turbineer
Mechanical
- Feb 20, 2007
- 11
Where I am: I have an inch assembly in a mm master model of a freeform, but primarily-continuous, design. I am doing multi-axis milling programming. I have to do various geometry additions to the component because of limitations in the physical production process. I am creating extra, also nominally-continuous surfaces on the edges of freeform design surfaces that I have divided with planes. This is a complicated explanation to tell you how I have arrived at my request, but my request is simple: which tolerances should I attempt to loosen to make my surface area grids work without error? Which ones should I avoid loosening or place limits on loosening?
What has not worked:
[ol 1]
[li]Using Surface Area drive mode (inside a Contour operation) to simply focus on the (Divided) surface I want and then extend that surface by %'s (in the Drive dialog) or by diagonal points. The failure mode of this is that the extension of my surface area keeps wrapping around a continuous shape of the design instead of extending in a tangent direction to the edge of the selected Divide surface. It would be great if tangent extension was a selectable option[/li]
[li]Using Guiding Curves drive mode forces me to select more geometry like Part and Cut Area. When I go through that exercise and it violates the part, selecting Check surfaces is just too much for NX (on an HPZ420) to handle. It churns all night. [/li]
[li]Using linear Extrude on the edge of a freeform surface. It's tough or impossible to choose a vector for Extrude that will keep the joint between a freeform and a flat extension approximately continuous.[/li]
[/ol]
What has sometimes worked:
[ol 1]
[li]divide my continuous design surface with a plane[/li]
[li]use the edge of this division as the seed curve for a sweep surface[/li]
[li]create guide curves off the design surface by A] Composite-duplicate my design curves B] Curve Length-extend them [/li]
[li]if an error reports that these guide curves are not tangent, loosen the Modeling Preferences / General / Distance Tolerance from 0.01 mm to 0.1 mm [/li]
[li]sweep my Divide edge off of the part with these guide curves [/li]
[li]Divide the Sweep into on-design-surface and off-design sections[/li]
[li]use the Sweep (off-design) surface and design surfaces as the Drive for a Variable Contour Surface Area [/li]
[/ol]
The failure mode of the last procedure, which works about half the time, is the age-old error like "Cannot build grid... Grid May Work if Selection / Chaining Tolerance is Changed..." I have never seen changing this particular tolerance help a situation like this. What other tolerances can I mess with to make this work? Is around 0.2 mm the absolute top end that I should consider tolerancing? My process can handle at least that much, but following general shape is still important, which I will not be able to explain here.
What has not worked:
[ol 1]
[li]Using Surface Area drive mode (inside a Contour operation) to simply focus on the (Divided) surface I want and then extend that surface by %'s (in the Drive dialog) or by diagonal points. The failure mode of this is that the extension of my surface area keeps wrapping around a continuous shape of the design instead of extending in a tangent direction to the edge of the selected Divide surface. It would be great if tangent extension was a selectable option[/li]
[li]Using Guiding Curves drive mode forces me to select more geometry like Part and Cut Area. When I go through that exercise and it violates the part, selecting Check surfaces is just too much for NX (on an HPZ420) to handle. It churns all night. [/li]
[li]Using linear Extrude on the edge of a freeform surface. It's tough or impossible to choose a vector for Extrude that will keep the joint between a freeform and a flat extension approximately continuous.[/li]
[/ol]
What has sometimes worked:
[ol 1]
[li]divide my continuous design surface with a plane[/li]
[li]use the edge of this division as the seed curve for a sweep surface[/li]
[li]create guide curves off the design surface by A] Composite-duplicate my design curves B] Curve Length-extend them [/li]
[li]if an error reports that these guide curves are not tangent, loosen the Modeling Preferences / General / Distance Tolerance from 0.01 mm to 0.1 mm [/li]
[li]sweep my Divide edge off of the part with these guide curves [/li]
[li]Divide the Sweep into on-design-surface and off-design sections[/li]
[li]use the Sweep (off-design) surface and design surfaces as the Drive for a Variable Contour Surface Area [/li]
[/ol]
The failure mode of the last procedure, which works about half the time, is the age-old error like "Cannot build grid... Grid May Work if Selection / Chaining Tolerance is Changed..." I have never seen changing this particular tolerance help a situation like this. What other tolerances can I mess with to make this work? Is around 0.2 mm the absolute top end that I should consider tolerancing? My process can handle at least that much, but following general shape is still important, which I will not be able to explain here.