Challenge

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

IImtiyaj Mathakiya21 Mar 2023

Clamp Unit & Pin-Clamp Unit Design

AIM:-

To design 3 different types of swivel clamp unit with different riser, Blade and Clamp Arm for the given car Panel and Design of a Units which consist of both a clamp unit and a pin unit combined for the given Car Panel with optimum use of material and space constraint also considering Panel Thickness as 1mm for the given car panel.

Two types of clamp units used to clamp the car panel.They are:

power clamp unit.
swivel clamp unit.

To weld these parts ,they must be fixed using 3-2-1 principle:

3-2-1 PRINCIPLE:

Fixture must correctly locate a workpiece in a given orientation with respect to a cutting tool or measuring device, or with respect to another component.locating and clamping are the critical functions of any work holding fixture.

A workpiece free in space can move in an infinite number of directions.For analysis,this motion can be broken down into twelve directional movements or "degres of freedom". All twelve degrees of freedom must be restricted to ensure proper referencing of workpiece.

The best and most effective method of part location is reffered to as the 3-2-1 method.

6 Translational degeers of freedom : +x,-x,+y,-y,+z,-z.

6 rotational degrees of freedom:

C-ROT around X - axsis
AC-ROT around X- axsis
C-ROT around Y- axsis
AC-ROT around Y - axsis
C-ROT around Z- axsis
AC-ROT around Z - axsis

If we fix the clamps as per the 12 degrees of freedom listed above,then we can arrest the panel in a fixed position.

6- degrees of fredom are restricted by 2- pin units.

6- degrees of freedom are restricted by 3-clamp units and rest units.

CLAMP UNIT:

Clamp unit is a unit designed to hold /clamp the car panel with NC blocks/mylars / rest by using a pneumatic clamp cylinders .

PARTS OF CLAMP UNIT:

Mylar/NC block/Finger: Finger is a movable part which is used to hold the car part from top against backup and they are usualy mounted on the clamp arm.
L-block: L - shaped blocks are used to ount the finger to clamp arm, besides allowing adjustments for locator pin in two directions.
Shim/Spacer: They allow the finger to be moved to the correct xyz locating and allow the customer to make adjustments to improve the quality of their product.
Blade: Part onto which the aforeside element are attached to.
Riser: L- shaped or T shaped tall block which regularly patterened holes to attach the above mentioned parts in modular way blade space.Riser is either a make part or standard part.
Stopper: The function of stopper is to restrict clamp going beyond the limit.Stopper is mounted between clam arm and rest/blade.Stopper has two parts male and female , when this two parts meets they restrict motion.

Factors should be considered while designing a clamp unit:

There should be adequate space between the cylinder & another part like riser, car panel because cylinder moves or swing while opening & closing
Pin clamp unit used where two panel or component are located for welding.
Clamping make in such way that it clamps two car panels at once
All parts should snap & butt properly to each other.
Make sure that parts of the clamping unit are 10 to 12 mm away from car panel so they do not damage car panel
Avoid any clash. It will not arises issue at assembly.

Below are general parts of swivel clamp unit.

a) Clamp Cylinder:

Cylinder designation: In this unit we used Clevis cylinder for clamping designated as CKG_1B_63_100Y

Nomenclature of cylinder as belows:

CKG1: Series of cylinder

B: Clevis width as 19.5 mm.

63: Bore size

100: Stroke of cylinder

Y: End bracket i.e. double knuckle joint (M6 without tap)

b) Clamp arm: It is part to which clamp mylar mounted & also clamp cylinder is attached to the end of arm with the use of clevis pin. It has two plates welded & helps in rotating of clamp arm about pivoting point of blade.

when it is at 90° open position & clamp arm mounting hole must be in line with cylinder rod axis.

Sharpe edges must be removed. Chamfer or fillet always provided for aesthetic & safety purpose.

c) Mylar/ NC blocks/ Fingers: These are parts are used to hold panel. They are globally called as Mylar. Top side Mylar is called as clamping Mylar & bottom side is called resting Mylar. Every clamping Mylar should have resting Mylar. It is jaw type. It prevent panel from deforming while welding. It is hardened to increase its wear strength. Following consideration should be taken into account while designing Mylar.

The clamp & rest Mylar has the same size.

Minimum distance between clamp mylar mounting face & car panel should be more than 5 mm.

d) Stopper:

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

e) Blade: Blade is part to which all other units are attached for e.g. mylar, stopper, clamp cylinder, riser. Blade is designed according to position of all other parts.

f) Riser: Risers can be of L-type, welded or square tube or frame type. These are basically manufactured parts are used to give height to assembly. It is machined at mounted ends only to save cost.

g) Bush: Bush is friction type bearing. It is lubricated with grease, oil. It permits relative motion between two mating parts. It is made of hard material also its ID & OD are precisely machined or grinded. It press fitted & after worn out it is replaced with new one instead of replacing other part which save cost. Mostly phosphor bronze or gun metal material used for making bush.

h) Shims/spacer: In fixture, we are providing tolerance to each part mostly manufactured. Those tolerances tend to stack up & reflect together. In order to avoid that we use shims so we can easily adjust after assembly so whatever stack up there we will rectify it through shims. Shims come in thickness of 0.1, 0.2, 0.5 etc.

We provide shim to accommodate clamp as well as rest mylar in two direction. Clamp & rest mylar can be adjusted in one direction only i.e. up or down. Also two way shim provided for locating pin to accommodate adjustment.

ISOMETRIC VIEW.