Re: [CAD_CAM_EDM_DRO] REPRAP COST EFFECTIVE?

Mike Payson wrote:

> 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.
>

Yes, there certainly are big problems in getting large changes in filled
area/layer, like the
lid of a box, to work.

Apparently you have seen some machines with a lot higher performance
than anything
I have seen, which definitely are the hobby-type.

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

Well, if you set up fixtures for the parts, it may be possible to make
the changeovers
very simple. For instance, you machine the face of a row of them
first. Then, you put them
in a fixture, drill one side of all of them, then flip the entire
fixture over to drill the
other side of all. Depending on the machine, it may be possible to do
quite a number of parts
in one setup.

> 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

Now, this doesn't apply to the specific part described by the OP. BUT,
it is true
that completely closed, hollow parts, parts with right-angle internal
passages and
all sorts of other unusual parts can be made by FFF machines that cannot
be made
in one piece by traditional subtractive machining. That is the arena
where FFF
and other rapid prototyping technologies shine. I'm closely following
some work
on using computer projectors to selectively cure layers of liquid
resin. I think
the complete info on how to do this will be available online in a few
months.
One guy got it working and then clammed up and took most of the info off
his blog. Some others are actively reverse engineering what he did
reveal and then
finishing all the remaining details. These machines will be able to
produce finer
resolution and thinner layers, and still keep up the production rate.
The goal is
something like .1 mm layers and 8-10 sec per layer, with totally arbitrary
complexity. Pixel resolution of 50 um has been pretty well demonstrated.

> Finally there is one point that argues against the RepRap for industrial
> use-- reliability.

The original Wright brother's airplanes were so hard to fly that they
killed one of
the inventors. I think the reprap-type machine is maturing a LOT faster
than the airplane,
but if you want one now, you have to live with some of the
shortcomings. The fact that
new designs are coming out every month or two is evidence of that progress.

Jon