One way to create innovative mechanical components, particularly those used in linear motion applications and corrosive environments, is to make them last longer and corrode less. And if the application has bearing surfaces, the options are more limited since even heat treated, 400 series stainless steel just takes longer to corrode.
But according to Chris Blaszczyk, manager of product development for MISUMI USA, low temperature, black chrome plating is a technology that offers a new alternative and impressive performance.
“The coating uses an electrochemical reaction process and is done at temperatures below 32F,” says Blaszczyk, “so it’s different from any other process out there. It is excellent for bearing surfaces and low temperature. Black chrome-plated parts can last more than 10 years and even up to 20 years of runtime.”
He says MISUMI didn’t realize the big advantage of this type of coating until the company started receiving calls from customers asking about the coating for their own parts. “Customers had applications where their tools would benefit from this process and wanted to send us the tooling to have it coated,” he says. “We tried to locate a U.S. supplier but couldn’t find any.”
He says low temperature black chrome-plating (LTBC) has been around in Japan since the 1960s but it has been used primarily in semiconductor, food and medical applications. Through the plating process, an alloy-like diffusion layer is formed at the outer margin of the part, allowing chrome particles to completely integrate the base material. It creates a bond which means the plating can’t be peeled or flake off.
The surface consists of a uniform film that creates an extremely resistant, rust protection layer, and plated components have fracture-resistant surfaces with a high level of alternate-bending strength. Because the components are black, they can also be used in applications specifying minimal light reflection, making them suitable for use in optical applications where low light reflection is required.
Blaszczyk says other materials MISUMI offers, including 52100 bearing steel, 440C stainless steel and electroless nickel plating, offer a different set of application advantages.
52100 bearing steel is used for many components and features a rigid construction but this high-carbon chromium bearing steel is susceptible to corrosion in harsh environments.
He says an often misunderstood concept is that stainless steel will not rust. Stainless steel will rust, but it rusts at a slower rate, creating the perception it is not rusting. It also exhibits other corrosion properties as well, when exposed to a harsh environment. It has a martensitic microstructure which exhibits magnetic properties and offers corrosion resistance that is lower than the common austenitic grades. It is a material fit for hardening.
Electroless Nickel Plating (EN) is an anti-corrosion coating process used for steel, stainless steel and copper materials. It offers high corrosion and abrasion resistance and 500 Vickers hardness (HV). The plating process will give conductivity to a non-metal surface and involves the chemical reduction of nickel ions and the deposit of nickel metal. Good for harsh environments, EN is suitable for corrosion resistance in adverse conditions.
MISUMI is now offering low-temperature black chrome-plating on a variety of its motion components including linear shafts, linear bushings, linear guides, ball screws and other hardware such as precision-class washers.
He says, although black chrome parts may cost significantly more than stainless-steel components, the key advantage is their ability to maintain linear performance. Parts will work for longer periods, in much harsher environments, than other coatings and metals.
“If the customer has a machine with a long life or a harsh environment, they would see a big advantage,” he says. He adds that, for the design engineer interested in the technology, one approach is to buy samples for testing the black chrome-plated components in a specific environment.
Focus on Innovation
Suppliers of precision mechanical components are continually seeking ways to refine their product offerings. New technologies designed to reduce friction, increase machine reliability and automatically lubricate rolling elements, and methods for fast, accurate positioning are all focus points for new product development. What follows in this section is a series of products that not only represent innovative thinking, but also offer new building blocks for engineers designing machinery.
SS 2 Miniature Spline Shaft Series
The Spline Shaft SS 2 Series from Kerk Motion Products is designed for light to moderate load applications where low cost, low friction and long life are critical design considerations. This includes any application that requires a rotary drive with adjustable linear position or a linear guide with high torsional stability.
The SS 2 Series is the smallest spline shaft in the Kerk line with an outside diameter of Ø.125 inch (3.18 mm). In an application currently using a ball spline, hex-, square- or D-shaft, it can provide a lower-cost alternative without sacrificing positional accuracy. Because of its low-friction performance, it can allow a user to downsize process equipment, reducing heat buildup and energy requirements.
The assembly consists of a solid steel or aluminum spline shaft treated with Kerkote® TFE coating, coupled with plain or thread-mount bushings, which eliminates the need for external lubrication and maintenance.
Stainless-Steel 'A’ Ball Bushing® Bearings
New stainless-steel ball bushing bearings from Thomson deliver high-speed, repeatable operation in extreme temperature environments. Machine builders will benefit from extended service intervals, longer bearing life, increased machine reliability and reduced service and support costs. When combined with stainless-steel 60 case shafting, shaft life is extended when compared to conventional shafting.
The new bearings deliver steady state travel speeds up to 10 ft/s (3 m/s) and accelerations to 450 ft/s2 (150 m/s2) without using derating factors. The new units also have a coefficient of friction as low as 0.001 to allow machine builders to use smaller, less expensive motors, belts, gears and ball screws in machines when replacing high-friction, plain bearings.
The bearings are available in standard sizes up to 1 inch with adjustable, closed and open configurations. Two accuracy classes provide immediate improvements in system positioning and repeatability. A self-aligning pillow block housing facilitates easy installation and use.
Self-Adjusting Power Linear Bush
THK’s self-adjusting type power linear bush is engineered with cages made of a synthetic resin to continually lubricate the rolling elements. A uniquely designed, hardened steel ball plate features a precisely ground groove that is slightly larger than the ball, which results in increased contact area between the balls and the ball plate. Together, these design features provide load capacities three times higher than conventional linear bushings and 27 times longer service life.
Offering extremely smooth and quiet motion due to its ball retainer and outer sleeve, the new units are constructed of a synthetic polymer that is lightweight, low friction and highly wear-resistant. These characteristics enable moving parts to have rapid motion, while requiring lower driving power and reducing energy costs.
The convex shape of the ball plate provides a pivot point at the center which allows a self-adjustment capability up to 0.5 degrees. These self-adjustment capabilities eliminate any possibility of edge pressure caused by inaccurate machining, errors in mounting or shaft deflection.
Double Stack Captive Hybrid Linear Actuator
The 28000 Series from Haydon Switch is a double-stack, captive hybrid linear actuator with a compact frame size only 1.1 inch (28 mm) sq. Designed for long life (several million cycles) and superior performance, the size 11 linear actuator features engineering thermoplastics in the rotor drive nut and a stainless-steel Acme lead screw.
The actuator is available in resolutions ranging from 0.000125 inch (.003175 mm) per step to 0.002 inch (.0508 mm) per step and delivers thrusts of up to 30 lb (133N) without compromising long life.
The captive linear actuator is designed with Haydon’s patented integral anti-rotation mechanism and is especially well-suited for applications in which external anti-rotation methods would be difficult or impossible to employ. Captive linear travel ranges from 0.5 to 2.5 inch (12.7 to 63.5 mm).
Patented DualVee® Integral Guide Wheels
Bishop-Wisecarver has been awarded a U.S. Patent for technology developed in the latest addition to its DualVee integral guide wheels product line.
Available in carbon steel or polymer versions, the integral wheels feature a one-piece design with the stud or bushing incorporated in the wheel. Larger sizes offer a machined inner bearing race, while the smallest sizes use a swaged retaining technology to secure the wheel to the stud. With a lower profile and larger diameter fastener than the company’s original DualVee, patented in 1967, new integral wheels provide greater rigidity and increased mounting torque capability.
DualVee provides users three different wheel options: the original V bearing guide wheels, studded V bearing guide wheels and the patented integral V bearing guide wheels. Wheels then run on either a single or double-edge track.
Shock-Absorbing Coupling Solutions
Ruland has expanded its line of zero-backlash jaw couplings to include more compliant spider elements for applications where greater shock absorption is desired. The zero-backlash jaw couplings are three-piece couplings comprised of two hubs with curved jaws and an elastic element. The spider, made of an advanced polyurethane material, provides dampening of impulse-type loads to minimize shock to the motor and other sensitive equipment.
Spider elements with three different hardness levels are offered. New blue spiders have a durometer of 85 shore; yellow spiders are 92 shore and red spiders are 98 shore. The availability of spiders with three hardness levels allows the end user to customize the jaw couplings performance given application parameters such as torsional stiffness and the amount of shock absorption required.
Hydraulic Shaft Locking Bushings
New model ETP-Octopus™ hydraulic shaft locking bushings from Zero-Max are ideal for simultaneous, quick locking and accurate positioning of sliding shafts. They are designed to be used on sliding shafts in automated systems such as machine tools, extruders and packaging systems.
By providing uniform and repeatable locking pressure, these ETP-Octopus™ bushings can be set up for fast and frequent locking/unlocking of linear slides or similar motion devices at one position or a series of positions from a remote switching location. The bushings are available with either aluma-bronze or steel sleeve bores for smooth, long-life operation.
Its unique hydraulic locking design and positioning flexibility make it superior to other locking mechanisms where torque transmission with no axial movement of the shaft mounted components is required.
Compact Servo Coupling Series
R+W America recently developed a series of couplings for mounting to flange output servo gearheads, opening up new application areas. This type of gearhead is utilized by many for its high stiffness and compact design. The BK8 now allows for an equally compact flexible interface between gearheads and driven components, protecting bearings and making alignment simpler.
The BK8 utilizes a stainless-steel bellows which allows for a high level of torsional stiffness to be maintained while compensating for small misalignment between the mating components. The couplings are available in a wide variety of sizes, covering torque ratings from 15 up to 1,500 Nm and for special applications up to 10,000 Nm. They can be made with a variety of coupling output hubs, in addition to the traditional clamping hub, such as expanding shafts and tapered conical clamping hubs.
Self-Lubricating Linear Bushings
A new family of self-lubricating linear bushings from MISUMI USA offers three times the rated life span of conventional bushings by utilizing a newly designed MX lubrication unit.
An integral fiber pad delivers the lubricant to the shaft surface through a capillary action to maintain a constant lubricating film between ball bearing and shaft. As a result, the maintenance interval on these linear bearings is extended, a significant time-saver for applications involving numerous mountings or difficult access. Reductions in assembly time are also realized because the bushings are pre-loaded with a lithium soap-based grease.
Self-lubricating bushings are offered in single or double bushing lengths with either flangeless, round, square or compact mini-flanged styles. Units are made of high-quality 52100 bearing steel with Duracone M90 or equivalent resin pad cases and retainers, plus Nitrile rubber seals. Products in this family are RoHS-compliant.