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How to Select Industrial Products

This is the place for engineers to learn about and teach others how to select industrial products. The blog is maintained by the Editorial team at IEEE GlobalSpec, the company that powers CR4.

Trying to Find 'Fabulous' Light Curtains

Posted April 01, 2013 6:05 AM by HUSH
Pathfinder Tags: how to select light curtains

I really wish they would make light curtains available in more colors, don't you?

Their appearance always clashes with the machinery. The silver and black parts picker looks HORRIBLE next to those yellow light curtains. Some people say black is neutral--but me, honey please! Don't even get me started on these orange coveralls! I say there is nothing wrong with being fabulous while also doing a little hard work.

So is the life for that fashionably-perfect in the manufacturing world. However, those light curtains do keep this tight tush nice and safe.

A light curtain's main advantage is that it does not impose a physical barrier on personnel. As such, an operator is able to access guarded components without mechanical or observational limitations. Maintenance processes are also eased by their use. Light curtains can be used to monitor cargo in or out of a restricted access area, as well as provide strictly one-way access.

A transmitter is established and an array of parallel infrared beams provide a boundary across the restricted access point. The transmitter can emit its rays in virtually any configuration provided the infrared beams conclude at a receiver. Mirrors are frequently used to relay beams around corners or obstacles which reduces the need for multiple transmitters, but for every mirror the beam range is reduced by 25%. An alignment laser or LED indicator is frequently integrated in the transmitter for accurate positioning. Manufacturers may elect to incorporate light curtains in standalone machinery and these devices will have increased sensitivity. Light curtains have variable and convenient installation patterns.

The infrared light beams are sequenced and modulated and the receiver is designed to recognize a specific infrared beam, decreasing the chance for issues from ambient infrared light. When a beam is obstructed by an opaque object, a safety relay halts the machinery or process within milliseconds. Some light curtains allow the process to resume once the obstruction is removed, while others require an operator to manually restart the process. A PLC (integral or external) is required for the light curtain to interface with the machinery it encloses. A timed mute feature allows operators to control the flow of materials through the perimeter without stopping the machine. Some muting scenarios allow the passage of humans, while if other muting sensors register a human or irregularity then the process will cease.

And while it may not be available in say, polka dots or glittery pink (my fave!), many light curtains offer much more important features. Self-checking circuitry has the capability to run a self-check during startup, operation, or continuously to ensure no loss of function. Latching safety relays will not remove the stop signal until the controls are manually reset outside the protected area. And muting is the temporary, automatically controlled deactivation of a safeguarding device during the non-hazardous portion of the machine cycle.

Anyhow, you can learn all about light curtains at the GlobalSpec Light Curtain Selection Guide. And though the search filter doesn't have a category for color, it can be useful for some other solutions.

Excuse me, time for lunch with the boys from floor 3 . Ciao!

(Images credits: Southern Industrial Equipment; Industry Direct)

2 comments; last comment on 04/03/2013
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How to Select Technical Training Equipment

Posted March 25, 2013 12:00 AM by Chelsey H

Technical training equipment is used to instruct technicians on the operation of vacuum, semiconductor fabrication, pneumatic, hydraulic, fluid process, electromechanical, energy power generation, automation, optics, physics, chemistry and thermodynamic systems. Technical training covers a wide variety of processes and it is critical that technicians have a complete understanding of the process in order to ensure safe and efficient operation.

Image Credit: Parker

The type of technical training equipment can include:

Ā· Demonstrators- Demonstrators are used to show how a process, technology, scientific principle should work. A cut-away pump, clear plastic engines or other training models are examples for demonstrators.

Fluid mechanics and pumps units. Image Credit: Geneq Inc.

  • Experiments - Technical training experiments allow students to explore how variations in process or system parameters affect performance or output. The product consists of the materials, parts and equipment required to perform the experiment.
  • Kits / modular units- Technical training kits consist of equipment, parts, and/ or materials such as pumps, motors, actuators, valves, fasteners, fittings, fluids, etc. that are kitted together for assembly, experimentation and learning exercises.
  • Simulators - Simulators do not physically perform the process, but provide a virtual version of the process, technology or scientific principle. Simulators allow students to interact and react to changes in system parameters.

Mining simulator. Image Credit: Thoroughtec

  • Training benches- Technical training benches consist of a series of components and sub-systems pre-mounted on a workbench.
  • Training laboratories - Training laboratories allow students to perform multiple laboratory exercises and can demonstrate many different processes, technologies, and scientific principles.
  • Training manuals / plans - Manuals, training guides and training system plans provide a list of the required components and sub-systems that can be purchased and assembled to provide a complete training system. Training system can be modified to suit the specific OEM needs.

Technical trainers, simulators, training kits and complete laboratories are available for a variety of technologies, subjects, and disciplines. For more information on technical training equipment, please see How to Select Technical Training Equipment on IHS GlobalSpec.

What type of technical training equipment do you use?

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How to Select Rodless Cylinders

Posted March 04, 2013 12:00 AM by Chelsey H

Rodless cylinders are linear devices that use pressurized fluid to move a load within power transfer operations. A rodless cylinder should be used if the footprint of the area is small, when the load needs to be moved some distance from the cylinder itself, and when the load must move within the length of the cylinder. They are suitable for long-stroke applications because they are protected from bending, piston binding, and uneven seal wear. Rodless cylinders are used in a variety of material handling, loading, feeding, lifting, and web cutting applications. They are also used in sliding carriers, conveyors, and spraying equipment. They are made of aluminum, steel, stainless steel, or plastic and driven by an electric motor, pneumatic or hydraulic assembly, or electrohydraulic pump.

Image Credit: Grainger

Rodless actuators can use a variety of actuators including Electrical, Hydraulic, Pneumatic, or Electrohydraulic. For more information on linear actuators, see GlobalSpec's How to Select Linear Actuators Selection Guide.

Type of Cylinder

Guided cylinders are directed by attached rods or rails. Unguided cylinders are directed by external hardware associated with the application.

Types of Coupling Styles

There are several basic coupling styles for rodless cylinders.

  • Band cylinders or direct-coupled cylinders are connected to the cylinder flange with a table, stage, or other moving element. Their name is derived from the zip-locked type band that keeps compressed air within the barrel of the cylinder. An advantage of band cylinders is that the barrels can be easily sized to carry a load.
  • Magnetically-coupled rodless cylinders are moved by a magnetic field and enclosed to prevent the ingress of contaminants. This design prevents contaminant entry into the cylinder. It is important to select a cylinder which will provide the correct coupling force between the carriage and the piston to support the mass of the load and the speed the load needs to be moved. The advantages of magnetically-coupled rodless cylinders include their compatibility with low pressure hydraulic services and that the re-coupling of the carriage to the piston simply requires placing the carriage over the location of the piston inside the cylinder. The disadvantages include a higher cost, and uncoupling at high speeds or hard deceleration.
  • Cable cylinders pass cables from the ends of a gland seal to a pulley that connects to the carriage. In turn, the carriage is attached to the cable from the opposite cylinder end. When the actuation mechanism (i.e. compressed air) enters the cylinder, the piston and the attached cables move from one end of the cylinder to the other. The direction of the carriage depends on the direction of the piston. Cable cylinders save space, and the carriage can be located some distance from the actual barrel and piston. This is unique to the cable cylinder. Cable cylinders are also inexpensive per inch of stroke.

Image Credit: About Air Compressors

Specifications for rodless cylinders include maximum stroke, carriage load, operating pressure, operating temperature, bore size, breakaway pressure, and mounting style.

Rodless Cylinder Features

Many products provide special features such as Air/oil tandem which provide smooth, hydraulic-like motion. This combination is only used in pneumatic cylinder. Other special features include Bumpers which cushion the impact at the ends of a stroke, Linear position feedback which can be analog or digital to provide continuous output of position, and Home, limit, or position switches have switched outputs that can limit travel.

For more information on rodless cylinders, read How to Select Rodless Cylinders on IHS GlobalSpec.

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Scissor Lifts Make Great Toys

Posted February 25, 2013 8:00 AM by HUSH

So many industrial products and process find alternative uses in the arts.

Paint isn't just a surface coating, but a means of visual expression and interpretation. Modern art sculptors have been using welding and brazing techniques for decades to create obtuse structures. Steampunk has become a clothing and aesthetic style that idolizes 19th Century steam-powered machinery.

And, in what is perhaps the performing art's introduction to industrial machinery, scissor lifts now participate in ballet. No really, have a look.

While as, um--beautiful, as that was, it's likely that the composer was simply living out a childhood fantasy of playing on scissor lifts. They do look like giant toys after all. It's unlikely though that the composer understood the industrious nature of his playthings.

Scissor lifts owe their mechanical capability to the pantograph. A pantograph is a series of linked parallelograms with hinged intersections that allow the operator to elongate the mechanism while still maintaining the integrity of the geometric figure. The structural components of the pantograph serve as opposing line segments within adjacent parallelograms; geometric changes are therefore uniform across the mechanism. True vertical lift is accomplished by using components of equal length.

When two pantographs are arranged so as to actuate from a single drive they extend correspondingly and loads can be balanced between them. A calculator exists for computing the linear input force required according to where the drive supplies power to the scissor mechanism, be it upon the base or a center pin .

Motor-driven propulsion is a valuable attribute in many situations requiring scissor lifts. This allows workers to position the lift on an as-needed basis which is particularly useful in maintenance and construction applications. 'Slab' lifts are restricted to paved, smooth surfaces; rough terrain lifts rely on robust tires and four-wheel drive to traverse off-road conditions.

To improve lift agility, manufacturers rely on a sharp turning radius and a short wheelbase. Parking brakes ensure lift location, and tires and casters come in non-marking, off-road, anti-slip, press-on, and urethane varieties. Economical and legal reasons prohibit scissor lifts from road travel; they are hauled or towed between job sites. However, some scissor lifts may be flatbed or railcar-mounted for specialty applications. Many mobilized lifts utilize outriggers for further foundational stability.

Furthermore, the control, maneuverability, and power source of a scissor lift is critical to its utility, other characteristics better describe the vertical capabilities of the lift.

  • Stroke: this is the range of height safely attained by use of a scissor lift. This is directly correlated with the number of scissor intersections and the length of the components used in the pantograph.
  • Size: this is the dimensions of the work platform elevated by the lift. Many lifts feature an extendable platform to increase the area's square volume.
  • Capacity: the maximum burden that the lift is designed to safely support, be it personnel or freight.
  • Tilt: in cargo-lifting situations it may be helpful to have a lift table that can pitch its load to an angle to make the load more accessible.

You can see IHS GlobalSpec's complete scissor lift selection guide here.

Also, if you have a scissor lift, remember that you should not operate it with your judgment impaired or on the road, like this idiot [language].

(Image credits: Wikipedia; Taylor Rental; IHS GlobalSpec; Craig Boyce)

2 comments; last comment on 03/02/2013
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How to Select Rotary Switches

Posted February 04, 2013 3:59 PM by Chelsey H

Rotary switches move in a circle and can stop in several positions. They are used to control many different circuits or select different valves for one circuit with a single switch. These devices have some advantages over other switches since turning the actuator can turn circuits on or off depending on the position and many different actuation positions are possible. Rotary switches can also be designed to have many contacts happening at once on a single switch position. While rotary switches can be found on many types of industrial equipment, they can also be found in consumer equipment such as in a car for adjusting things like fan speed. Rotary switches are becoming less common since complex switching operations are being done with digital equipment such as touchscreens. Mechanical rotary switches are still used however, especially in equipment where a computer failure could be a safety issue. Image Credit: Omega Engineering

Rotary switches have a rotating spindle. The rotors are on a spindle and each rotor has an arm projecting outward that can make contact with a terminal when the switch is in a certain position. Depending on the number of rotors, the switch can have dozens of different positions and each one can be attached to a particular circuit.

Parts of a rotary switch. Image Credit: Doctronics.co.uk

In order to put the rotary switch in the proper position, a detent mechanism is used. This mechanism makes the switch "click" into position and stay in place until enough force is applied, preventing the switch from turning freely and being put in the wrong setting accidentally. A detent uses a wheel with notches or grooves cut into it and attached to the rotor. When the wheel reaches the correct position a spring-loaded ball bearing or piece of spring steel pressing against the wheel presses into the groove holding it into place.

Important physical switch specifications to consider when selecting a rotary switch include mechanical life, number of poles, angle between positions, number of decks, number of poles per deck, and switch frame.

Multi-deck (left) and Single deck (right) rotary switch Image Credit: Elma

Number of poles per deck- The number of poles per deck is the number of separate circuits that can be activated through a rotary switch per deck. The output connections are usually called ways instead of throws. The construction of the switch provides a total of 12 ways but there may be 1, 2, 3, or 4 poles. The rotating contact will channel the signal from the pole to the output terminals. The number of terminals required determines how many positions a switch will have.

Stop Style

Rotary switches with an adjustable or continuous stop are commonly available. The stop style should be selected based on the need of the application.

Adjustable stops give the user the option to stop when desired. Adjustable stops allow the user to take a 12-position switch and adjust it to have any number of positions between 2 and 12. This stop should be used for low volume requirements.

Continuous stops, also known as no stops, do not have any stop positions on the rotary switch.

Fixed stops have the stop positions come fixed from the manufacturer and are not changeable by the user. They are better for volume production requirements so the user does not have to adjust the switch.

For more information on Rotary Switches please read IHS GlobalSpec's How to Select Rotary Switches guide.

1 comments; last comment on 02/04/2013
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