Re: [DIYbio] FreeCAD used for microfluidics (was: Microfluidics Chat Thread)

On Mon, Jan 5, 2015 at 1:42 PM, John Griessen <john@industromatic.com> wrote:
> On 01/05/2015 02:28 PM, scocioba@gmail.com wrote:
>>
>> That's a good question. Let me breakdown the situation for you:
>
> Being able to scale everything would be super since I can test macro-chips
> and then scale down. Does
>>
>> parameterization involve scripting and hard coding relationships between
>> shapes or is it a trivial task?


Parameterization should mean that a given component is parametric,
connecting components together for a given design is a different phase
of designing things. What I mean is, you would have parametric
channels, but also parametric curved channels, and then you would
connect a straight segment with a curve to create a channel that had a
curved section on the final device.

>
> I think both are possible -- python code or click on to associate.
> Thanks again for the
>>
>> offer. I'll try out freeCAD and bother you for tips when I inevitably get
>> stuck. Can freeCAD handle 2D well?

If 3D is handled well, 2D is just a simple slice of the 3D.

>
> Sure.
> Hatching and whatnot?
> Yes.
>>
>> Also if I export a PDF to scale of a micron-ranged drawing, what's the
>> smallest figure that can be drawn?

This is not so much limited to the CAD software, as what max
resolution (DPI) a PDF can handle, and then also what max DPI your
output device can handle. The CAD resolution is really just setting
the DPI, what DPI is needed depends on the manufacturing requirements
and the manufacturing system (i.e. laser printer, CNC, SEM/FIB
lithography mask/direct-etch, diffraction-limited lithography). All
these systems have some slop or 'play', it would be pointless to
export with 1 dot per nanometer, if your manufacturing system could
only address 1 dot per 10000 nanometers, coupled with blurring that
might happen too after PDMS replication for example.

>
>
> Will need to try out.
>
> Let's take this off list next unless others are interested

Basically the only downside of FreeCAD I've heard is that the
CAD-kernel it is based on is:
large, old, complex, lacking tests

all leading to instability and immense difficulty to maintain/fix/augment.

I started playing with BRL-CAD last night and it looks like it might
be really good. Originally developed by the U.S. military (or at least
their dollars), and has been industry-proven in that sense. The
interface is a bit clunky, but I think it is really bad simply because
no one has made a 'BRL-CAD for dummies' web page somewhere. Once I
figured out what I needed to do, it was quite simply to get a 3D shape
displayed, though I didn't look at exporting it in any formats.

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