Hi everyone, I’m Tom, and this is my review of the Replicape.
And i know some of you are getting tired of control board reviews, but with the Replicape,
i think i’ve covered all the main ones.
When you’re sorting them by processing grunt, there’s all the 8-bit Atmega-based boards
at rock bottom, they're just barely fast enough to run a basic printer and often struggle
with Delta configurations.
Typical examples of those are the RAMPS, the RAM-BO, the Sangunululonionio and everything
that sits on top of a physical Arduino Mega.
Then there’s the Smoothie-class of boards that use a faster, 32-bit Cortex M3 or M4
microcontroller, with, of course, the Smoothie # board itself, but also boards like the Azteeg
X5 mini that uses the same architecture and software.
And those boards are fast enough to run any printer at basically any speed.
Sure, they’re not like overkill fast, but they’re more than enough for anything.
And then there’s the all-in “more is better” class that builds on something like the Beaglebone
black, which is much closer to the amount of processing power your phone or tablet has
than to something like an Arduino.
The Beaglebone Black runs Linux on a one Gigahertz A8 core, so instead of having to use a separate
Raspberry Pi to get something like Octoprint running, that entire functionality plus the
controller itself is now integrated into the Beaglebone with the Replicape.
And the question that usually comes up at this point is gonna be “why can’t you
just use a Raspberry Pi instead?”
Any i’ll be covering that later in this video when i talk about the software side
of things, but for now, i want to start out with the Replicape # hardware.
And as some of you might know, when I’m not doing 3D printing…
things, i work as a hardware engineer for a large automotive supplier, and i have to
admit: The Replicape is actually really, really nicely built and engineered, and it’s pretty
obvious that cost wasn’t much of a concern when this was designed.
This is some industrial-level stuff right here.
So, as a board that plugs into a Beagle Bone Black, it doesn’t have any kind of processing
power itself, and only provides the high-power part of the entire controller / concept.
And that includes: Five beefy Texas %Instruments
DRV8825 drivers that provide enough current even for light-duty CNC mills.
And the output current can be precisely adjusted in software so that you don’t accidentally
melt your motor mounts, which is totally possible with these drivers if you aren’t careful.
It also carries three high-power MOSFETs and proper # drivers with a # freewheeling diode
for each of them.
Both of these extra features mean that the MOSFET will run more efficiently and reliably
than when you’re just leaving them out, and they’re typically not things that other
boards use, mostly because, well, you can do without them if you really have to.
The Replicape has two of the outputs labeled for hotends and the center one for a heated
bed, which all run off of the same input voltage, which, by the way, can be anywhere between
12 and 24V.
Each of these outputs can easily provide 15A of current or more - limited by the rating
of the connector - while the heated bed output should even keep up with somewhere around
30A, so these power outputs should be more than enough for anything that you might want
to use them with.
Most other boards already have trouble running the heated bed output at slightly over ten
amps, often because the connectors are going to melt down or because the MOSFET is not
properly controlled.
There are also three # smaller MOSFETs on the Replicape, intended for running smaller
stuff like hotend fans or LEDs, and they are run off of a buck-mode switching power supply
that efficiently converts whatever input voltage you supply the board with into a perfect 12V
rail, as long as you’re providing it with more than 12V.
So even if you want to drive your heated bed and stepper drivers from 24V because that’s
just more efficient overall, you don’t have to worry about getting 24V LEDs and fans as
well.
You can just use regular, cheap 12V ones.
As far as inputs go, it’s pretty much the standard fare.
One thermistor input for each heater output, six endstop inputs and one for a digital Dallas
temperature sensor.
Which isn’t really something that’s commonly used, but ahem, yeah.
It’s there.
Two more things about the Replicape hardware: One, it uses a mini automotive fuse for protecting
everything, which is awesome, and additionally to the one buck converter that makes 12V from
the input voltage, it has another one that’s supplying the Beaglebone Black.
Which means that you won’t have to worry about adding yet another 5V power supply,
like you have to with a lot of the Arduino-based platforms, even when you’re running off
of 24V.
So that was the hardware side of things and to sum everything up, again, while it isn’t
packed with 24 motor channels and a bazillion unnecessary features, it is an extremely well-made
dual extruder board or triple-extruder if you leave out the heated bed.
No, let’s move on to the software-ish side of things, and i’ll start out with that
Raspberry Pi question i mentioned earlier to get it out of the way.
And to understand that entire topic, you’ll have to know a bit about how processors work.
Simply speaking, there’s two ways you could use a processor - one is by simply running
the code on the processor with just one single task, a single thread and without any operating
system to manage the resources it has.
So, kinda like a Chinese factory worker that only does a single task or a very fixed sequence
of tasks all day long, over and over again.
Nothing else and nothing out of the ordinary.
This is the typical domain of real-time microcontrollers like the Atmega or the Cortex on the Smoothieboard.
They don’t run an operating system and only do that one specific task of controlling and
monitoring your 3D printer.
The other class is something like the ARM cores on your phone, the Beagle Bone or the
Raspberry Pi - or even the x86 CPU in your full-size computer or laptop.
They all run some sort of operating system to dynamically manage a # bunch of tasks that
are supposed to be running all at the same time instead of in a recurring, fixed sequence.
So more like a secretary who might stop working through emails once the boss - the operating
system - comes in and gives a new, high-priority task.
See how I used secretary in gender-neutral way there?
Yeah.
So the problem here is that, unless you use a very specialized real-time operating system,
there’s absolutely no guarantee that the set of tasks, for example, moving the stepper
motors one increment at a time, are done regularly.
For example when the network tasks come along and want the processor to send out the Octoprint
interface right now over WiFi, the task that’s in charge of creating physical pulses for
the stepper drivers, might end up not getting enough processing power to that regularly
and at the exact times it needs to.
And that would lead to pretty choppy movement.
So while these processors are overall fast enough to directly run a printer, you can’t
automatically assume that they’ll be as reliable as a dedicated microcontroller.
So the Beagle Bone Black # does run a full-blown Linux operating system, and it’s # not of
the realtime variety.
So how does it manage to keep the printer’s axis moving smoothly?
Well, unlike the Raspberry Pi, the Beagle Bone include a # pair of PRUs, which are essentially
two extra real-time microcontrollers.
It’s pretty much the same thing as having two of the processors from the Smoothieboard
integrated onto the Beagle Bone Black, and those two cores are what makes sure that the
the entire # Replicape keeps working in a synchronous fashion.
So obviously, the borders between the printer firmware and the operating system or printer
host are pretty blurred.
And to make things even less similar to what you’d expect with a Raspberry Pi, the Beagle
Bone Black doesn’t run from the Micro SD card that you can plug into the bottom, but
instead has additional flash memory on board and only uses the Micro SD card if you want
to change whatever’s installed # on the Beaglebone’s flash or if you want some extra
storage.
By default, the Beaglebone comes with Debian Linux installed, again, the same basic operating
system you’d use on a Raspberry Pi with Raspian.
Hence the name.
Rasp-ian.
Deb-ian.
And there are instructions available that guide you through each step of setting up
Redeem, which is what used to be the printer’s firmware and generally the software that interfaces
with the Replicape.
Then it tells you how to set up a host like Octoprint, maybe adding a slicer, and theoretically,
you’d be good to go.
So i grabbed a Micro HDMI to HDMI cable and a USB keyboard and mouse, connected the Beaglebone
to my monitor and started hacking away.
But.
This turned out to be a ridiculously complex and convoluted process that had me digging
around in a terminal window more than i usually like to, and in the end, things started falling
apart and were just generally not working.
I don’t know about you, but not only does it feel like the entire setup could be easily
automated with a script, but it’s just overall not something i really want to deal with when
trying to get a new printer running, especially since not only are there already enough things
you need to worry about, but there is also no way of just testing the printer unless
the entire software chain is properly set up on the Beaglebone.
So even though building on top of the preinstalled Debian distribution seemed like a good idea
at first, it clearly wasn’t the “best practice” option.
The alternative being a pre-built Thing image, which is based on Angstrom, an embedded Linux
distribution that is still somewhat similar to Debian, but this images comes with everything
ready to rock.
Flashing a new image to the Beaglebone Black is, again, quite similar to flashing a custom
ROM to your phone.
You basically download an image file, burn that to an SD card, which then boots up and
flashes the internal flash memory of the Beaglebone with the new image.
And lo and behold, everything was there.
Well, almost.
The Beaglebone now offers a web-based interface that gives you options to configure the firmware
settings and adapt it to your needs.
However, there really isn’t all that much that you can configure # feature-wise.
Of course, it supports both cartesian, so the typical box-type printers, as well as
Delta machines, and it does accelerated moves for both of them.
And that’s pretty much it.
There’s no automated bed tilt compensation, which i’ve grown to love, a lot, there’s
no automated PID tuning, no fancy controls for triggering LEDs or fans when certain events
happen, no support to turn on or off ATX supplies.
So really, feature-wise, it’s very-much what we had five years ago when the original
RepRap Sells Mendel was still cool.
Yeah, that was my first printer.
It was a mess.
There’s also generally very, very little documentation about the Redeem software daemon
and the Replicape in general.
Sure, it’s all open source, but that doesn’t mean that everything is super-obvious to do.
Marlin has a huge community behind it that has documented every nook and cranny of it,
Smoothie, of the Smoothieboard, has an enormously well-written Wiki behind it, that was mostly
created by the folks who make Smoothie, because they knew that, as an underdog, you kinda
need to do a lot yourself to get things going.
And Redeem and the Replicape kinda have neither of those.
It’s an even more niche product, and the documentation is even more sparse, so in the
end, either things work out perfectly and you’re happy with what you get out of the
box, or you’re pretty much on your own.
And because this is such a niche board, there isn’t really anything out there that you
could use instead of the Redeem package.
So once things are set up, well, they do work.
As intended.
However, for a 3D printer, you won’t, or at least, shouldn’t try to get every last
bit of speed out of the Replicape that it promises to give you, or you will very likely
end up with prints that look horrible when your entire printer starts resonating and
shaking around.
Basic functionality, it is, and i won’t go into the details of how insanely fast your
3D printer # could theoretically move with the Replicape, because it doesn’t matter.
So how much should the Replicape cost?
It’s very decent hardware, but it only gives you a very limited set of firmware features
# with that very specific hardware.
Yes, you can run Octoprint and even a slicer in the same package, but that’s all done
in the Beaglebone, which you still need to purchase separately for about 55 money units,
so dollars plus tax or Euros including tax.
The Replicape itself is 179 USD and ships from Norway, so it’s tax-free if you’re
anywhere in the European Economic Area, but if you’re not (hint: the US isn’t part
of the European Economic Area), then you’ll still have add everything that customs wants
as far as taxes and fees go.
You can also buy a BeagleBone Black and Replicape bundle for - you did the math - 234 USD.
And to be frank, that’s just way / way / too / much.
Yeah, the hardware is all nice and stuff, but what do you gain from all that?
Well, not that much, and you’re pretty feature-limited, too.
The only real gain over something like a Smoothieboard X5C plus a Raspberry Pi 2 are the stronger
motor drivers and MOSFETs, but then you end up with a much more flexible and standardized
system overall # and with 50 USD more in your pocket.
Where i do see the Replicape making sense is in CNC-mill-type machines, where the motors
are heavily geared down with for example a ball screw or regular lead screw, so they
need to rotate quite fast, but still need to output some amount of torque to actually
push the mill bit through the workpiece.
But in that application, you don’t need five axis and the heater outputs, but at least
the firmware won’t be a limiting factor.
It doesn't seem like that was really a use case that the Replicape was designed for,
though.
So for 3D printing, i don’t know, i’m just not feeling it.
Maybe though, one day when the software and documentation has improved by / a lot, but
not today.
Let me know in the comments if there’s something obvious that i missed why the Replicape plus
BeagleBone Black should be the ultimate 3D printing board and also, what are you looking
for in a controller solution?
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