Week 4:- Pin Unit Design Challenge
Pin unit is a unit design to locate car panel through pin.This unit consists up riser,Blade,Blocks,Shims/Spacer,Pin retainer and pin.Pin unit is design 3-2-1 locating principle,so that it restrict 6degree of freedom of the part.
Fundamentals of pin unit design
- It is necessary to have 2 pins to locate a car panel and one pin must arrest 4ways i.e 4 translational and other must arrest 2ways i.e 2 rotational of a car panel.
- The axis of car panel hole and axis of pin should be same in general.
- The pin tolerance for a Geo pin will be of closer tolerance (i.e -0.15) and for respot pin tolerance is -0.28.
- Pin should engage 3-5 mm distance from car panel entry surface.
- All pins should accomodate with 2ways adjustable shims.
- Round pins should be used in case of 4 way arresting of car part if the hole is round.
- Round pins can be used for 2way arresting of car part only if the hole is slot.
- Diamond pins should be used in case of 2way arresting of car part if hole is round.
- Dimaond pins should be used in case of 4 way arresting of car part if the hole is slotted.
There are 2types of pin units-
1.Fixed pin unit-Pin is fixed by means of pin retainer and riser.
2.Retractable pin unit-In this unit there is the provision of moving of pin in up-down direction.
Below parts are manufactured to create this unit are-
Pin:
Pin is the part which locates the car panel.It can be a manufactured or standard part.
- Pin should be grinding surface on shaft with fits on to 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 th rotation,which matches with the pin retainer.
- All machined planes should be perpendicular to the axis of the pin shaft.
- Pin must have provision like tapped hole from the bottom or a v-groove from the side.
- A pin must have hardened(Heat treatement) and Black oxide finished in general.
Pin Retainer:
A pin retainer is a part which hold the pin in position,It is also manufactured or a standard part which is easily available in market.
- Pin retainer should have a hole with a fit,on to which the pin will be fixed.
- The pin mounting surface of pin retainer should be machined surface.
- Pin mounting surface of the pin retainer should have a step to lock the rotation of pin.
- The pin retainer will be fixed to a block or a L-Block to the riser with 2dowel holes and at least with one threaded hole to match the tolerance.
Block/L-Block
These parts are mainly used to accomodate the shimming directions as per general fundamental.Also in some cases used for other design feasibility.
Shims/Spacers
Shims and spacers are some standard parts in general,which are used for adjustements of locators (NC Blocks and Pin retainers) for desired values with precise working of a unit with respect to car part.In other words to adjust the design to manufacturing deviation.
Blade
Blade is a part which connects the parts on a unit to a riser.Also it can be manufactured or a standard part which is easily available in market.
Riser
It is a part on which all the parts of a unit are mounted and it is mounted on the base plate of a tool.
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