Press Brake Application

KTI Technologies,Inc.                                                                                                                      From: SLC2000
Sales - Service - Equipment Installations                                                                                                                                         Phone (732) 446-3933
PO Box 241 Old Bridge, New Jersey 08857                                                                                                                                       FAX: (732) 446-3923

SAFETY LIGHT CURTAINS USED WITH PRESS BRAKE APPLICATIONS

It is important to understand that the use of safety light curtains be in full compliance with current OSHA & ANSI regulations. This responsibility falls onto the end-user of the equipment! The application must be suitable for safety lights and the equipment’s electrical control of the machine to be guarded by the safety light MUST meet all OSHA and ANSI current regulations.

The guarding of power press brakes using safety lights are the most difficult applications to safe guard. The press brake MUST be a part revolution clutch design. This type of design enables the ram of the press the ability to be stopped anywhere within the stroke cycle. If it is NOT a part revolution electrically controlled press brake SAFETY LIGHT CURTAINS CAN NOT BE USE. Other mechanical alternatives for safe guarding the machine must be evaluated!

If the power press brake is of the part revolution clutch design and it’s electrical control meets OSHA and ANSI current regulations safety light curtains are applicable however current OSHA and ANSI regulations govern the use and operating conditions of the safety light curtain.

OSHA and ANSI regulations state that all points of operation ( die pinch points ) be guarded by some approved present sensing device or by a approved mechanical guarding device. To use safety light curtains to guard the front of the power press’s work area the following criteria must exist.

A. The safety light curtain must span and protect the full length of the front and or back of the press brake’s work area. Point of operation areas or pinch points that are not guarded by the safety light curtain must be guarded by some other approved OSHA and ANSI guarding devices.

B. The mechanical positioning of the safety light curtain mounting distance from the point of operation ( this distance is measured from the center of the light curtain, detection area, to the nearest pinch point ) is determine by the actual measure stopping time of the press. The stop time value, measured in milli-seconds, is typically measured periodically, according to OSHA and ANSI regulations, using a portable stop time measurement device or by a stand alone permanent time based brake monitor mounted on the machine. Refer to OSHA and ANSI regulations for brake monitoring. ( All hand in die secondary operations require a time based brake monitor ). When the stop time value is determined this value is used in a OSHA & ANSI equation to determine the mechanical position of the safety light curtain from the point of operation. The philosophy behind this safety distance is to ensure that the mechanical system will physically stop prior to a body part or object reaching the point of operation. KTI Technologies is a manufacture of Time Based Brake Monitors and portable Stop Time Measurement devices.

C. The safety light vertical guarding height must be of proper size to ensure once the safety light is mounted that a person can not reach over or under the safety light curtain and reach the point of operation. In order to determine physical required sizing a measurement must be taken from the top of the bottom bed to the bottom of the ram when the ram is at top position and the stroke adjustment is adjusted fully upward. With this measured value typically 6 inches is added and this new value becomes your minimum vertical height requirement for the safety light curtain. When the safety light is mount typically 3 inches of the guarding area falls below the bottom bed and 3 inches of the guarding area is above the ram when at top position. By over extending the protection area above and below typically accounts for detection of angular intrusion above and below the work area. And as per OSHA and ANSI regulations you CAN NOT reach over or under the present sensing device to reach the point of operation.

D. As mentioned previously the guarding of power press brakes using safety lights are the most difficult applications to safe guard. OSHA and ANSI require that the end-user completely guard the point of operation. But under normal press brake operation you need to turn off the safety light curtain so to position and hold your work piece so that you can complete the work. However by turning off the safety light curtain you are no longer protecting the point of operation. Understanding this condition OSHA and ANSI regulations allow the muting of the safety light curtain at ¼ inch before die closure. At a ¼” before die closure the work piece can be position between the upper and lower die and leave little or no addition space for a finger or body part to be present. To accomplish this an additional control source is required to signal the safety light curtain to turn off at the ¼ inch position. This ¼ inch position however does not remain constant and changes each time a new die set is installed and the re-adjustment of the ram’s shut height is change to compensate for the new die height. Therefore the additional control source must have the ability for adjustment and be adjusted each time a new shut height is set to ensure that the safety light curtain is ONLY muted or turned off at no greater than ¼ inch before die closure.

On some presses the manufacture supply a PLS or press control contacts that are adjustable for the use of safety light muting requirements. On press that do not have this capability an additional stand alone muting package can be added that will signal the safety light to turn off and this device has the ability to be adjusted to maintain the OSHA and ANSI ¼ inch die positioning requirement. KTI Technologies is a manufacture of safety light curtain muting control devices.

It is recommended that safety lights with blanking capability be used so that the area selected for blanking and ¼ inch muting is the same area. In this manner only the area of the light curtain selected for blanking will be turned off by the muting control package leaving the other area of the light curtain still active.

APPLICATION SUMMARY:

1: The press brake MUST INCORPORATE A PART REVOLUTION CLUTCH DESIGN!

2. Determine the full scanning distance for the Safety Light Curtain.

3. Determine the actual mechanical stop time of the press for mechanical positioning of the Safety Lights.

4. Determine the minimum vertical guarding height.

5. Determine the operation for safety light curtain muting at ¼ inch die closure.

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