Shaft Alignment Tolerances
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©2008 LUDECA, INC. www.ludeca.com www.ludeca.com Short Flex Short Flex and and Spacer Shaft Spacer Shaft Tolerances Tolerances Is there really a need for Is there really a need for both? both?
description
Learn why it is absolutely necessary to have both the short flex and spacer shaft tolerances in your alignment tool.
Transcript of Shaft Alignment Tolerances
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Short Flex Short Flex andand
Spacer Shaft Spacer Shaft TolerancesTolerances
Is there really a need for both?Is there really a need for both?
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Flexible CouplingFlexible Coupling
A flexible coupling has two flex planesA flexible coupling has two flex planes(points of power transmission.)(points of power transmission.)
The shafts can only change their relative The shafts can only change their relative position at the two points of power position at the two points of power
transmission. transmission.
1 2
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Coupling Examples Coupling Examples
How many flex points? (points How many flex points? (points of power transmission)of power transmission)
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Misalignment Misalignment MagnifiedMagnified
What happens to the coupling when we have misalignment?
SHEAR?
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Misalignment Misalignment MagnifiedMagnified
This creates 2 ANGLES at each power of transmission point.
NO, It’s a FLEXIBLE coupling, so it will deform to accommodate the misalignment.
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Misalignment Misalignment MagnifiedMagnified
This creates 2 ANGLES at each power of transmission point.
What about OFFSET? Where does that come from?
For Short Flex Tolerances, the OFFSET is defined at coupling center.
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Shaft MeasurementShaft Measurement
Regardless of coupling type and Regardless of coupling type and length, the tools are measuring length, the tools are measuring the relative positions of shaft the relative positions of shaft centerlines of rotation.centerlines of rotation.
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Shaft MeasurementShaft Measurement
We are simply selecting how the We are simply selecting how the tool expresses the misalignment tool expresses the misalignment to see if we have too much to see if we have too much misalignment at the points of misalignment at the points of power transmission.power transmission.
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Defining TolerancesDefining Tolerances
Short Flex Tolerances Short flex tolerances Short flex tolerances expressexpress the misalignment the misalignment
as an as an AngleAngle between the shaft centerlines and between the shaft centerlines and as the as the OffsetOffset between the shaft centerlines – between the shaft centerlines –calculated at coupling center.calculated at coupling center.
Calculated offset at coupling center
4” or less
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Spacer tolerances express the misalignment at each flex plane.
Defining TolerancesDefining Tolerances
Spacer Tolerances
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Defining TolerancesDefining Tolerances
Spacer and Short Flex Tolerances both Spacer and Short Flex Tolerances both measuremeasurethe relative rotational centerline the relative rotational centerline misalignment but express it in different misalignment but express it in different terms.terms.
Short flex tolerances were developed many Short flex tolerances were developed many years ago to safely simplify the alignment years ago to safely simplify the alignment tolerances of tolerances of closeclose coupled (4” or less) coupled (4” or less) machines. machines.
Short flex tolerances are a derivative of Short flex tolerances are a derivative of spacer tolerances.spacer tolerances.
Notes:
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Example of both Example of both TolerancesTolerances
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TolerancesTolerances
What tolerances do I use?What tolerances do I use?
Short Flex?Short Flex?
Spacer?Spacer?
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Short FlexShort Flex
Short Flex tolerances have been over-Short Flex tolerances have been over-generalized to cover all types and generalized to cover all types and lengths of couplings.lengths of couplings.
As the distance between flex planes As the distance between flex planes increases, the possibility of aligning to increases, the possibility of aligning to short flex tolerances severely decreases short flex tolerances severely decreases when it should actually become easier.when it should actually become easier.
That Express Alignment has now That Express Alignment has now become a lengthy, tedious process!become a lengthy, tedious process!
Let’s examine this further…Let’s examine this further…
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Spacer Coupling EffectSpacer Coupling Effect
What is happening to the angle?
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Spacer Coupling EffectSpacer Coupling Effect
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Spacer TolerancesSpacer TolerancesExpressed at EACH FLEX PLANEExpressed at EACH FLEX PLANE
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Short Flex OnlyShort Flex Only
Short Flex tolerances need to
satisfy a given Angularity AND
Offset at the coupling center.Short Flex tol’s
have us correcting the
two alignments in the best condition!
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ConclusionConclusion
Short Flex – 4” coupling or Short Flex – 4” coupling or lessless
Spacer – more than 4”Spacer – more than 4”
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ConclusionConclusion
Unless more Overtime is your Unless more Overtime is your goal, make sure you know that goal, make sure you know that having having bothboth short flex and spacer short flex and spacer shaft tolerances will make the job shaft tolerances will make the job easier!easier!
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Thank youThank you !!!!
