Sample Hits and Spacer

[keego]

I'm trying to use sample hits on an autocircle but am having problems. I have my z for the circ at -5 and my spacer set to 4. It takes the sample hits fine but when it goes into the hole it only goes to -1. I thought spacer was used to define how far from the hole's perimiter the sample hits are taken. What's going on?

[Robert Masters]

Don't use a negative number for your depth.

[keego]

My depth is set to zero. Perhaps if I make it 4???

Yupp, that did it. Thanks Robert!

[Don Meredith]

My depth is set to zero. Perhaps if I make it 4???

Yes. That will measure the circle 4mm below the surface of the sample hits.

[Matthew D. Hoedeman]

SPACER = how from from nominal edge of hole it takes the sample hit
DEPTH = how far down below sample hit the touches are made in the hole

[keego]

SPACER = how from from nominal edge of hole it takes the sample hit
DEPTH = how far down below sample hit the touches are made in the hole

So in the case of using sample hits, it doesn't matter where my zaxis nominal is for the hole? Oh wait, it must use this somehow to determine where the surface should be? I'm confused.

[Matthew D. Hoedeman]

So in the case of using sample hits, it doesn't matter where my zaxis nominal is for the hole? Oh wait, it must use this somehow to determine where the surface should be? I'm confused.

The VECTOR of the hole determines the surface around the hole. The ANGLE vector determines the direction of the first hit. Space (FOR HOLES!) determines how far outside the nominal circle the surface touch is, the depth determines how deep from the sample hits it measures the circle. For EDGE POINTS, the INDENT determines how far from the nominal edge the sample hit is, the SPACER determines how far ALONG the edge from nominal the edge sample hits will be for sampling the edge to get an actual vector of the edge.

For holes in a NON-FLAT surface, say a hole that is square to the Z axis that is in a surface that's at an angle to the Z axis, you get what all jay-walkers get, a ticket. There is no easy way to use samples hits in this case. Using MORE THAN ONE sample hit will totally screw your results since the surface is NOT square to the hole by intent.

[Bill **********]

Pick your feature from CAD... Spacer sets the distance outside the feature from the CAD NOMINAL it will take sample hits Depth is how far below the sample hits it will measure the feature.

Bill

[keego]

But how does it know where the surface is to take sample hits?

[Don Meredith]

Assuming the Z-plus workplane, the 'target' value for Z. This shoud be nominal location for the hole. As long as the surface is within prehit and search distance, it should find it.

[Matthew D. Hoedeman]

But how does it know where the surface is to take sample hits?

XYZ is the center of the hole as well as a "point" on the theo surface of the part (as if there was no hole)

[keego]

Got it. Coming from MM4 I always use a negative z value (when in zplus workplane, and assuming the surface is z=0) for the nominal hole depth. Now I understand autocircle much better. Thanks!

[mjdevries]

For holes in a NON-FLAT surface, say a hole that is square to the Z axis that is in a surface that's at an angle to the Z axis, you get what all jay-walkers get, a ticket. There is no easy way to use samples hits in this case. Using MORE THAN ONE sample hit will totally screw your results since the surface is NOT square to the hole by intent.

I call this a skewed hole/feature. I work with automotive plastics, so we get these when die draw is not perpendicular to the surface. Are you saying there isn't an easy way to check these? I assumed that you would set the hole vector along the hole axis and maybe define a plane on the surface and project the hole along the axis to the plane. I'm not a PC-DMIS operator, so I do not know exactly how you would do that, but it seems like something that could be done. Maybe it isn't easy though. What are your thoughts on checking a skewed hole/feature?

[Bill **********]

Die draw sux!!! Checking elipses, holes not perpendicular to surface, especially in plastics, is lame at best.

Mike you and I need to have a verbal conversation or twelve. PM me for a land line #. You seem to be an engineer that is willing to listen and understand... Another one you will want to talk to is Matt Hodeman

Bill

[keego]

I call this a skewed hole/feature. I work with automotive plastics, so we get these when die draw is not perpendicular to the surface. Are you saying there isn't an easy way to check these? I assumed that you would set the hole vector along the hole axis and maybe define a plane on the surface and project the hole along the axis to the plane. I'm not a PC-DMIS operator, so I do not know exactly how you would do that, but it seems like something that could be done. Maybe it isn't easy though. What are your thoughts on checking a skewed hole/feature?

I would first measure this as a cylinder if it's got enough depth, then level to it, then measure a circle without sample hits, using the vector of the cylinder.