Week 10:- 2D Detailing Challenge

Aim :- To Draft a Key Sheet for the Complete Fixture assembly and Draft a Base Unit and the Fix Pin Unit drawings with all child parts for the complete Fixture assembly 

INTRODUCTION

 The fixture design after the 3D finishing process has to be done with 2D finishing before it is sent for manufacturing. All the dimensions of the fixture units and their child parts have to clearly mentioned in the drawing sheets. The detailing can be changed as per the requirement of the customer and company standards. GD&T must be used in order to reduce the cost of manufacturing.

All the views must be clearly visible and provided with dimensions in the drawing sheets.

GEOMETRIC DIMENSIONING AND TOLERANCING

Geometric Dimensioning and Tolerancing (GD&T) is a system for defining and communicating engineering tolerances. It uses symbolic language on engineering drawings and computer-generated three-dimensional solid models that explicitly describe nominal geometry and its allowable variation. It tells the manufacturing staff and machines what degree of accuracy and precision is needed on each controlled feature of the part. GD&T is used to define the nominal (theoretically perfect) geometry of parts and assemblies, to define the allowable variation in form and possible size of individual features, and to define the allowable variation between features.

 

DRAFTING

Drafting also called as engineering drawing, graphical representation of structures, machines, and their component parts that communicates the engineering intent of a technical design to the craftsman or worker who makes the product.

  At the design stage, both freehand and mechanical drawings serve the functions of inspiring and guiding the designer and of communicating among the designer, collaborators, production department, and marketing or management personnel. At this stage, exact mechanical drawings can clarify, confirm, or disqualify a scheme that looked promising in a freehand sketch. Actually, both the sketch and the exact mechanical drawing are essential parts of the process of designing, and both belong to the field of drafting. After the basic design has been established, drafting skills aid in the development and transmission of the wealth of data necessary for the production and assembly of the parts. For an automobile, a skyscraper, or a spacecraft, tens of thousands of drawings may be needed to convey all of the requirements of the finished product from the designers to the fabricators.

Key Sheet OF Fixture Assembly

Base Unit

A base unit is a steel or aluminium plate of 20-40mm to which all other pin and clamp units are attached. It must also provide space for parts like a pneumatic controller, eye bolts, pneumatic cable trunking paths etc.

DESIGN FUNDAMENTALS OF BASE PLATE DESIGN:

• The Base unit should enclose all the units to the periphery including in the open position.
• The Baseplate should be designed as per BCS coordinates.
• It should have datum holes and measuring holes with a pitch of 1000mm in general.
• Depending on the size of the plate the number of holes may vary.
• Datum holes should be places at nominal positions like X=150, Y=120, Z=380
• Datum holes should be at least 100mm from other units
• Datum holes should be covered with cover plates

PIN UNIT

  A pin unit is used to locate a component in a fixture, they can be separated based on the ability of motion of the pin as a fixed and retractable pin unit. The pin unit stops the motion of the component along a certain axis.

  

A fixed pin unit consists of a riser, blades, shims, pin retainer and pin.

• Riser: It’s the part used to change the height of the whole unit.
• Blades: These are plates mounted on the riser to which other parts like cylinders, arms etc are mounted.
• Shims: These are parts that are used to compensate for the stack-up tolerances of the mylars. They vary in thickness by 0.1mm, 0.2mm, 0.5mm etc.
• Pin and pin retainer: The pin which is fixed to the pin retainer

The primary purpose of this unit is to locate the panel using the pin. It restricts the degrees of freedom of the panel using the 3-2-1 principle

Round Pin Unit

Diamond Pin Unit