Week 4:- Pin Unit Design Challenge

Pin Unit is locating unit which arrest movement of component in fixture. Fig. shows an example of fixed pin unit. It consist of pin, pin retainer, blade, two way shims or spacer which control X, Y direction adjustment, block and riser.

Fundamentals of Pin Unit are as below:

• Main purpose of fixed pin unit is to locate component
• This unit is used arrest 6 degrees of freedom of component
• Two pins are used to locate component. First pin restricts 4 translational motion and other one restricts 2 rotational motion.
• The axis of pin should be coincidance to that of axis of hole of car panel.
• The tolerance of pin is -0.15 and -0.28 for geo and re-spot fixture respectively.
• The pin shoild engauge 3 to 5mm from car panel.
• Pin unit have 2 way adjustment using shims or spacer in X and Y direction.
• If hole is round then round pin is used to arrest 4 degree of freedom.
• If hole is slot then round pin is used to arrest 2 degree of freedom.
• If hole is round then diamond pin is used to arrest 2 degree of freedom.
• If hole is slot then round pin is used to arrest 4 degree of freedom.

There are 2 types of pin units:

1. Fixed Pin Unit: In this type of pin unit, pin is fixed using pin retainer.
2. Retracted Pin Unit: Pin is movable using cylinders.

Following components used in Pin unit:

1. PIN: Pin are main part in this type unit because it is used to locate conponent. 2 pins are used to restrict 8 degrees of freedom. In this type of fixed pin unit, pins are fixed or non movable.
2. PIN RETAINER: Pin Retainer are used support or carry pin in it as shown in figure.
3. BLOCK: Block can be machined in any desired shape according to fixture. It may be simple square or rectangular block or it may be L shaped block as shown in figure.
4. SHIMS OR SPACER: Shims or spacer are used to compensate tolerance stack up. In pin unit we need to control two direction that are X and Y using shims or space. Shims are generally thin sized plates used in group called Shimpack and spacer are used as single plate and can be machined accordingly.
5. BLADE: As shown in figure blades are bolted on riser.
6. RISER: Riser are used to increase height of unit and these are standard parts so need not detailed it or designed it.
7. Dowels and machined surface: 2 dowel holes required in each and every parts in pin unit for accurate assembly of unit and 1 to 6 free holes or threaded tapping is required.

FIXED ROUND PIN UNIT:

FIXED DIAMOND PIN UNIT:

RETRACTABLE ROUND PIN UNIT:

RETRACTABLE DIAMOND PIN UNIT:

FIXED DIAMOND PIN UNITS:

RETRACTABLE PIN UNITS: