Monday, December 26, 2016

Build report and first impressions: Geeetech G2s 3D printer

I just finished this build this week, it's buttoned up and printing some stuff now.




I'll give my opinion right up front: I would not recommend this printer. For the same money I'd go with the Geeetech Prusa i3 dual extruder clone, if you want a kit, or the Monoprice Maker Select if you want one ready to rock (not dual nozzle). There's nothing particularly wrong with it, but as far as I can tell, there's absolutely no reason to prefer a Delta. It has several disadvantages and no significant advantages other than novelty.

This is also absolutely not a good first printer buy.  Even if you are brave enough to get a kit as your first printer, there are better kits (the aforementioned i3 would be excellent). Deltas add a LOT of complexity for no gain, IMO.

Pros:
  • It takes a smaller footprint, but it also is much taller than a comparable conventional printer.
  • It's a tiny bit faster as far as Z axis movements, but that's insignificant in the time it takes to complete a print.
  • It's interesting to watch

Cons:
  • It's several times more difficult to calibrate than a conventional printer. I can calibrate an i3 in about 5 minutes.  I spent 6 hours on the Delta, and it's still not really right. Admittedly a lot of that is learning curve, but I think now that I know what I'm doing, there's no way I'd get the calibration down in less than an hour.  With a conventional printer, calibration is entirely mechanical unless you got something badly wrong in your calculations. With the delta printers, it seems like a matter of course to fiddle around with the firmware and recompile multiple times until the Z height, radius and plate bumps are all accounted for.  I've compiled at least 20 times so far and I don't think I'm done yet.
  • The build plate is not entirely usable, and the round shape pretty much precludes actually using the entire space.  If you try to print right to the edge, the platform hits the rod and you grind the motors.  It's just not really very practical.
  • It seems extremely prone to getting thrown off by getting the head caught on the print. I think the leverage on the arms accounts for this. 
  • There is a LOT more slop in this printer than in the cartesians that I've owned.  When the head is hovering with the steppers locked, I can wiggle the platform quite a bit by hand.
  • I don't particularly like Bowden extruders. They're a pain in the butt (almost impossible at times) to feed stock into, they don't work with flexible filament such as TPU, they are less accurate and require more retraction to keep from dribbling. The only advantage is less moving mass, so you can print faster and not get wobble in the print. Personally I'd rather just print slower.
  • When your print is done and the power to the motors shuts off, the printhead comes down on top of your print. Not fast, and it MIGHT hang instead of coming down, but it can come down. Not a problem with cartesian printers.

In short, it's a pretty cool printer and it's fun to watch, but unless that's your primary concern, get a conventional printer.  I have not built a Geeetech i3 but I probably will soon, so that I can get an actually practical printer in my stable that's not a Makerbot clone (I really, really hate the Makerbot gcode and toolchain).

I'll keep this one around, I guess just as a novelty at conventions and such.

I can't really complain about the accuracy really; this is a 25mm calibration cube print:




Notes on the build:
  • A lot of the time is spent peeling the paper off the acrylic.
  • The little thinner pieces of acrylic that hold the front of the LCD panel up are extremely fragile. I broke them both immediately during the build, and found the STLs for the part (part number RK-09) on Thingiverse.  The part was way too thick, I scaled it to 40% in the Z axis and printed two of them.
  • There were several problems with the provided hardware. There were plenty of leftover screws, but still not all the screws needed were included. I didn't just get a bad kit, I've found mention of this on the Geeetech forums.  They need to have someone sit down at a clean desk and try to assemble a printer with what's in the box.  They won't be able to.
  • The Bowden tube and fittings are not good. It's almost impossible to feed filament through them. There's no internal taper so the filament just hits the components. I have had to remove the tubing from the air fittings every time I have fed filament in, put the filament in first, then put the tubing back.
  • The extruders are very weak. The hobbed wheel they're using isn't very sharp, and the spring isn't strong enough. I stretched my spring, I've seen others online with the same problem insert an M4 screw and nut in the bottom of the spring holder to tighten things up.
  • The hotends are cheap junk. They work, but they're impossible to stop from leaking; I've tightened the primary three times and it's still oozing from the top. I've ordered a couple of E3D clones and when they arrive in a few weeks I'll be fitting them.  There are several options on Thingiverse for mounting them on this printer.
  • IMO Loctite on all screws securing the arms is MANDATORY.  Halfway through the first real print, one of them just fell off having worked its screw loose. They were all very tight to start with.  Glad I was sitting right there when this happened:

  • I replaced the Marlin firmware that is stock with Repetier firmware. I've long been a fan of Marlin, but Repetier seems much more advanced.  Certainly their configuration website is a fantastic advantage, as is the ability to save off and share configurations via JSON. I started with this configuration posted on Thingiverse.
  • I'm going to cut a piece of glass to print on. I have a slab slapped on there now and it works very well. I'll get out to the garage and cut a 210mm hexagon when I get a few minutes to do it (hate getting to the garage in winter).
  • The power supply has no real cover, it has mains wires just hanging about ready to shock you.  Printing a cover should be your FIRST order of business.  I printed this one from Thingiverse and it works quite well.
  • I had to boost my fume hood up by putting a 2x4 skirt underneath to get this thing inside.
  • The Bowden tubes make it necessary to print a bit hotter than I normally do, and that makes it smellier and I have to have some powered venting going on during print to keep the atmosphere in the house family-friendly.

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