Month: May 2016

Basics of Gearbox Selection

Guest contributor:  Tim Anderson, Stober

Selecting a gearbox can be quite difficult. Customers have a variety of gearboxes to choose from that are capable of fulfilling diverse requirements. A wrong decision could result in the purchase of a more expensive gearbox. The power transmission industry may need a gearbox that will support overhung loads while the motion control or servo industry may need a gearbox that will handle dynamic motion.

One of the first problem areas for sizing arises from sizing to the motor versus sizing to the load. Sizing to the motor may be simpler and result in a gearbox that works, but it will result in the purchase of a larger gearbox than is needed. This gearbox will also be overqualified for the application. However, sizing to the load will ensure a gearbox fits the application and is more cost-effective as well as potentially a smaller footprint.

Common Aspects of Sizing Applications

There are several aspects of gearbox sizing that apply to every situation. This section will detail those criteria and offer insight.

1. Service FactorGearboxSelection2

Before sizing an application, the customer should determine the service factor.
Service factor can be generally defined as an application’s required value over the rated value of the unit. Service factor should be determined for conditions such as non-uniform load, hours of service, and elevated ambient temperature.

How would one interpret a service factor? A service factor of 1.0 means a unit has just enough capacity to handle the application. There is no tolerance for additional requirements, which could cause the gearbox to overheat or fail. For most industrial applications, a service factor of 1.4 is adequate. This service factor signifies that the gearbox can handle 1.4 times the application requirement. If the application requires 1,000 inch-pounds, the gearbox would be sized to handle 1,400 inch-pounds. Different factors will affect how much service factor shoul
d be used in a given application. The changes to service factor depend on the

 2. Ambient Temperature and Environment

Higher ambient temperatures increase internal pressure, which will require an increase to the service factor used. High or low temperatures can require different seal materials and lubrication viscosities. The environment the gearbox will operate in is also an important consideration for sizing. Harsh environments can increase wear on the unit. Dusty or dirty environments often require special material to prevent corrosion or bacteria growth. Food or beverage plants require specific FDA compliant coatings and oil. Vacuum environments will require special grease and heat dissipation considerations, since there will be no air for cooling. Failure to account for these environmental features can result in a gearbox that cannot support the application properly. All of these aspects must be considered when sizing a gearbox.

3. Shock Load or Type of Load

High shock or impact loads can cause increased wear on the gear teeth and shaft bearings. This wear could cause premature failure if not accounted for when sizing. These loads will require an increased service factor. Uniform loads are loads that remain constant during the application, while non-uniform loads change during the application. Non-uniform loads, even if small, will require a higher service factor than uniform loads. An example of a uniform load would be a conveyor with a consistent product amount riding on it. A non-uniform load would be any sort of intermittent cutting application. This intermittent cutting force causes a periodic increase in the torque on the gearbox, which is a non-uniform load.

4. Output Style or Mechanism

Output mechanisms include a sprocket, pulley, or toothed pinion, to name a few. Different output configurations, such as double output shaft or shaft mounted bushing, will decrease how much overhung load the unit is rated for. Different output mechanisms add different shaft loads that must be considered. Most mechanisms will cause high radial load, but things like helical gearing can also cause an axial load. These outputs could require different bearings to account for the increased radial or axial load.

5. Output Shaft or Hollow Bore Size

When sizing an application, the output shaft and bore size must meet customer requirements. These could include a stainless output on the unit, and whether it has a keyed or keyless shaft, a keyed or keyless hollow bore, or a flanged  output combined with any of the previous. Getting the correct bore size on a unit may force the customer to purchase a larger gearbox or a different style of gearbox to fit their current shaft. In some instances, the customer can modify their shaft to use the most cost-effective unit while providing an optimal solution.

6. Housing Styles

It is also important when selecting a gearbox to consider how it will mount. A unit could have mounting feet, a flange on the output, or just basic tapped holes on one or more sides. These housing styles could limit how a unit is mounted so having a variety of options could prevent custom frames or brackets from being needed. For example, having tapped holes on the bottom face of the unit would prevent the need for a special L-bracket to mount around the output.

Power Transmission

Some elements that affect the sizing process are industry specific. For the power transmission industry, output RPM, motor horsepower and frame size, and overhung load all impact the application calculations.

• Output RPM   The customer must determine the ratio needed for the gearbox to operate, or provide input/output speed and operating hertz (Hz) for calculations. The standard is a 1750 input RPM at 60 Hz. Any changes will need to be specified when sizing as it will change the ratio calculation. Failure to account for changes will result in a gearbox that does not match the customer’s requirement.

• Motor HP and Frame Size  The gearbox size and input option must be determined GearboxSelection3before calculating the service factor. Once the gearbox is sized, use the required HP to compute the actual service factor. Large HP motors generate heat that can adversely affect the reducer’s mechanical ratings. This reduced rating, based on the increased heat, is known as the Thermal Capacity of a reducer, and must be considered when using large motors.

• General Shaft Load  The sizing must verify that the load will not damage the gearbox. The force, measured in pounds, that the output shaft is capable of sustaining is known as the Overhung Load rating. If the rating is less than the application, the speed reducer will be damaged.

Motion Control

For the servo industry, input speed, inertia, dynamic torque motion, specific shaft loads, and motor shaft diameter affect the sizing process.

• Input Speed  Input speed should not exceed the gearbox ratings or premature seal wear will occur due to increased pressure. Input speed can be accidently increased if there is an output mechanism with a ratio that is not considered when sizing, which is another reason why specifying any output mechanisms is so important.

• Inertia An inertia mismatch of less than 10:1 is desired for fine controlling of the output. This is important to obtain the high accuracy needed for some applications. Reducer size and ratio are main influences from the gearbox on inertia. Control engineers may request smaller mismatches or even specific amounts. Often a motor is chosen for its dynamic capabilities, not for its torque. It is common to use a motor with much more torque than needed for the application due to its increased rotor inertia. Some motor manufacturers even make motors specifically for high or low inertia ratings. This allows for better tuning of the application because of a lower inertia mismatch. When doing this, it is important to limit the output torque in the motor to prevent breaking the gearbox

• Dynamic Motion  Cyclic motion may require using a higher service factor than continuous motion. This is because constant starts and stops cause additional wear on the gear teeth and seals. Cyclic reversing, which is constant back and forth motion between two points, requires an even higher service factor than cyclic or continuous

• Specific Shaft Loads  Radial, axial, and moment shaft loads must be checked against the unit’s ratings. Failure in doing this could result in a broken shaft or damage to the bearings or gear teeth. Generally, the same service factor is applied to these ratings to determine an appropriately strong gearbox. Additional bearing types can increase these ratings if the application needs them.

• Motor Shaft Diameter or Length  The motor shaft must fit in the unit, and the shaft must be long enough for full engagement with the coupling. Without full engagement, input slippage could occur. While this will not affect the service factor needed, it is important to consider in order to avoid problems mounting the motor. Some manufacturers have a large input design allowing the reducer to accommodate the larger motor without increasing the unit size.

Conclusion

To achieve the best gearbox solution, customers should size from the load. This will ensure they receive cost effective solution that fits the application. The service factor, environment, ambient temperatures, shock load, output style, and hours of service are all important aspects for sizing. The more information the customer provides, the more accurate the sizing process. This will ultimately yield a solution that matches the customer’s requirements! There are numerous sizing programs available that can help determine what gearbox is most appropriate for your application

Virtual commissioning saves precious time

Guest contributor:  Steffen Winkler, Vice President Sales Factory Automation, Bosch Rexroth

Ever shorter product life cycles and the desire for smaller batch sizes constantly present designers and programmers of production machines and lines with new challenges. To save time and costs, machine builders increasingly rely on model-based engineering, which creates unimagined potential for efficiency enhancement and cost reduction especially during commissioning – thanks to Bosch Rexroth.

The commissioning of machines is a very elaborate process so far. The reason for this is, among others, that programmers can test and optimize their machine program only on the real machine. Thus, 70% of the time that is needed for the commissioning of the control technology is mainly used for time-consuming and therefore cost-intensive optimization measures of the program. This occupies machine space in the assembly hall and causes considerable additional expenses at approaching delivery dates, like additional night shifts.

However, a majority of this optimization tasks can be virtually performed before through model-based engineering. The advantages are obvious: Starting with the first CAD click, all design data could be created in a PLM system. On this basis, a behavior model of the machine is created. Bosch Rexroth therefore provides 3D models and behavior models of its components. In the simulation software, PLC programmers can then test new control functionalities directly at the behavior model of the virtual machine, without the machine must be set up in the assembly hall.

Controller waits for simulation results

Therefore, a simplified machine model additionally had to be used in the simulation environment so far. The computing power of current PC technology is usually insufficient to simulate the complete machine model synchronously to the real-time behavior of the PLC and motion control.

But this deficit is a thing of the past thanks to the Open Core Engineering from Bosch Rexroth. The controller adapts itself to the timing of the simulation and waits for its results before the next motion cycle is executed. Thus, a real behavior of the simulation of the complete machine model is guaranteed.

When the machine is put into operation at the customer’s site, the engineers only need to start it in the ideal case – more extensive optimizations are thus needless. Open Core Engineering supports all established system simulation platforms like MATLAB Simulink and environments on the basis of the open modelling language Modelica, like the 3DEXPERIENCE platform from Dassault Systèmes or SimulationX.

Consistently digital engineering in practice

The example of the American packaging manufacturer WestRock shows how huge the potential savings are in practice. For the model-based development of their machines, the company relies on the 3DEXPERIENCE platform from Dassault Systèmes, which also supports Open Core Engineering. Directly in the simulation environment, the engineers can thus check and optimize all machine movements and put the control virtually into operation. Subsequently, the knowledge gained here is directly incorporated in the engineering environment IndraWorks from Rexroth. In this way, WestRock could shorten the entire development time from design to commissioning drastically.

Read more about the success story WestRock

A new automation project: best price or best service?

by Harry Aghjian, CEO CMA/Flodyne/Hydradyne

Long Term Liability

In the world of automation, most projects are defined by the amount of risk the machine builder will incur. An important factor is knowledge of current standards: UL standards and OSHA standards, CE directives and many others may apply to your project depending on the final installation location of the equipment. The liability that the machine user incurs is over the life of a given machine.  That could be a long time — five, ten, 25 years?   We have all worked on machines that have been in service for over 50 years!

No matter how large or how small, from the start, an automation project needs to dynamically formulate a plan to mitigate the risk using common methods such as hard guarding (barriers) or soft guarding (ie. light curtains). As the machine performance specifications are defined, a given project engineer now has an enormous task on his or her hands. The project engineer must meet or exceed the performance requirements at the lowest market cost.

A Simple ExampleRexroth Indradrive Mi visual6741 (2)

 Let’s assume the automation project requires a single axis of point to point motion.  Let’s make one more assumption that this motion or axis requires an electric actuator and sufficient thrust as to be powered by a 380 or 460v, three phase power source (high power stuff).  The sum total of all the manuals that a project engineer needs to read and re-read to successfully size, program and integrate all of the ancillary components equal about 4000 pages of documentation!  That’s before doing the actual machine risk assessment.

In today’s competitive market where speed to market and innovation are keys to success, does a project engineer really have time to read 4000 pages?  One could simply duplicate the last project or BOM (bill of material) — but have we then truly been innovative and taken advantage the latest in automation technology?  The answer is to leverage the market knowledge.  Your technology supplier must first and foremost be a “source of knowledge”.   The product knowledge supplied can be more important than the given component.  The sum of these components, along with superior product knowledge, allows the project engineer to be innovative and accelerate the machine to market.

Product Knowledge is King

I was recently reading the latest web ad from a company that touts lowest price “direct” from their warehouse. In my opinion they lacked the key ingredients that a project engineer needs…product knowledge and local service. Product knowledge when sizing the automation system. Product knowledge when developing the BOM options. Product knowledge when starting up the automation system. Product knowledge when doing the risk assessment.

Most industrial automation suppliers provide competitive pricing. I ask that you judge your next supplier based on their knowledge and their ability to service your needs, at your location and at your convenience. Great service along with great knowledge will produce the most cost effective solution.

 

Basic operating principle of an Inductive Proximity Sensor

Guest contributor: Henry Menke, Balluff

Did you ever wonder how an Inductive Proximity Sensor is able to detect the presence of a metallic target?  While the underlying electrical engineering is sophisticated, the basic principle of operation is not too hard to understand.

At the heart of an Inductive Proximity Sensor (“prox” “sensor” or “prox sensor” for short) is an electronic oscillator consisting of an inductive coil made of numerous turns of very fine copper wire, a capacitor for storing electrical charge, and an energy source to provide electrical excitation. The size of the inductive coil and the capacitor are matched to produce a self-sustaining sine wave oscillation at a fixed frequency.  The coil and the capacitor act like two electrical springs with a weight hung between them, constantly pushing electrons back and forth between each other.  Electrical energy is fed into the circuit to initiate and sustain the oscillation.  Without sustaining energy, the oscillation would collapse due to the small power losses from the electrical resistance of the thin copper wire in the coil and other parasitic losses.

 Inductive proximity sensor cutaway with annotation

The oscillation produces an electromagnetic field in front of the sensor, because the coil is located right behind the “face” of the sensor.  The technical name of the sensor face is “active surface”.

When a piece of conductive metal enters the zone defined by the boundaries of the electromagnetic field, some of the energy of oscillation is transferred into the metal of the target. This transferred energy appears as tiny circulating electrical currents called eddy currents.  This is why inductive proxes are sometimes called eddy current sensors.

The flowing eddy currents encounter electrical resistance as they try to circulate. This creates a small amount of power loss in the form of heat (just like a little electric heater). The power loss is not entirely replaced by the sensor’s internal energy source, so the amplitude (the level or intensity) of the sensor’s oscillation decreases.  Eventually, the oscillation diminishes to the point that another internal circuit called a Schmitt Trigger detects that the level has fallen below a pre-determined threshold.  This threshold is the level where the presence of a metal target is definitely confirmed.  Upon detection of the target by the Schmitt Trigger, the sensor’s output is switched on.

The short animation to the right shows the effect of a metal target on the sensor’s oscillating magnetic field.  When you see the cable coming out of the sensor turn red, it means that metal was detected and the sensor has been switched on.  When the target goes away, you can see that the oscillation returns to its maximum level and the sensor’s output is switched back off.

Want to learn more about the basic operating principles of Inductive Proximity Sensors? Here’s a short YouTube video covering the basics:

The Future of Hydraulic Systems – HydraSmart

by Bryan Smith, Hydraulic Sales Manager at CMAFH

Automation technology needs are becoming more sophisticated as the industrial marketplace evolves. Efficiency and cost-effectiveness have never been more interrelated, and OEMs need to offer maximum value to stay competitive. The next tech revolution – Industry 4.0 – is here and as we all navigate these uncharted waters, CMAFH is proactively anticipating the need for advanced systems. Our customers have asked for, and we are designing, hydraulic systems that meet the following criteria:

– reduced dB (sound) levels
– reduced heat loads
– greater electrical efficiency

CMAFH designed a hybrid machine packaging hydraulic systems with electrical controls, and we call it HydraSmart. HydraSmart was designed initially to meet the criteria of our Plastics and Machine Tool customers. Working closely with a key customer we created two standard systems that will cover 95% of the industry’s needs.

Hydrasmart is an efficient plug and play HPU that provides variable pressure and flow, easily set by touchscreen. Using the proven technologies of variable speed drives and variable displacement pumps, along with some custom controls, we’ve created a power unit that has a small footprint. In many cases, HydraSmart consumes zero floor space as it is designed to fit within or under many injection molding machines allowing end users to maximize their output per square foot. It will also help your machines to become more energy efficient and much quieter. HydraSmart is typically used with all electric machinery such as injection molding or machine tool/CNC.

World, meet the HydraSmart Power Unit

HYDRAOBLIQUEIMG_7131

HydraSmartIMG_4155

In March of 2015, CMAFH had the opportunity to exhibit at the National Plastics Exhibition in Orlando showing two HydraSmart units as part of a larger display. CMAFH team members Gordon Johnson, Eric Grendahl and I had an exciting week that brought us exposure to thousands of customers. Traffic was steady at the five day event, and visitors were impressed by HydraSmart’s ease of use and small footprint. Pictured below, the ultra-compact HydraSmart unit is designed to reside within the framework of an injection molding machine.

Our efforts and investments in HydraSmart have brought many new and exciting opportunities. As a result, we have moved CMAFH electrical engineer Greg Parkhouse into a new role. Greg is now Special Projects Manager with primary emphasis and focus on the HydraSmart systems. Greg will be working closely with our engineering group, manufacturing group and sales and marketing group as we further develop this product.

If you want to know more about the HydraSmart system, please visit our website. We believe HydraSmart will be an expansive part of our systems business and the future in hydraulic systems.

HydraSmart is typically used with all electric machinery such as injection molding or machine tool/CNC. Learn more about the HydraSmart here or contact us at sales@cmafh.com for more information.

The Future of Cooling Technology in Industrial Enclosures

by Eric Corzine, Product Manager, Climate Control at Rittal

As industrial processes scale, the threats and challenges of cooling the racks of automation equipment increase exponentially. Sophisticated, sensitive electronics and drives are the backbone of many industrial systems. This equipment is often placed inside enclosures to protect it from environmental influences such as temperature, moisture and contaminants like corrosive vapors and dust. If these are not prevented, electronic components will inevitably fail, eventually leading to the shut-down of entire production systems. The failure of a production system can add up to losses for an operation.

What will the future look like?
The single most important environmental factor to manage in industrial enclosures is temperature.  Relative to each individual component, the heat of electronic components has increased significantly in recent years. At the same time, the density inside control cabinets has increased dramatically, resulting in a 50 – 60% increase in heat in the enclosures.

With the advent of microelectronics and new electronic components, the requirements for professional enclosure construction and heat dissipation have evolved dramatically over the last few years. Modern enclosure climate control systems must take these challenges into account, offering the best technical solution while guaranteeing optimum energy efficiency. If heat is not managed properly and the maximum permitted operating temperature is exceeded, the service life of these components is halved and the failure rate is doubled.

Trouble-free operation and functioning of production lines is heavily dependent on how the heat generated by electrical and electronic components is dissipated from the enclosure to the ambient environment. We distinguish three different types methods of heat transfer:

  • Thermal radiation
  • Thermal conduction
  • Convection

In the case of enclosures and electronic housings, we are mainly concerned with thermal conduction and convection. With thermal radiation, heat is passed from one body to another in the form of radiation energy, without a medium material, and plays a minor role here.

Whether we are dealing with heat conduction or convection depends on whether the enclosure is open (air permeable) or closed (air-tight). With an open enclosure, the heat (heat loss) can be dissipated from the enclosure by means of air circulation, i.e. thermal conduction, from inside to outside and is typically in a controlled environment such as data centers. However, if the enclosure has to remain closed due to harsher conditions, the heat can only be dissipated via the enclosure walls, i.e. through convection. Depending on the amount of heat loss of the components, these methods may not sufficiently cool the equipment and a climate control product may be required.

Identifying the proper cooling device depends upon the differences between the ambient temperature (Tu) and the desired enclosure internal temperature (Ti).

An additional factor to consider when choosing a means to cooling is the environment in which the enclosure is installed and the ingress protection (IP) rating required.  Each climate product has corresponding IP ratings:

Other innovative, hybrid cooling technologies have been developed that rely upon two parallel cooling circuits working together depending on the temperature differential. An integral heat pipe dissipates heat from the enclosure when the ambient temperature is below the setpoint, providing passive cooling. Active climatization is achieved when the compressor’s cooling circuit is engaged and provides cooling via speed-controlled components for demand-based cooling. Combining the two circuits reduces temperature hysteresis and provides more precise cooling. Not only is energy consumption far less than with conventional technology, but the improved temperature stability leads to longer service life of both the components within the enclosure and the cooling unit itself.

The reliability of electrical and electronic components in an enclosure can be put at risk not only by excessively high temperatures, but also by excessively low ones. The enclosure interior must be heated, particularly to prevent moisture and protect against frost. It is also necessary to prevent condensation within the enclosure. The latest generation of enclosure heaters has been developed with the help of extensive Computational Fluid Dynamics (CFD) analyses. The positioning of the heater is of fundamental importance for even temperature distribution inside the enclosure. Placement of the heater in the floor area of the enclosure is recommended in order to achieve an optimum distribution of temperature and hence efficiency. Thanks to positive temperature coefficient (PTC) technology, power consumption is reduced at the maximum heater surface temperature. Together with a thermostat, this results in demand-oriented, energy-saving heating.

Smarter, intuitive, and more efficient designs will need to be a staple no matter what setting the enclosure is in.  Designers will need to take careful consideration in the initial planning stages of projects, ensuring that the appropriate cooling technology is incorporated into designs.

ABOUT US

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CMA/Flodyne/Hydradyne is an authorized  Rittal distributor in Illinois, Wisconsin, Iowa and Northern Indiana.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.