kicad-developers team mailing list archive

[Cirilo Bernardo <cirilo.bernardo@xxxxxxxxx>]

Although scaling is allowed in the IGES and STEP specifications, I have
*never* encountered MCAD
software that allowed a scale other than 1 and in engineering there are
essentially no acceptable
reasons to use any other scale factor.  When engineers specify parts for an
assembly, the parts need
to be exactly as described and within specified tolerances. If PartA is
used multiple times or even used
only once in Project1 and in Project2 but PartA has instances with
different scaling then good luck even
getting your manufacturers to produce the correct part for you.  Those of
us who use MCAD models
are absolutely reliant on everything having a uniform scaling of 1. This is
particularly important when we
have a very close fit - just think of how everything is stuffed into a
mobile phone.

On Wed, Sep 30, 2020 at 3:23 AM Jon Evans <jon@xxxxxxxxxxxxx> wrote:

> Do other EDA tools allow model scaling?  Altium doesn't even allow VRML
> import in the first place.
>
> On Tue, Sep 29, 2020 at 1:10 PM Seth Hillbrand <seth@xxxxxxxxxxxxx> wrote:
>
>> Well, we've backed ourselves into a bit of a corner.  VRML is specified
>> in meters, so if we're assuming inches, we're a bit off in left field.  But
>> do we need three separate scale parameters?  We could reduce to 1, correct?
>>
>> In the official footprint library, we have 7 footprints that specify
>> non-unity scaling. (Banana_Jack_[1-3], NS-Tech_Grove_1x04, Fuse_Blade_ATO,
>> Fuse_Blad_Mini, Oscillator_SMD_TXC0_G158).
>>
>> -Seth
>>
>>
>>
>>
>> On Tue, Sep 29, 2020 at 9:30 AM Ian McInerney <Ian.S.McInerney@xxxxxxxx>
>> wrote:
>>
>>> We can't remove the scaling option until we make the VRML importer
>>> handle proper unit selection. I have routinely run into the case where I go
>>> OpenSCAD -> Wings3D -> KiCad and design a model using mm in OpenSCAD
>>> because it makes for easier computations (all the datasheet values are
>>> nicely given in mm) and then have to apply a scaling factor of 0.3937 to
>>> all the axes in KiCad to make it the proper size because we seem to have a
>>> hardcoded assumption about what unit system the VRML file is in.
>>>
>>> In fact, the KLC says: WRL files do not specify absolute dimensions.
>>> KiCad normalizes model parameters to units of inches and the internal units
>>> (dimensionless) of the WRL model must be scaled accordingly.
>>>
>>> -Ian
>>>
>>> On Tue, Sep 29, 2020 at 4:50 PM Seth Hillbrand <seth@xxxxxxxxxxxxx>
>>> wrote:
>>>
>>>> There has been some discussion to removing the scale option here
>>>> altogether.  The logic being that if you need the model scaled, you should
>>>> be doing this in your solid CAD not in your electronic CAD.  I have come
>>>> around to this idea and it might be worth implementing rather than doing
>>>> the scale limiting.
>>>>
>>>> -Seth
>>>>
>>>> On Tue, Sep 29, 2020 at 4:52 AM Mário Luzeiro <mrluzeiro@xxxxx> wrote:
>>>>
>>>>> Hi all,
>>>>>
>>>>> I'm wondering if it is safe to limit the scale of shapes to be
>>>>> positive values?
>>>>>
>>>>> Applying negative scales will cause inverted shapes and render issues
>>>>> on the models.
>>>>>
>>>>> Could be that anyone in the world is using negative scale values?
>>>>> or should be safe to limit it?
>>>>>
>>>>> This is related with this issues:
>>>>> https://gitlab.com/kicad/code/kicad/-/issues/5817
>>>>>
>>>>> Mario
>>>>> _______________________________________________
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>>>>>
>>>>
>>>>
>>>> --
>>>> [image: KiCad Services Corporation Logo]
>>>> Seth Hillbrand
>>>> *Lead Developer*
>>>> +1-530-302-5483‬ <+12126039372>
>>>> Davis, CA
>>>> www.kipro-pcb.com    info@xxxxxxxxxxxxx
>>>> _______________________________________________
>>>> Mailing list: https://launchpad.net/~kicad-developers
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>>>>
>>>
>>
>> --
>> [image: KiCad Services Corporation Logo]
>> Seth Hillbrand
>> *Lead Developer*
>> +1-530-302-5483‬ <+12126039372>
>> Davis, CA
>> www.kipro-pcb.com    info@xxxxxxxxxxxxx
>> _______________________________________________
>> Mailing list: https://launchpad.net/~kicad-developers
>> Post to     : kicad-developers@xxxxxxxxxxxxxxxxxxx
>> Unsubscribe : https://launchpad.net/~kicad-developers
>> More help   : https://help.launchpad.net/ListHelp
>>
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