September 08, 2015 Volume 11 Issue 34

Mechanical News & Products

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Round vs. square rails -- which are better for you?

Thomson invented the world's first anti-friction linear ball bushing bearings in 1946. For many years, these round-rail linear guides satisfied every linear motion control requirement. However, as machines required closer tolerances, the round rail didn't always fit the bill. Learn the pros and cons of each design type.
Read this informative Thomson blog.


New bearings reduce wear in heavy-duty applications

igus has introduced a new bearing with an improved iglide material, called TX2, that offers self-lubricating and maintenance-free properties for heavy-duty applications. TX2 increases wear resistance by a factor of 3.5 in load ranges with more than 100-MPa surface pressure. The material is ideal for components in machines that serve construction and agriculture, which can require more than 50 liters of lubricant annually. The material is also very resistant to temperature, chemicals, moisture, corrosion, and seawater, which opens up the applications base for its use substantially.
Learn more.


Aerospace fastener hole drilling and countersinking all in one step

Kennametal has introduced the HiPACS drilling and countersinking system for aerospace fastener holes. Designed to drill and chamfer holes in one operation, the high-precision tool meets the aerospace industry's stringent accuracy requirements while delivering increased tool life in machining composite, titanium, and aluminum aircraft skins. With an industry-standard interface, HiPACS can be utilized on any CNC machine. Three components eliminate the need for custom tooling: a reducer sleeve with a built-in high-precision pocket seat, a PCD countersinking insert, and two series of solid carbide drills.
Learn more.


Why precision metrology is critical for electric vehicle gearing

As the shift from internal combustion engines to electric motors in vehicles continues, the number of drivetrain components will dramatically lessen too. The remaining components will be even more critical to a vehicle's operation and longevity. One such area is the gear components necessary to convert the high-force torque from electric motors to the RPMs at the wheel.
By Michael Schmidt, Zygo Corporation
Read the full article.


Master CNC machining tolerances eBook

Need a refresher on the basics of applying tolerances to custom machined metal and plastic parts? In this ebook, Xometry provides some pointers on designing mating parts and parts for specific functions. Chapters include: general machining tolerances, clearance and interference fit, how to avoid over-tolerancing, CAD drawing prep and specs, and an inspection report cheat sheet.
Get this valuable resource from Xometry.


Specifying metal inserts for molded plastics

Teaming with insert manufacturers that offer engineering expertise throughout the design and manufacturing process can be worth its weight in gold. Learn how two OEMs overcame their metal insert challenges by using advice and products from Tri-Star Industries, including specialty stainless steel parts and modifying the knurling on some inserts.
Read the full article.


Posi-Lok keyless shaft bushings for secure shaft-to-hub connection

Zero-Max offers a variety of options within the Posi-Lok keyless shaft bushings (PSL) product line that allow users to rigidly and reliably secure shaft-mounted components into position for optimal operating results in their machines. Options include material choices, plating, and different mounting methods. Posi-Loks are a superior shaft-hub locking solution, eliminating the need for keyways that can weaken or cause excess wear to shaft components. All Posi-Lok models easily slide onto a shaft for mounting and provide reliable, zero-backlash performance.
Learn more.


Automation: ECONOmaster drilling units -- affordable, flexible, get the job done

Suhner's ECONO-master® is a low-cost, high-output automated drilling unit that puts holes in light metal, composite, thermoplastic, and even wood substrates at high speed with excellent accuracy. It features low power and air consumption. On a recent project for Mid-State Engineering, Suhner custom ECONOmaster drill units -- featuring selectable drill heads that can be used in combination or individually -- were used to automatically drill holes into fiberglass panels for truck trailer bodies.
Read the full article.


Great Resources: Ultimate Guide to Injection Molding

Xometry has put together a comprehensive resource for injection molding -- from the basic principles to applications, tooling, materials, design features, and more. Learn how to optimize your part designs and choose the right surface finishes, textures, and post-processing for your projects. A super-handy resource worth bookmarking.
Read the Xometry Ultimate Guide to Injection Molding.


Sealing fasteners may optimize your designs

Highly specialized sealing fasteners include sealing screws, sealing nuts, sealing bolts, and sealing washers. Unlike ordinary fasteners, sealing fasteners are configured with a rubber O-ring (or a rubber element) that, when squeezed, permanently seals out a wide range of contaminants from entering and damaging equipment while preventing leakage of toxins into the environment. ZAGO sealing fasteners are designed to withstand harsh weather and extreme temperatures and are vibration and pressure resistant.
Learn all about ZAGO's wide selection of sealing fasteners.


Spirit levels with adjustment and cross-measurement

They may seem like relics from the past, but spirit levels remain indispensable tools in everyday industrial operations. Two new types from JW Winco now offer even better and faster alignment. The cross spirit levels GN 2276 combine two perpendicular linear levels within a single, round aluminum housing to show the alignment in two planes at once, making installation and leveling easier and faster. The new screw-on spirit levels GN 2283 are used to check the horizontal position of jigs, machines, devices, appliances, and instruments. These are available in a directly mountable, flat version (AV) and as an adjustable version (JV) with an alignment cam.
Learn more.


New cast urethane materials and finishes

Xometry has added new urethane resins and finishes as options for quick and affordable low- to mid-volume production. Urethane casting is used to make end-use, highly durable parts with robust mechanical properties. It is considered a "soft-tooled" process, where a silicone mold is formed around a master pattern -- usually 3D printed. Xometry has materials in two main durometer classes, rigid (Shore D) and rubber-like (Shore A). Finishes include matte/frosted, semi-gloss, high-gloss, and custom.
Read this informative Xometry blog.
Get the Xometry Urethane Casting Design Guide.


New molded-in aluminum threaded inserts for plastics

SPIROL has introduced a new, high-performance series of Molded-In Inserts for plastics assemblies. The rugged design of the Series 63 Through Hole Inserts and Series 65 Blind End Inserts consists of multiple bands of helical knurls to maximize torque resistance, balanced with radial undercuts to achieve high pull-out (tensile) force. These Molded-In Inserts are designed to be placed in the mold cavity prior to plastic injection. They offer exceptional performance due to unrestricted plastic flow into the retention features on the outside diameter of the Inserts.
Learn more.


How to avoid premature linear screw actuator failure

At their core, electric linear screw actuators deploy mechanical technology such as ball bearings, ball screws, and roller screws that have a finite life. These components do not last forever -- even though that is the expectation of some customers. But how long will an actuator really last? Tolomatic engineers provide a way to calculate, estimate, and size the electric linear screw actuator to achieve the desired life for your applications.
Read this informative Tolomatic blog.


3D Printing: Desktop Metal qualifies 316L stainless steel for high-volume manufacturing -- thousands of parts per week

3D-printer machine maker Desktop Metal has qualified the use of 316L stainless steel for its additive manufacturing platform called the Production System, which provides some of the fastest build speeds in the market for mass production and can make thousands of parts per week. This article includes very useful cost-per-part and time-to-manufacture information using five different application examples.
Read the full article.


Tiny mechanical wrist gives new dexterity to needlescopic surgery

Vanderbilt engineers have invented a mechanical wrist less than 2 mm (1/16 in.) in diameter -- small enough for use in needlescopic surgery. [Photo: MED Lab, Vanderbilt University]

 

 

With the flick of a tiny mechanical wrist, a team of engineers and doctors at Vanderbilt University's Medical Engineering and Discovery Laboratory hopes to give needlescopic surgery a whole new degree of dexterity.

Needlescopic surgery, which uses surgical instruments shrunk to the diameter of a sewing needle, is the ultimate form of minimally invasive surgery. The needle-size incisions it requires are so small that they can be sealed with surgical tape and usually heal without leaving a scar.

Although it's been around since the 1990s, the technique, which is also called mini- or micro-laparoscopy, is so difficult that only a handful of surgeons around the world use it regularly. In addition, it has largely been limited to scraping away diseased tissue with sharp-edged rings called curettes or burning it away with tiny lasers or heated wires.

So a research team headed by Associate Professor of Mechanical Engineering Robert Webster has developed a surgical robot with steerable needles equipped with wrists that are less than 1/16-in. (2-mm) thick. The achievement is described in a paper titled "A wrist for needle-sized surgical robots" presented in May at the International Conference on Robotics and Automation in Seattle.

The new device is designed to provide needlescopic tools with a degree of dexterity that they have previously lacked. Not only will this allow surgeon-operators to perform a number of procedures such as precise resections and suturing that haven't been possible before, but it will also allow the use of needles in places that have been beyond their reach, such as the nose, throat, ears, and brain.

"The smaller you can make surgical instruments the better ... as long as you can maintain an adequate degree of dexterity," said Professor of Urological Surgery S. Duke Herrell, who is consulting on the project. "In my experience, the smaller the instruments, the less post-operative pain patients experience and the faster they recover."

That has certainly been the case with traditional minimally invasive surgery (MIS), which has become increasingly common in recent years. This method, which involves operating with instruments inserted through incisions that range from 3/8 in. to 3/16 in. (10 mm to 5 mm), generally causes patients less pain, less tissue damage, less scarring, and shorter recovery periods.

The effort to adapt robotic technology to MIS has been dominated by Intuitive Surgical's da Vinci Surgical System, a robotic surgical system designed specifically for the minimally invasive approach. Depending on the type of surgery, it requires incisions that are 1/3 in. (8 mm) or 3/16 in. (5 mm).

"Although it works very well for abdominal surgery, the da Vinci uses a wire-and-pulley system that is extremely difficult to miniaturize any further, so it won't work in smaller spaces like the head and neck," said Webster.

For the past six years, Webster and his colleagues have been developing a surgical robot that uses "steerable needles." This is a system of telescoping tubes that are made out of nitinol, a "memory metal" that retains it shape. Each tube has a different intrinsic curvature. By precisely rotating, extending, and retracting the tubes, an operator can steer the tip in different directions, allowing it to follow a curving path through the body.

This design allows the needles to operate in areas of the body that neither manual endoscopic instruments, which are straight rods equipped with a variety of end effectors, nor the da Vinci robot can reach. However, its usefulness was limited by the fact that the needles didn't have a wrist.

"Adding the wrists to the steerable needles greatly expands the system's usefulness," Herrell said. "There are a myriad of potential applications in some really exciting areas such as endoscopic neurosurgery, operating within small lumens such as the ear, bronchus, urethra, etc. This would allow us to do surgeries that at present require much larger incisions and may even enable us to perform operations that are not feasible at present."

The researchers made a number of unsuccessful attempts to build mechanical wrists that were small enough. "We kept trying to build the wrists out of a lot of small pieces, but we couldn't get them to work up to our standards," said Webster.

"Then we realized we had to start thinking outside of the box," said graduate student Philip Swaney. "Instead of combining a bunch of pieces, we started with a tiny nitinol tube and began thinking about what we had to remove."


Video credit: MED Lab, Vanderbilt University

The tube is extremely rigid, but they discovered that if they cut a series of tiny slots down one side, the rigidity decreased substantially: Enough, in fact, so they could get it to bend up to 90 degrees by pulling on a small wire that runs inside the tube that is attached at the tip. The wrist springs back to a straight position when tension on the wire is released.

"Once we got the idea, we realized it could be a real game changer so we had to build it," Swaney said.

Vanderbilt University applied for a provisional patent on the design in May.

Team members would like to test the system by using it for "transnasal" surgery: operations to remove tumors in the pituitary gland and at the skull base that traditionally involve cutting large openings in a patient's skull and/or face. Studies have shown that using an endoscope to go through the nasal cavity is less traumatic, but the procedure is so difficult that only a handful of surgeons have mastered it.

"It should be useful for a number of other operations as well," said Webster. "We think once we give this tool to surgeons they will find all kinds of applications we haven't thought of."

By the end of 2015, they hope to have completed the control software and the interface that allows the surgeons to operate the device. They are actively looking for a commercial partner who will take the new instrument through the FDA approval process, including initial clinical trials. "Our best case scenario is that the system could be available to surgeons in four to five years," Webster said.

The research was supported by National Institutes of Health grant R01 EB017467.

Source: Vanderbilt University

Published September 2015

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