What is Runout


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    Default What is Runout

    Runout, also called TIR for Total Indicator Reading, is the
    apparent radial motion of the surface of a turning rotor or
    shaft. It can be caused by the part not being round, or it
    can be caused because the center of rotation is not
    coincident with the geometric center of the part.

    (from http://www.dliengineering.com/ )


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    071030-0605 EST USA

    Note: The term runout can be applied to a non-round object, for example a spline. On the other hand an oval shaft can have zero runout but a large TIR. So runout and TIR are not synonymous.

    Where on your link to DLI Eng. are runout and TIR discussed?

    .



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    It is at the following link under glossary.

    http://www.dliengineering.com/vibman.htm



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    Oh, and, it's signified on drawings as, like, an arrow coming from the lower left hand side and heading to the upper right hand side.

    I love deadlines- I like the whooshing sound they make as they fly by.


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    A long, long time ago I was taught that TIR was Total Indicated Runout. So I Googled total indicated runout and found my memory is maybe correct. Sometimes google is handy to get variety of explanations/opinions in different references. I think the Total Indicated Runout interpretation is preferable because it resolves the oval shaft conundrum.

    And the different interpretations remind me of the DNC for Distributed Numerical Control and DNC for Direct Numerical Control discussion.

    An open mind is a virtue...so long as all the common sense has not leaked out.


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    I must admit that I recal TIR as Total Indicated Runout, but was not too sure to mention it.

    I was making flat filters for submarines and TIR was specified instead of Wedge on the plate.. with wedge you could argue that it was plus or minus the tolerance, effectively doubling it. TIR was, well, totaly indicated.

    I love deadlines- I like the whooshing sound they make as they fly by.


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    071030-1105 EST USA

    The reason I brought up the difference between runout and TIR is as follows:

    In building an automotive rear axle you have a pinion with a spline, and a yoke or flange with pilot diameters and a spline.

    A pinion in the US is usually made using something like 8620 and is mostly formed in the soft state including rolling the spline. There are also centers at both ends. After heat treatment the pinion will be somewhat warped. The centers are used to grind the journals, and the gear is lapped. The journals are what support the pinion and define its axis of rotation. Because of the heat treatment the axis of the spline may not coincide with the axis of rotation of the pinion.

    Put a master flange on the pinion and a pilot diameter on that flange will show a TIR that is not zero if there is runout of the spline.

    Production flanges or yokes also have their own spline to pilot diameter runout problem.

    Therefore it is appropriate to define runout as something different than TIR even though we used TIR with a master flange to determine runout. I can not directly measure the runout of the spline, nor is the runout the same for different axial locations.

    In actual production one measures the TIR of the "composite runout point" to determined acceptability of the assembly. This is the combination of a number of different sources.

    It gets more complicated. If the axis of the spline is not parallel to the axis of rotation of the pinion, then depending upon where you measure TIR there are different TIR readings. Thus, we define something called "composite runout point". This is the point at the center of the universal joint. and is important because this determines drive shaft radial motion.

    On my web site www.beta-aa.com on the AXLE PHOTOS page are photos showing approximate locations for the composite runout point.

    .



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    Default Spindle Run out

    Hi,

    I use a Hardinge VMC 600 II, spindle runout is within 10 microns, is this generaly acceptable.



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    It's all a matter of definition. Runout is defined by ASME B5.54-2005 standard (Methods for performance evaluation of CNC machining centers) as "total range of displacements measured by an instrument sensing against a moving surface or moved with respect to a fixed surface." So as far as ASME is concerned, runout = TIR. They also define TIR as "Total Indicator Reading." An oval or spline would have very high runout even if perfectly straight and perfectly rotated.

    What others are calling "runout" for splines and ovals is, according to ASME, "radial error motion" which is "error motion of a rotary axis normal to the Z reference axis and at a specified angular orientation." It's all about errors in the axis of rotation. Small wars have been fought in ASME/ANSI over these terms resulting in the definitive determination for documents written by these organizations (and all associated textbooks etc.) that Radial Error Motion is about errors in rotation such as eccentricity or tilt. Runout is deviation in the location of the surface of a rotating part which would include Radial Error Motion and roundness errors or the rotating part.

    We're writing an Application Note about this right now. I'll add a link here when it's done if I can find my way back.

    Noncontact Displacement Sensors: Capacitive and Eddy-Current



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    This is the promised Application Note on measuring shaft runout. It includes a description of electrical runout and how to deal with it if it's a problem. It also has standard defintions of TIR and Runout.
    Shaft Runout Measurement With Noncontact Displacement Sensors



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