Week 4:- Pin Unit Design Challenge

DESIGN OF FIX PIN AND RETRACTABLE PIN UNIT

INTRODUCTION

The fix pin and the retractable pin units are hole constraining fixtures for car panels.

FIXED PIN UNIT:

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

The parts of fixed pin are:

1. Pin
2. Pin retainer
3. Shim / spacer
4. Block
5. Blade or Adapter plate
6. Riser.

RETRACTABLE PIN UNIT:

A retractable pin unit is a unit designed to locate the car panel using pins, but the entire pin package parts will be mounted on the retractable pneumatic cylinder.

Types of retractable pin:

1. Single rod
2. Double rod

FUNDAMENTAL OF PIN UNIT:

It is necessary to have two pins to locate a car panel. One pin must arrest 4 ways (4 translational) and the other must arrest 2 ways (2 rotational) of a car panel.

1. pin should engage 3 - 5 mm from car part entry surface.
2. All pins should be accommodated with 2 ways adjustable shims irrespective of direction of arresting.
3. Round pin should be used in case of 4 way arresting of car part if the hole is round.
4. Round pin should be used in case of 2 way arresting of car part if the hole is slot.
5. Diamond pins can be used for 4 way arresting of car part only if the hole is round.
6. Diamond pins can be used for 2 way arresting of car part only if the hole is slot.

OBJECTIVE

The objective of the current project is to design and model two types of fix pin and retractable pin units along with retainers, blocks, shims, blade and riser in CATIA software.

DESIGN METHODOLOGY

1. The project is titled with the “P001_Z01_ST010_00_00”. All the parts in the feature tree of the CATIA must follow the same process for easy identification of parts in the assembly.
2. 
3. The centre of the hole is taken and the pin outline is modeled as per the standards.

Note: If there are any standards parts, it is advisable to use the standards parts as many as possible.

3. Retainers are mainly used to accommodate the shimming directions as per fundamental in general. Also in some cases used for other design feasibility.
4. 
5. The blocks are modelled in such a manner that the pin can be adjusted in longitudinal and translational direction.
6. 
7. A 5 mm space is provided between the block and retainers as the shims or spacer blocks are present.
8. 
9. The dowel holes are present in all the parts of the pin units which are to be assembled with tolerance should be designed with 2 dowels and at least of 1 to 6 threated / free hole(depends on size). And to be fine machined for the mounting surface with 3 to 5 mm step maching.
10. The blade is a plate which connects the riser to the block, usually the blades are standard parts if needed can be designed.
11. 
12. The riser is a part on which all the parts of a unit are mounted, and is mounted on the base plate of a tool. In general, the riser can either be make part or a standard part.
14. 

CONCLUSION

The fix pin and retractable pin units are modeled in the CATIA V5 software. In fixture design, it is advised to use the standard parts where ever it is necessary. If any new part is to be installed then the part can be modeled as per the customer requirements.