Information on SHED Test

SHED is an acronym for Sealed Housing Evaporative Determination. There three main types of SHED systems viz., Micro SHED (approx. capacity 48 cu ft), Mini SHED (approx. capacity 288 cu ft), and Vehicle SHED (approx. capacity 1680 cu ft).

Generally, SHED test machines are available in following varieties:
Fixed Volume (FV) / Fixed Temperature (FT) Chambers
Variable Volume (VV) / Variable Temperature (VT) Chambers
Onboard Refueling (OR) / Vapor Recovery (VR) Chambers

However, equipment can be built by manufacturers with customized options.

Variable Temperature (VT) SHED Chambers are used for hydro-carbon emission tests in vehicle components carrying fuel or permeation tests in fuel tanks. The test chamber provides protected test space with analyzer, lighting, window, volume compensation device and a refueling lead-through plus flushing and safety equipment.

When hydrocarbon emissions are measured for conformance testing of a vehicle’s fuel and vapor handling systems, SHED procedure is used. Flame Ionization Detection (FID) techniques are used for these measurements.

There are test specifications recommended by various Standards Organizations like Bureau of Indian Standards (BIS), Economic Commission for Europe (ECE), Environmental Protection Agency (EPA) Japanese Stanards.

Prepared by
Krish
Jythra Engineering Services

What is Digital Manufacturing ?

Digital manufacturing is also referred as Manufacturing Process Management (MPM). Digital manufacturing is an emerging technology and is a key element of Product Lifecycle Management (PLM). It is an important component within PLM.

The concept of concurrent development of both the product and the manufacturing process was introduced through concurrent engineering. Concept and product engineering are primarily concerned with development of a product, whereas manufacturing engineering is primarily concerned with development of the process to manufacture the product.

From software perspective, CAD and CAE tools are employed to help define what is to be made and MPM tools are employed to help define how it is to be made.

Digital manufacturing is a method to define manufacturing processes, manage the process information and support effective collaboration among engineering disciplines by using digital product data. It supports visualization, manufacturing simulation, ergonomics and other engineering analysis tools necessary to optimize the manufacturing process design. It also ensures the integration of product and process designs of overall product life cycle. Thus it ensures the product design to be sensitive to process constraints and capabilities.

Digital manufacturing includes software support for following functional areas:

• Translation of design data to manufacturing
• Process planning
• Operations planning
• Assembly definition and sequencing
• Detailed line, cell, station and task design
• Quality measurement and metrics
• Manufacturing documentation
• Collaboration between departments
• Knowledge base like best practices, lessons learnt etc.

The leading software in digital manufacturing is Delmia (a product of Dassault Systèmes) and Tecnomatix (a product of UGS-Siemens).

Jythra Engineering Services

Geometric Dimensioning & Tolerancing : Rules

Individual feature of size ( Rule #1 ) : Where only a tolerance of size is specified, the limits of size of an individual feature prescribe the extent to which variations in its geometric form, as well as size, are allowed.

All applicable geometric tolerances ( Rule #2 ) : RFS (Regardless of Feature Size) applies, with respect to the individual tolerance, datum reference, or both, where no modifying symbol is specified. MMC (Maximum Material Condition) or LMC (Least Material Condition) must be specified on the drawing where it is required.

Alternative practice ( Rule #2a ) : For a tolerance of position, RFS may be specified on the drawing with respect to the individual tolerance, datum reference, or both.