Part Accuracy

[coach-tim]

Hello all,

My first post here. Apologies if my protocol is incorrect.

I'm using wildfire 4 and am running into issues that I think are related to part accuracy settings. First of all, I'm copying geometry by tracing, in sketcher, profiles of imported parts. Secondly, I am modeling a relatively big part (4000 mm x 2000 mm), that has a lot of fine details (in the single-digit mm size range). I started having issues I've never seen before, like simple extrusions failing (could not intersect part with feature, etc., and also just failed features with no indications of why). In trouble-shooting and researching the problem, I think I've narrowed it down to part accuracy. I would like to switch to absolute accuracy for this. I'm having issues doing it.

I have figured out how to enable absolute accuracy in config.pro editor (tools/options, set value to >yes>). It then gives me the option (edit/setup/accuracy) to set to absolute. But when I try to set what I think is a modest value (.001), it rejects the value saying the range is .0178 - 1.779. From the reading I've done, I know others are setting this to much smaller values.

Any insight you might have to help me out would be greatly, greatly appreciated.

[TomU · Accepted solution]

Set the config option "default_abs_accuracy" to your desired accuracy before switching to absolute.  The value for this config option will (almost) always be accepted, even when values slightly larger or slightly smaller are not.

default_abs_accuracy  0.0001

If for some reason that doesn't work, run the insert arrow to the top of the model tree, create a small feature, change the accuracy, then delete the feature and resume everything else.  The allowed accuracy values are based on the current size of the model.  Making the model smaller will cause the system to allow a smaller accuracy to be entered.

[coach-tim]

Thank you all for your replies. It worked! - I really appreciate it.

However...

Now that I can set the part accuracy, the part will not regenerate at the new accuracy. It loses most of the protrusion depth references, and even the sketches related the features get totally wonked. It seems like almost every feature fails. Is this a common issue when increasing part accuracy? I would very much like to be able to keep the work done so far, but i'm afraid I might have to start the whole model from scratch...

[Inoram]

It can be common when changing accuracy on the fly, yes.  

But sometimes it is fairly easy to fix, sometimes just have to fix a sketch here and there. But without seeing the model every case is different.

You can try going bigger and regen, go bigger, regen, etc. and see if it fixes it self. I've gone as high as 0.0009" to fix things, but not in recent years. most things work at 0.0003"-0.0005" for me, if having issues.

[coach-tim]

Thanks again for your replies. I did manage to get it to regenerate. At one point, I set the accuracy and it worked, but all of the features were suppressed. I resumed them one at a time and was able to fix each issue. The issues were mostly missing references, some totally wonked sketches. I can say that one good thing about this little problem is that I learned a lot about how pro e calculates the geometry and interprets dimensions, and determines how features intersect. I think from now on I'll know from the get-go if I need to use absolute accuracy or not. Thanks!!

[TomU]

I have all of our start parts configured with the same absolute accuracy.  Yes, sometimes we take a hit on file size but having a consistent accuracy really helps with large models and small features and with reference sharing between models.

[dgschaefer]

A couple of other notes on accuracy.

Relative accuracy is a ratio between the largest edge in the model and the smallest allowed edge.  As such, it's unitless.  That's why seemingly simple features with small details fail on large parts.

Absolute accuracy is the absolute value of the smallest allowed edge.  That means it is expressed in the units of the model.  So, a 0.0001" absolute accuracy equates to 0.00254 mm.  I've forgotten that at times and entered 0.0001 for my absolute accuracy in a metric part which meant very slow regen times and feature failures that I didn't understand at first.

[Inoram]

I am just happy to see someone using absolute accuracy. Whenever I do get a native model to work with, they are always Rel 0.0012".

But my experience has been, people that use absolute use 0.0001"-0.0003"

I use the mold package, sometimes a 0.0001" doesn't split and you see no reason for the failure, 0.0003" works almost all the time.

[dgschaefer]

I've used nothing but absolute accuracy since I started with Proe in 1996. That's probably because I started in mold and molded part design where using absolute accuracy has always been important.