Re: [CAD_CAM_EDM_DRO] REPRAP COST EFFECTIVE?

On Sun, Oct 9, 2011 at 10:16 AM, Jon Elson <elson@...> wrote:

> This is not a logical part for a filament fabricator. They are best on
> thin parts
> that are like shells or boxes, ie. lots of exterior but mostly hollow.
>

I disagree... There are too many variables to make such a blanket statement.
And fwiw, parts that are mostly shell and mostly hollow are considerably
harder to print.

> The typical
> makerbot sort of machine might take 2 HOURS to make one of these parts.
>

well, or 15 minutes as the toolpathing software actually shows. ;-) Even if
you drop the speed to 50mm/sec (attainable by even a Makerbot) your print
time only goes up to ~25 minutes. Sure, that is a long time, but depending
on the cost of having them fabricated elsewhere, it may well be worth the
wait. It is important to remember that 90% of that time is not hands on
time. The printer needs to be monitored, but it does not need to be babysat.

> Also, in most cases these machines cannot make precise parts due to
> shrinkage,
>

This is incorrect. With a heated build platform, warpage is minimal, and if
you use PLA almost non-existent. It is also easy to design your parts to
minimize problems.

> and the parts are nowhere near solid. They are made of layers of thin
> plastic
> filament laid down layer by layer, but have air spaces between the strands.
>

This is true, but it is important to remember that the vast majority of an
objects strength comes from it's skin. A printed object is certainly not as
strong as a solid one, but for most applications it is plenty strong enough.

> Cost of the material is not zero, but it is not real high, either. Most

people use PLA

> or ABS for these machines. They are quite conservative with material,
> there is a little
> wastage in some cases to make a "foot" for the part on the build table,
> but otherwise
> all the material ends up in the part. I would doubt your part would use
> more than
> $2 - 4 of material. That is still probably a lot more than the cost of
> Nylon or Delrin
> in bars. But, the real difference is in time. I imagine you could make
> these
> parts in production on a mill in a couple minutes each, especially with
> some
> fixtures to hold several in a row.

Ok, here you are correct... If the part is a simple 2d spacer, I agree a
mill or router is probably a better choice. However if the holes are
actually from the ends, then the math changes considerably... That would
mean 3 separate setups, for one simple part-- compared to zero setup on the
reprap.

Another thing many people don't consider about 3d printing is that it makes
it possible to manufacture parts that would truly be impossible to
manufacture with any other method You can make one-piece parts with precise
internal cutouts that would require 2 or more pieces with any other method.
Once you get the hang of designing for 3d printing, you start realizing that
you can greatly reduce the part count of many objects.

Finally there is one point that argues against the RepRap for industrial
use-- reliability. These machines are FAR more reliable than they were even
a few months ago, but it is still very much a bleeding edge product. My
printer works great most of the time, and then I will randomly start having
problems for no obvious reason. It can take a while to learn the symptoms,
and figure out what the cause of the problem is. Once you troubleshoot the
problem, it is usually quite easy to fix most problems, and only rarely will
the fix require new parts, but nonetheless it is something you need to be
aware of.


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