kicad-developers team mailing list archive

[Cirilo Bernardo <cirilo.bernardo@xxxxxxxxx>]

Hi Maurice,

 I've had a look at the step file and it is unusable because the scale is
all wrong. The short edge of the PCB for example is over 7km long. I guess
this is OK if you really want a box that big.

 As for general issues using the VRML export to create a solid model for
MCAD, arcs and drill holes are represented by multiple segments. The VRML
export code will use as many segments as required to ensure a certain error
(I think 0.05mm) but in the MCAD world these drill holes will not be
circles so it is difficult to create a reference point without the MCAD
user manually adding reference points. In IDF there is no such problem -
lines are lines and circular arcs are circular arcs. (IDF export code
doesn't support Bezier curves - does anyone use/require them?) So an IDF
model of the board is more useful to MCAD users - it is also dimensionally
accurate.  If you really need to interact with MCAD, I suggest you practice
using the IDF export and if you wish you can even create outlines for the
components. On the MCAD side, the users will replace any important
component models with accurate models.  When IGES export is eventually
added then there will be no need for such fiddling.

 As for the other limitations of OpenCascade, as I said before Tom's
initial work showed a critical problem for OC STEP export: the file treats
every feature of every component as a "part", so if you only have a PCB
with a single QFP-160 I will have at least 162 parts (and 162 files to
represent each of those parts in the MCAD's native format). If I notice in
MCAD that the QFP is not accurately placed and I want to move it in the
MCAD, I need to reposition at least 161 parts. This is unacceptable and is
one of the main reasons why I have done no further work with OC/FreeCAD and
am instead working on IGES export, with STEP export planned for next year.
At this point in time I see no possibility of using OC for STEP export so
the STEP code will be based on "stepcode" (formerly the NIST Step Class
Library).

- Cirilo


On Fri, May 15, 2015 at 11:02 PM, easyw@xxxxxxxxxxxx <easyw@xxxxxxxxxxxx>
wrote:

> Hi Cirilo and all,
>
> please find attached an exported vrml file from kicad, converted from vrml
> to STEP
> the result is a step file readable by 3D sw e.g. solid works...
> board and components are separated parts and can be manipulated in 3D sw
>
> I use to send these kind of files to 3D people to be inserted in a
> mechanical layout system.
>
> Do you think this result could it be reasonable at this time?
>
> thank you
> Maurice
>
>
>
> On 5/15/15 12:12 AM, Cirilo Bernardo wrote:
>
>> Hi Maurice,
>>
>>   The STEP export has been discussed many times and OpenCascade is
>> not suitable; I would never accept a STEP file produced by OpenCascade
>> because it does not maintain the assembly hierarchy and other product
>> data. Tom's demonstration code was very simple and we were hopeful at
>> the time that OpenCascade will make life easier for us, but when I
>> imported the model in SolidWorks I saw that I had many dozens of parts
>> when I should only have had 3 parts. Inspecting the STEP file showed
>> that the file generated is just not acceptable for mechanical engineers.
>> The OpenCascade people offer a paid-for add-on which is supposed to
>> provide the functionality required but this is obviously not suitable for
>> us.
>> We will have STEP export one day, but STEP is a much more complex
>> standard than IGES so it will be implemented later. As for displaying
>> such models (STEP and IGES) that is a non-trivial issue and I have no
>> plans to do that.
>>
>> - Cirilo
>>
>> On Fri, May 15, 2015 at 2:19 AM, easyw@xxxxxxxxxxxx <robit@xxxxxxxxx>
>> wrote:
>>
>>  Hi Cirilo and all,
>>>
>>> as a first step to integrate STEP in kicad, I think exporting STEP plain
>>> board (no copper, no silk) and modules would be a great improvement.
>>>
>>> I don't know if would be possible to integrate some libs from pythonOCC
>>> http://www.pythonocc.org/features_overview/data-exchange/
>>>
>>> I found in mail archive that Thomas did a sort of export to STEP
>>>
>>>
>>> https://www.mail-archive.com/kicad-developers@xxxxxxxxxxxxxxxxxxx/msg06620.html
>>> what happened? any integration in kicad code?
>>>
>>> I noticed that step models are typically heavier in bites then vrml, so
>>> rendering would be also heavier...
>>> For that reason, and for the big existing 3D library, I would consider to
>>> maintain vrml models for 3D rendering and add STEP export (and eventually
>>> STEP import) in kicad
>>>
>>> please let me know your opinion...
>>>
>>> Maurice
>>>
>>>
>>>
>>> On 5/13/15 6:16 AM, Cirilo Bernardo wrote:
>>>
>>>  You might mention that for those who need to interact with mechanical
>>>> designers
>>>> KiCad can export IDF interchange files. For those who like to roll their
>>>> own,
>>>> FreeCAD will read the files; for those who send the files to another
>>>> shop,
>>>> they
>>>> can convert the IDF file to VRML and view it with a VRML viewer - no
>>>> need
>>>> to
>>>> install FreeCAD. Plus: coming up (maybe towards the end of this year),
>>>> KiCad
>>>> will be able to export to IGES to provide the mechanical designers with
>>>> a
>>>> much
>>>> more accurate 3D model of the project. IDF only represents components as
>>>> simple extrusions, but IGES can provide accurate 3D models. I made
>>>> component
>>>> models for the demo projects 'video' and 'pic_programmer' to show the
>>>> IDF
>>>> exporter at work. If you wish I can send you a tarball of the IDF files
>>>> and
>>>> the
>>>> resulting VRML files as produced by the idf2vrml tool.
>>>>
>>>> Making a few comparisons to Eagle:
>>>> 1. KiCad has a native IDF exporter, Eagle requires the user to install a
>>>> ULP.
>>>> 2. KiCad: 32 copper layers, 16 tech layers; Eagle: 16 copper (I don't
>>>> know
>>>> the
>>>> limit on tech layers).
>>>> 3. KiCad: free + no artificial limits placed on capabilities; Eagle:
>>>> artificial limits
>>>> placed depending on license fees.
>>>>
>>>> Although the feature is still in development, once KiCad can export IGES
>>>> models I expect this to become a free built-in capability. With Eagle
>>>> you
>>>> need to pay an *annual* license to a third party for IGES or STEP
>>>> export.
>>>> Note: I don't expect KiCad to have STEP export for at least another 2
>>>> years unless someone else with time on their hands is inspired to code
>>>> it;
>>>> I mean a meaningful STEP export which maintains product relationships
>>>> and a proper assembly heirarchy, not the flat file produced by FreeCAD/
>>>> OpenCascade which is absolutely useless to mechanical designers.
>>>>
>>>>
>>>> - Cirilo
>>>>
>>>>
>>>> On Wed, May 13, 2015 at 1:48 AM, Adam Wolf <
>>>> adamwolf@xxxxxxxxxxxxxxxxxxxx
>>>>
>>>>>
>>>>>  wrote:
>>>>
>>>>   Hi folks,
>>>>
>>>>>
>>>>> I'm preparing a presentation on KiCad for Maker Faire Bay Area this
>>>>> weekend.  (Fun fact: the presentation after me is someone designing a
>>>>> Raspberry Pi daughterboard *on KiCad on a Raspberry Pi*).
>>>>>
>>>>> The audience will be folks who may be interested in making PCBs, and
>>>>> may
>>>>> work with fancy pants PCB designers, but are probably closer to the
>>>>> beginner side.
>>>>>
>>>>> I'm hoping to cover a little of KiCad history, newish features (openGL,
>>>>> Python, P&S routing, differential routing), upcoming features (eeschema
>>>>> revamp...), and the new release rhythm and nightlies.
>>>>>
>>>>> I know there's the longish videos by the CERN folks on the differential
>>>>> routing, but does anyone have fun videos of openGL mode being awesome,
>>>>> or
>>>>> the P&S routing?
>>>>>
>>>>> I can make my own, but if someone already has them and is willing to
>>>>> share, I'd love to include them.
>>>>>
>>>>> I hate to offer this, but if anyone else has suggestions on things I
>>>>> should mention, feel free to send them on.
>>>>>
>>>>> Thanks everyone!
>>>>>
>>>>> Adam Wolf
>>>>> Cofounder and Engineer
>>>>> W&L
>>>>>
>>>>> _______________________________________________
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>>>>>
>>>>>
>>>>>
>>>>>
>>>>
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>>>>
>>
>>
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