Week 4:- Pin Unit Design Challenge

                                                                                                         PIN UNIT DESIGN

OBJECTIVE:

     To design two different types of fixed pin unit with different pins ,riser, blade,&block  and 2 different types of retractable pin unit with different pins,riser,blade and cylinder.

SOFTWARE USED:

     CATIA V5 R20

COLOR CODES IN BIW FIXTURE:

                                               

TYPES OF PIN UNIT:

    The types of pin units are:

• Fixed pin unit.
• Retractable pin unit.

FIXED PIN UNIT:

     Fixed pin unit design is used to locate the car panel using pins.

     pin,pin retainer,block,blade and riser are the parts of fixed pin unit in genral.

     pin retainer is used to hold the pin firmly.

                                     

PICTURES OF FIXED PIN UNIT-1:

                                       

                                       

                                                                        

PICTURES OF FIXED PIN UNIT-2:

                                        

                                        

                                                                                         

RETRACTABLE PIN UNIT:

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

   Pin,pin retainer,block,shims,blade,pnumatic cylinder, riser are the parts of the retractable pin unit.

                                                    

PICTURES OF RETACTABLE PIN UNIT-1:

                                                     

                                                                       

PICTURES OF RETACTABLE PIN UNIT-2:

                                                                  

TYPICAL PARTS OF PIN UNIT:

   The different parts of pin unit are:

1. Pin.
2. Pin retainer.
3. Shims.
4. L-Block/Shim block.
5. Blade.
6. Riser.

PIN.

        It is used for the locating purpose of the panel.Typically, the locating pins are used to locate a body part in a position sufficiently accurate to execute the welding process.

        The body part is constrained by a set of approximately locating pin so total constraint by locating pin should be fully constrained at all times to prevent annoyment.

        There are dozens of styles of locating pins that can be utilized in design.

        A pin can be either a make part or standard part also.    

                                                         

        CONSIDERATION WHILE DESIGN & MANUFACTURE OF PINS:

1. Pin should have grindeing  surface on shaft  with fits on to which the pin retainer will be fitted.
2. The mounting surface of the pin should be a fine machined surface.
3. A pin should have a step machine surace to lock  the rotation,which matches with the pin retainer.
4. The mounting  block with the blade should be a machined surface.
5. All machined planes are perpendicular to the axsis of the pin shaft.
6. Pin must have a fastening provision like tapped hole from the bottom or a v-groove from the side.
7. A pin must be hardened ( 55-60 HRC ) & black oxide finish in general.

                                                   

PIN RETAINER:

        A pin retainer is part whic holds the pin in position the pin retainer can either be a make part or a standard part also.

        pin retainer is used to hold the locating pin firmly.     

                                                               

                                                                                                                          

        CONSIDERATION WHILE DESIGNING & MANUFACTURING OF PIN RETAINER:

1. A pin should have a hole with fit,on to which the pin will be fixed.
2. The pin mounting surface of the pin retainer should be a machined surface.
3. The pin mounting surface of the pin retainer should  have the step to lock the rotation of the pin.
4. The pin mounting surface of the pin retainer to the block should be a machined surface.
5. The pin retainer should be fixed to a block or L block to the riser with 2 dowel holes & atlest with one screw hole to maintain the tolerance.

                                                               

SHIMS:

        Shim is generally used to adjust the design to manufacture deviation.

        In genral,A shim is a thin and often tappered or wedged piece of material,used to fill small gaps or spaces between objects.

        Shims are typically used in order to support ,adjust for better fit, or provide a level surface.

        Shims may also be used as spacers to  fill gaps between parts subject to wear.

        Shims are the small parts comes with the thickness of 0.1mm,0.2mm,0.5mm,1mm etc.

        This will compensate tolerance which reflects at the mylars.

        We give tolerance to all parts of the fixture.Due to this tolerance the mylars will either lift up or down from its defined position.

        To adjust the mylars for gettinf its defined position we use shims.

        shims will added above the mylars for adjusting accroding to tolerance.

                                                                          

        APPLICATION OF SHIMS:

1. In automobile,shims are commonly used to adjust the clearance or space betwen two parts.For eg, shims are inserted into or under bucket tappets to control valve clearance.Clearance is adjusted by changing the thickness of the shim.
2. In assembly and weld fixture precision metal shims are used between two parts so that the final production parts are created within the product drawing's specified tolarance.

                                                                                

L-BLOCK/SHIM BLOCK:

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

                                                          

RISER:

        Riser is a manufacturing part used to rise the assembies of fixtures.

        One end of the riser will be attached to the base unit while the other end will be attached to the blade.

        It is the part on which all the parts of the unit are mounted  on the base plate of a tool.In general the riser can either be make part or a standard part.

        There are two types of riser:

• 'L' type riser.
• 'T' riser

BLADE:

        Blade is a part like a plate,which connects the parts of a unit to a riser.In general , the blade can either be a make part or a standard part.Blades are the plates which are attached or mounted with cylinders,arms,etc.

DOWEL HOLES & MACHINED SURFACE IN PIN UNIT:

        All make parts which are assembled with tolerance should be designed with2 dowel holes & at least 1-6 threaded or free hole ( depends on size).And to be fine machined for the mounting surface with 3-5 mm step machining (SURFACE TO BE FLAT,PARELLEL & PERPENDICULAR TO O WITHIN 0.015 T.I.R).

BOUGHT OUTS:

        BOUGHT OUTS used in this project to design a pin unit are,

• Cylinders.
• Fasteners.

     1.CYLINDERS:

         std:SZK_30_8_T12(make_TUNKERS):Pnumatic cylinder in aluminium block design with precision guide  of the piston rod,secured against rotating.compact housing made from high strength aluminium with mounting options on several sides.Drive mechanism with circular-section cylinder for thrust forces and extraction forces of approx.350/250N. Total stroke 40mm.Integrated inductive sensing system(T12).

                                                           

         std:SZK_40_BR3_A32_T12(make:TUNKERS): Retract cylinder with side mounting on piston rod for offset centwering pins,flat housing, of high strength aluminium material,Drive via oval - shaped oblong cylinder dia 40/63 for thrust and tensile forces upto approx.1200N,push rod secured  against twisting,40mm combined stroke length upto request.

                                                           

    2.FASTENERS:

         HEXAGON ALLEN CAP SCREW ( std: EN_ISO_4762_Steel hexagon cap screw).

                                                  

         Washer(std: EN_28738_8_STEEL GRADE_CLEVIS_PINS_PLAIN_WASHER).

FORMULA & CALCULATION:

        FORMULA  to calculate the length of the screw,

           length of the screw = [ 1.5*(std. hole size)] + { distance between the surface of the part to the first surface of the other part}.

         To fix the pin retainer and the shim block using a standard screws we need to find the length of the screw using  the above mentioned formula.

                                                                  

         Since the given tap holes is M8 & the distance is 30mm,

           length of the screw = [1.5*8 ] +30 =42 which is close to 45mm.

  therefore, length of the screw = 45mm  Allen cap screw.

         Then the standard size of the screw should be 45mm for connecting the pin retainer  & the shim blocks for this example.

MATERIALS USED:

          In general, The materials used for pins,shims,pin retainers ,blades & riser are:

1. PIN: C45,EN31,SAE 8620 STEEL,etc,
2. PIN RETAINER: steel/ASTM A-36,SS type 303 or 304,etc.
3. SHIMS/SPACER:S.A.E.1010 CRS FULL HARD COLD ROLLED STRIP STEEL S.A.E 1010 FULL HARD,S.A.E.1020 HRS,etc.
4. BLADE:STEEL ASTM A-36,etc.
5. RISER:STEEL ASTM A- 36,etc.

HARDNESS:

         In,general,the hardness of the material for pins,pin retainer,shims,shim bock,blade & risers are:

              55-60HRC/58-62 HRC to a depth of 0.5 to 0.7mm after grinding.

SURFACE FINISH:

        In general, The hardness of the materials for pins,pin retainers,shims,shim block,blades & risers are:

1. pin:Chrome plating,zinc coating,pins with tin codes shall have 1 to 2 micrones of nitride added to surfaces.
2. pin retainer: BLACK OXIDE FINISH,no black oxide finish for "SS TYPE"  components ( surfaces tobe flat, parellel perpendicular to o within 0.015 T.R.I.)
3. shims/spacers: BLACK OXIDE FINISH( SURFACES TO BE FLAT AND PARELLEL TO WITHIN 0.015mm T.R.I)
4. Riser: SURFACES TO BE FLAT, PATELLEL & PERPENDICULAR TO WITHIN 0.015mm T.R.I.

PIN TOLERANCE:

        The pin tolerance for geo pin willbe closer of tolerance -0.15mm and for respot pin is of -o.28mm.

PURPOSE OF PIN UNIT:

        As by 3-2-1 principle , the introduction of two pins helps to arrest the 6 degrees of freedom(4 axizl & 2 radial movements)wheares other 6 degress of freedom  are arrested  by introducing  minimum three supports.

        Typically,the locating pins are used to locate a body part in a position sufficiently accurate to execute a welding process.

        The body parts is constrained by a set of appropriate locating pins so total consTRAINT  by locatin pin should be fully constrained at all times to prevent any movement.

                                                         

FUNDAMENTALS OF PIN UNIT DESIGN:

        It is necessary to have two pins to locate a car panrl. And here one pin must arrest 4way( i.e. 4 translation) & other must have arrest  2 way (i.e 2 rotational) of a car panel.

1. pin should engage 3 to 5 mm from car part  entry surface.
2. All pin should be accomodated with 2 way adjustable shims irrespective of  directing of arresting.
3. Round pin should be used in case of 4 way arresting of car pannel if the hole is round.
4. Round pin can be used for 2 way arrsting of car panel only if the hole is slot.
5. Diamond pin should be used in case of 2 way arrsting of car panel if the hole is round.
6. Diamond pin  should be use in case of 4 way arresting of car panel if the hole is slotted.
7. The axsis of the car panel hole & the axsis of the pin should be same in general.

                               

CONCLUSION:

       Hence as per the objective the 2 different types of fixed pin unit ( P001_Z001_ST010_00_00) With different pins, rin retainers , blocks ,blade, amd riser & 2 different  types of retratable pin unit (P001_Z001_ST010_00_00) With different pins , blocks,blade, and risers are designed and rendered using CATIA V5 R20.