Week 5:- Rest Unit & Clamp Unit Design Challenge

DESIGN OF CLAMP UNIT

OBJECTIVE:

To design 3 different types of power clamp unit with different riser, blade, block and clamp arm & to design different types of rest unit for the given car panel.

SOFTWARE USED:

CATIA V5

CLAMP UNIT:

A clamp unit is a unit designed to hold/clamp the car panel with NC blocks/mylars/rest by using a pneumatic cylinder. Clamp arm, finger, rest/backup, L-block, shims, riser pneumatic cylinder are the typical parts of the clamp unit. Clamping force should be considered while designing clamp unit.

Clamp Arm

Riser

Pneumatic cylinder

shimpack

Clamp mylar mylar

Rest mylar

REST UNIT:

A rest unit is used to support the car panel; also it resists the clamping force of the finger with the help of rest mylars & thus clamps the car panel. Rest unit consists of rest mylars, shim packs, riser. Clamping force should be considered while design rest unit. Mostly to avoid extra part, to reduce the weight & to reduce the cost of the fixture the rest unit is combined with the clamp unit.

Below figure shows the combination of clamp and rest unit which is designed in this project by considering the basic principles of clamp and rest unit.

Rest mylar

Blade/support block

Shimpack

Riser

TYPES OF CLAMP CYLINDER & REST UNIT:

• Power clamp Cylinder unit.
• Swivel cylinder clamp unit.

In this project both types of cylinders used power clamp unit & Swivel type design.

PURPOSE OF CLAMP & REST UNIT:

The purpose of clamping tools is to securely hold the workpice in position without obstructing the production process. High clamping force combined with compact dimensions is therefore the most important requirements for a clamping tool.

CLAMPING:

The process of holding the position of the workspace in the jig or fixture is called clamping. The primary device used for holding a work piece is clamps/clamp unit.

RESTING:

The car panel rests on the rest unit; also it resists the clamping force for the finger & thus clamps the car panel.

CLAMP ARM OPEN POSITION:

In this project, clamp arm open position and closed position also done. Here are some images of clam arm open position and closed position,

CLAMP ARM OPEN POSITION

FORCES ACTING IN CLAMP & REST UNIT:

To design a clamp unit we have considered some forces which act in clamp unit for clamping purpose. The forces acts in clam unit are, Clamping force holding force. Clamping force is not same as holding force

CLAMPING FORCE:

Clamping force signifies the force applied to the earpiece by the drive mechanism via the clamp arm during gripping or clamping operations.

CLAMPING FORCE (Fs) = 48*S^3 = FORCE IN NEWTON.

HOLDING FORCE:

Holding force, on the other hand, denotes the maximum force, after knocking the knee-lever (over center position), that can be applied by the work piece on the griper/clamp arm without destroying the mechanism.

Therefore, particular attention must be paid to the maximum force when, for example during the production process (welding) there is a possibility of the 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.

PLP LOCATION & CLAMP PLAN:

PLP (principle locating points):

Principle locating points which are used for the accurate location of the panel’s subassemblies to maintain the geometry of the assembly. There are lots of holes on the panel which are not accurate due to stamping operations. So plop are defined in the drawings.

The PLP holes should be precise.

+ Y _

- X +

CLAMP PLAN:

Clamp plan provides the information of location of pins, rest units, clamp unit, dumps, etc.

It is the important input from the customer. The clamp plan /position should not be changed without the knowledge of customers.

It gives the detail of the exact position of the clamping units by mentioning a coordinates in the particular position.

4.P001_Z01_ST010_01_04_ U_80_BR5_A00_T24_2_TUENKERS

3.P001_Z01_ST010_01_03_ CKZ2N50-105RP-BA019P2 SMC Cylinder

2. P001_Z01_ST010_01_03_ CKZT50-135T SMC Cylinder

1. P001_Z01_ST010_01_04 CKG1A63-100IZ SMC Cylinder

5. P001_Z01_ST010_01_03_ CKZ2N80-135RT-AA025P(E)SMC cylinder

CYLINDER SELECTION:

FORMULA & CALCULATION:

1. Validate or selecting a power clamp cylinder.
2. Clamping force acts at the end of each mylars.
3. Holding force.

• validate or selecting a Clamp cylinder:

I have designed selection of clamps on the basis of outreach & sheet thickness.

1. How to choose sheet thickness? The thickness of panel is said to be considered as 1mm for this project.
2. How to find out outreach of clamp arm?

By measuring the distance between pivot center of cylinder and center of clamping mylars we can get the outreach of clamp arm.

Below given details is the outreach of the clamp arm taken from the respected clamp unit used in this project.

1. 1. P001_Z01_ST010_01_04 CKG1A63-100IZ Clamp unit-1 Outreach of the clamp-180mm
2. P001_Z01_ST010_01_03_CKZT50-135T Clamp Unit-2 Outreach of the Clamp-100mm
3. P001_Z01_ST010_01_03_CKZ2N50-105RP-BA019P2 Clamp Unit-3 outreach of the clamp-150
4. P001_Z01_ST010_01_04_ U_80_BR5_A00_T24_2_Clamp Unit-4outreach of the clamp-150
5. P001_Z01_ST010_01_03_ CKZ2N80-135RT-AA025P Clamp Unit-5 outreach of the clamp-300

After choosing the sheet thickness and outreach of the arm, now we can refer the graph shown below for selecting a suitable power clamp cylinder as per our requirement.

By relating the sheet thickness & outreach from the above graph, we can find the bore capacity of clamp cylinders. Based on the bore capacity the cylinders will be selected for the clamp unit.

Select Cylinder makers:

Clamp cylinder: It is a pneumatic cylinder device works with pressurized air (5 bar pressure is standard used to clamp automobile parts).The clamp cylinder is used to open & close the parts fixed to the clamp arm.

1. Clamp cylinders are bought out parts. Some of the manufactures are TUNKERS, ZYTRAN, DESTACO, FESTO, and STEEL SMITH. 2. Clamp cylinder is generally 40, 50, 63 &80 bore capacity (have to choose as per sheet thickness vs. outreach graph). 3. Open up to 135 degrees for horizontal clamp mounting. 4. Open up to 105 degrees for vertical clamp mounting.

UNIQUE PARTS OF CLAMP CYLINDER:

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

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

Clamp arm: Clamp arm is a part to which all the movable parts are fixed. In general clamp arms are available as based on the position of arm. They are,

• Middle arm-A10
• Right arm-A11
• Left arm-A12
• In the Project SMC make & Tunkers Make cylinder selected

Bore Size Selection:

Maker: SMC make

Model Selection:

1 Common precaution for each size

1) Use air filtered through a 5-μm-element filter.

2) Before piping is connected to the slim-line power clamp cylinder it should be thoroughly flushed with air.

3) Only use the clamp arm in our catalog. Do not weld an arm to the cylinder.

4) make sure to use a speed controller and adjust it to more than 1sec. when changing from clamping to unclamping (or vice versa).

2 Slim-line power clamp cylinder mounting

Procedure

1. A) Place the work piece, supply air at clamp side without installing clamping block, and operate the clamp arm to the end of clamp.
2. B) Under the above conditions, adjust shim so that the space between the work piece and the clamping block is about 0 mm.

Theoretically there is no clamping force for holding a work piece under this condition.

1. C) In order to generate clamping force from the state described in step B, insert additional shim. The thickness of the shim differs

Depending on the arm length and pressure, so please refer to the graph on pages 186 and 187 as a guide. About 10% errors may

Occur due to the difference in tolerance of the power clamp cylinder body.

Procedure

1. A) Supply air at clamp side without installation of upper hard stop, and operate the clamp arm to the end of clamp.
2. B) Under the above conditions, adjust shim q so that the space between the upper hard stop and the lower hard stop is about 0
3. Theoretically there is no clamping force to the lower hard stop under this condition.
4. C) In order to generate clamping force from the state described in step B, insert additional shim. The thickness of the shim differs

Depending on the arm length and pressure, so please refer to the graph on pages 186 and 187 as a guide. About 10% errors

May occur due to the difference in tolerance of the power clamp cylinder body.

1. D) Under the state described in step C, adjust shim w so there is contact between the clamping block and the work piece.

Allowable load for clamp arm end

Refer to the graph on below for parts weight of the arm.

Use within the allowable arm end load range according to the distance “L” from the fulcrum to the mounting tool’s center position

And the arm opening angle “θ”.

Maker: Tunkers make

Due to their enclosed structure, TÜNKERS standard clamps, with sizes 50 to 80, provide solutions for clamping

And gripping forces up to 4 kN. In addition to the robust construction, with integral needle roller bearings for

Optimum force transmission and high load cycles (up to 3 million), a particular feature of TÜNKERS Clamps is

The slim version with the oblong-section cylinder. This allows optimum accessibility in fixtures, for the use of

Spot welding guns.

All the standard series knee-lever clamps are equipped with integrated limit switches in cassette form, thus facilitating

Replacement and adjustment. As an option, the products are available with manual feed.

1.A.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 aluminium housing, Oval-shaped cylinder in the sizes 50, 63, 80, Forked clamping arm, standard hole pattern for adapting contour blocks, Continuously adjustable opening angle 5°-135°, optional: Weld immune inductive sensing of closed and opened position (T12)

2.B.U/U2... Universal Clamp

Variable high-performance clamp for clamping of medium and large-sized car body components with continuously adjustable opening angle and new force optimized knee lever mechanic. With the same force as a Vario Clamp, smaller cylinder diameters are used and so the air consumption is reduced by 30%. Enclosed aluminum housing, oval-shaped cylinder in the sizes 50, 63 and 80. Fork shaped clamp arm with standard hole pattern for adapting contour blocks. Continuously adjustable opening angle in the range of 5° to 135°. New two-parts switch for easy replacement.

MATERIALS USED:

In general, materials used for mylars, clamp arm, shims, shim block, blades & risers are:

1. MYLARS: UHMW, Nylon66, PP, Teflon (polytetrafluroethylene (PTFE)).Materials of clamp block and rest block to be decided as per the A class panel or B class. Most of the exterior panel holding Teflon material is used. Sometimes Aluminum blocks also used.
2. CLAMP ARM: SAE 4140 or SAE 1045.
3. SHIMS/SPACER:A.E 1010 CRS FULL HARD COLD ROLLED STRIP STEEL S.A.E.1010 FULL HARD, S.A.E.1020 HRS, etc.
4. SHIM BLOCK: STEEL ASTM A-36, NM STAINLESS, STEEL ASTM A-36, SS TYPE 303 or 304, etc.
5. BLADE: STEEL ASTM A-36, etc.
6. RISER: STEEL ASTM A-36, etc.

HARDNESS:

In general, the hardness of the material for clamp arm, shims, riser, block and blades are:

55-60 HRC/58-62 HRC to a depth of 0.5-0.7mm after grinding.

SURFACE FINISH:

In general, the hardness of materials for pins, pin retainers, shims, shimblock, blades & riser are:

3. CLAMP ARM: Munsell No.3.75YR6/14 safety orange.
4. SHIMS/SPACER: BLACK OXIDE FINISH (SURFACE TO BE FLAT AND PARELLEL TO WITHIN 0.015MM T.R.I).
5. RISER: SURFACE TO BE FLAT, PARELLEL & PERPENDICULAR TO WITHIN 0.015 T.R.I.

DESIGN TREE:

In structure tree all the manufacturing parts should be first and standard parts should be last. Structure tree helps to study or understand the parts in the assemblies easily.

CONCLUSION:

Hence as per objective, the three different types of power clamp unit by validating a power clamp cylinder and by considering a clamping force acts at each end of the molars & three different types of rest unit by considering holding force has been designed, Also the materials, surface finish & heat treatment used in the parts of clamp unit, purpose of clamp unit & clamp plans are briefly explained in detail.