Week 4:- Pin Unit Design Challenge

Week 4:- Pin Unit Design Challenge

QUESTION NO:- 1. Design 2 Different types of Fixed Pin Units with Different Pins, Riser, Blade, and Block.

QUESTION NO:- 2. Design 2 Different types of Retractable Pin Units with Different Pins, Riser, Blade, Cylinder, and Block.

ANSWERS:

In industry, while assembling a car several processes has to be performed on it at a part level so that it is fit for the roads. the process that is performed at the part level can be summarized in one word as joining processes.
and to precise do this operation on a car panel requires the panel to be held properly at the same position so that the robot can work upon it to hold the panel in the position we use various fixtures which is an assembly of various units like rest units, fixed unit, retractable pin unit, rough locator units, sensor units base unit, etc. this project focusses on the design of fixed pin unit and retractable pin units with design consideration which are usually taken into account while making a fixture.

FUNDAMENTALS OF PIN UNIT DESIGN

FORMULA & CALCULATION:

Formula to calculate the length of the screw,

length of the screw= [1.5x(std. hole size)]+{distance between the surface of the part to the first surface of the other surface}

MATERIALS USED

A. pin: C45, EN31, SAE 8620 STEEL, etc

B. Pin Retainer: STEEL/ASTM A-36, SS type 303,304, etc

c. Shims/ Spacer: SAE 1010 CRS FULL HARD. COLD ROLLED STRIP STEEL S.A.E. 1010 FULL HARD, S.A.E 1020 HRS, etc.

D. Shim bLOCK: STEEL ASTIM A-36, NM Strainless, STEEL ASTM A-36, SS type 303 or 304, etc.

E. BLADE: STEEL ASTM A-36 etc

F. Riser: STEEL ASTM A-36 etc

HARDNESS:

In general, the hardness of the materials for pin retainers, shims, blocks, blades & risers are:

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

SURFACE FINISH:

PIN: chrome plating. zinc coating, pin with TiN codes shall have 1 to 2 micron of nitride added to the surface.

PIN RETAINER: Black oxide finish, no black oxide finish for "SS type" components (surface to be flat and parallel & perpendicular to 0 within 0.015`T.I.R).

SHIMS/SPACER: Black oxide finish (surface to be flat and parallel to within 0.015mm T.I.R).

RISER: Surface to be flat, parallel & perpendicular to within 0.015 T.I.R

PIN TOLERANCE:

The pin tolerance for a geo pin will be closer tolerance i.e -0.15 mm & for respot, the pin is -0.28mm.

PURPOSE OF PIN UNIT:

• AS by the 3-2-1 locating principle, the introduction of two-pin helps to arrest the 6 degrees of freedom (4 axial & 2 radial movements) whereas other 6 degrees of freedom are arrested by the introduction minimum of three support.
• Typically, the locating pin is used to locate a body part in a position sufficiently accurate to execute a welding process.
• The body part is constrained by a set of appropriately locationg pins so total constraint by locating pin should be fully constrained at all times to prevent any movement.

FUNDAMENTALS OF PIN UNIT DESIGN:

It is necessary to have two pins to locate a car panel and here one pin must arrest 4 ways (i.e translation) & other must-have arrests 2 ways (i.e rotational) of a car panel.

1. Pin should engage 3 to 5 mm from car part entry surface.

2. All pins should be accommodated with 2-way adjustable shims irrespective of the direction of arresting.

3. ROUND PIN should be used in case of 4 way arresting of car panel if the hole is round.

4. ROUND PIN can be used for 2 way arresting of car panel only if the hole is slot.

5. DIAMOND PIN should be used in case of 2 way arresting of car panel if the hole is round.

6. DIAMOND PIN should be used in case of 4 way arresting of car part if the hole is slotted

7. The axis of the car panel hole & the axis of the pin should be the same in general.

This fig shows the 1st point in the fundamentals of pin unit design.

This fig shows the 3rd point in the fundamentals of pin unit design.

This fig shows the 4th, 5th & 6th point in the fundamentals of pin unit design.

TYPES OF PIN UNITS:

• A fixed pin unit is a unit designed to locate the car panel using pins.
• Pin, Pin retainer, shims, block, Blade, and riser are the parts of fixed pin units in general.
• A pin retainer is used to hold the pin firmly.

RETRACTABLE PIN UNIT:

• A retractable pion unit is a unit designed to locate the car panel using pins, but package parts will be mounted on the retractable cylinder.
• Pin, Shims, L-Block, Pneumatic cylinder, and riser, are the parts of a retractable pin unit.

TYPES OF PIN UNITS:

A fixed pin unit is a unit designed to locate the car panel using pins.

Pin, Pin retainer, shims, block, Blade, and riser are the parts of fixed pin units in general.

A pin retainer is used to hold the pin firmly.

RETRACTABLE PIN UNIT:

• A retractable pion unit is a unit designed to locate the car panel using pins, but package parts will be mounted on the retractable cylinder.
• Pin, Shims, L-Block, Pneumatic cylinder, and riser, are the parts of a retractable pin unit.

TYPICAL PARTS OF FIX UNIT:

The different parts of the fixed pin unit are as follows.

1. PIN
2. PIN RETAINER
3. SHIMS
4. L-BLOCK/ SHIM BLOCK
5. BLADE
6. RISER

PIN:

• It is used for the locating purpose of the panel.
• Typically the locating pins are used to lactate body parts in a position sufficiently accurate to execute a welding process.
• The body parts are constrained by a set of appropriately locating pins a total constraint by locating the pin should be fully constrained at all times to prevent any movement.
• There are dozens of styles of locating pins that can be utilized in a design.
• A pin can either be a make part or a standard part also. below I have the commonly used pins.

One of the most common pins is a stepped pin with either a small or large head.

CONSIDERATION WHILE DESIGNING & MANUFACTURING OF PINS:

• the pin should have a grinding surface on the shaft with fits on to which the pin retainers will be fitted.
• The mounting surface of the pin should be a finely machined surface.
• A pin should have a step machine surface to lock the rotation, which is matched with the pin retainer.
• The mounting surface of the pin retainer to the blocks should be a machined surface.
• All machined planes should be perpendicular to the axis of the pin shaft.
• Pin must have a fastening provision like a tapped hole from the bottom or v-groove from the side.
• A pin must be hardened (55-60 HRC) & oxide finish in general.

PIN RETAINER:

• A pin retainer is a part that holds the pin in position, the pin retainer can either be a make part or a standard part also.
• A pin retainer is used to hold the locating pins firmly.

CONSIDERATION WHILE DESIGNING & MANUFACTURING OF PINS RETAINERS :

• Pin retainers should have a hole with a fit, on to which the pin will be fixed.
• The pin mounting surface of the pin retainer should be a finely machined surface.
• The pin mounting surface of the pin retainer should have the step to lock the rotation of the pins.
• The pin mounting surface of the pin retainer to the blocks should be a machined surface.
• The pin retainer will is fixed to a block or an L-Block to the riser with 2 dowel holes & at least one screw hole to maintain the tolerance.

SHIMS

• Shim is generally used to adjust the design to manufacturing deviation.
• In general, A shim is a thin and often tapered or wedged piece of materials used to fill small gaps spaces between objects.
• shims are typically used in order to support, adjust for better fit, or provide a level surface.
• Shims may also be used as spacers to fill gaps between parts subject to wear.
• Shims are small parts that come with a thickness of 0.1mm, 0.2mm, 0.5mm, 1mm, etc.
• These will compensate for the stack-up tolerance which reflects at the mylars.
• We give tolerance to all parts of the fixture. due to this tolerance, the mylars will lift up and move down from its defined position.
• To adjust the mylar for getting the position, we use shims.
• Shims will be added above the mylar for adjusting according to tolerance.

APPLICATION OF SHIMS:

1. In automobiles, shims are commonly used to adjust the clearance or space between two parts. for example, shims are inserted into or under bucket tappets to control valve clearances .clearance is adjusted by changing the thickness of the shim.

2. In assembly and weld fixtures precision metals shims are used between two parts so that the final production parts are created within the product drawing specified tolerance.

L-BLOCK/SHIM BLOCK:

• These parts are mainly used to accommodate the shimming direction as per fundamental in general.
• Also in some cases used for other design feasibility.

RISER:

• The riser is a manufacturing part used to raise/height the assemblies of fixtures.
• One end of the raiser will be attached to the base unit while the other end will be attached to the blade.
• It is a part on which all the parts of a unit are mounted on the base plate of a tool. In general, the riser can either be made part of a standard part.
• Raiser can be of two types they are----

1. L-TYPE RISERS
2. SQUARE TUBE RISERS

L-TYPE RISERS: L- type risers are of welded type. Where the stiffener will be added at the center for support. As shown in the below figure the wedge-shaped structure is known as stiffener which is used to support/withstand the load.

Square Tube Risers: Square Tube raisers are of frame type.

F. Blade:

• A blade is a part like a plate, which connects the parts of a unit to a riser. In general, the blade can either be made part of a standard part.
• The blade is the plates that are attached to the raiser.
• The blade is also attached or mounted with cylinders, arms, etc.

Dowel holes & machined surfaces in pin unit:

All make parts that are to be assembled with tolerance should be designed with 2 dowel holes& at least 1 to 6 threaded or free holes ( depends on size). And to be finely machined for the mounting surface with 3 to 5mm step machining (SURFACES TO BE FLAT, PARALLEL &PERPENDICULAR TO O WITHIN 0.015 T.I.R.).

BOUGHT OUTS :

Bought outs used in this project to design a pin unit are,

1. Cylinders.
2. Fasteners

Cylinders:

• std: SZK_40_BR3_A12_T12 (Make: Tunkes): Retract cylinder with side mounting on piston rod for offset centering pins, flat-strength aluminum material, drive via oval-shaped oblong cylinder 40/63 for thrust and tensile force of up to approx. 1200N, push rod secured against twisting double- supported in the bronze bushing, integrated inductive sensor, guide rod secured against twisting, 40 mm combined stroke 40mm intermediate stroke lengths upon request.

Fasteners

• Hexagon Allen cap screw (std:EN_ISO_4762_Steel hexagon cap screw)
• Washer (Std:EN_28738_8_steel grade_ clevis_ pins_plain_washer).

CONCLUSION:

Hence, As per the objective, the 2 different types of fixed pin units with different pins, pin retainer, blades & riser & 2 different types of retractable pin units with different pins, pin retainer, blades riser & cylinder are designed and rendered using CATIA V5 successfully.

THANKS