Week 5:- Rest Unit & Clamp Unit Design Challenge

                                                                                      WEEK 5 CHALLENGE

                                                                                            CLAMP UNIT & REST UNIT DESIGN

AIM - To design 3 Different types of Power Clamp Unit with Different Riser, Blade, and Clamp Arm and design 2 Different types of Rest Unit for the given Car Panel.

DESCRIPTION 

• A Clamp is a device that is used to hold the part tightly, yet, firmly in the assembly, The clamp prevents any sought of movement of the assembly in the fixture and ensures proper operation on the part without any distortion.
• The clamp must be placed in such a way that it does not interpret the operation. The clamp plan is the data provided by the customer. The clamp plan provides information on the location of pins, rest units, Clamp units, Dumps, etc.
• It gives the details of the exact position of the clamping locations in form of coordinates. The clamp position in some cases will be in such a way that it might damage the tool, or very near to pin position. In such cases, We should not take the decision to change the clamp plan without discussing it with the customer.
• 3-2-1 Principle = The 3-2-1 method is a work-holding principle where three pins are located on the 1st principle plane, i.e. either  XY, YZ, ZX. And two pins are located on the 2nd plane which is perpendicular to the 1st plane, and at last one pin on the plane which is mutually perpendicular to the 1st and 2nd planes. The ultimate goal is to constrain the movement of the workpiece along all three axes.
  • Every component we know has 6 degrees of freedom. They are listed below:
    • Translational motion along x-axis.
    • Translational motion along y-axis.
    • Translational motion along z-axis.
    • Rotational motion along x-axis.
    • Rotational motion along y-axis.
    • Rotational motion along y-axis.

3. Minimum = From the above figure, We can see three locator blocks positioned at the primary locating surface. These three locators restrict the axial upward and downward movement along with it the two radial movements both clockwise and Anti clockwise are also restricted. So, a total of four radial movements is restricted to the two mutually perpendicular axes. The three locators, on the whole, have restricted six Degrees of freedom.

2. Round Locating Pin = The pin added in the location of the hole restricts the axial movements of two perpendicular axes (both positive and negative). Thus, restricting Four Degrees of freedom.

1. Round Locating Pin = The round locating pin is added to the slot in order to restrict the remaining radial movement in both clockwise and anti-clockwise. This, therefore, restricts the remaining two degrees of freedom. Thus, the 3-2-1 principle is used to restrict the 12 degrees of freedom of a part.

DESIGN METHODOLOGY 

• CLAMP UNIT

1. The designing process is started by giving a project title and proper structuring of the Specification tree
2. The standard pneumatic cylinders and Clamp arm which are the bought-out parts are downloaded from the Tunkers website and copied into the project.
3. The Clamp mylars and rest mylars are designed and positioned in such a way that the movement of the car panel is restricted. The Clamp Mylars are attached to the clamp for the open and closing movement.
4. 5 mm shims/spacers are designed for the adjustment of the pin in multiple directions
5. The risers are designed such that all the above parts are mounted on them. The risers are mounted to the base of the fixture
6. Blades are designed to mount the rest mylar with the Riser. The usage of the blade depends upon the design of the riser and the position of the rest mylar.
7. The parts that are to be assembled are provided with dowel holes and threaded holes.
8. The yellow part in clamp unit shows the opening of clamp arm to 90 degrees.

• REST UNIT

1. The rest units are designed to support the car panels using Mylar.
2. The primary purpose of the rest unit is to rest the car panel.
3. The parts of the rest units are as follows - Mylar, Blade, Risers

MYLAR - Mylar is the part that holds the panel from above and below during the operation. The top side of Mylar is called the clamping Mylar. Whereas, the bottom side Mylar is known as resting Mylar. Every Clamping Mylar will have a resting Mylar. It holds the panel in such a way that it does not deform during the welding process. 

RISER - A riser is a part that is used to raise the height of the fixture. The raiser is fixed to the base of the fixture and the blade is mounted on the riser. There are two types of raisers L type riser and Square Tube risers.

BLADE - Blades are plates that are attached to the riser.

DESIGN METHODOLOGY OF REST UNIT

• The rest mylars are positioned below the panel in order to support them
• The blades are designed to support the rest mylar with the riser.
• 5mm Shims  are added between the Rest mylar and the riser
• The riser is designed in such a way that it supports the rest mylar.

 

FORCES ACTS IN CLAMP & REST UNITS: -

• To design a clamp unit we have considered some forces which acts in clamp unit for clamping purpose. The forces acts in clamp units are,
  • Clamping force.
  • Holding force.

Clamping and holding force are not same.

• CLAMPING FORCE - Clamping force signifies the force applied to the work piece by the drive mechanism via the clamp arm during gripping or clamping operations.

             Clamping force (Fs) = 48 x S3 = Force in newton

• HOLDING FORCE - Holding force, on the other hand, denotes the maximum force, after locking the knee-lever (over-centre position), that can be applied by the work piece on the gripper/clamp arm without destroying the mechanism. Therefore, particular attention must be paid to the maximum holding force when, for example during the production process (welding, bonding), there is a possibility of distortion of the component or if the clamp arm is used as a fixed stop. If the holding force specified in the technical details is exceeded, this will inevitably result in destruction of the mechanism, the clamp arm or the bearing position.

IMAGES

• CLAMP UNIT - 1

With Isometric, Top, Front and Right side view

• CLAMP UNIT - 2

• CLAMP UNIT - 3

 

• FINAL

CONCLUSION

Hence, the Clamp unit and the rest units are designed for the given car panel as per the requirements.