CAD/CAM discussion forum > 3D CAD/CAM > Problem STL files in VX

Problem STL files in VX

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Kevin

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Message 1 of 13

 Problem STL files in VX
01-03-2005 07:26 . am | View his/her posts only
I mentioned this some time back, but I do get STL errors flagged up in Magics from VX part files. This is a concern to me as this is the route 99% of my work gets output through and I don't want to have to pay for fixes.

Take the attached part. When this is saved as an stl (also attached) from VX 10.7 it shows up hundreds of bad triangles and edges in Magics. This is a very simple part (its not a real part just a demo part).

I need to rely 100% on this output. I do know VX can import and fix stl files but I don't need the hassle of doing this. It should export STL perfectly most of the time - just like most of the competition.

I also tested a lot of the supplied training files and virtually every one flagged errors in Magics.

I say Magics because in the UK this is the main software used by bureaus. If you go to Materialise and download the stl viewer and next day software you can test these errors here as well.

www.materialise.com

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ChrisWard2k2

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Registered: 2011-11-22

Message 2 of 13

01-03-2005 09:06 . am | View his/her posts only
Hi Kevin

To study this, I need to know the exact STL settings you used, so that I can make the exact same STL output as you.

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Kevin

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Message 3 of 13

01-03-2005 10:34 . am | View his/her posts only
Hi Chris,

I've attached a couple of screenshots relating to this file, but I've tried all the settings (ASCII/Binary, Refined, unchanged, Flipped/unchanged etc) and I get exactly the same errors each time. I've confirmed this with my regular supplier using Magics. I checked using the Materialise Next Day software available free from www.materialise.com.

I'm trying to switch the bulk of modelling to VX but if I can't rely on the straight output (ie without having to re-import and fiddle) from VX I'll have to stick with tried and tested means using other software for an upcoming project where an STL based workflow will be used (by which I mean using stl files to create rapid prototypes then using these as masters for resin tools).

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ChrisWard2k2

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Message 4 of 13

01-03-2005 09:19 . pm | View his/her posts only
Hi Kevin

I'm waiting on Materialise to get back to me. In the mean time, I have checked VX STL output, from your file, mostly using your settings, in SolidView Lite. The data is good. One thing I did notice in your screenshot is that you have not input a value for maximum mesh, which I set to 5.0

You seem to be under the impression that a bureau will automatically load your STLs to Magics, but popular though it is, this not necessarily the case. What they will do is to load your data into the application provided by the manufacturer of the machine they are going to perform the RP with.

Your own VX Reseller, IDS, is a supplier of RP machines and they have numerous examples of successfully processed parts. Most RP machines are tolerant of things like overlapped/duplicate triangles, inverted normals etc. You can view your STL in VX to check that the triangulation has not missed-out any fine features or has any vertex points off shape.

I will check the file in Magics as soon as I can.

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Kevin

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Message 5 of 13

02-03-2005 06:28 . am | View his/her posts only
Thanks Chris,

All I need to know is can I rely on VX STL data 99% of the time (there will always be a 1% - usually on a deadline!!). The companies I use all use Magics to verify data and repair it. They don't all have in house facilities for creating the parts. Many sub contract out to others. What I pay for is the service - send the file and its their problem. In fact I've found it lower cost to use these types of services rather than using bureaus that have just one specific type of machine - but thats maybe something the bureaus can answer! The issue is I need to be confident I can rely on the STL data from VX - as seen by Magics. If it flags errors on parts thats another source of delay and cost in the workflow.

The other service I use a lot is Materialise Next Day because it is excellent value and 9 times out of 10 it IS Next Day. OK the build is only 0.2mm layers but for many parts this is fine. More bureau are offering this kind of service now but to do so many require that the stl loading and quoting is done via web based or software based systems which are intolerant of any stl errors they flag up.

For example materialise Next Day software uses a subset of the Magics software to load the parts and move the quotes through. I've used this service since it started and always check the validity of the STL file this way. If it is clear in the Next Day software it is clear in Magics so my suppliers have reliable data to work with. The Next Day system doesn't let you progress the order if it flags up errors,but it does have a fixing system built in which tries to apply automatic fixes to parts. Sometimes this works, sometimes not, so then you are offered a "human" alternative via STL Fix which is a 100 Euro charge minimum.

In the last few months I have used Next Day on maybe 20 parts or so. Always on a deadline. The few projects I've used VX on this way all flagged up part errors in the Next Day system and Magics. So the problem is why are these errors appearing.

The interesting thing from my perspective is that the only issues I've had with errors have come from non mainstream modelling kernel products.

Parasolid and ACIS based systems - I can't recall ever having errors flagged from parts generated in these systems
ThinkDesign - EVERY part flagged up errors - it was totally useless
VX - some parts are OK some flag up errors (the errors tend to be associated with bad edges)

Whatever the cause, I am 100% confident that VX developers can resolve it (if indeed it is a VX issue - it may be a deficiency in the Next Day system or Magics). But I'm raising this because when you are about to get a

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Kevin

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Message 6 of 13

02-03-2005 06:35 . am | View his/her posts only
Adding maximum mesh size value makes no difference to the errors in Next Day.

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ChrisWard2k2

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Registered: 2011-11-22

Message 7 of 13

02-03-2005 09:49 . am | View his/her posts only
Hi Kevin

I'm still waiting for Materialise to respond. Their text is riddled with errors, I hope this is not indicative of what their software is like "under the hood".

Do you have Magics on your PC? Can you e-mail me screenshots of the errors shown? Might it be the case that this is merely a computational tolerance problem, or are we saying that VX is missing-out triangles or not solving within the shape boundary?

One of the UK VX customers is a leading Rapid Prototype Bureau, but they have not reported any problems with VX STL.........

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Kevin

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Message 8 of 13

02-03-2005 10:41 . am | View his/her posts only
Hi Chris,

You sound like my IT manager brother in law! Always complaining about the "quality" of Microsoft software under the hood :-))

I've attached some screenshots from Next Day software showing the errors and effects of fine fixing. As you can see (starting at A) the errors are typically to do with edges and contours. Even if you apply fine fixing it still shows up errors then kicks you automatically into the STLFIX service. Maybe its just a cynical ploy by Materialise to scare us into using STLFIX when we are on a deadline!

From what you say it sounds like Next Day/Magics is being a bit too fussy about defining edges. There are certainly no missing triangles in the file.

Thinking about this a bit more though edge defects would imply a tolerance issue between Magics/Next Day and VX. The other CAD systems I've used with this service based on Parasolid and ACIS all used modelling tolerances of the 0.000001 units (well at least thats what the Ashlar developers say ACIS is built around). If there are no "tolerant edges" in the file this would be the part tolerance. These systems give no errors (usually) in Next Day. ThinkDesign had a habit of adjusting tolerance to force feature creation (for example you might start at 0.001 but try shelling and the pop up says this will work at 0.1mm tolerance) and that app had errors every time in Next Day.

I know we discussed before that VX uses 0.001 units, so maybe Magics is using something else between the two? If so its a bit daft considering most RP building processes are a lot less accurate than that.

Maybe you should give me the details of the UK bureau using VX and I'll start using them if Materialise keep booting my files out of Next Day!

When the guys at IDS move offices maybe they'll get a Dimension in house and start offering Next Day Services using VX :-)

Its becoming clear that the issue doesn't appear to be at VX's door, so maybe I'll go and kick on Materialise's instead!


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ChrisWard2k2

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Registered: 2011-11-22

Message 9 of 13

02-03-2005 11:49 . am | View his/her posts only
Hi again Kevin

I think STL imperfections detected by Magics are genuine enough, the issue then being "are they critical?". The answer must be no, because if it were yes, you could not safely rely on "Fine Fixing" to automatically change the shape of the design data in order to satisfy the requirements of the RP process. The next question of course would be, "are there imperfections actually defined within the STL data, or do they occur when Magics builds it's graphical representation of that data". Scary stuff, because the answer is probably yes for both conditions. It is interesting to note that VX, SolidView Lite and Magics have all built their graphical representation (of the imported STL data) differently.

Your example file is simple of course and the shape rect-linear. I would expect Parasoids and ACIS based CAD applications to be able to output that kind of shape well. However, the real test is the organic, double curvature shapes that the professional industrial designers use to lure us all into parting company with our money

I have asked the developers to consider if the code that produces VX STL output can be further enhanced.

The Dimension RP machines that IDS supply are fabulous. They are safe to use in the office environment and the material is ABS - so you end up with a protype that is tough and functional rather than the fragile SLA efforts that everyone first thinks of. They look cool too, like a space-age coffee machine! Given that you do so much RP work, it might be more economical (and certainly faster and more convenient), if you plugged one into your VX workstation........

The UK RP Bureau that uses VX is Malcolm Nichols Ltd http://www.mnl.co.uk -you may well be using them already, they enjoy a deserved reputation for quality.



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Kevin

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Message 10 of 13

02-03-2005 12:34 . pm | View his/her posts only
Thanks for the feedback Chris,

Well I'm going to bite the bullet and press on using VX for a new project that will be based on stl workflow! So here goes!

With the progress I've seen in VX over the last couple of years I'm happy sure this is an area that will be touched up.

As for the Dimension, yes, the guys at IDS have tried to flog me one :-) When I was down training I checked out some samples and they are pretty good. In an ideal world I'd have one but as the company I work quite closely with nearby has just (today!) purchased a new Envision Perfactory machine with a 25mm/hr build rate I'm looking at SAME day prototypes now!! With a 25 micron build layer!!

I know of Malcolm Nicholls. Maybe I'll give them a try next job.





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ChrisWard2k2

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Message 11 of 13

03-03-2005 10:50 . am | View his/her posts only
Still waiting for Materialise.......

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Kevin

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Message 12 of 13

03-03-2005 11:05 . am | View his/her posts only
You would have got the parts quicker :-)

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ChrisWard2k2

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Registered: 2011-11-22

Message 13 of 13

04-03-2005 09:15 . am | View his/her posts only
Hi Kevin

I still have not received a response from Materialise, though I have chased them. Meanwhile, all the sample data, screenshots etc is in the hands of the VX Florida development team.
See also