Week 6:- Clamp Unit & Pin-Clamp Unit Design Challenge

Aim : To design 3 different types of swivel clamp unit with different riser, blade and clamp arm of the given car panel and design a pin clamp unit for the given car panel.

Introduction :

Swivel clamp unit :

A swivel clamp unit is a unit designed to clamp/hold the car panel with NC blocks / rests / mylars by using a pneumatic clamp cylinder which swivels around the pivot pin.

Usually clamp open position is 90° during the removal of car panel.

Shims are used in the upward and downward directions only to cover the stack up tolerance.

A clamp unit totally restricts 3 degrees of freedom in a fixture to position parts and hold them firmly during the operation. This restricts 1 translational motion and 2 rotational motions.

Factors to be considered while designing clamp units :

• Ensure adequate clearances between all the units so that they wont clash each other while the cylinder operates during the opening and closing.
• Pin clamp units are used where two panels or components are located for welding.
• Clamping should be such a way that it clamps all the car panels at once
• Make sure that parts of the clamping unit are 10 to 12 mm away from car panel so that they do not damage car panel.
• Ensure proper clearance between cylinder and other parts of the same unit while its operating, so that it wont clash while its swiveling action around the pivot point.

Typical parts of swivel clamp unit consists of ;

a) Swivel clamp cylinder :

A swivel clamp cylinder is a pneumatic device which works with the pressurised air to clamp the parts while it translates insides the cylinder to open and close the clamp arm. The cylinder swivels in a certain amount around the pivot point, while its operation.

Clamp cylinders are bought parts, some of the manufacturers are : Tunkers and Destaco.

Image : Swivel clamp cylinder

b) Clamp arm :

A clamp arm is a bought out part, to which all the movable parts are fixed. In general a clamp arm is a part of the 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 : Middle arm - A10, Right arm - A11, Left arm - A12.

Image : Clamp arm

c) Clamp mylar :

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

Image : Clamp mylar

d) Rest mylar :

A rest mylar 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.

Image : Rest mylar

Mylars are the parts which are in actual contact with the car panels.

e) Stopper :

The function of the stopper is to restrict the motion of clamp arm. It avoids clamp arm to rotate beyond limit. It has two parts male & female as shown below.

Image : Female stopper

Image : Male Stopper

Image : featuring stopper functioning in an assembly

f) Blade :

Blade is a part to which all other parts of the unit like mylar, stopper, clamp cylinder, riser are attached and hence it is designed considering the positioning of all the other parts.

Image : Blade

g) Riser :

Riser is a part which lies upon the base unit and carries the blade upon it.

Image : Riser

h) Shims/spacer :

Shims are used to adjust the stack up tolerances and comes in the sizes of 0.1 mm, 0.2 mm, 0.5 mm and so on to totally form a bundled thickness of around 5 mm approximately. Shims can be removed and added for adjustments.

Image : Shims

i) Bush :

Bush is a friction type bearing lubricated with grease, oil, to ensure smooth rotation of the clamp arm about the pivot point. It is assembled in between shaft pin and clamp hole.

Image : Bush

Bushes are also added at the swivel point of the cylinder and at the swivel rod end as shown in the image below.

Image : Bush positions

Hence considering all the required parts swivel clamp units are designed as shown below.

Image : Design of swivel clamp unit 1

Image : Design of swivel clamp unit 2

Image : Design of swivel clamp unit 3

Pin Clamp unit :

A pin clamp unit consist of a pin unit additionally along with the clamp unit.

Hence it restricts 2 more degrees of freedom because of the pin additionally, which are 2 translational motions.

A pin clamp unit is used in case a hole is placed near to the edge of the panel so that the manufacturing cost and some place on the base unit can be reduced.

Image : Pin-Clamp unit

Conclusion : Three different types of swivel clamp unit and one pin-clamp unit are designed and serves the purpose of holding and locating the car panel as shown in the images below.