[Arm-netbook] Existential 3D Printing Moments

[Luke Kenneth Casson Leighton]

---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68


On Fri, May 19, 2017 at 3:02 AM, Neil Jansen <njansen1 at gmail.com> wrote:
> On Thu, May 18, 2017 at 8:42 PM, Luke Kenneth Casson Leighton
> <lkcl at lkcl.net> wrote:
>
>>  btw apologise i should have said, the conversation with aleph objects
>> was private and not to be announced, they haven't given permission to
>> do that, as they are *considering* and we are *assessing* - privately
>> - the feasibility.
>
> My apologies, the phone was breaking up a bit during the first bit of all
> that.  Feel free to delete my reply or any others that reference it.  This
> is a pretty low-key mailing list so either way I don't think much will come
> of it.  Mostly a miscommunication on my part, for which I apologize.

 nono it was me, i just forgot to mention it.

>
>>  a couple of things i forgot to mention, one is to emphasise the
>> "bang-per-buck" part.  [...]
>> this kind of design assessment trick i've only ever heard being used
>> by people who make beowulf clusters, the word "cluster" being the key
>> word.
>
> Those are fun problems to solve.  You're right that there are a lot of
> variables, and many different approaches.  And if you've got a few important
> criteria like cost or time, it's easy enough to weed out the bad ones.

 yehyeh.

> Speaking of Beowulf clusters .. Not to go too far off topic, but has anyone
> given any thought to a Beowulf cluster of EOMA68's?

 lol yeeees :)

> Are there any hard realities that would prevent the EOMA68 from working in
> this fashion?  Any bandwidth issues or technical limitations?

 size, power budget.  in about 5-8 years it won't be an issue.
EOMA200 is better suited to clustering.  bigger PCB size and a much
higher power budget.

>>  * mendel90 - i've had mine running at 200mm/sec (yes, really,
>> 200mm/sec *print* speed and a 250mm/sec travel speed).
>
> I should have covered print speed in my last email.  You would be surprised
> at how slowly we printed during our production run.  We ran them real nice
> and slow, less than 100 mm/sec.  Going back to bang-for-buck, this was how
> we approached the problem.  Lots of slow-ish machines, rather than a few
> very expensive fast machines.  It worked out for us.
>
> Here are a few pics of our farm in the early stages.  Don't laugh; they
> worked well.  I'll see if I can dig up some more pictures later.
>
> * http://i.imgur.com/56F2nYP.png
> * http://i.imgur.com/8cXbl72.png

 nice!  hey that 2nd one looks pretty much the same as the anycubic i have here.

>>  cost is around $500 so 2500 / 500 = 5.  5 x 200mm/sec = 1000 mm/sec
>
> By that logic, our machines were comparable to that.  Slower, cheaper, but
> the math works out.

 yehyeh.  if you have 1/2 the speed but 1/2 the cost.... it's the same
end-result.

>> what i am looking at therefore is parts which will get me sustainable
>> speeds that the MendelFlex can reach, but without the pricetag of an
>> Ultimaker-2, MendelFlex or Lulzbot Taz 6.
>
> I still propose that you could do cheaper / slower machines and still hit
> your speed requirement overall.  But if I go along with your thinking, why
> can't you just build a bunch of MendelMax / MendelFlex /
> whatever-you-call-them over there in Asia?

 that's what i'd like to consider.  there are some specific areas
where e.g. just an extra $5 on 24v electronics will allow you to then
put an extra $5 onto 900steps/rev motors which then allows you to
increase the speed by.... say... 20%, for a 2.5% increase in budget.

 and now you can use a 24v heater you can spend another extra $5 on an
E3Dv6 volcano clone, now you can get *another* 20% increase in speed
for only a 2.5% increase in budget.

 then you get a mutley3d flex3drive for $100 and because the hotend
can now cope you can get a whopping *100%* increase in speed for a 50%
increase in budget.

 this is the kind of logic that i will be applying.

>  20mm x 20mm Extrusion like that
> is RIDICULOUSLY cheap.  If you DIY over there period, you'll hopefully find
> that the extrusion and hardware will be pleasantly cheap.

 yehyeh.  i was considering optimising the design for minimising
extrusion, and rigidising the frame with panels (like the ultimaker),
but if it's $1.50 for a 350mm length why bother with minimising
extrusion, just get some strips of lexan 50mm wide and strap them in a
cross across the diagonals.  i've got a little video showing how
effective that is: https://www.youtube.com/watch?v=Qb-WjZY5qyI

>
>> now, neil, this is the kind of speed at which an arduino 2560 *cannot
>> cope*, and, also, where the design flaws inherent in RAMPS - using
>> prototyping Evaluation Boards (polulu-style drivers) - start to show
>> up.
>
> Yea but Arduino 2560's and RAMPS boards are MUCH cheaper than anything with
> an ARM Cortex.

 it may surprise you to know that i'm a big fan of the melzi 2.0....
except they're 1.3A driver ICs and that's not going to be enough.  i'm
already getting regular extruder-skipping on the anycubic, and that's
even at 50mm/sec.

i can't bring myself to use RAMPS.  i just... can't.  phil hands knows
the story very well, he had one of the original sanguilinos (huxleys)
just like you: the polulus are *prototyping* boards *specifically*
described by the manufacturer as for *evaluation purposes only*.  his
printer used to stall out for a couple of seconds on one axis as the
ICs overheated.  he read the datasheet and found that there's a
*ceramic insulator* on the *top* of the IC (meaning that a heatsink is
pretty useless), and that the IC is designed for heat to be wicked
away *through the PCB* via the exposed pad.  and  a frickin 18x18mm
PCB just ain't gonna cut it.

 i just... i can't bring myself to spend backers' money on stuff that
i know is crud, neil.

 sso i've been spending some time tracking down board designs and so
on.  Arduino Due: https://world.taobao.com/item/539393961702.htm RMB
75 so that's around $12.

 and TRAMS uses TMC2100s, where their Reference Design has full PCB
and schematics available: if i'm doing 10+ i can just send that to
mike and he can make them.  TRAMS is *real* basic.  4 steppers, 2
beefy power MOSFETs (extruder, printbed), 2 smaller ones for fans.

 does it need ethernet? no... because you can get an ethernet
"shield".  does it need WIFI?  no... because you can get a WIFI
"shield".  etc. etc. etc. etc.


> That was kinda what I was getting at.  There's a brick wall
> that you hit when you want to go that fast.  You'll need a better motion
> control system, more rigidity, better everything really.

 ... yeh.  i know.  so that's why i wrote the mechanical rigidity
page, so that i remind myself that i know what i'm doing, but also
remember and record all of the things that i've seen on the reprap
forum, all the tiny little bits of good advice, all documented here:
http://reprap.org/wiki/Mechanical_Rigidity

>  All of that adds
> up, especially when you're building so many of them.

 not necessarily (or, if it does it *has* to be assessed via the same
logic above: what percentage speed improvement will be attained
divided by what price increase.  if number equals greater than e.g.
1.5 then go for it).  i've specifically been thinking on and off for a
*long* time about how to ensure - *at a low cost* - that a frame and
the moving parts remain rigid, so that higher speeds don't shake
things to bits.

 so far it's 2020 extrusion cube with lexan "X"s on three sides and
the base, and open "picture frame" (ultimaker2 style) lexan  borders.
this makes the extrusion absolutely rock-solid.

 MGN9C rails so that the problems associated with rods go away.
triple lead screws (i might consider quadruple) on the printbed, NO
CANTILEVERING.

 i am still debating whether to duplicate the ultimaker-2's XY
arrangement or whether to go with a quadruple-pulley variant of the
1990s rikidenki plotter.


>  What's great about the
> RAMPS boards, the Arduino clones, and all that, is that they're incredibly
> cheap.  You could probably buy a dozen for the price of a single "bleeding
> edge" type ARM Cortex motion controller.

 ... yeh which i wouldn't consider getting - not when the cost of e.g.
duet WIFI is the same as an entire taobao cheap-and-cheerful 3D
printer, much as i *really* love what dc42 is doing.   so that's why
i've tracked down TRAMS (which has 2A silent drivers and a single PCB)
and a taobao due clone.

 i.e. *for the money* TRAMS plus a taobao-due-clone gives that
"bang-per-buck increase" that a "bleeding edge" ARM Cortex board
simply cannot give.  yes i could get a duet WIFI with the 2.5A TMC2660
drivers... but they're *$200* and that extra 20% increase in current
for a 150% increase in price over a TRAMS+taobao-due-clone simply
cannot be justified.



>  What I'm arguing is that you
> shouldn't discount slow if it's cheap.  You'll have less jams, less filament
> issues in general, because you're not pushing the hotend and extruder as
> hard.  If something breaks, well shit, replace it and don't sweat it.

 :)

 well, here's the thing: i actually quite like trying out things that
other people aren't doing.  but also taking calculated risks.

> As a car analogy, think of a Formula 1 car running in a Le Mans type race.
> It would probably do OK for the first few laps, but the risk of it breaking
> down over 24 hours is much higher.  Slow and steady and reliable wins here.
> Le Mans cars aren't pushed into the red like an F1 car is.  They're cheaper
> too.  A team can race a fleet of Le Mans cars for the price of F1 cars.  If
> one makes to the end, they still win.  If that one F1 car breaks down or
> crashes, they win nothing.  Not a perfect analogy, but you get the idea
> hopefully.

 yehyeh i do.  the latest ford GT40 supercar uses a 6 cylinder
mass-produced eco-boost engine.  its increased fuel economy but also
its reliability from huge amounts of testing meant that they pissed
all over ferrari at le mans.


> One of our mentors was an early Makerbot employee that left.  Man, the
> stories from that place.  I'm glad that it's going tits up.

 i didn't know it was... but it doesn't surprise me.  you isolate
yourself from the innovation, it's gonna have consequences

>>  i loove their colours :)
>
> Me too, however I do wish that they (or someone else) would make a decent
> Olive Drab Green.

 i was _so_ disappointed when they stopped the "village green" filament :)

>
>>  i'm really really happy to hear of (and then test) known filaments
>> that are of the same quality... particularly if they have the same
>> kinds of eye-popping colours.
>
> Our production runs used PushPlastic exclusively:

 ahh that was the name i couldn't remember.  thank you.  that's one to
evaluate, then.

l.