[Arm-netbook] Existential 3D Printing Moments

Luke Kenneth Casson Leighton lkcl at lkcl.net
Fri May 19 06:03:15 BST 2017

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

On Fri, May 19, 2017 at 5:08 AM, Neil Jansen <njansen1 at gmail.com> wrote:

>>  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.
> As you can see from the pics, we ran on the cheapest 12V power supplies that
> we could find.  Before that I tested 24V, it wasn't worth the cost.  Again,
> brickwall economics here.  We went cheap.  The 12V power supplies were
> purchased in bulk and were maybe $14 USD each?

 yeh meanwell's my favourite and there's no difference between 12 and
24v prices.

> The 3D printed mounts and
> the little PCB's were practically free and it would turn the supply on and
> off between jobs whereas our 24V bricks were on all the time.  The ONLY
> thing that we splurged on at the time was the E3D nozzles and that was more
> of a crapshoot.  I would have done better to cheap out on those as well, I
> could have printed more reliably with the cheaper J-Heads.

 i wonder what was going on as the only time i've had problems with an
E3Dv6 is when the fan on the heatsink wasn't running.  that was bad.
heat travelled up the tube and melted the filament *above* the hotend
entry point.  all bets were off at that point.

> Don't bother minimizing extrusion if you do end up redesigning (gah!).  It's
> cheap as dirt nowadays if you're buying the generic stuff.  If you want
> rigid, well there you go.

 i do - and i know how it's achieved.  i've had an excellent 3D visual
manipulation ability for like... 35 years.

> I have a junk box full of Melzi's, they were horrible, but it was all
> manufacturing defects from a crappy Chinese company.  The Chinese version
> took some artistic leeway that the original (British IIRC?) designer
> probably never intended.


> I've used both as I've said.  Mine never stalled out.  I used cheap-as-dirt
> A4998's.  Of course, I was running them < 100mm/sec and they were happy
> there.


>>  i just... i can't bring myself to spend backers' money on stuff that
>> i know is crud, neil.
> You're starting to sound like a German engineer now :)  They're not crud if
> you use them within the constraints that I outlined.  No need to turn your
> nose at them.  What I'm trying to get at is that you've got this huge point
> of diminishing returns, you can place yourself on either side of it.

 i will stop when the speed/$ improvement is parity.  anything that
gives a 1:1 ratio (or less, obviously) is not worth it and is "out"...
*unless* an improvement can in turn have a cascade effect of allowing
*another* improvement that *does* increase the speed/$ ratio.

>>  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.
> Dang those Due's are getting cheaper, back in my day those were a pretty
> penny.

 yehyeh - my favourite's the STM32F072 as it has a built-in crystal (a
not very good one) but then the PLL can phase-lock to the USB bus from
whatever it's connected to, compensating for crystal inaccuracies.
price? $1.70.  STM32F072-NUCLEO board? $10 on digikey.

 mad.  absolutely mad.

>>  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.
> <3 TMC2100's.  Our PnP was going to use TMC2130's. Great German drivers.
> However #1 they're hard as shit to import into China, which sucked for us at
> the time.  You can get damn near anything in China but this was one of those
> parts that just isn't really something that they use.  It was, to this day,
> the only part that I could not find on Taobao.  We may have smuggled our
> samples in from Hong Kong.


 well.. https://world.tmall.com/item/551108503978.htm?spm=a312a.7700714.0.0.3zdhiQ
 RMB 23.  about $4.

 so that looks prooobably like it's sorted...

>  #2 they're only really necessary if you want to
> squeeze performance out of your stepper motors.  For our farm we never did
> that, we didn't need to.

 $200 for a 50-100mm/sec printer with low-cost steppers...
 $300 for a 200-250mm/sec printer with only-slightly-higher-cost steppers...

 a 2x or greater speed improvement for only a 1.5x cost... that's an
opportunity i can't ignore

>>  MGN9C rails so that the problems associated with rods go away.
>> triple lead screws (i might consider quadruple) on the printbed, NO
> You're a madman.  You sure like to over-engineer things, don't you? :)

 no, i simply like to properly and comprehensively assess all six
degrees of freedom, which i am honestly constantly amazed that 3d
printer designers don't do, and i like to properly and i do _mean_
properly research what the best mechanical options are.  but... that's
taken me about... 2-3 years to do (!)

>>  well, here's the thing: i actually quite like trying out things that
>> other people aren't doing.  but also taking calculated risks.
> Sounds like you've already got your mind made up.

 i've got an _approach_ (an assessment criteria) where my mind's made
up, but nothing else.  the one thing that i might add is "risk".  as
in it would *really* piss me off to have a chain of improvements that,
at the end of the design process, there's something i missed which
made the whole exercise totally frickin useless.

 i had that happen once before.  not a huge fan of it happening again :)

>  I'm not here to tell you
> what to do.  I'm just sharing my experience and what worked for me.


>  Like
> many technical problems, it's all about the approach.  There are as many
> different approaches as there are engineers and business men.  You know what
> is ultimately best for your situation.  If it were me in your shoes though
> .. well, I'd never put myself in that position again, haha.  Nope, one and
> done, thank you very much.


> Any of my future products I make will be CNC
> machined, laser cut, or injection molded, and then outsourced.  As long as
> it's a durable product, it's not really any worse than the energy expended
> to setup a printer farm.

 yehh we're not quite at the medium-volume phase yet, i don't want
10,000 people dropping by the forum expecting "user support" on "how
to compile and patch linux kernel drivers"

> ...annd from your previous-previous email, I forgot to reply to this little
> bit:
>>   love it.  well let's get you on the list for a pre-production prototype
>> ok?
> Yea, hook a brother up.  The pre-production is the A20


> or is it the older
> one?  Are there any basic breakout boards or dev boards for it to plug into?

 yeah i have a breakout board PCB done (one component - the PCMCIA
socket) and am also planning to get early devs a microdesktop as well.

> If you need an address or anything like that just let me know.

 later.  i just need numbers initially.


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