Automated Bushing for CNC Lathe Fixturing
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Solution Overview
Problem
In CNC lathe machining, existing fixturing methods are inefficient for parts with cylindrical or circular profiles, as they require skilled machinists to create custom fixtures and flip the workpiece, leading to increased costs and tool wear.
Innovation Solution
An automated method that analyzes a customer's CAD file to generate machining instructions for both the part and a custom bushing, allowing the part to be machined in two orientations and held by the bushing during secondary machining, with a cylindrical shape and compression slot to transfer grip force without damaging the part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional fixturing methods are used for lathe machining, then skilled machinists can create custom fixtures to hold the workpiece, but this increases device complexity and requires manual intervention
Solution Approach 1:
The bushing is divided into functional segments: a gripping portion with external features for workpiece engagement, a body portion for structural support, and a chuck interface portion for mounting. This segmentation allows each part to be optimized for its specific function while simplifying the overall fixturing system
Solution Approach 2:
The bushing is designed to be self-configuring through its monotonically decreasing diameter profile, which automatically determines the gripping portion location and dimensions based on the workpiece geometry. The software automatically generates bushing parameters from the workpiece CAD model, eliminating manual fixture design and setup
2Strength
If the workpiece is held in the chuck for machining, then the chuck can provide secure holding force, but the cutter cannot access the portion of the part in contact with the chuck
Solution Approach 1:
The bushing serves as an intermediary between the chuck and the workpiece. The chuck holds the bushing, which in turn holds the workpiece through its gripping portion. This intermediary structure provides secure holding force while positioning the workpiece such that the cutter can access all surfaces including those near the chuck interface
Solution Approach 2:
The bushing extends the holding capability into a new dimensional space, allowing the workpiece to be positioned and secured in orientations and locations that were previously inaccessible to the chuck alone, thereby enabling cutter access to all workpiece surfaces
3Manufacturing precision
If custom fixtures are created for each workpiece, then precise holding can be achieved, but this increases manufacturing time and cost
Solution Approach 1:
The bushing is designed as a universal fixturing component that can accommodate various workpiece geometries through its monotonically decreasing diameter profile and configurable gripping portion. The same basic bushing design serves multiple functions: holding, positioning, and presenting the workpiece to the cutter, eliminating the need for multiple custom fixtures
Solution Approach 2:
The bushing parameters (diameter profile, gripping portion dimensions, length) are automatically adjusted based on the specific workpiece geometry from the CAD model. This parameter customization maintains manufacturing precision for each unique workpiece while using the same manufacturing process and basic component design
4Productivity
If traditional fixturing is used for cylindrical parts, then the workpiece can be held, but this increases tool wear and machining duration
Solution Approach 1:
The bushing is designed and positioned in advance to optimally present the workpiece to the cutter. The gripping portion and body portion geometry are predetermined based on the workpiece CAD model, ensuring that the workpiece is held in the optimal position for machining from the outset, thereby reducing tool wear and machining time
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 method enhances efficiency by reducing material waste, machining time, and tool wear, while enabling precise machining of complex parts without the need for custom fixtures, thereby improving the overall CNC lathe machining process.
Implementation Method 1
A compression slot is formed in the bushing which enables the bushing to transfer the grip force from the chuck of the CNC lathe to the part without any damage to the part
Data Source
AI summary
A process for creating custom fixtures for parts that are to be CNC lathe machined is fully automatic and requires no human interaction. The customer's CAD file is computer analyzed to determine whether the part's dimensions fit within an available CNC lathe turning center for forming out of a cylindrical stock bar. The longitudinal axis is identified, and a set of tool paths is developed for cutting the part from two respective directions. A corresponding tool path is developed for CNC lathe cutting a bushing, preferably from the same bar stock, which generally represents the negative space around circular cross-sections of the part, in monotonically increasing diameters from the first end of the part. The bushing is then used to hold the part in the chuck during machining the second end of the part from the opposite direction.