Week 5:- Rest Unit & Clamp Unit Design Challenge

Clamp and Rest Unit

Aim: To design clamp and rest units with different types of blades, clamps and risers for the given car panel. Designing 3 clamp units and 2 rest units.

Types of Units designed:

1) Rest Unit:

• It is the simplest unit to design and has the minimum number of parts.
• It is used to rest the component.
• No clamping finger is used. There is no force applied from above to hold the panel.
• It is usually added with other units to reduce cost of production.
• It is combined with either locating unit or all three are put together.

2) Clamp Unit:

• It is used to clamp the panels together to be able to carry out different process on it like welding.
• The clamping forcing needs to be monitored. The clamps usually open up to 90^o but can be designed for more depending on the requirement.
• There are two types of clamp unit, swivel type and power clamps.
• Swivel types has pivot point around which the rod translates and lifts the clamping mylar up or down.
• Power clamps are easier to design with clamping mylars directly attached to the cylinder arm.

Design Methodologies:

• 3-2-1 Principle: This principle is used for locking the 6 degrees of freedom of the component. A resting unit locks 3 degrees of freedom. The up and down movement and 2 rotational degrees of freedom.
• For locking all 6 degrees of freedom, 3 supports are placed to form the first datum.
• Next, we add clamping units to and add minimum of 2 pin units to arrest all 6 degrees of freedom.
• For the support or rest unit a simple resting mylar is designed and is attached to a riser wither directly of with the help or a blade.
• For a clamp unit, the resting mylar is designed and the clamping mylar is placed directly above it with a gap or the thickness of the car panel sheet.
• The clamping mylar is connected to the cylinder and can move up-to 90 degrees for removal or addition of the component.
• The cylinder is attached to the riser.
• The resting mylar is connected to the riser with the help of an arm.

Factors to consider while designing clamp unit:

• There should be enough space between the cylinder and other parts for free and correct movement of the calm arms.
• All parts should snap at correct positions.
• All clamp unit parts should be at least at a distance of 10mm in order to not damage the panel.
• Clamps should be made such that it can clamp 2 panels at once.

Clamp Plan:

• Clamp plan is provided by the customer and should not be modified without their knowledge.
• It mentions the cad data and the parts and placements of the units along with tolerances.
• In case of changes, the modified positions needs to be approved my the customers before implementation.

Forces on Clamp Units:

• Clamping force: It is the gripping forces acted on the panel due to the gripping of the clamping mylar.
• Holding Force: it is the maximum force by the resting mylar after locking it into position. It is an important factor and if the force level is exceeded then it can cause distortions in the components after procedures like welding are carried on it.

Parts of a Rest unit:

Resting Mylar: It is the part which is directly in contact with the workpiece. The car panel rests on the resting mylar, just restricting it’s up and down motion.

 

L-block: When the mylar needs to be adjusted in two directions, a blade can be added to the assembly. Or when there is space restrictions, L-block can be used.

Shims: It is used to manage the stack up tolerances and a pack of shims having an overall thickness of 5mm is used.

Riser: It is the resting part which is attached to the base and supports all other parts on it.

 

Rest Unit 1:

Rest Unit 2:

Parts of Clamp Unit:

Resting Mylar: Same as in rest unit, it is used to hold the component in place and the holding force is kept in mind while designing.

  

Clamping Mylar: the clamp holds the component from above and is placed directly above it. The clamping force is determined by the outreach of the clamp mylar. It is calculated by calculating the horizontal distance between the center of the finger touching the car panel and the center of the rotating axis of the span arm.

  

Blade/Arm: Used to attached the resting mylar to the riser.

 

Shims: Used to compensate for the stack up tolerances and is usually of an overall thickness of 5mm.

Cylinder: It is a bought-out part and the span arm is attached to the cylinder which is connected to the clamping mylar.

Yellow arm indicates the open position.

Riser: Is the attached to the base plate and all the other parts are mounted on it.

  

Clamp Unit 1:

Yellow Parts indicates the open position.

Clamp Unit 2:

Yellow Parts indicates the open position.

Clamp Unit 3:

Yellow Parts indicates the open position.

Assembly:

 

Conclusion:

Thus, designing of 3 power clamp units and 2 rest units with different designs is completed using Catia V5 software.