UNITROL announces a new safety function that is now standard on all 9180 series SOLUTION controls without extra cost. This patent pending function keeps the electrode force very low until it is safe to apply full welding force. Existing SOLUTION controls can also be upgraded for this SOFT TOUCH function. The SOFT TOUCH system cannot be installed on any other brand welding control.
HOW IT WORKS: After initiation, electrodes start to close under LOW FORCE. A Unitrol TOUCH SENSOR system decides when the electrodes have closed on or near the metal being welded. If an obstruction is detected prior to closing, the electrodes will go back to the fully opened position. No adjustment of SOFT TOUCH is needed when changing welding force or electrode spacing.
The system is field adjusted (lockable settings) so that force between electrodes for the advance portion of the stroke remains low enough to avoid major injury to the operator’s fingers. For press welders, this will even reduce force between electrodes to considerably less than the dead weight of the ram.
FAIL SAFE SYSTEMS:
If the sensor switch is already closed when the welder is being initiated, the electrode will not even start to move, and the display will show which sensor input is closed at that time.
If the sensor wires from the SOFT TOUCH system have become disconnected or are making poor contact, the electrodes will close under low force and then return after a short field-settable delay (1-999 cycles).
WHAT HARDWARE IS NEEDED: To make this system operate, you will have to add a 5-way externally piloted solenoid valve, a shuttle valve, and a precision pressure regulator system to an existing 4-way externally piloted (or direct acting) solenoid valve. Unitrol offers three kits for easy installation:
HEAVY WEIGHT RAMS: This #9181-34W kit is used on:
PRESS WELDERS that have dead weight (with air disconnected from welder) of over 50 pounds. The kit is factory pre-plumbed for fast installation and includes all necessary components and interconnecting tubing.
LIGHT WEIGHT RAMS: This 9181-34Y kit is used on:
LIGHT WEIGHT GRAVITY-DROP RAMS: This #9181-34H kit is used on:
PRESS WELDERS that have dead weight (with air disconnected from welder) of less than 50 pounds and drops smoothly by gravity. The kit is factory pre-plumbed for fast installation and includes all necessary components and interconnecting tubing.
REDUNDANT SENSOR: You can also add your own proximity switch or LVD system adjusted to close a switch when the electrodes are less than ?? apart to the system. The SOLUTION will not turn on the high-pressure valve until both metal is detected and the proximity switch has been closed. This is often useful for applications where the parts being welded are not flat prior to the welding process.
By Roger Hirsch, President, Unitrol Electronics Inc.
Last fall we received a panic call from a company that had a large number of our Unitrol SOLUTION resistance welding controls. After two accidents in their resistance welding department within a two-month period of time, OSHA was threatening to close their welding department down if an acceptable way of guarding the welder’s electrodes could not be found.
THE PROBLEM: Because of the parts being spot welded, the welder operators had to hold parts in a way that put their fingers close to the electrodes. They tried to change the fixtures so that a margin of safety was achieved, but that only slowed down production and was not even possible for the majority of parts being welded.
He explained that a safety system had to be installed that did not depend on any operator settings or adjustments. And when electrodes were changed or holders were adjusted to alter the electrode spacing, the safety system had to continue to operate without the need to make adjustments
FIRST IDEA: The first attempt at finding a solution was to use a light curtain to protect the area between the electrodes. However this idea was quickly abandoned when they realized that the operator had to hold and move parts near the electrode and would be in the light curtain zone. Also when jobs were changed and the electrodes adjusted, very fine tuning of the light curtain system would have been required.
SECOND IDEA: They then decided to install a ring guard system. With this type of guard, a wire loop on the end of a rod is set around the top welding electrode. The loop is sent downward at the beginning of each weld before the electrode starts to move. The electrode will not close if the loop stops short of a set distance (as would happen if the loop contacted a finger).
Ring guard systems were installed on six welders and then shown to the OSHA advocate. He said this application of a ring guard would not pass an OSHA inspection. The problem was that a ring guard could be easily defeated by the operator. Also he pointed out that the actual safety value of a ring guard was completely dependent on the mechanical adjustment of the wire ring by the setup person. In other words, the only time it was safe was when the ring was set at the proper height and the operator did not bend or rotate it out of place.
The OSHA advocate told them that they had to find a FULLY PASSIVE SYSTEM.
He explained that a safety system had to be installed that did not depend on any operator settings or adjustments. And when electrodes were changed or holders were adjusted to alter the electrode location, the safety system had to continue to operate without the need to make adjustments.
THE SOLUTION: Unitrol took up the challenge and developed SOFT TOUCH, a fully passive patent-pending system that provides very low electrode force when the area between the electrodes is not safe, and only applies full electrode force when it is safe to do so. This new development was done using electronic sensing rather than mechanical switches or moving parts.
HOW SOFT TOUCH WORKS: SOFT TOUCH is a fully passive fail-safe system that is controlled by the Unitrol SOLUTION welding control. Because SOFT TOUCH is part of the control and not just an add-on system, it is fully integrated into the welding sequence. This means that the system works right out of the box without the need to wire together and program multiple components.
SEQUENCE: When the foot or hand switch is closed to start a weld
REDUNDENT SYSTEM: If desired, a limit switch can be added to the welder and adjusted to close when the space between the electrodes is less than 1/4″. In this case, the SOLUTION control has to see both that there is metal between the electrodes and that the limit switch has been closed. This is useful where the weld surfaces on parts, such as C-shaped loops, are not touching at the start of a weld sequence and use the electrodes to push them together.
FULLY PASSIVE: There are no operator adjustments. Even if electrode height is changed or welding pressure is adjusted, the SOFT TOUCH system operates without any setting changes. In fact, there is nothing for the operator to adjust. All settings are locked in the cabinet.
THE RESULT: The company installed SOFT TOUCH on one welder, and it cleared the OSHA advocates inspection. They eventually installed 22 systems and are back to operating on a 3-shift production schedule.
ADDING SOFT TOUCH TO YOUR WELDER: The SOFT TOUCH system is NOW available for installation on new and existing Unitrol SOLUTION welding controls as well as non-Unitrol brand controls. The kit includes a padlockable NEMA-12 enclosure that houses the precision pressure setting components, and special valves that are to be added to the welders existing solenoid valve (please note that this will not be included when adding SOFT TOUCH to a non-Unitrol brand control).
SEE THE MOVIE: You can see a short video of SOFT TOUCH as well as OSHA information that relates to resistance welder guarding.
T. J. Snow can help you size a SOLUTION control with the SOFT TOUCH feature for any spot welder including PRESS WELDERS, ROCKER ARM WELDERS, and TRANS-GUNS.
Disclaimer/Note: Even with SOFT TOUCH installed, you should never test the functionality of the system by putting any part of your body between the weld tips.
SOFT TOUCH installed on a 200KVA press welder
The padlockable NEMA-12 regulator box used by the SoftTouch system.
SOFT TOUCH can only be used when connected to Unitrol controls. Because of liability concerns, SOFT TOUCH cannot be connected to other brands.
Successful operation of a SOFT TOUCH system requires three things:
SOFT TOUCH depends on reading electrical continuity between the electrodes. If the material being welded has a coating that does not easily conduct electricity, the SOFT TOUCH sensor will not consistently see continuity, and the system will not operate successfully.
Material that might cause problem include HOT ROLLED STEEL (that has not been pickled), wire that has a drawing soap or wax coating, metal with oxide coatings, and rusty metal.
If in doubt, submit some sample coupons of the material being welded to Unitrol for evaluation before quoting a system.
SOFT TOUCH can be added to any existing UNITROL control. Contact TJ Snow and provide the serial number of the control. We will let you know what cost is involved to add SOFT TOUCH.
Use the following steps to select the appropriate SOFT TOUCH option to match your customer’s welder:
|TYPE OF WELDER||ELECTRODES CLOSE SMOOTHLY BY GRAVITY* THEN, FORCE BETWEEN ELECTRODES IS MORE THAN 50LBS||ELECTRODES DO NOT CLOSE SMOOTHLY BY GRAVITY*
IF A PRESS WELDER, RAM WEIGHS LESS THAN 50LBS
|RAM WEIGHS LESS THAN 50LBS AND FALLS QUICKLY BY GRAVITY*|
|PRESS OR PROJECTION WITH 5″ DIAMETER
OR SMALLER STANDARD CYLINDER
||#9181-34H. This includes a parts kit easily installed by the customer.|
|PRESS OR PROJECTION WITH 5-1/2″ DIAMETER
OR LARGER STANDARD CYLINDER
|ROCKER ARM WITH 5″ DIAMETER OR SMALLER
CYLINDER-PRESS OR PROJECTION WELDER WITH
FIXTURE TYPE CYLINDER (SavAir, Grossel, OHMA, etc.)
|ROCKER ARM WITH 5-1/2″ DIAMETER
OR LARGER CYLINDER
Contact T. J. Snow today for more information about how SOFT TOUCH can be used in your resistance welding process to improve safety.