Week 5:- Rest Unit & Clamp Unit Design Challenge

Challenge:

1. Design 3 Different types of Power Clamp Unit with Different Riser, Blade and Clamp Arm for the given Car Panel.
2. Design 2 Different types of Rest Unit for the given Car Panel.

3-2-1 principle

Every part has 6 degrees of freedom (3 linear + 3 rotaries) which need to be arrested to ensure the proper location of the part in space. The location principle used to achieve this is called the 3-2-1 principle.

Any rectangular body may have three axes along the x-axis, y-axis, and z-axis. It can move along any of these axes or any of its movement can be released to these three axes. At the same time, the body can also rotate about these axes too. So the total degree of freedom of the body along which it can move is six. For processing the body it is required to restrain all the degrees of freedom (DOF) by arranging suitable locating points and then clamping it in a fixed and required position

The basic principle used to locate the points is desirable below. Six Points Location of a Rectangular Block. It is made to rest on several points on the jig body.

3 stands For - Minimum 3 Rests with clamps to establish a part plane thus restricting 1 up-down motion plus 2 Rotary motion. 3 locators position a part in a primary plane or direction. Provide a rest to the workpiece on three points on the bottom x-y surface. This will stop the movement along the z-axis, rotation concerning the x-axis and y-axis. Supporting it on the three points is considered better support than one point or two points.

Fig 1:- Primary Datum

For the primary locating datum, the area of the triangle formed by the three locating points should be as large as possible.

2 stands For – Two locating pins in a round hole that restricts motion in the two directions in the established plane. 2 locators then position the part in a second direction (e.g., in/out). Rest the workpiece on two points of the side surface (x-z), this will fix the movement of the workpiece along the y-axis and rotation concerning the z-axis

Fig 2:- Secondary Datum

The distance between the two locating points is as large as possible for the secondary locating datum, and the line segment connecting the two locating points should be parallel to the primary locating datum if possible.

1 stands For – A Round locating Pin in a slot that restricts the rotary motion in the established plane about the round pin. 1 locator for the tertiary direction. Provide support at one point of the adjacent surface (y-z) that will fix other remaining free movements

Fig 3:- Tertiary Datum

Fig 3:- Clamp unit arrangement to control DOF of the panel

All the DOF of the given panel is controlled by different Clamp units & rest units.

Clamp unit: - A clamp unit is a unit designed to clamp/hold the car panel with NC blocks/ Mylar/ rest by using a pneumatic clamp cylinder & below are different parts of a clamp unit in general. Usually clamp open position is 90°. Fingers are attached to the clamp Mylar. In a clamp unit shimming to one side is more than enough because it will restrict translation motion in upward & downward directions only. There is another type of clamp unit known as the swivel type. There is a pivot pin around which the clamp arm rotates.

Fig 4:- Typical Clamp units

Fig 5:- Simple Clamp unit

TYPES OF CLAMP UNITS:

1. Power Clamp unit.
2. Swivel cylinder clamp unit.

CLAMP PLAN:

1. The customer provides the clamp plan which consists of the position of the clamp, pins, rests and dump, etc.
2. It has the exact coordination of these components and in addition, it also has the hole’s dimensions and tolerances.
3. As this is critical input data, it must not be modified.
4. In case the spot for weld and the clamp position is nearby and it may create a problem later and there is a need to change the position of the clamp, the same must be done so with the permission of the customer as it will be easy for the customer to make changes from his side also.

Fig 6:- Clamp Plan

A typical Fixed Clamp unit consists of the following parts.

1. Mylar/NC Block
2. Block
3. Shim/Spacer
4. Blade/Adaptor
5. Riser
6. Clamp Cylinder

Mylar/NC Block

• NC blocks or popularly also known as Mylar is the ones that hold the panel.
• It prevents the panel from deforming while welding.
• They always come in pairs.
• Top Mylar is known as clamping Mylar and bottom Mylar is known as resting Mylar.

Few points to remember about Mylar:

• Generally, Mylar clamping block clamp cross section (the area in the contact panel) is considered as 20mmx20mm.
• Most of the OEMs/Tier 1 prefer Mylar to have a 5mm allowance material for machining. Most Mylar is CNC machined if it is clamping 3D profile.
• Depending on the angle of the cross-section, Mylar will be shimming either in one direction or in 2 directions.

The general Thumb rule is if the section is inclined more than 15 deg or the clamping surface is a 3D profile then 2-direction shimming is provided. The reason is simple mathematics. The equation of inclined line/ plane will be having 2 parameters to control and we control with shimming in 2 directions. Less than 15 deg does not mean that there are not 2 parameters. These are there but they are neglected if angle is less than 15 deg.

Fig 7:- Mylar/NC Block

Block:- The L-shaped plate is called a Block or L block. This part is used as a connection between the Pin retainer and Blade. Generally, blocks are used to provide shimming. Blocks don't need to be only used for shimming, their uses change as per the requirements, At some places, it is used just to connect one part to another.

Fig 8:- Blocks/L- Blocks

Shim:- Shims & Spacers are some standard parts in general, which are used for adjustments of locators (NC Blocks & pin retainers) for desired values for the precise working of a unit concerning car parts. In general to adjust the design to manufacturing deviation.

Fig 9:- Shim/Spacer

Blade:- The plate which connects Riser to the Block/Clamp cylinder is named Blade. This plate plays an important role in building the unit. The plate can be of any shape. But we need to keep in mind that the plate should be as compact as possible.

Fig 10:- Blades

Riser:- The part which is mounted on the base plate and holds a blade or pin cylinder on it is called Riser. The riser can be a Standard Part or a manufactured part, it varies from project to project. A riser can be a Single part or welded part. Standard risers also have various shapes and sizes.

Fig 11:- Risers

Clamp cylinder:- A clamp is a pneumatic device that works with pressurized air. It is used to open and close the parts fixed to the clamp arm fixed to the clamp body.

• They are in general of 40, 50, 63, and 80 bore capacity.
• Horizontal clamp mounting opens up to 135deg.
• Vertical clamp mounting opens up to 105deg.

V 50.1, 63.1, 80.1 BR3 Vario Clamp:- Vario clamp with toggle joint mechanism and continuously adjustable opening angle, Over-centre-lock, Enclosed aluminum housing, Oval-shaped cylinder in the sizes 50, 63, 80, Forked clamping arm, the standard hole pattern for adapting contour blocks, Continuously adjustable opening angle 5°-135°, optional: Weld immune inductive sensing of closing and opening position (T12).

Fig 12:- V 50.1 Vario Clamp Cylinder

VU_63_BR2_A05_T12_135_GRAD_TUENKER:- Vario clamp, Naams version, for clamping of medium and large body panels with step-less adjustable opening angle, integrated toggle lever mechanism, self-holding type. Enclosed aluminum housing, flat oval cylinder in sizes 50, 63, and 80. Fork-shaped clamp arm with standard hole pattern for receiving contour pieces. Opening angle variable from 5 ° -135 °. Options: - Inductive sensing, weld immune for the open and closed position (T12) – Hand-applied version.

Fig 13:- VU_63_BR2_A05_T12_135_GRAD_TUENKER Clamp Cylinder

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

• Clamp arms are different for the different bores of the cylinder
• Clamp arms are available in different hole pitch

Clamp arms are available as:

Fig 14:- Clamp Arms

Clamp Unit-1

Fig 15:- Clamp Unit-1 all views

Fig 16:- Clamp Unit-1 Clamping & unclamping

Clamp Unit-2

Fig 17:- Clamp Unit-2 all views

Fig 18:- Clamp Unit-2 Clamping & unclamping

Clamping Unit-3

Fig 19:- Clamp Unit-3 all views

Fig 20:- Clamp Unit-3 Clamping & unclamping

Fig 21:- Clamp Units with panel (all view)

Fig 22:- Clamp Units with panel

Fig 23:- Clamp Units with panel

REST UNIT:

• A rest unit is a unit that is designed to support or rest the car panel on it.
• Its sole purpose is to rest the panel onto it and thus no force or clamping is done.
• But as it is a simple design, it can be combined with other units to reduce the cost of the overall project.
• For example it can be used along with locating unit to locate and rest the panel or with a clamp unit to clamp and rest the panel.
• Or the rest unit, locating unit, and clamp unit can be used together in one single project.

Components of Rest unit:

• NC block
• Spacer/ Shim pack
• Blade
• Riser

Fig 24:- Typical Rest units

Rest Unit-1

Fig 25:- Rest Unit-1

Rest Unit-2

Fig 26:- Rest Unit-2

Fig 27:- Rest Units with panel (all views)

Fig 28:- Rest Units with panel

Fig 29:- Rest Units with panel (bottom view)

Fig 30:- Clamp units & Rest Units with panel

Fig 31:- Clamp units & Rest Units with panel

Design Tree

CONCLUSION:

3 types of Clamp units & 2 types of rest units were designed & properly positioned.