Skip to main content

What’s the “CMM runout error”?



What’s the “CMM runout error”?

When you measure the runout on CMM, the CMM induces a lot of error into the measurements. If you have 2 axes in your CMM program for the runout, for example, the axis of a feature, a circle, and the axis of the datum -A-, a cylinder, each axis of movement during the measurement is going to add an element of error. The axis of the features and datum -A- always are off to the axes of CMM. That “off” is a very little angle, A1/A2 angles, but that “little angle” end up magnifying error substantially when , for example, it is about a .0005 tolerance.

You can simply see it if you examine the difference in the A1/A2 angles between the features. You cannot change the A1/A2 angles on CMM. On a Roundness tester you make A1/A2= zero before measuring the runout. A roundness tester allow us to correct the A1/A2 angles, to center the part axis on the spindle so that the runout will be in the part in which the axis feature-datum have 0° angles to the axes of the machine.


The A1/A2 angles are the root cause of the CMM runout error, and of the deviation between 2 different fixturing on 2 different CMM’s, between 2 different CMM’s, between the CMM and the Roundness tester, and between the CMM and the Dial indicator.

As a conclusion for the CMM runout error: No problems when the part is perfect .When the parts are not perfect the CMM may reject good parts, parts in which the runout is on the high side of tolerance.

Comments

Post a Comment

Popular posts from this blog

Nephilim

N 'eh - Ph 'ih- L 'ee- M /  Nepheeleem Zacharia Sitchin (July 11, 1920 – October 9, 2010)  wrote the " Nephilim " (נְפִילִים) is derived from “nafàl" and means “fall". The term Nephilim occurs in Genesis 6:1-4, describing the point of time when three things began: men began to increase in number, came into existence the daughters of men , and the sons of God went to the daughters of men and had children by them. Is the "nephillim" really only a Hebrew word? That question is very subtle, however I think it has been more a limit of thinking for linguists rather than a serious argument. Let's begin first with the probable meaning the linguists think it is. We know that the " fall"  in every language means moving downward from a higher position involuntarily, usually by an accident, which maybe was the reason why Michael S. Heiser, PhD candidate, Department of Hebrew and Semitic Studies , University of Wisconsin
7 comments
Read more

Total positional tolerance at material condition

Total positional tolerance at material condition (Hole) Suppose the Ø 1.005 / 1.010 hole is inspected and there are six parts with different ID dimensions. Their actual sizes checked with run out methods give that their actual axis is to be .006” over and up from the true position even though they have different actual ID’s. We want to know which part is within true position tolerance at MMC. Parts to be acceptable require some calculation when is used the run out method.             In GD&T, maximum material condition (MMC) refers to a hole that contains the greatest amount of material.             To understand and memorize simply and logically the concept, I suppose that you have a part designed as a square with one hole in the center, Ø 1.005 / 1.010 . You have produced just 5 parts and measured their holes. The hole of part #1 is on the low side of its tolerance Ø 1.005" and the hole of part #5 is on high side of its tolerance Ø 1.010". Here is the question: W
1 comment
Read more

Word creation. The "D" letter origin and the "D" pictogram rule of the word creation.

  In this article I will cover  the origin of the letter  D letter, and the pictogram concept of the word creation.  It was my first discovery of the word creation. In this blog I will give my discoveries, the rules of word creation of the European languages. Multiple theories exist as to how language first originated. Nobody is sure which one is true. Certified Translations Get Pricing Order Translation What is the Oldest Language in the World? There are over 7,000 languages in the world. Could there have been a time on the earth that we all spoke one language? If so, what is the oldest language in the world?  So what was the first language?  Discovering the first language that people spoke is difficult because so many languages died and were considered lost in history. However, ancient languages still survive until today; these languages may have been transformed a lot but their old origins may be traceable. Written languages existed but this does not denote how long people spoke be
3 comments
Read more