Cnc machining nm09/2
Review questions — Section 4
Download 0.53 Mb.
|
- Navigate this page:
- Practical exercises — section 4
- Linear programming — exercise sheets 1 -3
- Circular interpolation — exercise sheet 4
- 4.6 Preparing NC programs
- 4.6.2 Direct input
- 4.6.3 Computer aided programming
- 4.6.4 Voice numerical control
Review questions — Section 4Note: Show all workings Question 1 Given that the circle diameter is 60 mm and the width across the flats is 40 mm. Calculate the length of ’W’. 
Question 2 Calculate the chordal distance between points ‘A’ and ‘B’. 
Question 3 From the information given, calculate the value of radius. 
Question 4 Calculate the diameter of the largest circle which can be drawn inside the triangle shown. 
Practical exercises — section 4CalculationsCalculations Student instructions
Linear programming — exercise sheets 1 -3Work out the values for ‘x’ and ‘y’ for the points shown on exercise sheets 1 -3. Fill in your answers in the coordinates box on each sheet. 
Circular interpolation — exercise sheet 4Work out the values for ‘x’ and ‘y’ for points 1 -7 in exercise 4 and write your answers in the coordinate box on the sheet. 
Exercise 5 An NC controlled boring machine is to be programmed to drill a number of gear boxes as shown below. In the co-ordinate tables provided, complete the drilling tool path values starting and finishing at point ‘A’ in both Incremental and Absolute terms. 
4.6 Preparing NC programs4.6.1 Manual systemsIn any manual programming system, the programmer is required to write a complete manuscript which must include all tool co-ordinates as well all the appropriate machining codes. Earlier systems used a Buffer Teletype which was like a large typewriter with a chip set and buffer memory that could encode man readable data into a numeric code. With the evolution of micro computers, Buffer Teletypes are rarely used simply because computers now perform the encoding process much faster as well as offering many other advantages. Once encoded, data is normally down loaded to a tape punch which stores the program in the form of a punched tape. 4.6.2 Direct inputCNC machines have a Machine Control Unit (MCU) which can accept part programs keyed directly into the control unit via an alpha-numeric keyboard. This direct input can be via:
4.6.3 Computer aided programmingThis aspect of NC part programming uses a stand alone computer which has been loaded with a Computer Aided Manufacturing (CAM) software package. Depending on the nature of the industry the computer can be a mainframe, a mini or a micro computer such as is found in personal computers. Like in any computer, the heart of the system is the software. Software such as SmartCAM, MasterCAM and GeoPath are all examples of CAM software. These brand names like many others have the facilities to:
4.6.4 Voice numerical controlVoice programming of NC machines (abbreviate VNC) involves vocal communication of the machine procedure to a voice-input NC tape preparation system. VNC allows the programmer to avoid steps such as writing the program by hand, key punching or typing, and manual verification. One of the principal companies specialising in voice input systems is Threshold Technology, Inc., of Delran, New Jersey. To perform the part programming with VNC, the operator speaks into a headband microphone designed to reduce background acoustical noise. Communication of the programming instructions is in shop language with such terms as ‘tum’, ‘thread’, and ‘mill line’, together with numbers to provide dimensional and coordinate data. Before the voice input system can be used, it must be ‘trained’ to recognise and accept the individual programmers voice pattern. This is accomplished by repeating each word of the vocabulary about five times to provide a reference set which can subsequently be compared to voice commands given actual programming. The entire vocabulary for the Threshold system contains about 100 words. Most NC programming jobs can be completed by using about 30 of these vocabulary words. The advantages of VNC lie principally in the savings in programming time and resulting improvements in manufacturing lead time. Savings in programming time up to 50% are claimed. Improvements in accuracy and lower computer skill requirements for the programmer are also given as benefits of VNC. Directory: file -> view view -> Western Europe after wwii view -> Author study: paul fleischman view -> Qpa1 7ela study Guide view -> Arctic Oil/Gas Neg view -> November 1970 Approximately 150,000-500,000 deaths Bhola Cyclone Bangladesh view -> Grade Level: 6 Unit of Study: Caribbean glce view -> Citation: Duffield, Katy view -> Table of Contents Lesson # view -> Chinese Wind Energy Disad Download 0.53 Mb. Share with your friends:
| ||||||||||||||||||||||||||||