automatic constraints settings?

[sjohnson-2]

MY company just upgraded to Creo. One immediate annoyance is the automatic constraints. Lets say I want to assemble a hex screw into a round hole, about the simplest of constraints. I'd normally pick an axis on the screw and an axis on the hole, then the underside of the screw head and the face of the part.

When I choose the two axes, Creo wants to do an angle offset, and when I choose the surfaces it wants to make them normal. These are the LEAST likely choices I'd make with an axis and two surfaces. Is there some kind of setting controlling this, where I can tell Creo to assume two axes will be aligned and two faces most likely co-incident? I'm about ready to turn off the auto constraints entirely, as they are even less useful than they were before.

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[Dale_Rosema]

See if this thread helps you:

http://communities.ptc.com/message/211921#211921

Thanks, Dale

File > Options > Configuration Editor

[sjohnson-2]

That'll help me turn it off if I need to, but I'd like to tune the selections that Creo makes instead. There has to be some logic somewhere telling Creo to assume two axes are most likely to be at angle (in what universe?) and two surfaces will most likely be normal.

[vzak]

Sean,

I'm just re posting from the older thread mentioned by Dale - this covers all supported combinations.

In short, if you set auto_constr_always_use_offset = Never - you will ALWAYS get Coincident as default suggestion, for planes / lines (axes) / planes + lines. This will address your desire to get axes coincedent ... but will also always choose coincedent for planes as well (not angle or offset). See full info below.

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Corrected flow of "decision making" in Creo :

1. If you set auto_constr_always_use_offset = Never - you will ALWAYS get Coincident as default suggestion, for planes / lines / planes + lines.
2. If you set auto_constr_always_use_offset = Yes - you will always get offset type of constraint, never Coincedent
3. If you keep auto_constr_always_use_offset = No (default) - this means you accept Creo smartness to suggest MOST CLOSE constraint to your current situation. Current position may be more close to Coincedent, Distance, Angle, or Normal.

Correlation of these four is defined by 3 additional config options and the check works in the following order:

1. a. Check if position fits Angle or Normal. For this use values set for options:

- comp_angle_offset_eps
- comp_mormal_offset_eps

1. b. IF position does not fit ANGLE or NORMAL, then it will be either Coincident or Distance. Here decision is made based on the value of :
   
   auto_constr_offset_tolerance = (0.5 of the model size by default). If initial distance is biggest than this value you will receive Distance, if less – Coincident. Note that value is relative to the size of each component being assembled.

[sjohnson-2]

Ah. thanks!