Helical sweep thread problem

[ptc-5911303]

If any body could help me to find a reason for why the thread profile goes all skewed.

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[TomD.inPDX]

Nice one

Try making it a surface rather than a remove material and see what the origin is following.

You can post the file in the advanced editor and we can have a look.

[ptc-5911303]

Hello thanks for your offer to help really appreciate it, as whats happened here has completely baffled me.

[TomD.inPDX]

I hate that! All that trouble just to have it be an education version I cannot open these.

[ptc-5911303]

Ah rats sorry thats put a spanner in the works then ay, its meant to be a standard 1.5mm pitch but on a larger diameter an OD of 293mm could that be the cause of the skewed profile?

[TomD.inPDX]

As David is suggesting, it may be a graphic artifact and the part properly defined.

Changing the accuracy setting to a much lower value will show better resolution.

[TomD.inPDX]

Enlarging my diameter to 12" shows similar artifacts in both the surfaces and the edges but clean right up with accuracy set to .00005 Absolute.

...its a tough thing to get use to in Creo.

[ptc-5911303]

oh right I see that's looking like what i thought it would initially turn out like!! but anyway I went into model properties and it will only let me set the accuracy as low as relative 0.0001.

[TomD.inPDX]

Yea... well.. there is a few tricks to that as well.

You have to enable absolute accuracy in config.pro:

enable_absolute_accuracy yes

And then you should set the default absolute accuracy...

default_abs_accuracy .00005

Even when you do this, you will get error messages when you try to deviate from this.

This is probably the most frustrating implementation for keeping CAD efficient that I have -ever- experienced!

[TomD.inPDX]

Here is the rest of them...

PTC recommends changing the lower bound to a very tight standard only for high precision tooling models.

Personally, I think PTC should just make is "perfect" to start with

[ptc-5911303]

Well that weren't half a hassle!! but after doing what you said this is the result hoorah!

[TomD.inPDX]

Congrats! You might mark David's answer as correct.

[dschenken · Accepted solution]

Make the part accuracy smaller - relative to the thread depth the pitch is almost non-existent, suggesting this is a small feature relative to the part.

[TomD.inPDX]

The pitch is 1.5 so it is not that small.

There is something wrong with a reference.

Never had a helical sweep do that to me.

[dschenken]

Pitch as a function of the thread diameter. The threads are almost vertical - 1:50 or less.

This looks like the advance of a microscope thread or small ratio of advance to diameter.

[TomD.inPDX]

I am going to suggest there is something strange with the reference on the OD of the part. In this one, I use a vertex (end of arc, edge) to align the OD. This is a 3" OD with a 1/16th" pitch.