CNC Circuit Mill/V2 Design Rationale: Difference between revisions
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*Round Bar. Advantage: High uniform rigidity on curved surface. Lathe-machinable. 2-flat and circular face mounting versatility. Drawback: Difficult to do planar measurements, difficult to drill along non-centerlines, low contact rigidity when mounting on its curved surface. | *Round Bar. Advantage: High uniform rigidity on curved surface. Lathe-machinable. 2-flat and circular face mounting versatility. Drawback: Difficult to do planar measurements, difficult to drill along non-centerlines, low contact rigidity when mounting on its curved surface. | ||
*'''Comments:''' | |||
Round bar is out immediately; the marginal rigidity uniformity compared to blocks is negligible; lathe machinability is unnecessary because the precision of frame parts are already uniform through cutting of stock metal; circular mounting is unnecessary because the simplicity and rigidity of rectangular wireframe was chosen. Blocks > Round Bars in all cases. | |||
=Axis Frame Part Volumetric Allocation= | =Axis Frame Part Volumetric Allocation= | ||
Revision as of 19:34, 16 May 2012
Frame Objectives
The function of the frame is to move a part of the frame in 3 dimensions (relative to its base).
For performance, a good frame has:
For design, fabrication, assembly, and usage, a good frame also has:
- Uniform Dimensions and Other Parameter Values
- Maximum Simplicity (without sacrificing performance)
- Ease of fabrication, assembly, disassembly, and usage
- Modularity
- Durability
- Scalability
- Safe Operation
For the CNC Circuit Mill, a good frame also has:
- Workpiece mounting platform
- Large working volume of moving part relative to the mounting platform.
Choosing an Axis System
- Selected - 3 linear axes: all linked. Advantage: scalability
- 3 linear axes: 2 linked, 1 separate. Advantage: rigidity
Frame Material
- Selected - 6061 Aluminum Alloy for rigidity, ease of machinability, and accessibility
Frame Overall Shape
Axis Frame Part Shape
- Block Advantage: High approx-uniform rigidity. 6-flat face mounting versatility. Drawback: Massive.
- Angle: Advantage: Lightweight. More rigid than flat bar. Perpendicular 2-plane rigidity. Drawback: 2-flat face mounting options.
- Flat Bar. Advantage: Most Lightweight. Drawback: 1-flat face mounting option. Rigid only along 1 plane.
- Round Bar. Advantage: High uniform rigidity on curved surface. Lathe-machinable. 2-flat and circular face mounting versatility. Drawback: Difficult to do planar measurements, difficult to drill along non-centerlines, low contact rigidity when mounting on its curved surface.
- Comments:
Round bar is out immediately; the marginal rigidity uniformity compared to blocks is negligible; lathe machinability is unnecessary because the precision of frame parts are already uniform through cutting of stock metal; circular mounting is unnecessary because the simplicity and rigidity of rectangular wireframe was chosen. Blocks > Round Bars in all cases.
Axis Frame Part Volumetric Allocation
- Multiple
- Singular
Axis Drive
- Selected - Stepper motors provide high resolution in a simple open-loop system
- AC or DC motors with encoders necessitate complex closed-loop control systems
Rotary-to-Linear
- Selected - Leadscrew and Nut for high mechanical advantage and lifetime operation
- Belts stretch and have low mechanical advantage
Axis Supports
- Selected - Precision Shafts for ease of manufacturing and direct mounting
- Precision V-Rails
- Precision Extrusions
Spindle Drive
- Selected - Outrunner Brushless DC Motor has maintenance-free operation, over 90% efficiency, commutator-free long lifetime, precision speed control possible, quiet operation, more torque than inrunners
- Brushed DC Motors require regular maintenance, short lifetimes, noisy operation
http://www.youtube.com/watch?v=fPLdHeRQp_w