Tony’s recent comment to my post about my alternate extruder controller board mount really deserves its own post.  Tony’s comment was:

That’s a pretty logical place for it. Other than needing some more wiring, I wonder why they didn’t design it that way? I wonder if it might introduce some EMI noise?

I’m about 95% sure I know why they designed the extruder mount on the extruder itself rather than the side of the ‘bot.  As designed the entire extruder is completely modular.  You could swap in a brand new extruder assembly in about 30 seconds (four bolts, one ethernet cable).  Heck, if you had a second Z stage and extruder you could probably swap in a new extruder in 15 seconds (one ethernet cable, swap Z stage).  They’ve said from the beginning they wanted their system to be totally modular and hackable – and that it is.

I haven’t noticed any symptoms of EMI noise on my prints.  In fact, I’m getting some really great prints with my current Skienforge settings.  I have a little blobbing and stringing – but I suspect that could be fixed with some attention to oozebane etc.

There are a few really great things about my setup:

1. More modularity. A totally new extruder (let’s say dedicated to PLA or a different color ABS) would not require a second extruder board.  This means with a printstruder and printed dinos (I’m still refining those designs) you could have a totally modular extruder for about $65 worth of hardware rather than $175 ($125 plastruder kit + $50 extruder controller board).
2. Visibility. I can easily see what’s going inside the extruder and whether the idler wheel is moving – without lines on the idler wheel.
3. Less work. It’s one less thing to take off the extruder when I need to do any kind of work on the extruder.  It’s not much time, but it is still a benefit.
4. Ergonomics. My ‘bot is sitting on a surface about 5 feet off the ground.  Having the motherboard rotated 90 degrees counter clockwise allows me to front-load the SD card.  This is easier for me because of the surface height, but I also had to do it because otherwise the side mounted extruder board would have blocked the SD card slot.  Frankly, I would rotate the motherboard even if the extruder isn’t side-mounted.
5. Centrality. This keeps all of the electronics all in one spot and makes inter-board cabling slightly easier. 1
6. Less movement. I doubt moving the extruder board around on the Z stage would ever cause a problem – but it certainly won’t when it is side-mounted.

However, this setup isn’t perfect:

1. Less modularity. One could argue that having the extruder board side-mounted decreases the modularity of the system.
   1. Counterpoint: That said, if you already have an entire second extruder complete with extruder board, there’s nothing stopping you from swapping it in as easily.
2. More wires. I now have six wires2 running to the extruder board.  Disconnecting/reconnecting six wires is more work than disconnecting/reconnecting one ethernet cable.
   1. Counterpoint: In just about any circumstance where you are disassembling your extruder you’re going to need to disconnect those six wires anyhow.
   2. Counterpoint: I picked up a six pin male/female connecter set the other day.  Once I clip the wires I can again have a plug-n-play extruder without needing to fiddle with screw based connectors or with the extruder board in the way.
3. More maintenance. Those same six wires need to be maintained/wrangled instead of one ethernet cable.
   1. Counterpoint: As you can see from the pictures I’m using the little blue twist-ties that came with the ethernet cables to essentially bundle the wires together.  I just wind the twist tie around the bundle and compress it to form a tight coil.  Works really well with several of these placed at intervals.  Clean and still flexible.
4. Shielding. There is less shielding on the six thing wires versus one large ethernet cable.
   1. Counterpoint: This has not been an issue for me.
5. EMI noise. I’ve never had problems which I would attribute to EMI noise from wiring, but I suppose it is possible.
6. More work. It is slightly more work to put the extra holes in the side of the bot to allow the motherboard to be mounted 90 degrees counter-clockwise and mount the extruder board on the side.
   1. Counterpoint: Perhaps 5 minutes of work total?
7. Z stage blockage. My extruder board is attached by only three bolts because one of them interfered with the Z stage.
   1. Counterpoint: This just isn’t that much of an issue, especially with the extruder board remaining stationary.

Overall, I find the benefits far outweigh any problems that side-mounting the extruder might cause.

1. But, as you can see from the prior post, not much neater. [↩]
2. Two each for the thermistor, nichrome, and extruder motor. [↩]