CAD/CAM discussion forum > 3D CAD/CAM > Large Repeated Patterns

Large Repeated Patterns

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John

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Registered: 2004-10-14

Message 1 of 10

 Large Repeated Patterns
02-07-2005 03:02 . pm | View his/her posts only
I'm running into slow performance and very large file sizes and I'm wondering if there is a better way to do what I'm trying to do. Here is the situation. I'm trying to model a spanish tile roof for a plastic model that I'm working on. I created a single tile piece. Then I created a 4x4 tile section and combined the parts into a single part. Next, I created a new part, inserted this 4x4 tile section and used the pattern to make a 10x10 section from this, for a total of 40x40 tiles. This isn't actually the final size I want (it's smaller), but I still end up with an exported IGES file of almost 20MB. The STL file is also about the same size.

Any suggestions on the best way to handle making the entire roof for a small house? The roof will be a scale 40' x 20', for example, but I'll be scaling it down to 1/160 of this size, which means the final part will be about 3" x 1.5". I need a resolution no better than about 0.002" (I think).

Thanks,
-- John

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Kevin

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Message 2 of 10

03-07-2005 07:52 . am | View his/her posts only
I'm not so sure a 20MB IGEs or STL file is that large for this. Most of our files are over 10MB, some over 80-90MB. What size are the VX files? Remember although the VX file may be small due to patterning, STL and IGES don't recognise this and have to create and define the geometry for all the individual tiles.

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John

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Message 3 of 10

03-07-2005 01:40 . pm | View his/her posts only
The VX file is 35MB. I guess my real question is this: is there someway to limit the amount of data put into an STL file when I know there is more data in the model than can be rendered with either milling or with an SLA? My part at this point is 1" x 2" in actual size. So it seems like I should be able to reduce the amount of data considering that an SLA machine has layers that are only .001" tall. My model is only .036" tall.

I checked the export options carefully for STL files and noticed that I was using ASCII instead of binary export. Changing to binary got the file size down to a more manageable 3MB.

I'm still curious if there is a preferred way to do what I'm doing that will maximize regen performance.

Thanks,
-- John

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ChrisWard2k2

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Registered: 2011-11-22

Message 4 of 10

03-07-2005 08:17 . pm | View his/her posts only
Hi John

Performance wise, you can certainly gain a huge improvement by building the model as a VX assembly. Draw one tile as an individual Part Object. Create a new Part Object for the Roof Assembly. Right-mouse click and insert the tile model as a component. Array (pattern) that component to make the roof. This will keep the VX file relatively small and you should find that performance of dynamic pan-zoom etc is good (unless your PC is closely related to an abacus).

Concerning STL, I think that you could lose a certain amount of detail because you are looking at a very small scale. Tile thickness for example - if a full size tile is about 3/8" thick, it would be only 0.002" thick at a scale of 1/160. Although an SLA machine might build in layers of 0.001" (more commonly high resolution layer thickness is approx 0.004", using a laser beam of 0.003" to 0.004" diameter), this does not give a model feature accuracy of 0.001", especially features that are not vertical in Z axis. I would expect the absolute best overall tolerance to be around +/- 0.003". If the actual machine that is going to be used is metric, it may pay you to produce your model in metric units.

3Dmonkey is correct about the export file sizes (STL is generally bigger than IGES) - all the geometry detail has to be described within these files and thus they can get to be "big". However, big is not a problem! If the prototyping company can accept binary STL files then great. Otherwise, if you have, say, a 1GB STL ASCII file, it can be zipped and sent via FTP or saved to a CD/DVD. It does take a long time to export a large STL file (the file will be large because of geometry complexity).

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Kevin

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Message 5 of 10

04-07-2005 04:29 . am | View his/her posts only
For doing this kind of detailed SLA work I would recommend using a bureau that uses the Viper machine as this has the best resolution on the market for general SLA work. Alternatively if you can source anyone using the Envision Perfactory machine this is designed specifically for small highly detailed parts - especially for jewelry work.

How is the part going to be manufactured? Plastic or metal casting? Another option would be to make the SLA blanked with no detail and specify a texture in the mould.

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John

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Registered: 2004-10-14

Message 6 of 10

04-07-2005 02:37 . pm | View his/her posts only
If it's not one thing, it's another. I originally created the 2-tile, 2x2 tile, and full tile roofs as assemblies and it was very fast. However, I'm creating the tile roof at full size (16" long reveals). Then I want to create new versions of this assembly that are at different scales, like 1:160 and 1:87 (model railroad scales). However if I insert the entire roof into a new assembly, then apply the scale command, the solid model is no longer a valid solid model. It becomes pure white on the screen (the wire frame looks ok). If, however, I export it as an IGES file, then open the IGES file, there are lots of areas that need patching up. Exporting it as an STL file produces truncates file that is only 10 bytes long. The only way I can scale it without losing itegrity is to merge the components in each assembly where I insert another assembly. This is a very slow operation for the entire roof, but it does allow me to scale successfully.

So it sounds like I must be doing something wrong in my use of the scale command. Any ideas?

My plan was to use either a Viper or Perfactory so I can get the .001" layer thickness, which is very important for such small models. As to production, I haven't decided yet, but I'm thinking of making RTV molds from the master and casting parts in Polyurethane resin. This is not at all unusual for the model railroad market where volumes are low and the expense of an aluminum mold is high (it's all relative). One option is to make the molds on my desktop CNC machine.

Before I send the STL file to a machine, I'm going to fill the back side so the pattern will only be on the top of the roof, and the entire roof will be about the right thickness for the model (on the order of .05"-.1" thick).

Thanks,
-- John

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John

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Registered: 2004-10-14

Message 7 of 10

04-07-2005 02:55 . pm | View his/her posts only
I was curious about the scaling problems so I did another test. I took the tile roof assembly that wouldn't scale properly and exported it as an IGES file. Then I created a new assembly and imported the IGES file into that assembly. Finally, I scaled the imported model and this worked just fine. So is there perhaps a bug in the scale command?

-- John

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ChrisWard2k2

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Registered: 2011-11-22

Message 8 of 10

04-07-2005 06:11 . pm | View his/her posts only
Hi John

You are on the right lines - an assembly cannot be scaled (it does not have geometry, only the graphical instance of geometry). However, you can create a further part object for export purposes, use insert component to insert the roof assembly and then <right-mouse pick all> to merge all the sub components in one go. This works fine, and you then have geometry that will scale. Before you scale, blank the components (they are still there after the merge).
However, many rapid prototypers can apply the scale in the SLA software, in which case you do not need to carry out this procedure. Incidentally, if you ever need to dumb-down 3D geometry, instead of IGES, use VX's own VXN format. It is faster and highly accurate

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John

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Registered: 2004-10-14

Message 9 of 10

04-07-2005 08:22 . pm | View his/her posts only
I had tried to use Merge Component on the tile roof after inserting it, but I got an error message that it couldn't find one of the sub components. In order to get Merge to work correctly, I have to make sure I do a Merge Component in each sub assembly when I insert a component from a lower assembly. This works just fine, except it means I can't select a component, right click and select Edit Part anymore, which means I can't use the in-context design as easily (the Edit Part command doesn't appear in the context menu for the history's Insert Commponent entry either--grump).

The approach I've had to take is to use one or more merge components at each level, but supress them while I'm donig in-context design. When I'm ready to update the scaled version, I have to go into each assembly and unsupress the merge component. It seems like there has to be an easier way. I still need to use this approach anyway because I need to perform some boolean operations on the roof when I'm all done since some of the roof sections aren't rectangular.

Is there a reason the merge component doesn't work the way I was trying to use it?

John

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ChrisWard2k2

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Registered: 2011-11-22

Message 10 of 10

05-07-2005 01:34 . pm | View his/her posts only
Hi John

If you are managing the Objects in the way I have described, there should not be a problem - the clue is in the error message - if the system cannot find one of the sub-components, there must be a reason for this. Could it be that you were trying to merge a component that itself was comprised of sub-assemblies? If so, the "component pile" is too remote for merge to work. Or, it may be that the geometry for one of the components resides in a seperate file which has since been relocated.

You do not have to boolean your assemblies, you can make copy Part Objects of the tile and thus produce the correct size tile for specific positions. Also, remember that my suggestion is to produce a Part Object of merged components specifically for export, this is the most expedient way to work.
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