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Trouble measuring cones

Hello,

I'm a CMM / PC-DMIS noob, but am doing a project that requires the use of this tool.

I'm currently doing a research project that requires me to use the CMM to measure some parts so as to determine some machining tolerances.

These parts are very small, largest of which is about 12mm in height and 5mm in diameter. These are essentially small tubes with a flat top (for me to measure a plane) and an internal conical interface. I am using a 1mm diameter x 20mm probe with a Renishaw TP200 for measurements.

So, what I need to do is to find the conicity of the internal cone. The tolerance should be within <6 microns.

From what I understand from the PC-DMIS documentation, in order to measure a cone, I need to measure a minimum of 6 points; the first 3 of which must be on a plane perpendicular to the long axis of the object to be measured. However, I'm not able to place the tubes perfectly perpendicular to the CMM tabletop such that the probe can descend in a Z axis, touch 3 points, then descend a little more in the Z axis to touch another 3 points to compute a cone. Due to the off-axis alignment, I'm facing some issues with the first part - achieving a minimum of 3 points perpendicular to the long axis.

I don't have CAD models. It's all manual measurement and surface data using the CMM probe.

Would any of you gurus have a solution to my problem?
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  • Hi Jefman, I managed to figure it out. Thank you for your help.

    Would it be possible for the CMM to determine the centroid of the cone with certainty if I can only measure <180° of the cone? Currently I am using 10 points to define the cone, but can only access the part from one side.
Reply
  • Hi Jefman, I managed to figure it out. Thank you for your help.

    Would it be possible for the CMM to determine the centroid of the cone with certainty if I can only measure <180° of the cone? Currently I am using 10 points to define the cone, but can only access the part from one side.
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