Week 4:- Pin Unit Design Challenge
AIM
1) To Design 2 Different types of Fixed Pin Unit with Different Pins, Riser, Blade, and Block.
2) To Design 2 Different types of Retractable Pin Unit with Different Pins, Riser, Blade, Cylinder, and Block.
PIN UNIT
- Pin unit is a unit designed to locate the car panel using pin.
- A pin can either be a make part or a standard part also.
- Pin unit consists of Pin, Pin Retainer, Riser, Blade, Block, Shims or Spacers.
- It is the part of the 3-2-1 locating principle of fixture design.
- It restricts 6 degrees of freedom.
PRINCIPLES OF PIN UNIT DESIGN
- Pin should have grinding surface on shaft with fits on to which the pin retainer will be filled.
- 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 to the blocks should be a machined surface.
- All machined planes should be perpendicular to the axis of the pin shaft.
- Pin must have a fastening provision like tapped hole from the bottom of a V groove from the side.
- A pin must be hardened (heat treatment) and black oxide finished in general.
FUNDAMENTALS OF PIN UNIT
- It is necessary to have two pins to locate a car panel.
- One pin must arrest 4 ways (4 transitional) and the other must arrest 2 ways (2 rotational) of a car panel.
- The axis of car panel hole and the axis of the pin should be same (in general).
- The pin tolerance for a geo pin will be of closer tolerance i.e.-0.15mm & for re-spot pin is -0.28mm.
- Pin should engage 3-5 mm from the car part entry surface.
- All pins should be accommodated with 2 ways adjustable shims irrespective of direction of arresting.
- Round pin should be used in case of 4 ways of arresting of car part if the hole is round.
- Round pin should be used in case of 2 way arresting of car part if the holes is slot.
- Diamond pins can be used for 4 ways arresting of car parts only if the hole is round.
- Diamond pins can be used for 2 ways arresting of car part only if the hole is slot.
TYPES OF PIN UNIT
- Fixed Pin Unit: In this type of unit, the pin is fixed by means of pin retainer & riser.
- Retractable Pin Unit: 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.
- Standard pins can be used or a new pin can be designed as per requirement.
- Pin should have grinding surface on shaft with fits on to which the pin retainer will be filled.
- 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 to the blocks should be a machined surface.
- All machined planes should be perpendicular to the axis of the pin shaft.
- Pin must have a fastening provision like tapped hole from the bottom of a V groove from the side.
- A pin must be hardened (heat treatment) and black oxide finished in general.
- There are two types of pins such as
- Round type pin.
- Diamond type pin.
ROUND TYPE PIN
DIAMOND TYPE PIN
PIN RETAINER
- A pin retainer is a part which hold the pin in position, the pin retainer can either be a make part or standard part.
- Pin retainer should have a hole with a fit on to which the pin will be fixed.
- The pin mounting surface of the pin retainer should be a machined surface.
- The pin mounting surface of the pin retainer should have a step to lock the rotation of the pin.
- The pin mounting surface of the pin retainer to the blocks should be a machined surface.
- The pin retainer will be fixed to a block or a L block to the riser with 2 dowel holes (pins) & at least with one screw hole to maintain the tolerance.
BLOCK
Blocks are mainly used to accommodate the shimming directions as per fundamental in general and also in some cases used for other design feasibility.
SHIMS/ SPACERS
- Shims 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.
- It is also used to adjust the design to manufacturing deviation.
BLADE
- Blade is part like a plate which connects the parts on a unit to a riser.
- The blades can be either a standard part or it can be designed as new part.
RISER
It is a part on which all the parts of a unit are mounted & is mounted on the base plate of a tool.
DOWEL HOLES & MACHINED SURFACE
- The parts which are to be assembled should be designed with 2 dowl holes & at least of 1 to 6 threaded/ free hole (depends on size) 7 to be fine machined for the mounting surface with 3 to 5mm step machining.
DESIGN METHODOLOY
- Firstly, the pin is designed with the required dimensions as per the panel the of the car and the collar for the pin is also designed.
- The hole is made in the bottom of the pin and the pin outline is molded as per the standard.
- If there are any standard parts, it is advised to use those parts as many as possible.
- Secondly, The pin retainer is designed and the retainers are mainly used to accommodate the shimming direction as per fundamental in general.
- Then the Block is modelled as per the design requirements and is designed in such a manner that the pin can be adjusted in longitudinal and translational direction.
- 5 mm gap is provided between the block and the retainer as the shims or spacers are placed.
- The dowel holes are present in all the parts of the pin unit which are to be assembled with tolerance should be designed with 2 dowels and at least of 1 to 6 threaded/free holes and to be fine machined for the mounting surface with 3 to 5mm step machining.
- The blade is used to connect the riser to the block.
- Blades are standard parts and can also be designed new as per the requirement.
- The riser is placed and it is the part on which all the parts of unit are mounted and is mounted on the base plate of a tool.
- Riser can used from standard parts or also can be designed new as per required.
FIXED PIN UNIT DESIGNS
TYPE 1
PIN (ROUND)
TYPE 2
PIN (DIAMOND)
PIN RETAINER
BLOCK
SHIMS
BLADE
RISER
L TYPE RISER
T TYPE RISER
RETRACTABLE PIN UNIT
TYPE 1
PIN (ROUND PIN)
TYPE 2
DIAMOND TYPE PIN
PIN RETAINER
SINGLE ROD CYLINDER
DOUBLE ACTING ROD CYLINDER
BLOCK
TYPE 2 BLOCK
RISER
TYPE 1
L TYPE
TYPE 2
FIXED PIN UNIT
1)TYPE 1
2)TYPE 2
FIXED PIN UNIT ASSEMBLY IN A PANEL (BOTH TYPE)
RETRACTABLE PIN UNIT
1)TYPE 1
RETRACTABLE PIN UNIT
2)TYPE 2
RECTABLE PIN UNIT ASSEMBLY IN A PANEL (BOTH TYPE)
CONCLUSION
Thus the design of both the fixed pins and retractable pins by using different pins, blocks, risers and blades are studied and designed as per requirement.