[Arm-netbook] Existential 3D Printing Moments

[David Niklas]

On Tue, 30 May 2017 03:51:01 +0100
Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:

> ---
> crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68
> 
> 
> On Mon, May 29, 2017 at 3:44 PM,  <doark at mail.com> wrote:
> > On Fri, 19 May 2017 01:42:52 +0100
> > Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:  
> >>
> >> On Fri, May 19, 2017 at 12:35 AM, Neil Jansen <njansen1 at gmail.com>
> >> wrote:  
> > <snip>  
> >> 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.  
> > Could you be more specific? Why can't the arduino cope?  
> 
>  there are more experienced people who know the precise details.
> bottom line: an 8-bit 16 mhz processor is simply not fast enough to be
> able to send the data to the stepper motors in a way that they will
> remain properly synchronised.
> 
>  example: X axis gets changed direction/speed, and Y needs to be
> changed at the exact same time.  but because it takes e.g. 50uS (0.05
> ms) to get round the "compute" loop, the print head has moved on (say)
> 0.2mm in that time, it's going so fast, so X and Y are no longer
> properly synchronised.
> 
>  only by going to a 32-bit processor running at say 100mhz can you get
> the timing synchronisation back.

I understand now. I thought that the arduino was faster...



> >> david crocket (dc42) has specifically designed the duet series so
> >> that you can consider exceeding PWM rates of 150 khz, which is what
> >> you need if you want to sustain 500mm/sec for example (and do not
> >> want problems to occur at speeds well below that).  
> > Link?  
> 
>  google it please.

This looks like it:
http://forums.reprap.org/read.php?147,33082,471483


> >> also i forgot to mention that i've been using the E3Dv6 "volcano"
> >> which, when you use a 0.5 to 0.8mm nozzle can easily do flow rates of
> >> something mad like.... 200c^3/min - particularly when combined with
> >> the huge 40:1 gearing of the flex3drive which can *accurately*
> >> deliver the kinds of torque needed.  the volcano basically turns the
> >> heat chamber round, so that the heat area is 20mm long instead of
> >> the usual 10mm.  
> > Torque for what?
> > Again, maybe a link would help us stay on the same page.  
> 
>  google them, please.  i have a lot else to take care of.
<snip>

I thought you were waiting for the PCBs to get done (which was going to
take another week I think), and had nothing better to do than play with
that oh-so-giggly-and-fun little girl in the youtube vids?


Thanks,
David