Project Abstract

<p> <strong>t</strong>Rapid prototyping is widely used to reduce time to market in product design and development. Today’s systems are used by engineers to better understand and communicate their product designs as well as to make rapid tooling to manufacture those products. Computer Numerically Controlled (CNC) milling machines are part of this technology. This project will present the design of a small CNC machine, and production, and analysis of a small CNC machine. This machine has the characteristics demanded by the industrial and academic designers. Studying the existing machines aided in setting specifications for the new design. Comparing the performance of the new machine with existing machines will improve future designs. <br></p>

Project Overview

<p> </p><p>Introduction &amp; Problem Solution 1</p><blockquote><p>1.1 Solution Methodology 2</p></blockquote><p><strong>2 Chapter 2 </strong>– Performance Metrics of Numerically Controlled Machines 4</p><blockquote><p>1 2.1 Geometrical Errors 42.1.1 Backlash 92.1.2 Scaling Mismatch 102.1.3 Squareness Error 122.1.4 Cyclic Error 132.1.5 Lateral Play 152.1.6 Reversal Spikes 161 2.1.7 Stick Slip 182.1.8 Vibration 192.1.9 Master-Slave Changeover 202.1.10 Straightness 222.1.11 ASME Standard Test Method 23</p></blockquote><p><strong>3 Chapter 3 – Performance Evaluation of Existing Machine 25</strong></p><blockquote><p>3.1 Discussion o f Measurements of Microkinetics Performance 263.2 Discussion o f Measurements of Prolight Performance 31</p></blockquote><p><strong>4 Chapter 4</strong>&nbsp;– Design Specifications for the New Machine 36<strong>5 Chapter 5</strong>&nbsp;– Design of the New Machine 39</p><blockquote><p>5.1 The Hardware 405.1.1 The Structure 405.1.2 X &amp; Y Axis 415.1.2.1 Axis Motor 435.1.2.2 Axis Actuator Hardware 455.1.2.3 Rolling Contact Bearing 485.1.2.4 Motor Mounting 545.1.2.5 Linear Slides 565.1.3 Z Axis 615.2 The Software5.3 Driver and Electronics</p></blockquote><p><strong>6 Chapter 6 </strong>– Measurement of Performance of the New Mill<strong>7 Chapter 7</strong>&nbsp;– Discussion of Results<strong>8 Chapter 8</strong>&nbsp;– Recommendation for Future Work <strong>Appendices</strong>A. G &amp; M CodesB. Calculation Sheet for the Ball ScrewC. Important PartsofEMC.INI FileD. Diagram ofThe Driver’s CircuitE. Calculation and Selection o f the Stepper MotorF. Engineering Drawings of GVSU Mill<strong>References</strong><strong>Table of Figures</strong>Figure 2.1.1 the hardware required for the Renishaw ballbar test. 5Figure 2.1.2 feed in, out, angular overshoot arcs and the data capture arcs. 6Figure 2.1.3 the data capture range of the ballhar transducer is approximately 2mm. 7Figure 2.1.4 a plot o f time vs. transducer travel shows the period of machineacceleration and how it would affect the integrity o f the data collected. 7Figure 2.1.1.1 an example of positive backlash. 9Figure 2.1.1.2 the interpolation of the inward step in the ball bar plot. 10Figure 2.1.2.1 an example of a scaling mismatch error. 11Figure 2.1.3.1 positive and negative squareness. 13Figure 2.1.4.1 an example of cyclic error. 14Figure 2.1.5.1 an example of a lateral play in the y axis. 15Figure 2.1.6.1 an example plot of a reversal spikes error. 16Figure 2.1.6.2 an example o f the effect of a reversal spikes error on the actual circle milled on the part. 17Figure 2.1.7.1 stick-slip error as shown on a diagnostic problem. 18Figure 2.1.7.2 the effect of stick-slip on the machined part. 19Figure 2.1.8.1 a typical plot showing vibration error. 20Figure 2.1.9.1 a master-slave changeover error as captured by the ball bar diagnostic plot<strong>.</strong>&nbsp; 21Figure 2.1.9.2 master slave changeover every 45″. 21Figure 2.1.10.1 three distinct distortions in the plot caused by an error in the y axis straightness. 22Figure 3.1.1 a plot of the ballbar test on the Microkinetics CNC express. 27Figure 3.1.2 representation of the angular error and how it can cause a scaling mismatch error. 29Figure 3.2.0 diagnostic plot of the proLIGHT on the same scale as the Microkinetics. 32Figure 3.2.1 a plot of the ballbar test on the proLIGHT CNC machining center. 32Figure 3.2.2 duplex arrangement angular contact bearings. 34Figure 5 a solid model of GVSU mill. 39Figure 5.1.1.1 the structure of GVSU mill. 40Figure 5.1.2.1 the X, y axis including the linear slides. 41Figure 5.1.2.1 the axis drive system. 42Figure 5.1.2.2.1 lead screw and nut. 45Figure 5.1.2.2.2 ball screw and nut. 46Figure 5.1.2.3.1 deep groove ball bearing. 48Figure 5.1.2.3.2 the driver and the follower pulley diameters and distance. 51Figure 5.1.2.4.1 timing belt, and timing pulleys. 54Figure 5.1.2.5.1 illustration of the dovetail slides. 56Figure 5.1.2.5.2 illustration of the linear ball bearing slides. 57Figure 5.1.2.5.3 illustration of the crossed roller bearing slides. 58Figure 5.1.2.5.4 the guided linear sliding system. 59Figure 5.1.3.1 the spindle assembly. 61Figure 5.3.1 the drive rack and the G201A inside. 66Figure 6.1 the first diagnostic plot of the new machine using a 50 mm ballbar. 69Figure 6.2-1 diagnostic plot of the second test on a 100 pm plot scale as the first test.72Figure 6.2-2 diagnostic plot of the second test on a 50 pm plot scale. 72Figure 6.3 diagnostic plot of the final test. 74Figure 7.1 percent deviation from the compromised performance values. 79Figure 8.1 self aligning linear bearing may cause unwanted movement of the axis 82<strong>List of Symbols and Abbreviations</strong><strong>CNC </strong>Computer Numerical Control<strong>mm </strong>millimeter<strong>m</strong>&nbsp;meter<strong>pm </strong>micro meter 9 theta, the value quoted for squareness by the diagnostic softwareDy the wavelength of the cyclic sinusoidal error<strong>ASME </strong>American Society of Mechanical Engineers<strong>CW </strong>Clockwise<strong>CCW </strong>Counter-Clockwise<strong>ISO </strong>International Organization for Standardization<strong>JIS</strong>&nbsp;Japanese Industrial Standard<strong>oz.in.</strong>&nbsp;ounce per inch<strong>RPM</strong>&nbsp;Revolution Per Minute<strong>VAC </strong>Volts of Alternating Current<strong>Ibf </strong>pounds of force<strong>lb</strong>&nbsp;pounds of weight<strong>Deg. </strong>degree<strong>CMM </strong>Coordinate Measuring Machine<strong>DC </strong>Direct Current<strong>Fa </strong>axial force<strong>L </strong>lead of a ball screw (inches)<strong>T</strong>&nbsp;torque<strong>e</strong>&nbsp;efficiency<strong>n</strong>&nbsp;pi(p belt inclination angle<strong>C</strong>&nbsp;distance between centers of pulleys<strong>Ri</strong>&nbsp;radius of the motor pulley<strong>Ri</strong>&nbsp;radius of the screw pulley rad radians<strong>F</strong>&nbsp; B m a x the maximum radial force<strong>a</strong>&nbsp;angle of warp of smaller pulleycoefficient of friction between pulley<strong>HP </strong>Horse Power<strong>AFBMA </strong>Anti Friction Bearing Manufacturers Association<strong>P </strong>equivalent load<strong>Fr </strong>applied constant radial load<strong>V </strong>rotation factor<strong>X </strong>radial factor<strong>Y </strong>thrust factor<strong>L </strong>fatigue life expressed in millions of revolutions<strong>C </strong>the basic dynamic load rating<strong>NC </strong>Numerical Control<strong>CAD </strong>Computer Aided Design<strong>CAM </strong>Computer Aided Manufacturing<strong>DOS </strong>Disk Operating System<strong>PCI </strong>Peripheral Component Interconnect<strong>EMC </strong>Enhanced Machine Controller<strong>API </strong>Application Programming Interface<strong>NIST </strong>National Institute of Standards and Technology<strong>GUI </strong>Graphical User Interface<strong>MDI </strong>Machine Device Interface<strong>PC </strong>Personal Computer<strong>TIL </strong>Transistor – Transistor Logic</p> <br><p></p>