04- Principles of Location
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Transcript of 04- Principles of Location
NTTF, Bangalore
PRINCIPLES OF LOCATION• IN INTERCHANGEABLE MANUFACTURING
PROCESS WHEN A WORKPIECE IS PLACED ON A MACHINE TABLE, SPINDLE, JIG OR FIXTURE IT MUST BE PROPERLY POSITIONED BEFORE IT IS CLAMPED
• IT IS THE DUTY OF THE LOCATION SYSTEM TO PROVIDE ALL NECESSARY CONSTRAINTS SO THAT THE WORKPIECE IS CORRECTLY LOCATED AND ALL POSSIBLE MOVEMENTS OF THE WORKPIECE ARE RESTRICTED.
NTTF, Bangalore
TWELVE DEGREES OF FREEDOM• A WORK PIECE IN SPACE IS FREE TO
MOVE IN ANY DIRECTION AND CAN HAVE TWELVE DEGREES OF FREEDOM
• EACH DIRECTION OF MOVEMENT IS CONSIDERED ONE DEGREE OF FREEDOM
• IT CAN MOVE IN EITHER OF OPPOSED DIRECTIONS ALONG THREE MUTUALLY PERPENDICULAR AXES AND MAY ROTATE IN EITHER OF TWO OPPOSED DIRECTIONS AROUND EACH AXES i.e. CLOCKWISE AND COUNTERCLOCKWISE
NTTF, Bangalore
THE DUTY OF THE LOCATION SYSTEM
THE LOCATION SYSTEM MUST, IN CONJUNCTION WITH THE CLAMPING SYSTEM COMPLETELY CONSTRAIN THE WORKPIECE OR ELIMINATE AS MANY OF THE 12 DEGREES OF FREEDOM AS IS NECESSARY FOR THE OPERATION TO BE COMPLETED WITH THE REQUIRED ACCURACY
NTTF, Bangalore
DEGREES OF FREEDOM IN SPACE
NTTF, Bangalore
THE CHOICE OF LOCATION SYSTEM
• THE REQUIREMENTS OF THE LOCATION SYSTEM DEPEND UPON THE OPERATION BEING PERFORMED AND UPON THE WORKPIECE BEFORE THE OPERATION.
NTTF, Bangalore
PRIMARY DATUM
• Primary datum: This establishes the orientation of the part (stablise the part ) to the datum reference frame.The part contacts the datum plane with at least three points of contact.The primary datum restricts FIVE degree of freedom ( four rotary and one linear)
NTTF, Bangalore
SECONDARY DATUM• Secondary datum: This locates the part
(restricts part movement) within the datum reference frame.Requires a minimum of two points of contact with the secondary datum.The Secondary datum restricts THREE additional degree of freedom ( Two rotary and One linear )
NTTF, Bangalore
TERTIARY DATUM
• Tertiary datum: This locates the part(restricts part movement) within the datum reference frame.Requires a minimum of one points of contact with the secondary datum.The tertiary datum restricts the ONE degree of freedom ( Linear )
NTTF, Bangalore
Primary, Secondary and Tertiary Datums
NTTF, Bangalore
THE 3-2-1 RULE
• The 3-2-1 rule defines the minimum number of points of contact required.
• The 3-2-1 rule only applies on a part with all planar datums.
NTTF, Bangalore
DATUM REFRENCE FRAME
NTTF, Bangalore
CONSTRAINING REMAINING DEGREES OF FREEDOM
• THE 10TH DEGREE OF FREEDOM IS ARRESTED BY FIRST CLAMP AGAINST SECONDARY DATUM
• THE 11TH DEGREE OF FREEDOM IS ARRESTED BY SECOND CLAMP AGAINST TERTIARY DATUM
• THE 12TH DEGREE OF FREEDOM IS ARRESTED BY EITHER DOWNWARD CLAMP OR BY GRAVITY ( IF WORKPIECE IS HEAVY)