Understanding Wireless Handwheels

Canadian Industrial Machinery asked Heidenhain Corp. National Sales Manager Chris Weber to explain

January 1, 2011

With wireless technology there is no risk of getting a handwheels cable tangled in the machine or workpiece.

The HR 550FS wireless handwheel system was designed to allow the machine operator unrestricted freedom of movement within the working space.

CIM: How important are sightlines when machining?

Weber: They are especially relevant on large machines because the operator needs to move freely around the workpiece while maintaining control of the machine. When manually positioning a machine for datum setting or probing, it is always best to be in close proximity to the part that is being interacted with.

It is not best machining practice to move a machine when you cannot clearly see potential impact points. With cabled handwheels there is always the risk of exceeding the cable length or having the cable get hung up on the machine or workpiece.

CIM: How was the handwheel developed?

Weber: The HR 550FS wireless handwheel system was designed to allow the machine operator unrestricted freedom of movement within the working space. On large machines that require the machine operator to control and influence the machining process in the working space, wireless operation is not only more convenient, but also safer. Stumbling blocks and the risk of getting caught in long handwheel cables are avoided.

CIM: How does the wireless handwheel communicate with the machine?

Weber: For radio communication, the wireless handwheel system uses 2.4-GHz ZigBee® transmission technology with a special proprietary communications protocol.

CIM: How do you know if you can use one?

Weber: The following procedure is very important to determine whether a wireless handwheel system can be used in a certain radio environment:

Step 1. Ascertain permission for use of the 2.4-GHz ISM band by the wireless handwheel system in your area.

Step 2. Identify known radio participants at your site. Ideally, you can provide information regarding the availability of the 2.4-GHz ISM band at the intended place of use of the wireless handwheel.

If you cannot identify the devices using the 2.4-GHz ISM band at the intended place of use, we recommend making measurements with a suitable spectrum analyzer and a WLAN detector.

These detectors can obtain a usage profile of the 2.4-GHz ISM band. By means of these devices, occupation of the frequency spectrum by other devices can be identified sufficiently, and other WLAN networks that could disturb communication can be detected.

Step 3. Select an available radio channel for the wireless handwheel system.

Step 4. If no available radio channel can be found despite these measures, we advise against using the wireless handwheel system.

CIM: What are the transmission limits for this device?

The handwheel's display consists of a header and six status lines.

Weber: The wireless handwheel system currently is available only in combination with the iTNC 530 control. If several wireless handwheel systems from Heidenhain are to be used within a certain range, an individual, free channel must be selected for each wireless handwheel system.

CIM: What is the role of the docking station?

Weber: The docking station serves two purposes. It recharges the batteries in the handwheel and it serves as the wired interface to the control system.

The wireless handwheel has a rechargeable battery for mobile operation on the machine. During operation it continuously communicates via radio with the docking station, which communicates directly with the control via a serial cable connection.

To ensure the required, unambiguous assignment of the handwheel to the docking station, so-called “pairing” is carried out during commissioning.

Once they have been paired, a wireless handwheel and a base station can be operated only with the assigned device. For reasons of security, paired devices are also marked optically with the five colored stickers included in the delivery. After successful pairing, the stickers must be affixed to the wireless handwheel system.  Available colors are gray, blue, red, green, and yellow.

CIM: What is the benefit of the mechanical detent option?

Weber: Mechanical detents provide a tactile indicator of distance traveled. One “click” can be programmed to equate to a specific increment of travel.

CIM: What information is displayed?

Weber: The handwheel display consists of a header and six status lines.

The header provides information on the active radio operation, field strength, and the battery’s state of charge.

The status lines display important machine conditions and information, such as position of the selected axis, spindle speed, feed rate, error messages, active basic rotation, and tilted working plane. They also show the functions of the five soft keys, which the machine manufacturer can assign as desired.

The colored, raised axis keys permit traverse of up to six NC axes. In addition, the machine manufacturer or integrator can configure an axis key for selection of the so-called “virtual tool axis.” In addition to the soft keys, the machine manufacturer can assign special functions to the six function keys. They also can be illuminated by LEDs.

The axis feed rate is activated when the arrow key is pressed, and each spindle speed can be set with an override potentiometer.

The handwheel also features the usual safety elements such as an emergency-stop button and two permissive buttons.

For more information, visit www.heidenhain.us.