Optical and Tactile Seam Tracking for Arc and Laser ... -...

Optical and Tactile Seam Tracking for

Arc and Laser Applications

Tom Graham

Abicor Binzel

FABTECH Canada 2014

Sensor Technology

Sensor Technology for Joining

Seam Finding Touch sensor

Optical systems offline use

Seam Tracking Arc sensor

Optical systems online use

Seam Measurement/Quality Control Optical systems offline use

Sensor

Technology

Tactile

Sensors

Optical

Sensors

Capacative

Sensors

Eddy

Current

Sensors

Others

FABTECH Canada 2014

Why seam tracking?

• Regarding typical robotic and hard automation applications, it is

common to have a very repeatable means of taking the process to the

part. In order to ensure good process control, it is also necessary to

have repeatable parts and tooling to ensure high first pass quality.

• When parts and / or tooling are not robust enough to suit the process

requirements, it then becomes necessary to add other technologies to

address upstream tooling or process limitations.

• Seam tracking is a method in which parts variance can be accounted

for and addressed in automation based systems through 2 main paths:

• Tactile (contact)

• Sensor (vision or other non-contact)

FABTECH Canada 2014

Quality problems in joining technology

Causes of Potential Quality Problems

Tolerances: • Component

• Jig

• Joint preparation

Process influences: • Distortion during welding

• Inaccuracy robot / machine

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Fillet, Lap, Edge Weld

Flange, Coach Joint

Butt Joint

Flange, Coach Joint with offset

Joint Types Overview

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Ideal Situation

Quality problems in joining technology Positioning Errors – Requirement for Sensors in Welding

Normal joint and

programmed

position

Good results

Error Gap

Real position and

programmed touch position

Error Positioning

Poor results

Machines need intelligence to detect changes and errors can

be avoided.

Real situation

Optical seam tracking

FABTECH Canada 2014

Improve weld quality by active positioning of welding head along seam

Able to help reduce thermal distortion through more accurate placement of process energy

Improve first pass quality and throughput

Applicable to all common welding processes

- Laser; MIG; MAG; PLASMA

Applicable for multiple material types.

- Stainless, Aluminum, Steel, etc.

Able to be used with different robot interfaces and analogue interfaces for linear axis

Decreases the programming efforts for complex components

Non Contact Seam Tracking

FABTECH Canada 2014

Theory of Laser Triangulation

Optical Sensor Technology

• The laser beam emitted from a

laser diode is converted by an

optical laser line generator into one

line.

• If this laser line hits a measurement

object, it will be diffusely reflected

in an angle and hits a cloud of

individual, more or less bright

points of light onto the camera chip.

• These individual pixels are filtered

and summarized in an ASIC- Chip.

• The result is a set of row data

representing the real contour of the

measurement object.

FABTECH Canada 2014

Data evaluation takes place in three steps:

1) The laser diode sends light to the

measuring part.

2) Filters (Soft- and Hardware) remove

reflections and all other light

influences.

3) The analysis software is calculating the

tracking point


FABTECH Canada 2014

Types of Optical Sensors


Projection of point movement by scanner - used with He-Ne-Lasers

- for online application, not wide spread

- Old design of Sensor

Line projection - intensity is spread over the laser line – lower at point projection

- Light distribution to the whole field of view

- no moving parts, no mech. wear

- small design

- high frequency of measuring

Projection of point – movement of beam and camera

- high dynamic of light intensity by control of laser power for every point

- High sampling rate by one line detector

- Additional movement of camera is avoiding reflection effects

Detector Laser diode

(cylinder

lense)

Laser diode Scanner Detector Laser

diode Scanner Detector

(one row)

Field of view

FABTECH Canada 2014

One-Line Sensors vs. Multi-Line Sensors

Detail One-Line Multi-Line

Seam geometry information Y,z, gap, area, mismatch, length of laser line Y,z, gap, area, mismatch, length of laser

line

Angles Not available, theoretical about comparing two

or more pictures and robot information

A, B, C right, C left, C total

Measurement redundancy None In every picture

plausibility None, because of missing redundancy Yes, because redundancy

3D applications Only with additional software or multiple part

measurement

Possible, due to all necessary information

in one picture

Arithmetic average Not available, theoretical possible calculating

robot position with sensor measurements

Available

Concave-convex part

detection

Not possible Available, due to distance in x of laser line


FABTECH Canada 2014

Optical seam tracking for arc

welding application

Optical seam tracking for

laser remote welding

application


Tactile seam tracking

FABTECH Canada 2014

The filler wire can be use used as the mechanical sensor. Additional options include use of stylus as tracking mechanism

Telescoping arm and swivel axis compensate for any deviations from the programmed path (lateral and height)

1. Lateral compensation by the swivel axis (Y)

2. Laser/optic motion by robot(X)

3. Height compensation by the telescopic arm (Z)

End result: Lateral and height tracking of the seam

Tactile Seam Tracking

FABTECH Canada 2014

(A) Joints guiding the tip on both sides:

• No lateral Y-force necessary

• Z-force in laser beam direction sufficient

(B) Joints guiding on one side, angular approach:

• No or small lateral Y-force necessary


(C) Joints guiding on one side, perpendicular approach:

• Lateral Y-force in joint edge direction necessary



FABTECH Canada 2014

Left figure:

Without seam tracking at least 4 positions are needed.

Right figure:

With seam tracking, theoretically, just 2 positions are needed

Programming of taught positions

Upper plate

Bottom plate

Bottom plate

Upper plate

50 50 50 50

Simplified Programming by Tactile Seam Tracking

taught positions

programmed trajectory

edge at the seam


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Video front view Video back view


FABTECH Canada 2014


FABTECH Canada 2014

Improve weld quality by active positioning of welding head along

seam.

Reduce thermal distortion through more accurate placement of

process energy

Enables a rigid process to better accommodate variation from

incoming parts.

Applicable to all common welding processes

- Laser; MIG; MAG; PLASMA

Applicable for multiple material types.

- Stainless, Aluminum, Steel, etc.

Type of seam tracking selected is dependent upon what the process

dictates. There is typically no single solution to any process, material,

joint combination (i.e. each has their advantages and limitations).

Technical impact to process can vary based on process selected.

Increases in system complexity require higher skilled technicians to

maintain and support the technology.

Conclusions - Seam Tracking

Thank

You

Presentation by:

Tom Graham

Strategic Account Manager

Abicor Binzel

Cell: 317-850-9929

E-mail: tgraham@ abicorusa.com

LinkedIn: www.linkedin.com/in/tomgraham7295/

Optical and Tactile Seam Tracking for Arc and Laser ... -...

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