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rjethwa7-Bedrock
7-Bedrock
July 11, 2013
Solved

Facets on curves

  • July 11, 2013
  • 5 replies
  • 8907 views

Hi. Hopefully this is an easy one to answer..

Whenever I pull a tube or curve, or blend a corner greater than 20mm, the curve is not one smooth surface - instead it's shown as multiple flat surfaces. Anyone know why, and how I stop Creo from doing this? I need one prefect smooth surface.

On small blends (<5mm) it's smooth, but not sure if this is just because of the scale.

I 3D printed a previous piece thinking it would be smooth even though it had facets on screen, but the model did indeed come back with facets as shown on screen.

Any help would be great

Thanks

Rajesh

Best answer by TomD.inPDX

Graphics quality settings...

You can have better display of graphics but it will have some CPU cycle overhead. I use these settings when I want to do screen images:

Model_display_quality_settings.PNG

Green means do not turn on.

Entity_display_quality_settings.PNG

BUT: WARNING! If you use these setting, change your config.pro to include the following setting:

Save_model_warning.PNG

Reason being that saving the part or assembly will also save a LOD version of the facet model by default. If you are not using JT files, change this setting by default to keep your saved and version files at a reasonable size. I am not sure how PTC actually uses the LOD data, but it is a huge overhead if you don't need it. It doesn't seem to affect previews. LOD means "Levels of Detail" and is a holdover from the old virtual world days.

5 replies

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TomD.inPDX17-Peridot
17-Peridot
July 11, 2013

You can control the smoothness of the STL file with the STL dialog. Interesting that you noted similar characteristics between what is on the screen vs what printed. This really should not be the case. If you re-import the STL file, you will see what was exported.

Here is an exaple:

STL_dialog.PNGDefault settings

The import on the left is default. The right was exported using .01, .05, .1

STL_result.PNG

I have my default graphics quality settings fairly low.

As for the on-screen graphcis quality, there are several settings. I know just how annoying it is to not be able to see intersects or other accurate representations on the screen. I will add some info in the next post.

Dale_Rosema
23-Emerald III
Dale_Rosema23-Emerald III
23-Emerald III
July 11, 2013

You must have faster typing fingers today.

Dale_Rosema
23-Emerald III
Dale_Rosema23-Emerald III
23-Emerald III
July 11, 2013

The model is probably smooth, but you resolution is not. There can be performance issues when setting your resolution really high.

For you 3D printing, are you exporting an .stl file? If so, you can adjust the Chord Height and the Angle Control down to get a better triangulation, but remember this is still triangulation. The smaller these numbers, the smaller the triangle used to make the part, the larger the .stl file size will be.

I, myself, have done a lot of 3D printing and attest to the number/size of triangle will make the part smoother and smoother. It will just take a lot more processing time to get there.

Thanks, Dale

T
TomD.inPDX17-Peridot
17-Peridot
July 11, 2013

I can see a useful tool for the dialog to help users determine an appropriate setting as in Course/Medium/Fine along with the fine tuning settings already available. The defaults really are very course.

I did confirm that changing graphics quality to very high did not alter the default export settings.

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rjethwa7-BedrockAuthor
7-Bedrock
July 15, 2013

Hi all

Thanks for the responses.

Clearly I have stumbled at the first hurdle >> where do I find the dialouge box where I adjust those settings? I am using Creo Elements / Direct Modelling Express - can't even find the version number but a downloaded it from PTC within the last couple of months.

In my FIle menu, I have options for Settings, Options, and Customize, but cannot find the options you've suggested above.

Thanks..

T
TomD.inPDX17-Peridot
17-Peridot
July 15, 2013

The options in Direct Modeling Express is simpler but should be just as effective.

You access the option when creating the export file:

STL_in_Express.PNG

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rjethwa7-BedrockAuthor
7-Bedrock
July 16, 2013

Antonius - Thanks; I thought that was it.

What values should I put in each box for a smooth surface? Is it 0.5 and 0.1? I really don't mind going lower - I'd rather have a bigger file which may cause niggles sending to others, rather than a model that again comes back with facets. By way of example, the widest curve I have pulled is around 50mm diameter.

Plus in the above chain, there's mention of adjusting graphics settings for better on-screen viewing. Can I make these changes in DME?

Finally, how do I open an STL in DME? Or do I need to find a standalone STL viewer? Any recommendations? I want to view the final STL on my screen to confirm smoothness before I send it away for machining.

Thanks!..

Dale_Rosema
23-Emerald III
Dale_Rosema23-Emerald III
23-Emerald III
July 16, 2013

In regular Pro/Creo you can hit apply before save. That gives you a preview. Is there a way for you to do that?

Also, on the chord length, I got to a point where it would let me put in a smaller value than what it returned. Not sure why the limit.

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rjethwa7-BedrockAuthor
7-Bedrock
July 16, 2013

Doesn't seem so. I hit save, and then a progress bar shows.

Here are my filesize results for a hollow bar that measures approx 25cm x 1cm x 4 cm (numbers refer to Distance and Angle values):

1) 0.5 / 0.05 = 3,731,460kb!

2) 0.5 / 0.1 = 3,731,460kb!

3) 0.5 / 1 = 46,746kb

4) 0.5 / 5 = 513kb

5) 0.5 / 20 = 513kb

6) 0.3 / 0.8 = 566kb

7) 0.5 / 0.8 = 60,884kb

So clearly 1) and 2) are absurd, but what I don't understand is that filesizes for these two, plus 4) and 5) are exactly identical; I thought that changing the values would gradually increase the filesize.

Anyway, I'm guessing the 0.5 / 0.8 is the smoothest without being ridiculous.

When I open this one up though, on various surfaces, I can see lines fanning out from a single points; they have no rhymn or reason on the way the object is modelled, so am assuming the are ghost lines and won't be present on the end machined piece. Is this a safe assumption?

Thanks everyone for your help so far

T
TomD.inPDX17-Peridot
17-Peridot
July 16, 2013

Very nice. In a previous discussion we noticed that some STL algorithms take into account the orientation of the part in consideration of the STL process. I do not know if Modeling Express does this or not.

Having triangles fan out from a point is no big deal. It has to map triangles somehow, even it is it a flat surface.

I might opt for the shorter distances over the smaller angle. The 3) 0.5 / 1 is a nice target also.

T
TomD.inPDX17-Peridot
17-Peridot
July 16, 2013

That's odd. There are tons of free STL viewers but both PTC products DME and PVE do not allow you to view them. You definitely want to get yourself a viewer. You want to know what you are sending to the shop for growing parts.

I'm not endorsing these guys but here is one you might consider:

http://www.solidview.com/Products/SolidViewLite

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