Introduction

The purpose of this article is to explain the draw-wire sensor kit and the ignore next bend push button kit.  Discussed will also be the purpose and application for use on short stroke, linear movement machines (such as brake presses and folding machines).  

These kits are designed to be used on legacy machines that will be connected using our T4 or U3 supplied I/O modules.

Both kits were designed out of necessity to capture accurate bend count, with any number of accumulated bends equal to one part.  Prior attempts at capturing bend count were unsuccessful as most signals were not accurate.

Topics covered in this article: 

• Theory of operation
  • Application
  • Purpose
  • In Use
  • Adapter Script

Theory of operation

Draw Wire Sensor:

• • Note:  This sensor stroke is 0 to 40 inches which scales to the 0-10vdc analog signal.

Ignore Next Bend pushbutton:

• The "ignore next bend" lighted pushbutton was designed to work in conjunction with the draw wire sensor to "ignore" the next bend (or fold) if a re-bend is required. 

• This is usually required if the tooling or ram did not make the bend fully and operator needs to re-start that bend.

• The operator will normally need to go to the machine's operator panel and revert the sequence back one cycle.  The Ignore Next Bend pushbutton is normally placed near the operator station to allow the operator to press this pushbutton after the sequence is stepped back.
• The pushbutton is lighted and will stay lit until the next bend is made.  The pushbutton can also be turned off manually by pressing one more time to de-activate the Ignore Next Bend function.

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Application

Typical uses:

• Press Brake (40inch linear travel or less)
• Folding machines (manual types 40inch linear travel or less)
• Slow moving stamping machines (40inch linear travel or less)
• Hot press or plastic molding machines (40inch linear travel or less)

Examples:

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Purpose

• To measure ram (or linear) movement and convert that physical travel to 0-10vdc analog signal.  
• This signal is then scaled and a voltage threshold is set in the adapter script (usually just after the linear measurement has reach its farthest point and is returning to its starting position).

Prior to the sensor, the approach was to connect to the foot pedal or a hydraulic sensor measuring amperage to the pump.

The following graph shows the signal from a foot pedal connection on a press brake.  The part being made required 5 bends, but the foot pedal did not accurately give a usable pulse and the cycle count was not accurate.

After installation of the draw wire sensor, the ram movement is measured and the signal is not dependent on how many times the operator presses the foot pedal or how much pressure is placed on the hydraulic pump (or current load to the motor).

The result is a clean, easy to capture peak signal which allows for voltage threshold setting.

The following graph shows the same 5 bend part being made, but is now capturing the movement of the ram.

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Adapter Script

#Draw Wire Sensor and Ignore Next Bend pushbutton adapter script
#Date added: 2022-11-08
#Last revised by: C.Shaffer
#Date Revised: 2022-11-16
#Revision Detail: Updated the Ignore Next Bend pushbutton logic


version: 2

#FLEXIO DIGITAL OUTPUT

pins:
FIO4: #Output to Labjack Relay Driver board
mode: digital
direction: output
value: pushbutton-in

#FLEXIO ANALOG INPUT

FIO6:
mode: analog

variables:

#ANALOG INPUT SAMPLES

bend_count_sample: #[INPUT] Analog 0-10vdc from draw wire sensor [OUTPUT] analog 0-10vdc = 0-40 inches of travel
- source: AIN2
- resample: 0.1
- min-delta: 0.1
measurement_sample: #[INPUT] Analog 0-10vdc from draw wire sensor [OUTPUT] analog voltage * 3.93 = inches of travel
- source: AIN2 * 3.939
- resample: 0.5
- min-delta: 0.3
pushbutton_sample: #[INPUT] Discrete 24vdc from Ignore Next Bend normally open pushbutton contact
- source: FIO6
- resample: 0.1
- min-delta: 0.1

#ANALOG INPUT to DIGITAL

bend-count:
- source: bend_count_sample
- threshold: 2.5 #voltage threshold will need to be adjusted based on the bend point (voltage) at BDC (Bottom Dead Center)
# - invert #Used if sensor signals need to be inverted
- falling-edge #bend count threshold set on the falling edge of the signal
- and: not pushbutton-in
- count
pushbutton-cancel:
- source: bend_count_sample
- threshold: 2.5
# - invert #Used if sensor signals need to be inverted
- falling-edge
- off-delay: 0.25
pushbutton-in: #Ignore Next Bend push button toggle ON
- source: pushbutton_sample
- threshold: 2.4
- toggle:
default: false
reset: pushbutton-cancel


#EXECUTION

execution:
- source: AIN2 #[INPUT] Analog 0-10vdc from draw wire sensor [OUTPUT] analog 0-10vdc = 0-40 inches of travel
- min-delta: 0.25 #monitors change in voltage and is TRUE when > 0.25vdc is detected
- value-change
- off-delay: 5 #5 sec off delay
- state:
- ACTIVE: this
- READY: true


#DATA MAPPING

data-items:
- execution
- bend_count_sample
- bend-count
- pushbutton_sample
- measurement_sample

In Use

Shown below is a preview of the draw wire sensor mounted on a Cincinnati press brake.  

The ignore next bend push button is demonstrated in the second video.  

• Note:  Once the bend is made (and voltage threshold is met), the push button light will go out.

Videos:

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