04-08-2012, 11:49 AM
DESIGN REVIEW OF PLAIN PLUG GAUGE FOR MANUFACTURING, ASSEMBLY AND COST CONSIDERATION
DESIGN REVIEW OF PLAIN PLUG GAUGE FOR MANUFACTURING, ASSEMBLY AND COST CONSIDERATION.docx (Size: 516.61 KB / Downloads: 48)
1. Introduction
1.1 Go no-go gauge
A Go No-go gauge (or Go/no go) refers to an inspection tool used to check a work piece against its allowed tolerances. Its name derives from its use: the gauge has two tests; the check involves the work piece having to pass one test (Go) and fail the other (No Go). It is an integral part of the quality process that is used in the manufacturing industry to ensure interchangeability of parts between processes, or even between different manufacturers. A Go No-go gauge is a measuring tool that does not return a size in the conventional sense, but instead returns a state. The state is either acceptable (the part is within tolerance and may be used) or it is unacceptable (and must be rejected). They are well suited for use in the production area of the factory as they require little skill or interpretation to use effectively and have few, if any, moving parts to be damaged in the often hostile production environment.
Plug gauges are:
1) Used to inspect holes or slots
2) Used as master gauges
3) Made as per ANSI/ASME b89.1.5
Plug gauges are not:
1) Lapping stick or re-sizing tool
2) Used to measure actual size
3) Used on delicate tools
1.3 List of parts
SR. NO DESCRIPTION NUMBER OF PARTS
2 handle 1
1 Gauging surface 2
5 Front plate 2
3 Back plate 2
8 Screw 2
1.4. Brought out parts
The following parts are not manufactured instead purchased from outside:
1) Screw
2) Front plate
3) Back plate
2. Manufacturing of Gauge Surface and Handle
I. Blank turning
In this operation the main gauging surface is turned and dimensions are maintained up to 0.5 to 1 mm greater than the required gauging size. This is done so as to include the grinding allowance and during hardening and tempering process the material should not vary.
II. Hardening
Surface hardening, a process that includes a wide variety of techniques (list 1), is used to improve the wear resistance of parts without affecting the more soft, tough interior of the part. This combination of hard surface and resistance to breakage on impact is useful in parts such as a cam or ring gear that must have a very hard surface to resist wear, along with a tough interior to resist the impact that occurs during operation. Further, the surface hardening of steel has an advantage over through hardening, because less expensive low- and medium carbon steels can be surface hardened without the problems of distortion and cracking associated with the through hardening of thick sections. There are three distinctly different approaches to the various methods for surface hardening. Now the job gauge is hardened in a heat treatment furnace and heated between 950ºC to 1000ºC.
List 1
1. Diffusion methods
Carburizing
Nitriding
Carbonitriding
Nitrocarburizing
Boriding
Thermal diffusion process
2. Applied energy methods
Flame hardening
Induction hardening
Laser beam hardening
Electron beam hardening
3. Coating and surface modification
Hard chromium plating
Electro less nickel plating
Thermal spraying
Weld hardfacing
Chemical vapor deposition
Physical vapor deposition
Ion implantation.
III.Sub zero cooling
The gauging surface is now kept in a sub zero equipment where it is cooled below -80oC for duration of 2 hours then taken out of the equipment and allowed to cool upto room temperature.
During hardening process molecules of the job become unstable which is undesirable. In order to make the molecules stable sub zero process is done.
IV. Stress reliving and tempering
4.1 Purpose:
1. To relieve the internal stresses induced due to cold working, hardening. Internal stresses cause sudden and brittle failure of the component.
2. To reduce hardness
3. To increase uniformity
4. To refine grain size
5. To increase machinability
4.2 Operation
In this process, the gauging surface is heated to a temperature between 5000C and 5500C below its recrystallization temperature, kept at this temperature for 1 to 2 hours and cooled to room temperature in air. Due to this internal stresses are partly relived, without loss of strength and hardness.
V. Grinding
In cylindrical grinding, the work piece rotates about a fixed axis and the surfaces machined are concentric to that axis of rotation. Cylindrical grinding produces an external surface that may be straight, tapered, or contoured. The basic components of a cylindrical grinder include a wheelhead, which incorporate the spindle and drive motor; a cross-slide that moves the wheelhead to and from the work piece; a headstock, which locates, holds, and drives the work piece; and a tailstock, which holds the other end of the work.
VI.Inspection
The next process is the inspection process, in which the gauging surface is kept in a standard room which is always maintained at 20oC±0.5oC.this job is allowed to rest for 2 to 4 hours and inspected by a metro scope as per drawing. Any precision job around the world is inspected in this room. This is done because when a job is being inspected in different country the temperature varies as a result the measured dimension also varies in microns. So in order to avoid this error any precision company has a standard room which is always maintained at 20oC±0.5oC.