Feed Axis Control Device Overload Protection

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Solution Overview

Problem

Electrically driven feed axes in production machines, such as stamping and forming machines, face reliability issues during setup due to mechanical blockages and overloads, which can lead to motor damage or failure from excessive current flow and heat buildup, especially when material properties and temperature variations are involved.

Innovation Solution

An axis control device implements a position correction method that detects overload through parameters like temperature, current, voltage, or force, and adjusts the target position to reduce load by reversing the movement direction, thereby lowering current and heat input, ensuring the feed axis operates within safe limits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the control system applies full load to the drive to reach the target position, then the positioning speed and force increase, but the current flow increases three times higher than permissible, causing motor overheating and potential damage

Engineering Contradiction:
Improvepositioning speedVSAvoidmotor reliability
Core Design Contradiction:
SpeedVSReliability

Solution Approach 1:

The control system dynamically adjusts the target position based on real-time load detection. When overload is detected, the system automatically corrects the target position to reduce load, creating a dynamic adaptation mechanism that prevents motor damage while maintaining positioning capability

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system implements continuous feedback through load detection devices that monitor current, torque, or temperature. This feedback loop enables the control system to detect overload conditions and automatically correct the target position, preventing motor overheating and damage

Inventive Principle:
Principle #23Feedback

2Force

If the axis operates at maximum current to overcome mechanical blockage, then the force to overcome blockage increases, but the temperature of the induction coils rises rapidly above permissible limits

Engineering Contradiction:
Improveaxial forceVSAvoidmotor winding temperature
Core Design Contradiction:
ForceVSTemperature

Solution Approach 1:

The system prepares for potential overload by implementing preventive measures through load detection and automatic target position correction. This cushioning approach prevents the motor from entering dangerous temperature zones by anticipating and correcting overload conditions before they cause damage

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The control system changes operating parameters by adjusting the target position in response to detected overload conditions. This parameter change reduces the current and temperature parameters to safe levels while maintaining the ability to overcome mechanical blockages when necessary

Inventive Principle:
Principle #35Parameter changes

3Manufacturing precision

If the target position is manually adjusted to an inaccessible position, then the positioning precision improves, but the feed axis experiences maximum load continuously, leading to motor overheating and failure

Engineering Contradiction:
Improvepositioning precisionVSAvoidaxis reliability
Core Design Contradiction:
Manufacturing precisionVSReliability

Solution Approach 1:

The load detection device provides continuous feedback on the axial load, enabling the control system to detect when the feed axis is under maximum load due to manual positioning. This feedback triggers automatic target position correction to reduce load and prevent motor failure

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts the target position based on real-time load conditions. When maximum load is detected from manual positioning, the system automatically corrects the position to reduce load, creating a dynamic safety mechanism that preserves both positioning capability and motor reliability

Inventive Principle:
Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution effectively prevents axis failure by reducing load and heat, allowing safe continuation of the setup process without altering the setup sequence, thereby enhancing the reliability and safety of the feed axis during production.

Implementation Method 1

Load detection can, for example, involve temperature measurement in the feed axis, particularly at a motor winding of an electric motor in the feed axis

Methodology Applied
Scientific EffectTemperature measurement: Thermography

Implementation Method 2

electrical control parameters for the electric motor can be used as a measure of the load, in particular the current or voltage across a motor winding

Methodology Applied
Scientific EffectCurrent measurement: Ohmmeter

Implementation Method 3

force or torque measurement to determine the forces or torques exerted by the feed axis

Methodology Applied
Scientific EffectForce measurement: Force

Implementation Method 4

A maximum current that is completely converted into heat causes the temperature of the induction coils in the electric motor to rise rapidly above a permissible temperature limit

Methodology Applied
Scientific EffectJoule heating: Joule Heating

Data Source

PatentEP2762987B1Method for increasing the fail safety of a feed axle and axle control device
Publication Date: 2019.08.07 OTTO BIHLER HANDELS BET
  • EP2762987B1 patent drawingFigure 1

AI summary

The method involves carrying out load-dependent position correction of the target position during overload by the axis control unit in order to reduce the load of the feed axis. The axis control unit carries out the position correction of the target position when the temperature in the feed axis, the current through a motor winding of the feed axis, the voltage across the motor winding of the feed axis or the force or torque, which are respectively effected by the feed axis, exceeds a predefined threshold value.