TIPS WITH TONY: Machining Versus Molding for Magnesium Parts

In our latest tip, we’re talking about magnesium, and how to use it in product design for metal parts that need to be lightweight yet strong.

Magnesium works well for reducing component weight in place of steel or aluminum as it’s the lightest structural metal currently available. This lends itself well to a range of applications in the automotive, aerospace and electronics industries.

It’s heavily used in vehicle lightweighting to lower fuel consumption, reducing automakers overall carbon footprint. It’s also used to create lighter and thinner electronics or simply whenever a lightweight yet strong backbone material is needed in a part. Be sure to test and review magnesium’s material properties closely as it’s not always the proper substitute for other metal or plastic materials.

Magnesium versus

Steel

Aluminum

Plastic

75% lighter

33% lighter

Greater stiffness

Thinner walls

Similar or greater mechanical properties

Improved strength and wear resistance

Consolidation of parts

Consolidation of parts

Higher temperature

Machines faster

Machines faster

Creep resistant

Reduced tooling costs

Improved corrosion resistance

Fewer supports needed

What manufacturing methods are there for magnesium? Proto Labs offers both CNC machining and injection molding for prototype and low-volume mag parts, though magnesium die casting also used in the industry.

How do I choose the right manufacturing method? Quantity, lead time, size and material properties will greatly impact which manufacturing method to use.

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EYE ON INNOVATION: From Phones to Drones with Motorola’s ‘Flying Robots’

In 1973, Motorola demonstrated a prototype of the world’s first portable cellular telephone. By 2004, the company commemorated manufacturing its 30-millionth cell phone.

These days, Chicago-based (Schaumburg) Motorola Solutions, the direct successor to Motorola, Inc., is focusing its business on meeting a growing demand from law enforcement, military and other governmental agencies for high-tech intelligence and data-gathering tools. One prime example: Motorola is getting into the drone biz.

USA Today recently reported that Motorola is partnering with Danvers, Mass.-based CyPhy Works, a developer of tethered drones. These are drones that use a “microfilament tether,” allowing them to be powered through a generator or another power source on the ground and to stay in the air indefinitely.

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Sportech Uses Quick-Turn Machining for Design Validation

From frozen trails to rugged desert valleys and muddy creeks, power-sports vehicle drivers put their machines to the test. Producing custom parts for many of those snowmobiles, utility vehicles and motorcycles — on short production cycles and with manufacturers gearing up for large-scale production — is another sort of test for Minnesota-based Sportech, Inc.

Sportech prototyped durable nylon clips and hooks with CNC machining.

Sportech is a product development partner to seven of the eight largest power-sports vehicle makers. The company specializes in full-service design, development and production of custom parts and accessories, going from concept or rough sketches to 3D CAD modeling and rapid prototyping. Its services include thermoforming, drape forming, CNC routing and integrated assembly. Products include windshields, body panels and screen-printed parts for motorcycles, snowmobiles, all-terrain vehicles (ATVs) and utility vehicles (UTVs).

While Sportech has grown into a leading product developer for original equipment manufacturers, what hasn’t changed since the company’s early days is the challenge of meeting tight product development deadlines.

In our latest case study, read how Sportech used quick-turn CNC machining at Proto Labs to validate the design of components before shifting to large-scale production.

It’s Gaming System Meets Med Device for Latest Cool Idea! Award

Recovering from respiratory ailments such as pneumonia is not exactly fun and games. A new, innovative respiratory therapy system, however, which helps patients with respiratory therapy, is designed to be exactly that — a fun game.

Memphis-based Compliant Games, which has developed a respiratory therapy system that uses video games as part of the system, and helps pediatric and nursing home patients comply with respiratory therapy requirements, has been presented with the latest Proto Labs Cool Idea! Award.

Compliant Games is “channeling the healing power of children’s video games,” say the developers, with a system that improves adherence to respiratory therapies by patients. The system transforms common respiratory therapy tools into low-cost telemetry (wireless transmission and monitoring) instruments for doctors and their patients.

How does it work? The patient watches and follows along with a video game exercise on an iPad or other computer tablet. When prompted, the patient breathes through an air tube that wirelessly interacts with the game. Active, in-game feedback reinforces correct technique for the patient.

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TIPS WITH TONY: Ribs and Radii

Designing ribs and radii into your injection-molded part is not only important to increase strength and stability — it improves material flow, eliminates thick areas that create issues like sink, and ultimately, enhances the cosmetic appearance of your part.

Ribs
A thick part will have several issues with sink or voids creating cosmetic, functional or molding concerns. The addition of ribs reduces the amount of volume in part thickness while still providing the part with the same overall height. Some believe that eliminating the volume/part thickness can decrease the strength of a part. This is not true — adding ribs can actually improve stability, strength and cosmetics depending on the material selection and part geometry.

Watch rib-to-wall thickness ratios. To prevent sink, the thickness of the rib should be about half of the thickness of the wall.

A major design consideration that is often overlooked is rib-to-wall thickness ratios. If you have a rib feature that is too thick on a wall, you’ll create thick areas that can result in unsightly sink or shadowing on the opposing surface. Avoid this by following a guide of 40 to 60 percent wall thickness for any rib.

 

 

Coring Out
Coring out is a technique where you remove material from a plastic part, leaving distinct walls and ribs that provide enough strength and mating surfaces for other parts in the assembly. It is necessary to make the part moldable and also saves cost and weight. Leave ribs in the right location and size to maintain strength, particularly in bending, and retain surfaces and features that interface with other parts in the assembly.

Ramps and Gussets
Continuing the discussion on strength and resin flow improvement, ramps and gussets are important features that you can build into your design. Sharp corners create high stress points whereas gussets and ramps are stress relievers, working to improve overall part quality.

Radii
Adding radii — edges or vertexes that have been rounded — to your part will improve how resin fills the mold as plastic can flow poorly around sharp corners. When you have sharp corners, resin can create stresses that cause the part to warp or bend, and may provide a location that can break since this is a weaker transition point. Resolve this by adding a generous angle to both the outside and inside corners.

Ideally, you should model radii so the inside and outside radii use the same center resulting in larger radii on the outside curves. This will help you retain a consistent wall thickness throughout your part.

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