PIN UNIT DESIGN

AIM : pin unit is a unit designed to locate the car panel using pin. Pin unit consist of riser, blade, block, shims or spacer, pin retainer & pin. pin unit is the part of the 3-2-1 locating principle of fixture design. It restricts 6 degrees of freedom of the part.

Fundamental of pin unit design

• itis necessary to have 2 pins to locate a car panel & here one pin must arrest 4 way(4 transitional) & other must arrest 2 way(i. 2 rotational) of a car panel.
• Theaxis of the car panel hole & the axis of the pin should be same (in general)
• Thepin tolerance for a Geo pin will be of closer tolerance i. -0.15mm & for re-spot pin is -0.28mm

• Pinshould engage 3 to 5 mm from car panel entry surface.
• Allpins should be accommodated with 2 way adjustable shims irrespective of direction of arresting.

3)round pins should be used in case of 4 way arresting of car part if the hole is round.

4) Round pins can be used for 2 way arresting of car part only if the hole is slot.

1. S)Diamondpins should be used in case of 2 way arresting of car part if hole is round

• Diamondpins should be used in case of 4 way arresting of car part if hole is slott

There are 2 types of pin units

]) Fixed Pin unit :In this type of unit the pin is fixed by means of pin retainer & riser.

2) Retractable Pin uni t- In this type of unit there is the provision of moving of pin in up-down direction.

])Pin:Pin is the part which locates the car panel. It can be a make part or standard part

1. Pinshould be grinding surface on shaft with f its on to which the pin retainer will be fitted.

1. Themounting surface of the pin should be a fine machined surface.
2. Thepin should have a step machine surface to lock the rotation, which matches with the pin retai
3. All machined planes should be perpendicular to the axis of the pin
4. Pin must have a provision like tapped hole from the bottom or a v-groove from the side A pin must be hardened (Heat treatment) & black oxide finished in general PinRetainer:

5. A pin retainer is a part which hold the pin in position,the pin retainer can either bea make part or a standard part.

   1. Pinretainer should have a hole with a fit, on to which the pin willbe f i
   2. Thepin mounting surface of the pin retainer should bea machined
   3. Thepin mounting surface of the pin retainer should have a step to lock the rotation of the pin
   4. Thepin mounting surface of the pin retainer to the blocks should bea machined
   5. Thepin retainer will be fixed to a block or a L block to the riser with 2 dowelholes (pins) & atleast with one screw hole to maintain the tol

   3) Block/L Bl ock:

   These parts are mainly used to accomodate the shimming directions as per fundamenta lin general. Also in some cases used for other design feasibility.

   4) Shims/Sf2acers:

   Shims & Spacers are some standard parts in general.which are used for adjustments of locators(NC Blocks & pin retainers) for desired values for the precise working of a unit with respect to car part. In generalto adjust the design to manufacturing deviation.

   5) Blade:

   Blade is part like a plate, which connects the parts on a unit to a ri ser. In general the blade can be either a make part or a standard part.

   6) Riser:

   I t is a part on which all the parts of a unit are mou nted & is mou nted on the base plate of a tool.

   7) Dowel holes & machi n ed surface:

   All make parts which are to be assembled should be designed with 2 dowel holes & at least of 1 to 6 threaded/ free hole(depens on size) 7 to be fine machined for the mounting surf ace with 3 to 5 mm step machining.

   1. Design 2 Different types of Fixed Pin Unit with Different Pins, Riser, Blade, and Block?