Romer Sigma checking

Hi Quizmaster, the problem is you are not just looking at the repeatability of the arm with the test you are performing. . . .since you are doine a manual plane line line alignment, you are including the repeatibility of the operator. . . Namely depending on where the individual hits are taken that are used in the measurement of each feature. . . If you are going to continue this method, you should use multiple alignments and after the first full alignment, enable auto trigger, making sure to approach each point from the same direction each time. . . This will improve the repeatibility of your alignment. On the issue of measuring the circles, same issue applies. . . .on a part that is only 1.5 mm thick, and 25mm in diameter, if any of your hits fall too high or too low, you will get bad results, also, having the multi point circle, now you also have to take roundness into account. . . If the form is not perfect, and parts NEVER are perfect, different hits will yield different locations for the resulting circle. . . There are always ways to make the arm more repeatable but it does require a good bit of technique and training. . . .

HTH

Hi Superintern and thanks for the response, even though it took me some time to reply.

When it comes to the aligment I already had that in mind so my program is build in the way that i measure the aligment, then all the circles and then the program loops up and starts over right after the aligment. This way i keep the fixation off the part and the aligment the same.
When it comes to the circles I measure them with the probe resting against the table so that the points I take should hit on the same level.
But when it comes to the roundness you have a point =) because the arm is manuall I cant secure that the hits are taken on the same places so...

If i understand you right then you recommend that I stop measurering circles and start taking point if I want to "only" check the arm.....
But as my first question was, how do you guys check your arms ?