form a strong bond with each other. It’s important to note that not all materials play well with one another.

The compatibility chart below indicate whether a chemical or mechanical bond is recommended for key thermoplastic and thermoset materials.

mechanical bonding

Three types of mechanical bonding techniques.

Mechanical Interlocking
What happens when your materials are not compatible, the desired bonding strength cannot be achieved, or you want to ensure your materials don’t peel apart from repeated use? This is where designing a mechanical interlock, which physically holds the overmolded material to the substrate, makes sense. There are many ways to design these into parts (see example), so discuss the options with your manufacturer.

Overmoling

Learn more about overmolding in our free webinar we’re hosting with RTP Company on Tuesday, Nov. 15 at 1 p.m. CT. REGISTER TODAY!

If you have further questions regarding rapid overmolding at Proto Labs, contact one of our application engineers at 877.479.3680 or customerservice@protolabs.com.