CNC PRACTICUMMAE 165

Eric BerlinJason Sarkozi

Brandon TsugeMatthew Woo

05/14/10

Overview Introduction Steps for CNC

Computer Modeling and Programming Machine Preparation Machining Finish Product

Conclusion

Bridgeport CNC Machine

Introduction A CNC machine is a computer numerically

controlled machine It is used to mill and drill work pieces in

need of tight tolerances. The CNC used was a Bridgeport made in

1995 with 3 axes. Calibration and tool changing needed to be done manually. Current machines utilize up to 5 axes with automatic tool changers.

Process: Modeling

Sample Solidworks Model

Sample Featurecam Model

Parts are first modeled in a CAD program like Solidworks

Models can then be imported into a CAM program, where various parameters and tools are chosen. A text file is exported and is then used by the CNC machine.

Process: Preparation

Tools for CNC Machine

•The tools are lined up neatly in a rack in the order they will be used in the CNC machine.•Lubricant is used for the countersink drill bits to remove heat•Safety goggles should be worn at all times during the CNC process

Process: Machine Preparation

Alignment Process

Setting the Z-Axis Process for Each Tool

•Use a vice and spacers to hold the part elevated•Make sure that the sides of the part are parallel to the axis of the path•Use a test indicator to run parallel with the part to test for any displacements on the probe

•Use a spring loaded edge finder to align the part with the tool.•When the tip of the tool spins flush with the tool itself, then the edge of the part is at the center of the edge finder

Process: Machine Preparation

•A dial is used to make sure the distance from the tool to the part is two inches.•Record the Z position offset of two inches to the memory•Repeat the process for each tool used in the CNC process

Dial Used to Accurately Line the Tool with the Part

A lubricant and Air Tube is Used to Cool the Part

•Lubricant is used to lubricate and remove the heat from the part•If no lubricant is used, you can lose the temper of the tool meaning that the tool will become softer

Process: Machining

Center Hole Milled OutAll Holes Drilled and Tapped or Countersinked

Holes are spot drilled, the drilled then finished with a tap or countersink. The center hole is milled out. During the process the air pump continuously blows away debris.

Video of Machining

Process: Finished Product

Cleaned, Finished Product

The part is removed from the milling machine

The burrs are removed with either a “deburring tool” or a hand file

The part is rinsed off with water and simple green to remove any metal chips that may be hanging on to the part

The end result is a clean, finished product

Conclusion Standard CNC machines

generally can machine accurately to .001 - .0005 in.

Cutting speeds depend on many factors (material being machined, lubricants being used, type of cutting tool, etc.) but are generally in the .003 - .012 in. chip per tooth range

Pros: relatively accurate, cheap and fast for mass production, high removal rates, programmable

Cons: set up time, initial capital outlay, expensive for prototyping

Pictures