Author Topic: Does anybody here export STL or OBJ format for 3D printing?  (Read 567 times)

Lar

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Re: Does anybody here export STL or OBJ format for 3D printing?
« Reply #45 on: December 04, 2017, 02:11:22 PM »

Here is the STL file, as in my last image with the 3 sets, from Cura. It opened in Dcad and C4D ok.


Lar

Dr PR

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Re: Does anybody here export STL or OBJ format for 3D printing?
« Reply #46 on: December 04, 2017, 08:57:53 PM »
Blankman,

I built my first S100 system in 1976 - wire wrapped some of it and some from kits. Wrote my own OS at first and it was pretty simple! Later I got CP/M.  I hacked a Hitachi B&W TV to make a video monitor. I had a used Teletype Model 43  with upper and lower case with red an black ribbon - very fancy! I bought a Z80 Macro Assembler from TDL (a bunch of grad students at MIT) on paper tape. It took the Teletype 45 minutes to load the program! I used it to write one of the first screen oriented word processors. Later I got an OAE optical tape reader - 4 minutes to load the assembler!

I modified an ordinary cassette tape recorder to be a data recorder and designed my own interface - wire wrapped. Only 45 seconds to load the assembler!!! Then I designed and wire wrapped a floppy disk controller using one of the first two uPD765 disk controllers imported into the US (the chip used five years later in the IBM PC). Got two used 8" floppy drives and it only took 4-5 seconds to load the assembler. Wow!!!!

Eventually the machine had a whopping 64 kilobytes of dynamic RAM!! All in all it cost me $3400 (I bought a new 1972 Camaro for $3200). I did all of this while finishing my PhD in microbial physiology. Used the computer to crunch numbers for enzyme kinetics experiments. After I graduated I was hired by Hewlett-Packard as a programmer, and then in 1980 I went to a small industrial process control company where I programmed and designed electronic equipment. I still work for the same small company, although I am semi-retired.

I started using ProDesign - later DesignCAD - in 1987. Believe me, I have seen a lot of bugs, and I know what you are talking about with problems with Solid Subtract (all the solid Booleans). Still, it is a very useful program, and has the best user interface of any program I have ever used.

I have created STL files from DesignCAD, but years ago. I exported DXFs and used AccuTrans 3D to convert to STL. There were a lot of leaks that the printer driver had to fix. I haven't tried exporting STLs from the latest DesignCAD. I hope you figure out work-arounds for the problems in DesignCAD because I may want to do some 3D printing in the near future!

Phil
« Last Edit: December 04, 2017, 09:01:18 PM by Dr PR »
DesignCAD user since 1987

BlankMan

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Re: Does anybody here export STL or OBJ format for 3D printing?
« Reply #47 on: December 05, 2017, 06:36:01 AM »
Interesting history Phil, thanks for sharing.

In 1976 my first computer was a single board Super Elf RCA 1802 based. hex keypad, 256 bytes of memory, video interface to a TV, data interface to a cassette player, and two (I believe) S-100 slots. I think you could get an expansion board for it. I designed an expansion board for it that had 10 S-100 and all the electronics to create/mimic the necessary S-100 signals from the 1802. I could load a Solitaire program via the hex keypad and play Solitaire on the TV on it!

Couple years later I built a big S-100 based cabinet system and ran, yep you guessed it, CP/M. With 2 (Al) Shugart 8" floppy drives. That's where I later wrote the drivers to use 5-1/4" floppy drives and hard disks. I remember having to interface to some 40 pin WD (Western Digital) controller chip. I remember having 32K S-100 memory boards where the 32K filled the entire board! And all socketed in case of failure. Unheard of these days.

Later in the early 80's when the PC was born I partnered and opened a computer store. We specialized in business and networking the PC, pretty much unheard of at the time but we also had a storefront. There we had my S-100 system earmarked to be a dial-in multi-user system. I also designed an expansion broad for the Apricot PC there. I remember when Oracle Database was a PC app and we sold it. It didn't take me long to realize living in a retail environment is not my cup of tea. I went back into the industrial design/computer management world but kept my interest in the business.

As far as STL files, yes I have a number of workarounds to get a usable one. And as you mentioned they don't have to be perfect, and very few are, because most slicers can correct a lot of defects. But some of them that DC3 puts out they just can't handle. A lot times they'll slice them to what looks like a printable model but because the surfaces are so mangled they miss putting supports where supports are needed. A lot of slicers let you manually add supports but that doesn't work either because again it doesn't detect the surface that needs the support.

As I mentioned I draw in BasicCAD, What I found is the order that things are done has a big impact on how the STL/OBJ exports turn out. I first thought that SolidSubtract was the culprit but SolidAdd is just as bad. So once I have the drawing done I spend a lot of time reordering the operations to get the best possible i.e. usable export. A lot of time. IMO it's BS that I have to do that. That IMSI puts out something this bad. Even before this STL problem FilletEdge for years can destroy an object by not stopping where it should and cuts through the piece. And they don't fix it!

I need to play around with Blender more (and try Cura) now that I discovered the latest version can fix meshes. It was able to fix that second object I posted but I modified it in DC3 then Blender couldn't fix. Once again I reordered the operations in DC3 and once again Blender could fix it. Go figure eh...






Newbie? Not.
Been using DesignCAD 3D since ~1990
Still have version 4 floppies...

Dr PR

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Re: Does anybody here export STL or OBJ format for 3D printing?
« Reply #48 on: December 05, 2017, 09:30:32 AM »
Both Solid Add and Solid Subtract (probably all solid Boolean operations) screw up the surface normals in grid facets that get cut. DesignCAD's OpenGL Gouraud shading does strange things with these surfaces. Part of a facet will shade correctly for the light source and the other part will shade as the reverse (shadowed) part. So part of the outside surface of an object is actually the inside surface.

The latest DesignCAD versions have a normals viewer that allows you to see the surfaces with reversed normals. You can also flip the reversed normal back to the correct normal by selecting the facet and reversing point order in the Info ox.

I wonder if this is contributing to the messed up STL files? You might try looking at a solid that you know will produce a screwed up STL file and see if some surfaces have reversed normals. Then compare this to the STL output and see if it is the reversed normal surfaces that are messed up in the STL output.

Even if that is the problem, and you can fix it by reversing normals, it is still a PITA to have to clean up the mess.

Phil
DesignCAD user since 1987

ev

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Re: Does anybody here export STL or OBJ format for 3D printing?
« Reply #49 on: December 08, 2017, 03:35:33 PM »
I'd like to mention MeshLab and FreeCAD here also. Both offering a wide range of functions in mesh repair and solid generation out of mesh imports. Blender was referred to, already.

Lar

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Re: Does anybody here export STL or OBJ format for 3D printing?
« Reply #50 on: December 08, 2017, 04:32:54 PM »

I just installed Free CAD. Looks promising. Is parametric, and open source, and really is free. The built-in renderer is still under development, but can link to a certain renderer (I can't remember which one) if it is installed on your system. I tried some importing. The STL's and OBJ's from dcad imported without issues. The DXF's got really messed up. Like really, REALLY messed up. The manual is helpful but sometimes they don't tell you where to find the command they are explaining.


And now I can reliably report that dcad's Solid Surfaces do not come over via DXF, in all the programs I tried. When S/S's were introduced they did not come over in Cinema 4D (I had to convert them to Solids before exporting). DT made some adjustments to the exporter but they still failed. I gave up, thinking it was a C4D thing. But now, since this topic came up, I could not get them to DXF into Cura or FreeCAD.


Lar

paul craig

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Re: Does anybody here export STL or OBJ format for 3D printing?
« Reply #51 on: December 09, 2017, 04:42:12 PM »
Lar, this is not directly related to the STL question, but it might help address some of your thoughts about the DXF files when exported.

In the past, I have sent my files for etching to my film maker as DWG, but recently he asked for my latest work to be in DXF. However when I tried to export directly in DXF, I found
at least one of them was gi-normous. Checking my file explorer, a DCAD file is about 4 time smaller than that exported into DWG, thus I could not send them with my email server.
I checked, and was advised to zip the files, and send them that way. Like most quasi amateurs, I thought zipping meant I would lose some definition. But no, apparently, when you
open a zipped file it is checked by an algorithm to see whether all the data packets have been transferred properly and accurately. This does not happen when a DWG file is transferred
"en-clare" since it is not checked by such a system.

Since I am not clued up on the difference between DWG and DXF I cannot comment on why the files are so dissimilar in size, but perhaps others know more.

HTH

Paul

Lar

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Re: Does anybody here export STL or OBJ format for 3D printing?
« Reply #52 on: December 09, 2017, 06:35:27 PM »

Since I am not clued up on the difference between DWG and DXF I cannot comment on why the files are so dissimilar in size, but perhaps others know more.
DWG is a specific file type while DXF is geared for export so it has to cover many possibilities.That's my guess. Also, dwg would have been improved over the years while dxf maybe hasn't improved that much.

Dr PR

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Re: Does anybody here export STL or OBJ format for 3D printing?
« Reply #53 on: December 09, 2017, 07:31:57 PM »
DXF is an ancient file exchange format. It has been tweaked over the years, but is basically the same as when it was introduced decades ago.

DXF is an ASCII text format. DWG is a binary format, as is the native DesignCAD DCD file format. Because DXF is an ASCII text file, everything is written out in text characters, and it takes a lot of numeric digits to express the much more compact binary values. Consequently, DXF files are a lot larger than their binary counterparts.

For example, a single 8-bit binary byte can represent values from 0 to 256. But to express the value "256" in ASCII requires three 8-bit characters, or 24 bits. A two byte 16-bit binary word can represent from 0 to 65536, but it takes five ASCII characters - five bytes -  to represent the same thing. See why DXF files are so much larger?

Phil
DesignCAD user since 1987