Computer Aided Engineering Applications 3. Advanced Manufacturing

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1 Computer Aided Engineering Applications 3. Advanced Manufacturing 3.1 CAM systems 3.2 Geometry of surfaces 3.3 Product data exchange 3.4 Data Communication 3.5 Automated Manufacturing systems 3.6 Part programming Engi6928 -Fall 2014

2 3.1 CAM systems Structure of an Automated manufacturing system SCADA Data IO Product description PDE CAM software NC CODE MCU Machine Hardware Control Commands The presentation goes over the primary modules shown in this figure.

3 3.2 Geometry of curves and surfaces Polygon models only require vertices and lines and planar surfaces for B-Rep representation. Complex models require curves and curved surfaces to represent its geometry. Water tight surface A combination of surfaces which are connected to form a closed volume. Solids are water tight surfaces. Analyticcurve Analytic curves are defined by an algebraic equations. Ex: circle, ellipse, parabola, hyperbola.

4 3.2 Geometry of curves and surfaces Synthetic curve -A Free form curve defined by a set of points or control points. Parametric polynomial curve A curve which is defined using a parameter u. Analytic curves are not good for free form design. For design of shapes like car bodies, ship hulls, synthetic curves are required.

5 3.2 Geometry of curves and surfaces Continuity between curve segments Position continuity Slope continuity Curvature continuity Requires minimum of a cubic polynomial Higher degree polynomial fittings cause oscillations

6 3.2 Geometry of curves and surfaces Hermite cubic spline A splinethat passes through two given end points with two given slopes. Can connect multiple points in a similar manner with curvature continuity. has global control.

3.2 Geometry of curves and surfaces Bezier curves (P. Bezier 1962) Only control points are used. No tangent vectors. Can be manipulated using the control polygon.

7 3.2 Geometry of curves and surfaces Bezier curves (P. Bezier 1962) Only control points are used. No tangent vectors. Can be manipulated using the control polygon. Each control point affects the final curve according to the blending function. Degree of curve = highest power of blending polynomials = number of control points -1. Blending function of a cubic Bezier A cubic Bezier

3.2 Geometry of curves and surfaces Bezier curves (P. Bezier 1962) Convex hull property The curve is tangent and touches the first and last control points.

8 3.2 Geometry of curves and surfaces Bezier curves (P. Bezier 1962) Convex hull property The curve is tangent and touches the first and last control points. Has global control, degree of curve increments with control points Rational Beziers Each control point has an associated weight. Results in more control.

9 3.2 Geometry of curves and surfaces NURBS Non-uniform rational B-splines A generalization of Bezier. Multiple rational Beziers joined with knots. Can represent any analytic/ synthetic curve, line or surface. (conic sections, cubics, Beziers) Local control control points and degree are separate. Degree specifies how many neighbouring points are affected. Blending function of a NURBS Construction of NURBS

10 3.2 Geometry of curves and surfaces NURBS Defined by degree, control points, and knots. Degree 3 (cubic), 5 (quintic) NURBS often used. Control points (N) >= degree +1 Exclusively used in almost all CAD programs to represent geometry at the kernel level. " Standardized... Simplifies data exchange Kinksare knots in a NURBS where only positional continuity is preserved. Kinks in NURBS Kinks in NURBS

Solids are formed by a set of NURBS patches knit to from a water tight shells.

11 3.2 Geometry of curves and surfaces NURBS surface modeling NURBS surfaces are rectangular patches with two parameters u, v. Iso-uv lines are NURBS curves. Solids are formed by a set of NURBS patches knit to from a water tight shells. Software dedicated to surface modelling handles NURBS well. Editing NURBS patches could result in leaks on the shell. NURBS patch Watertight NURBS model

12 3.2 Geometry of curves and surfaces Recent developments Subdivision models (used in animation industry) to NURBS model conversion. T-spline modeling Solid modelling Surface modelling

13 3.2 Geometry of curves and surfaces Control points knots Increasing weight of a control point from 1 to 5 Changing a control point of a degree 3 curve vsa degree 7 curve

14 3.3 Product data exchange Four types of product Data Shape geometry, topology Non shape color, units, identifiers, annotations Design Material, FEA, Factors of safety Manufacturing tolerances, BOM, process plans A good natural fileformat should allow standardized storing of as much as product data as possible, for archival or exchange purposes.

15 3.3 Product data exchange Translators direct vs indirect + runs quickly +smaller data size -Require 2nC2 translators + Require 2n translators + eliminate dependence - Standardization?

16 3.3 Product data exchange 1. STL file A simple file type for 3D. Defines the solid using set of triangular faces (facets) No inner loops. No edge definitions (linear). Facet normal points to the free space. CCW order of vertices serves as a redundancy check. ASCII and binary types.

3.3 Product data exchange STL file Mesh density controllable. Is an approximate polygon model. So certain geometric data are lost in translation.

17 3.3 Product data exchange STL file Mesh density controllable. Is an approximate polygon model. So certain geometric data are lost in translation. STL errors self intersecting triangles Common STL errors detected in MeshLab Topology errors non manifold models, not water tight. (holes, isolated triangles, duplicates, etc.) Model errors. i.e. Errors in the original model itself Normal inconsistencies. Surface normal errors. Open source tools for processing MeshLab

$DXF\DWG Drawing interchange format The native format in AutoCAD which is considered the de facto standard for 3D$

18 3.3 Product data exchange 2. DXF\DWG Drawing interchange format The native format in AutoCAD which is considered the de facto standard for 3D parts. DWG is used for 2D drawings. Has shape and non shape data. The file structure:

19 3.3 Product data exchange 3. IGES Initial graphic exchange specification The main body of file has an entity list, followed by a list of parametersfor each entity. The entities have both shape and nonshape data. The entities include NURBS Allows new entity definitions in file. Developed in 1980`s, new developments are difficult to standardize using the standard definitions.

20 3.3 Product data exchange

21 3.3 Product data exchange 4. STEP ISO Ongoing project. Attempts to define a natural file for all shape, non-shape, design and manufacturing data. (Common data format for entire life cycle) Multiple application domains (Mechanical, electrical, etc.) ᣠΆ Shares data in the form of applications. Ex: AP203 defines geometric entities. Application layer in STEPS

3.3 Product data exchange Rhino to SolidWorks

IGES NURBS surface geometry fully exported

22 3.3 Product data exchange Rhino to SolidWorks workflow Organic Freeform modelling using NURBS surfaces in Rhino Parent child relationship preserved in the workflow Export IGES NURBS surface geometry fully exported Solid modeling in Sold works., shelling, features, Assembling

23 3.1 Data Communication Structure of an Automated manufacturing system SCADA Data IO Product description PDE CAM software 粠 ҡ NC CODE MCU Machine Hardware Control Commands

24 3.4 Data Communication Data communication is used to transfer data to and from manufacturing machines. These data are essential for process control, where the efficiency and quality of the production line is tracked and corrected as necessary. Also required for factory automation, remote monitoring etc.. The data is often displayed on SCADA(Supervisory control and Data Acquisition) units, which can be a panel or a GUI interface in a PC.

25 3.4 Data Communication Data coding (Data format) For data communication, the sender and receiver should be aware of the way data is stored in the payload bits (1`s and 0`s) received. Common methods include ASCII strings, binary data structures (sequences of ints, 肐 ҡ floats, Booleans etc.). Data encryptionencodes the data so that it cannot be decrypted without the decryption key/s. Communication protocol A set of standardized rules for data exchange. i.e. Data formats, Error detection, Flow control, Acknowledgement, Routing, Addressing, Retries

26 Keywords to know 1. Data format -digital vs analog -encoding (data type) 2. Error checking 3. Flow control -Acknowledgement 4. Retries 5. Addressing 6. Routing 7. Encryption sender 8. Communication Medium ᣠΆ -RF -wired -Acoustic 9. Channel 10. Bandwidth receiver

The connection parameters: Baud rate, Parity, Start bit, Stop bit, COM port.

27 3.4 Data Communication 1. Serial links-rs232 (Serial, USART) Typically a +-13V digital serial signal. Data buffers are used to transmit and receive data. The connection parameters: Baud rate, Parity, Start bit, Stop bit, COM port. Minimum requirements are the RX, TX, and Ground lines. Low power devices communicate serial at much lower voltage signals (5V/ 3.3V) which can be converted to RS232. UART 5V MAX 232 RS V

28 3.4 Data Communication 1. Serial links- RS232 Minimum connection RX TX GND RX TX GND Example: ASCII communication. ᣠҩ Baud :9600(104.1 us per bit) Start bit :1, Data bits:8, Stop bit:1, Parity: none PAYLOAD Range of communication: ~10 m (depends of baud, shielding)

29 3.4 Data Communication 1. Serial links- RS232 Data reception and transmission are standard operations in many languages. C, Matlab etc. Software like hyper terminal, cool term allows to send and receive serial data. Hardware flow control would improve link quality. 鎠 ҥ s = serial('com1'); //open COM port 1 set(s,'baudrate',4800); //set BAUD fopen(s); //open device fprintf(s, TEST') //send Test out = fscanf(s); // receive and store to out fclose(s) // close serial port

30 3.4 Data Communication Example: RS232 (UART) communication with Matlab. instrreset clear clc փ serialone=serial('com24', 'BaudRate', 9600); fopen(serialone); %% fprintf(serialone,'ps2500') fprintf(serialone,'pp2500') fprintf(serialone,'ts2500') fprintf(serialone,'tp300')

31 3.4 Data Communication 2. Local Area Networks- LAN LAN is good for network of devicesand allows much higher data rates (100 Mbps) Confined to 10Km in distance. WLAN uses a wireless medium(2.4ghz ᣠҧ RF). LAN uses wired medium(twisted pair) LANs have well established protocolsfor networking, traffic control, and error recovery. TCP/IP and UDP protocols are popular.

32 3.4 Data Communication 2. LAN/ WLAN LAN communicates packets of Data. Each device in the network is assigned an IP address. Different Portscan be used under the same IP address so that many application can access the LAN. Applicationscan run as a client(a requesting machine) or a server(a responding machine) The packet header contains the data of source and destination, error checking info. Error checking is performed using check sum. (a number representing the addition of all data bits in the payload)

33 3.4 Data Communication TCP and UDP are two different transport layer protocols. The main differences: Transmission Control Protocol User Datagram protocol Requires a connection withthe host for data transfer. Lower speed Highly reliable ( flow control and acknowledgements) No connection required. ᣠҧ Higher speed Low reliability (no retries,no flow control)

34 3.4 Data Communication Example 1: TCP communication with Matlab clear clc instrreset close all Client Application Remote IP Remote Port clear clc close all Server Application Remote IP Local port t = tcpip( ',4012,'NetworkRole', 'client'); fopen(t) pause(1) fprintf(t,'g01 X1.00 Y1.00') fclose(t) t = tcpip(' ',4012,'networkrole', 'server'); fopen(t) while(1) if (t.bytesavailable>0) data = fscanf(t) end end fclose(t) Connect to localhost i.e PORT: 4012

3.4 Data Communication Example 2: Machine network Machine 3 Local IP : 19

35 3.4 Data Communication Example 2: Machine network Machine 3 Local IP : MCU application LAN Protocol /Role: UDP Local PORT : 3005 Remote IP /PORT: n/a COM10 COM Baud ᣠҧ Central computer Local IP : Central Application to control machine 2 Protocol /Role:? Local Port:? Remote IP:? Remote Port:? Machine 1 Local IP : MCU application Protocol /Role: TCP Server Local PORT : 1005 Remote IP/PORT : any Machine 2 Local IP : MCU application Protocol /Role: TCP Server Local PORT : 1005 Remote IP/PORT : any

36 3.4 Data Communication Example 3: UDP communication with Matlab clear clc close all hudps= dsp.udpsender('localipportsource', 'Auto','RemoteIPAddress',' ','RemoteIPPort',250 00) clear clc close all hudpr= dsp.udpreceiver('remoteipaddress',' ','localipport', ,'MessageDataType','int8') 100 for i=1:360 step(hudps,int8(sind(i)*128)) end release(hudps) Sender Protocol /Role: UDP sender Local Port: Any Remote IP: Remote Port:25000 count=1; while(count<360) datareceived = step(hudpr); if ~isempty(datareceived) signal(count)=datareceived; count=count+1; end end plot(signal) release(hudpr) Receiver Protocol /Role: UDP receiver Local Port: Remote IP: Any Remote Port: Any Note: here we used the DSP system toolbox, since the computer lab does not have the instrumentation toolbox

GL9: Engineering Communications. GL9: CAD techniques. Curves Surfaces Solids Techniques

GL9: Engineering Communications. GL9: CAD techniques. Curves Surfaces Solids Techniques 436-105 Engineering Communications GL9:1 GL9: CAD techniques Curves Surfaces Solids Techniques Parametric curves GL9:2 x = a 1 + b 1 u + c 1 u 2 + d 1 u 3 + y = a 2 + b 2 u + c 2 u 2 + d 2 u 3 + z = a