Week 5:- Rest Unit & Clamp Unit Design Challenge

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.

INTRODUCTION

A clamp unit is a unit designed to clamp to hold the car panel with N/C blocks/ Mylars/ Rest by using a pneumatic clamp cylinder and below are the different parts of a clamp unit in general.

It consist of following parts:

• Clamp arm
• Finger
• Back-up/Rest
• Shims/spacers
• Pneumatic clamp cylinder
• Standard riser

FINGER

A finger is a NC block which is mounted on the clamp arm of the cylinder and will press the car panel towards the rest so that it holds the car panel.

REST

A rest is a NC block, which is fixed to the unit to support the car panel also it resists the clamping force of the finger and thus clamp the car panel.

CLAMP ARM

A clamp arm is a bought out part to which all the movable parts are fixed, In general a clamp arm is part of clamp cylinder.

Clamp arms are different for different bore of the cylinder.

Clamp arms are available in different hole pitch.

Clamp arms are available as Midddle Arm- A10 , Right Arm- A11 , Left Arm- A12.

CLAMP CYLINDER

A clamp cylinder is a pneumatic device works with pressurised air. The clamp cylinder is used to open and close the parts fixed to the clamp arm fixed to the clamp body.

Clamp cylinder are bought out parts, some of the manufacturers are Tuenkers and Destaco.

Clamp cylinder are in general 0,50,63 and 80 bore capacity.

Opens up to 135 for horizontal clamp mounting.

opens up to 105 for vertical clamp mounting.

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 are perpendicular to the 1st palne and at last one pin on the plane which is mutually perpendicular to the 1st and 2nd palnes. The ultimate goal is to constrain the movement of the workpiece along all three axes.

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 the two radial movement both clockwise and anti clockwise are also restricted so a total of four radial movements is restricted to the two mutaually perpendicualr axes.

The three locators on the whole, have restricted six degrees of freedom

2. Round locating pin

The pin ddded in the location of the hole restricts the axial movements of two perpendicular axes. 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 both clockwise and anti-clockwise. 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

1. The designing process is started by giving a project title and proper structuring of the specification tree.

2. The standard pneumatic cylinder and clamp arm which are the bought-out parts which is to be downloaded from the Tuenkers website and copied into the project.

   

3. The clamp mylars are 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 power cylinder arm for the opening and closing movement.

          

                                              1                                                                                                         2                                                                                                 3                                                   

4. 5mm shims are designed for the adjustment of the pin in multiple directions.

5. The risers are designed such that all the above parts can be mounted on this. The risers are mounted to the base of the fixture.

        

                                                          1                                                                                                                                       2         

6. Blades are designed to mount the rest mylar with the riser. The usage of blades 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.

BELOW ARE THE IMAGES OF POWER CLAMP UNITS

The yellow part shows the open position of the clamp arm. 

                                                                Isometric View

                 

                                                                Front View

REST UNIT

The rest unit are designed to support the car panels using mylar.

The primary purpose of the rest unit is to rest the car panel.

The parts of the rest units are as follows.

• Mylar
• Blade
• Risers

Mylar

Mylar is the part that hold the panel from above and below during the operation.

The top side of mylar is called 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.

The above image shows basic clamping and resting mylars.

RISER

A riser is a part that is used to raise the height of the fixture.

The riser is fixed to the base of the fixture and the blade is mounted on the riser.

There are two types of riser L type riser and square tube riser.

BLADE

Blades are plates that are attached to the riser.

DESIGN METHODOLOGY OF REST UNIT

1. The rest mylars are positioned below the panel in order to support the panel.

2. The blades are designed to support the rest mylar with the riser.

3. 5mm shim are added between the rest mylar and the riser.

4. The riser is designed in such a way that it supports the rest mylar.

BELOW ARE THE IMAGES OF THE REST UNITS

ASSEMBLY OF REST UNITS TOGETHER

                                     ISOMETRIC VIEW

                                        FRONT VIEW

The above image shows the rest unit assembly with the car panel.