Internal Toothing EDM for Precise Planetary Roller Extruders

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Solution Overview

Problem

The existing methods for producing internal toothing on planetary roller extruder housings are inefficient and lack competitive pressure due to standardized manufacturing processes, with spark erosion showing potential but requiring improvements in precision and cost-effectiveness.

Innovation Solution

The use of electrodes with a rounded end and a dielectric system for spark erosion, allowing for precise control of the erosion process, including the use of numerically controlled movements and fresh dielectric for enhanced material removal, and the employment of disc-shaped electrodes for efficient machining of internal toothing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional milling or grinding methods are used for internal toothing, then manufacturing precision and surface quality are achieved, but production efficiency is low and costs are high

Engineering Contradiction:
Improvetooth surface qualityVSAvoidproduction efficiency
Core Design Contradiction:
Manufacturing precisionVSProductivity

Solution Approach 1:

The patent replaces traditional mechanical cutting methods (milling, grinding) with spark erosion (electrical discharge machining). This substitution allows for efficient material removal while achieving precise tooth flanks and high surface quality on internal toothing, resolving the contradiction between production efficiency and manufacturing precision.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Stability of the object's composition

If all manufacturers use the same standardized manufacturing processes, then consistency is maintained, but competitive pressure and innovation are eliminated

Engineering Contradiction:
Improveprocess consistencyVSAvoidcompetitive flexibility
Core Design Contradiction:
Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

The patent introduces spark erosion as a new manufacturing parameter and process type, enabling manufacturers to differentiate their production methods. This parameter change allows for competitive flexibility and innovation while maintaining consistent quality outcomes through controlled electrical discharge parameters.

Inventive Principle:
Principle #35Parameter changes

3Productivity

If spark erosion is used for internal gearing, then production efficiency and cost-effectiveness improve, but precision control and process stability require improvement

Engineering Contradiction:
Improveproduction efficiencyVSAvoiderosion precision
Core Design Contradiction:
ProductivityVSManufacturing precision

Solution Approach 1:

The patent implements feedback control in the spark erosion process by monitoring and adjusting electrical discharge parameters during machining. This ensures precise control over material removal rates and tooth geometry, maintaining manufacturing precision while achieving high production efficiency.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent employs dynamic adjustment of electrode positioning and movement speeds during spark erosion. This dynamic control allows for optimized material removal while maintaining precise tooth flank geometry, resolving the contradiction between productivity and precision.

Inventive Principle:
Principle #15Dynamics

4Area of stationary object

If electrodes are designed to penetrate deep into housings for complete toothing, then comprehensive coverage is achieved, but device height and complexity increase

Engineering Contradiction:
Improvetooth coverage areaVSAvoiddevice height
Core Design Contradiction:
Area of stationary objectVSDevice complexity

Solution Approach 1:

The patent segments the electrode into multiple sections or uses multiple electrodes of different lengths to machine different portions of the internal toothing. This segmentation allows for complete tooth coverage without requiring a single extremely long electrode, thereby reducing device height and complexity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent approaches the internal toothing problem from multiple spatial dimensions by using electrodes that can be positioned and moved in various directions (radial, axial, rotational). This multi-dimensional approach enables complete tooth coverage while maintaining compact device dimensions.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 approach enables precise and efficient production of internal toothing with significant cost savings and improved surface quality, allowing for the production of various gearing types, including 45-degree involute gearing, with reduced electrode wear and increased production flexibility.

Implementation Method 1

Electric discharge machining (EDM) is a thermal, abrasive manufacturing process. This process is used for electrically conductive materials. The workpiece is placed under current/voltage and an electrode is guided along where deformation is to take place. Sparks form on these surfaces and fly to the guided electrode. Due to the sparks, erosion, a removal of material, forms on the processed surface.

Methodology Applied
Scientific EffectElectrical Discharge Machining: Electrical Discharge Machining

Implementation Method 2

Due to the sparks, erosion, a removal of material, forms on the processed surface.

Methodology Applied
Scientific EffectErosion: Erosion

Implementation Method 3

When machining the workpiece, a dielectric is provided at least in the gap between the workpiece and the electrode.

Methodology Applied
Scientific EffectDielectric: Dielectric

Data Source

PatentEP3291939B1Spark erosion of the internal toothing of planetary roller extruders
Publication Date: 2022.07.20 ENTEX RUST & MITSCHKE GMBH
  • EP3291939B1 patent drawingFigure 1
  • EP3291939B1 patent drawingFigure 2~3
  • EP3291939B1 patent drawingFigure 4~5

AI summary

According to the invention, the circumference of electrodes used for the spark erosion of planetary roller extruders is provided with a skewed and/or rounded portion and is automatically replaced under certain circumstances. Also, the dielectric is drawn off at the bottom and fresh, cooled dielectric is added from the top.