1. DCLASS System:
The DCLASS system was developed by Del Allen at Brigham Young University (Allen and Smith, 1980). DCLASS was intendedto be a decision-making and classification system (thus the name DCLASS). It is a tree-structured system that can generate codes for components, materials, process, machines and tools. For components, an eight-digit code is used:
Digits 1-3 Basic shape
Digit 4 Form feature
Digit 5 Size
Digit 6 Precision
Digit 7-8 Material
PART FAMILY CODE
A 2 0- 2 - 3 - 2 - A1
A20--BASIC SHAPE
2 --FORM FEATURES
3 --SIZE
2 --PRECISION
A1 --MATERIAL
Computer-Aided Manufacturing (Tien Chien Chang, A. Wysk, Hsu-Pın Wang second edition pg:490)
2. MICLASS System:
The MICLASS system was originally developed by TNO of Holland and is currently maintained in the USA by the Organization for Industrial Research. It is a chain- structured code of 12 digits. The code is designed to be universal; therefore, it includes both design and manufacturing information. Information such as the main shape, shape elements, position of shape elements, main dimessions, ratio of the dimensions, auxiliary dimension, from tolerance and the machinability of the material is included. An additional 18 digits of code are also available for user-specifield information. These supplemental digits provide flexibility for system expansion. MICLASS is also one of the earliest interactive coding systems. MICLASS has been adapted by many U.S. industries.
Computer-Aided Manufacturing (Tien Chien Chang, A. Wysk, Hsu-Pın Wang second edition pg:487)
3. T-Code:
The T-code is used to specify the tool number. It is used only when an automatic tool changer is present. It specifies the slot number on the tool magazine in which the next tool is located. Actual tool change does not occur until a tool change M-code is specifield.
Computer-Aided Manufacturing (Tien Chien Chang, A. Wysk, Hsu-Pın Wang second edition pg:368)
4. M-Code:
The M-code is called the miscellaneous word and is used to control miscellaneous functions of the machine. Such functions include turn and the spindle on/off, start/stop the machine, turn on/off the coolant, change the tool and rewind the program (tape).
M-00 program stop
M-01 optional stop
M-02 End of program
M-03 Spindle CW
M-04 Spindle CCW
M-06 Tool Change
M-07 Flood coolant on
M-08 Mist coolant on
M-09 Coolant off
M-30 End of tape
Computer-Aided Manufacturing (Tien Chien Chang, A. Wysk, Hsu-Pın Wang second edition pg:369)
5. Encoder:
Encoders usually are arranged to measure angular displacement. They output digital signals. The construction of an encoder is rather simple. It consists of a light source, a glass disk with painted patterns and a photoelectric sensor. The light emitted from the light source, usually a photodiode, an either pass or be blocked by the pattern on the glass. It is detected by the photoelectric sensor when the light passes through the glass. The outputs is a series of electric pulses. A Schmitt-trigger device is used to convert the output signal into a square-wave signal. The resolution of an encoder depends on the number of blackened cells painted on one ring(track) of the disk. For example, if an encoder has 100 blackened cells per track, the solution is 360º / 100= 3,6º . When the shaft turns one rotation, the encoder outputs 100 pulses.
There are two types of encoders: incremental and absolute. The output is a series of pulses. There is no reference of the actual position. In order to determine the actual position, an external device must keep track of the output and accumulate the position coundt. For example, from a home position, the encoder registered two motions. The first motion outputs 1000 pulses and the second one outputs 300 pulses. The current position can be sumed up to be ( 1000 + 300 ) / 100 = 13 rotations. When connecting an incremental encoder to a DC motor, it acts somewhat like a stepping motor. The encoder resolution is equivalent to the stepping-motor. However, a controller is needed to count the pulses received and to determine whether to continue the motor rotation or stop. An absolute encoder is more complicated than an incremental encoder. It outputs a binary number denoting the rotational angle from a reference on the encoder shaft. Several tracks of patterns are painted on the disk. Each row of the pattern has coded position information.
The output of an incremental encoder can be characterized by the following equation.
f = Ke . ω
where
f = output pulse frequency, pulses/s
ω = input angular speed, rpm
Ke = encoder gain
The output of an absolute encoder is the shaft angle.
Computer-Aided Manufacturing (Tien Chien Chang, A. Wysk, Hsu-Pın Wang second edition pg:332)
6. Cold Forging:
Cold forging is big business. In 1980, Precision Metal Magazine stated that at that time, closed die forgings were going to top $2,5 billion for the year. I’ll try to make you aware of what cold forging can do for you by making parts near net shape. This chapter will make you ask yourself what parts you use that are near net shape.
You make yourself more valuable to you company by having an understanding of the fundamental process of forging so that you can know if any parts fall into that category. If you can identify parts whose dimensions fall within the ability of the cold-forging process, that’s all you have to know.
You might not know how to desing the die, what kind of equipment to use, or how the metal moves under pressure. But if you know something about the process, just ask yourself if it could make your part near net shape. You don’t necessarily have to take the responsibility on your shoulders. If you think it’s possible, let the cold-forging people look at the parts and tell you what they think of the possibilities.
Cold forging is a process which forms metal at room temperature to a desired shape by forcing a lubricated slug into a closed die under very high pressure. The voulme of the slug is very important. Automatic sorters are sometimes used to seperate the blanks by their gram weight into over, under, and correct gram weight. Usually a slight adjustment of the pres can be made to compensate fort he slight change in gram weight as long as the parts in any one run are the same.
The force could be generated either by hydroli or mechanical presses. The process deforms the matal plastically. In this process, the metal is reformed in to continuous, unbroken lines that folow the contour of the part, increasing resistance to shear and breaking. The lines are forced together, making the part much stronger. Even an untrained eye can see the deformation ratio increases as the jobs get done.
Advanced Machining Technology Handbook (James Brown pg: 45)
No comments:
Post a Comment