Week 10- Assembly Workbench

DESIGN AND ASSEMBLY OF CV JOINT AND QUICK RETURN MECHANISM

Objective:

The main aim of this report is to explain the procedure involved in design and assembly of CV joint and Quick return mechanism with the help of given 2D drawing sheets.

Description:

CV joint:

Constant-velocity joints (also known as homokinetic or CV joints) are mechanical joints which allow a drive shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction or play. They are mainly used in front-wheel drive vehicles. Modern rear-wheel drive cars with independent rear suspension typically use CV joints at the ends of the rear axle halfshafts and increasingly use them on the drive shaft.

CV joint parts:

For the given cv joint there are 3 parts. They are,

• Vertical holding cups
• Centre shafts
• Horizontal C cups.

The input given to create CV joint is shown in the above picture.

Part creation for the CV joint:

The following steps are involved in part creation for the CV joint,

• The positioned sketches are created under the construction elements with iso-constrained geometry in the sketcher workbench with reference to the given sheets.
• These sketches are created in the appropriate planes to create solid parts.
• With help of those sketches solid parts are created using the pad command in the part work bench along the required direction.
• Then the parts are added and removed with help of Boolean operations according to the requirements.

Assembly:

The following steps are involved in the assembly of parts created before to form an CV joint.

• The assembly process is carried out in the assembly work bench and the assembly file has .CATProduct as its extension.
• The assembly of CV joint starts with reference to the reference elements created in the part level.
• In part level the reference points, axis and planes are published to ease of access in the assembly work bench. Those publications are child features, if the parent features are modified in the part level its publications also gets modified.
• Previously created parts are opened in the assembly work bench as child features of product, then a new part is created to serve as an assembly reference.
• This assembly reference is fixed to arrest its all degrees of freedom to hold the parts together.
• After the fixation, the parts are assembled with giving the coincident and offset relations to the appropriate planes, axis and points.

Quick return mechanism:

A quick return mechanism is an apparatus to produce a reciprocating motion in which the time taken for travel in return stroke is less than in the forward stroke. It is driven by a circular motion source (typically a motor of some sort) and uses a system of links with three turning pairs and a sliding pair.

Quick return is a common feature of tools in which the action is performed in only one direction of the stroke, such as shapers and powered saws, because it allows less time to be spent on returning the tool to its initial position.

Quick return mechanism parts:

For the given quick return mechanism there are 5 parts. They are,

• Slotted link
• Pivot block
• Sliding block
• Crank

The input given to create Quick return mechanism is shown in the above picture.

Part creation for the Quick return mechanism:

The following steps are involved in part creation for the quick return mechanism,

• The positioned sketches are created under the construction elements with iso-constrained geometry in the sketcher workbench with reference to the given sheets.
• These sketches are created in the appropriate planes to create solid parts.
• With help of those sketches solid parts are created using the pad command in the part work bench along the required direction.
• Then the parts are added and removed with help of Boolean operations according to the requirements.

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Assembly:

The following steps are involved in the assembly of parts created before to form an quick return mechanism.

• The assembly process is carried out in the assembly work bench and the assembly file has .CATProduct as its extension.
• The assembly of quick return mechanism starts with reference to the reference elements created in the part level.
• In part level the reference points, axis and planes are created and published to ease of access in the assembly work bench. Those publications are child features, if the parent features are modified in the part level its publications also gets modified.
• Previously created parts are opened in the assembly work bench as child features of product, then a new part is created to serve as a assembly reference.
• This assembly reference is fixed to arrest it’s all degrees of freedom to hold the parts together.
• After the fixation, the parts are assembled with giving the coincident and offset relations to the appropriate planes, axis and points.

Conclusion:

The steps involved in design and assembly of CV joint and quick return mechanism is explained with some reference images of parts and final assembly.