Week 4:- Pin Unit Design Challenge

Report on Pin Unit Design

Aim:To design two different type of fix pin unit with different Pins, Riser, Blade, and Block and two retractable pin unit with Different Pins, Riser, Blade, Cylinder, and Block.

Fix pin unit:

Fixed pin unit is a unit designed to locate the car panel using pins.table

Pin, pin retainer, shims, blocks, blade, riser are the part of fixed pin units.

Pin retainer is used to hold the pin firmly.

Typically, the locating pins are 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 locating pin so total constraint by locating pin should be fully constrained at all times to prevent any movement.

Retractable Pin Unit:

Retractable pin unit is unit designed to locate the car panel using pins, but the entire pin package parts will be mounted on the retractable pneumatic cylinder as shown in below fig 3.

Retractable pin unit is the opposite of fixed pin unit which can be moved up & down also which can be retracted till certain distance.

It is mainly used for unloading the complex panel after welding.

Parts of the pin unit:

1. Pin: This is the part which holds the fixture in the place.
2. Retainer: This is the part which holds the pin.
3. L-Block: This is the part which connects the retainer to the riser.
4. Riser: This is the part which is the base of the assembly of the pin unit, all the other parts are mounted on the riser. The riser can be of two types L-Type riser or a T-Type riser.

Parts of the retractable pin unit:

The retractable pin unit has the same parts as that of the fixed pin unit except that the pin is connected to a hydraulic/pneumatic cylinder instead of a retainer. The cylider retracts the pin when the part is to be moved.

Fundamentals of pin unit design:

It is necessary to have two pin to arrest the car panel. One pin should arrest 4 DOF and the other should arrest 2 DOF

1. Pin should engage 3 to 5 mm from the car part entry.
2. All pins should be accommodated with at least 2 shims irrespective of direction of arresting
3. In 4 ways arresting round pin should be used
4. If the hole is slot round pin can be use for 2 way arresting
5. Diamond pin should be used for 2 way arresting if the hole is round
6. Diamond pin should be used for 4 ways arresting if the hole is slotted.

The axis of the car panel should be same as the axis of the pin.

The geo pin tolerance can be -0.15 mm, for re-spot pin – 0.28 mm

Design methodoly:

• The pin has a flat portion of its collor to prevent it from rotating on its axis in the retainer.
• The pin is designed according to the size of the hole in which it will fit.
• The retainer is designed and then blades, L- Blocks and the riser.
• Adjustments are made to get a proper part.
• All parts have holes in which standard bolt will fit to assemble the pin unit
• The Riser has hole on its base to fix it to the shop floor
• All the parts have a 5mm gap in betweeen them to fit the shims

Parts of the pin unit:

Pin:

A pin is a part which locates the car panel. A pin can be a make part or standard part.

• The pin should have grinding surface on the shaft on which the pin retainer will be fitted.
• The mounting surface of the pin should be a fine machined surface.
• The pin should have a step machine surface to lock the rotation, which matches with the pin retainer.
• The mounting surface of the pin retainer should be a machined surface.
• All machined planes should be perpendicular to the axis of the pin shaft.
• The pin should have a tapered hole from the bottom for fastening.
• Pin must be hardened and black oxide finished in general. (The hardness factor should be 55 – 60 HRC)
• Material: 20mm CR5

Pin Retainer:

Pin retainer is the part which holds the pin in the position, it can be make part or standard part.

• Pin retainer should have a hole with a fit on to which the pin will be fixed.
• Mounting surface of the pin retainer should be a machined surface.
• The pin mounting surface should have a stepped surface to block the rotation of the pin.
• The mounting surface of the pin to the block should be machined.
• The pin retainer will be fixed to the L-Block to the riser with 2 dowel holes and at least one screw hole to maintain the tolerance.

Block/L-Block:

• These parts are mainly used to accommodate the shimming direction as per fundamentals in general.

Shims/Spacers:

• These are for obtaining the desired precession with respect to car part. Shims are placed between retainers, risers, blades and block to make minor adjdust ment in the fixture to match the hole on the car panel. These are standard parts.

  These are made up of several plated of different thickness, depending on the need the shims of appropriate size and numbers are added.

Riser:

• The part on which every other part is mounted. This part is mounted on the base plate of the tool. This is a T-type riser.

Types of pin:

Diamond pin: To prevent over constraint sometimes diamond pins are used:

Retractable pin unit:

This pin unit has a hydraulic/pneumatic cylinder to extend/retract the pin in the part.

This enables the worker to move the part when needed and fix it in a place.

Pin unit with single rod cylinder and normal pin:

Pin unit with double rod cylinder and a diamond pin:

Cylinders:

In this pin unit Tunker cylinders are used

• SZK_40_1_BR3_T12_TUENKERS:

• SZKD_40_BR4_A23_T12_TUENKERS:

Different Pin units with Panel

Conclusion:

Two pin units for Fixed pin unit, two pin units for Retractable pin unit and different types of pins were designed.