Archive for January, 2012

maxon’s Modular Spindle Drives

Mechanical engineering often faces the task of converting rotational movements into powerful linear movements. The associated development costs can now be cut dramatically by using modular spindle drives in maxon motor’s modular system.

maxon's modular spindle drives the GP 22 S and GP 32 S

The GP 22 S and GP 32 S gearheads, specifically adjusted for spindles, are designed to withstand high loads, and the special spindle intake means that customer-specific spindles can be assembled with ease in significantly less time.

There are three different standard spindle types to choose from: metric spindles, trapeze spindles and spherical rotating spindles. The spindles are available in steel or ceramic variations up to 200 mm in length and supplied with matching Spindle nuts.

Gearheads, motors, encoders and controllers from maxon’s standard program are used to drive the spindles. The individual components of the spindle drives are all compatible to help create highly effective drive solutions. These modified planetary gearheads are available in two different sizes, with diameters of 22 mm and 32 mm. Reduction ratios of 3.7:1 to 1093:1 provide maximum torques up to 6 Nm and speeds of up to 1600 min-1. The additional axial bearings of these gearheads can also withstand powerful axial forces from the spindles.

 Depending on the application, maxon’s DC brushed or brushless motors may be used to drive the system. Motors may be fitted with compatible encoders which is critical for accurate positioning. The EPOS positioning controller is recommended to control the motor-encoder combination. It can also directly evaluate end-switches and other sensors. If a standalone system is desired, the programmable EPOS P variation may be used.

For more information on Maxon’s Spindle Drives, click on the link below:
 http://www.electromate.com/products/series.php?&series_id=102232   

EDITORIAL CONTACT:
Warren Osak       
sales@electromate.com
Toll Free Phone:   877-737-8698  
Toll Free Fax:       877-737-8699
www.electromate.com

maxon academy – start you’re e-learning now!

Have you heard about the maxon academy?  It is a unique tool that helps you deepen your knowledge on drive technology. The maxon academy is a training platform that offers printed publications, e-learning modules as well as seminars all centered around motion control. Choosing the right combination of motors and controllers is crucial in any application and this platform will help you gain the knowledge you will need to select the perfect combination for your unique application.

A part of the maxon academy’s e-learning modules that may be of particular use to you are the in-depth presentations by Dr. Urs Kafader on motor data, drive selections and thermal calculations.  These presentations breakdown the most important information into an easy-to-understand format that further explains all of the factors that need to be taken into consideration when you are selecting the appropriate drive technology to meet your individual needs.

Interested in learning more?  Visit us online!  And feel free to comment here with any questions you may have, our experienced applications engineers are here to help!

EDITORIAL CONTACT:
Warren Osak       
sales@electromate.com
Toll Free Phone:   877-737-8698  
Toll Free Fax:       877-737-8699
www.electromate.com

Linear motor Lowdown

Linear motors have earned a reputation as highly precise and efficient alternatives to conventional rotary-to-linear transmission systems. Find out why, plus learn about the ultra-precise and energy-efficient linear shaft motor.

To fully appreciate the chief advantages of linear motors, it is helpful to compare them to ballscrews, another high-precision rotary-to-linear transmission system. Although typical ballscrews are roughly 90% efficient, servomotor efficiency (typically 75% to 80%) — plus losses introduced by the coupling and gearbox — reduces the power supply going toward actual work to 55% in some cases. In comparison, typical linear motors drive loads directly, which boosts overall efficiency.

When the flat iron core motor (bottom) was introduced, it was more efficient than alternate forms of linear motion systems. However, in time, tubular linear motors (top) have proven to be much more efficient, producing far fewer eddy currents and eliminating cogging issues.

Linear motor evolution

Linear motors are sometimes described as rotary motors cut open and rolled out flat. In fact, some of the first linear motor designs are just that. When the iron core “flat linear motor” with this design made its debut, it earned market share as a powerful and efficient alternative to other forms of linear transmission systems. However, its efficiency is limited by losses caused by eddy currents and cogging, which in turn limits this motor’s suitability for high-precision applications.

Next, the coreless (U-shaped) linear motor was developed to address the iron core motor’s problem areas. The “U” has its own advantages and drawbacks: The innovative U-shaped design addresses the losses from eddy currents and cogging, but can introduce lower motor stiffness and greater heat generation, which limits its use in ultra-high-precision applications.

For these ultra-high-precision uses, linear motors first appeared to be the Holy Grail of motion control, offering the promise of infinite positioning options and super-high efficiency. However, in some arrangements, heat from the motor’s inefficiency is channeled directly to the work point. This increases the amount of work the linear motor is able to perform, but thermal growth caused by the generated heat complicates submicron positioning.

Subsequently, linear shaft motors were developed. These units consist of a stack of permanent magnets contained in a tube, plus a forcer of cylindrically wound coils. As we’ll explore, linear shaft motors are optimized for the most power-efficient linear transmission possible, while also maximizing stiffness.

The linear shaft motor uses the repelling nature of like magnetic poles to optimize magnetic field strength. By kinking and redirecting the magnetic field, maxiumum strength is located at the current crossing point.

Motor design 101: Lorentz law and Fleming’s law

The basic law behind motor design is Lorentz force law. This law states that the amount of force (F) a motor can generate is equal to the current (I) in the winding, times the magnetic field strength (B), times the vector cross product (X), times the length of wire in the wire spool (L).

Therefore, in order to develop a more efficient linear motor, the amount of current (I) must be reduced. To do this — while maintaining the same force output — the remaining variables of Lorentz force law must be both increased and optimized.

A recent study by University of Virginia (UVA) researchers found that the linear shaft motor uses roughly 50% less input power to achieve the same work output of a comparably rated coreless linear motor. We will now explore each aspect of Lorentz force law and see how the design achieves this efficiency boost.

The vector cross product (X): Fleming’s law (often called the left-hand rule) helps us to understand that the optimal crossing vector for current to cross the magnetic field in order to create linear motion is 90°. The design of a traditional linear motor arranges the coil to have between 30% and 80% of its length at a 90° angle to the magnetic field. The rest of the coil is basically a return path, which creates losses due to added resistance. In addition, this return path can generate renegade forces that oppose the intended forces. In comparison, the cylindrical design of the linear shaft motor allows 100% of the coil to be at the optimal 90° crossing vector. No additional forces are generated besides the intended linear force.

Length of wire in the wire spool (L): This is where the design gets tricky. Adding too much length increases losses due to added resistance. The linear shaft motor balances length of wire with losses due to added resistance. In the motors tested by UVA, the coil length of the linear shaft motor is about 1.5 times the length of the coreless linear motor.

The magnetic field strength (B): Whereas most linear motors use back iron to redirect the magnetic field, the linear shaft motor features a magnetic pattern that uses the repelling nature of the like magnetic field to optimize magnetic field strength. Kinking and redirecting the magnetic field ensures that the maximum field strength is located at the current crossing point.

The amount of force developed in a given magnetic structure is a function of the flux density at the air gap between the components that move relative to the stationary segment. Because the reluctance of air is roughly 1,000 times greater than that of steel and directly proportional to the air gap length, minimizing it reduces the magnetomotive force (MMF) required to generate a given field strength. MMF is also a direct function of the amount of current supplied, so reducing this parameter dramatically decreases power losses — as the losses are proportional to the square of the current.

Practical matters

How is linear shaft motor efficiency useful and practical in general automation? To find out, let’s consider two aspects of critical importance to engineers who specify motors: Heat and lifetime cost.

All linear motors heat up, due to wasted energy. When this heat is generated, it must go somewhere. The first major side effect of heat is thermal growth of the load to which the coil is attached. Further, the bearings, grease, and any sensors in the general area are also subjected to this excess heat. Over time, heating and cooling cycles can have negative effects on both mechanical and electronic components. In addition, thermal growth is likely to cause issues with binding and increased friction.

The Linear Shaft Motor (tubular style servomotor)from Nippon Pulse achieves submicron resolution and can be operated at nearly half the cost of a coreless lenear motor. It was designed in partnershiip with a number of machine tool manufacturers for efficiency and stiffness.

UVA testing confirms that even when both motors are attached to identical plates — with equal temperature rise within the coil – the heat transferred from a linear shaft motor is about 33% less than that from a comparably rated coreless linear motor. (In the UVA tests, the plates measured 100 × 150 × 10 mm. Both motors operated at 10 lbs of force for 24 hours. Temperature rise at the coil registered 41.3° C; at the coreless linear motor plate, 30.8° C; and at the linear shaft motor plate, 23.1° C.) 

By requiring less energy, the cost of operating the system also decreases. Assuming the U.S. average cost per KwH of 12.17 cents, the annual operating cost of a coreless linear motor is $540.91, while the operational cost of the linear shaft motor is $279.54, measured at the ac supply to the servo drive.

Reprint of Motion Systems Design article by Jeramé Chamberlain Nippon Pulse America Inc. Radford, Va. | Dec 1, 2011

For more information on Nippon Pulse America’s Linear Shaft Motors available from Electromate, click on the link below:
 http://www.electromate.com/products/?keyword=linear+shaft+motor&d=105293

EDITORIAL CONTACT:
Warren Osak       
sales@electromate.com
Toll Free Phone:   877-737-8698  
Toll Free Fax:       877-737-8699
www.electromate.com

Zaber’s A-LST-C Series High Load, Motorized Linear Stages with Dust Covers

Device Overview:

  • 254, 500, 750, 1000 and 1500 mm travel 
  • 100 kg load capacity 
  • Up to 420 mm/s and up to 560 N thrust 
  • Built-in controller; daisy chains with other A-series and T-series productsDescription:Zaber’s A-LST-C stages are computer-controlled and have travel ranges from 254 mm up to 1500 mm. These stages are available with various leadscrew pitches so you can select the device with the resolution and speed capability that you need. Zaber’s innovative stage design is capable of speeds up to 420 mm/s, and can support loads up to 100 kg. The flexible, stainless steel dust cover protects the internal lead-screw and bearings.

For more information on Zaber’s A-LST-C Stages, click on the link below:
 http://www.electromate.com/products/series.php?&series_id=105501     

EDITORIAL CONTACT:
Warren Osak       
sales@electromate.com
Toll Free Phone:   877-737-8698  
Toll Free Fax:       877-737-8699
www.electromate.com

Introducing GalilSuite Software

Galil has recently released GalilSuite Software, a new version of GalilTools, providing a more powerful and flexible tool for configuring, analyzing and tuning Galil motion control systems. GalilSuite includes enhanced servo tuning capabilities with multiple tuning methods and allows the various analysis tools such as the scope, tuner and terminal tools to be executed individually. The new software also allows multiple connections to be made from GalilSuite to multiple controllers. The GalilSuite software package provides five tools for working with Galil controllers:

GalilSuite Software

Terminal – for entering and receiving controller commands

Editor – for writing, saving and executing application programs

Tuner – for selecting controller PID parameters for optimal servo system response

Scope – for plotting controller data such as motor position and velocity

Watch – for displaying controller and I/O status

In GalilSuite each of these tools are independent and can be launched and run individually. This feature makes it easier for the design engineer to create a flexible development environment for testing control systems. Individual tools can be shown in a full screen for the best viewing, while other tools may be minimized or not executed at all.

A new feature of the Terminal Tool is the Command Helper with Syntax checker. The enhanced Editor Tool is full featured and provides cut, paste, copy, insert and find/replace functions in addition to a syntax helper which includes label detection and syntax help. Another new feature of the editor is that it allows for a collection of programs to be saved in a project and multiple projects can be created.

The Tuner Tool provides numerous methods for servo tuning including Crossover, General, Curve Follower and Manual that allows the user to select the optimum method for the system. The user can also select the final test profile as a sine wave, step response, profiled move or custom user code. For each method, the tuner scope captures and displays the controller command position, encoder position, position error and torque in response to the specified test profile. The Manual Method has advanced settings that allow parameters such as feedforward, notch, poles and integrator limit to be specified.

The Scope Tool is easier to use and has more features than the previous version. One enhanced feature is that a virtually unlimited number of traces can be displayed. The scope also provides a drag and drop feature allowing selection of a parameter from the controller data record by dragging it into the scope display. The scope has better triggering for data capturing and a snap feature for viewing specific data points that have been captured.

The improved Watch Tool provides an easy-to-read display of various controller data such as controller and amplifier status, I/O, and motion parameters. Digital input and output status is displayed with virtual LEDs. Data such as axis position and error are shown in numeric format in a table. The update rate of the data capture is selectable.

GalilSuite software is in BETA release and is available for free download to users of Galil controllers. GalilSuite currently works with Windows 7 or Windows XP operating systems (Mac and Linux support will be available in the future) with current generation Galil controllers. More information and the BETA download can be found at: http://www.galilmc.com/support/software-downloads.php

Click on the link below for additional information-

Galil’s Motion Controller Family

For more information, please contact:      

EDITORIAL CONTACT:
Warren Osak       
sales@electromate.com
Toll Free Phone:   877-737-8698  
Toll Free Fax:       877-737-8699
www.electromate.com


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