New 3D Printer: Tevo Little Monster + Duet Conversion

For some time I’ve been considering the purchase of a delta 3d printer.  After much research, I settled on a Tevo Little Monster (TLM below).  It was a bittersweet purchase, since I had to sell my first printer (after 5+ years of ownership), my Makerbot Replicator (original), to both make capital, and make some room for it.

Tevo Little Monster and the C-Bot: New best friends.

Tevo Little Monster and the C-Bot: New best friends.

This blog post is mainly written as a resource to myself to track info, troubleshoot problems, and list upgrades.

TLM Links:

TLM Pros:

  • Price:  I picked it up for $750 and free shipping.
  • Print Volume:  The machine is a beast: 45″ tall (without the spool holder, which makes it even higher), with a diameter of around 23″. It has a print volume of roughly:
    • 500mm tall (I was able to squeeze out 510mm)
    • 350mm diameter.
  • One of the main reasons I bought this printer was is ‘beautiful in simplicity’ construction: Despite the size listed above, the frame is only made up of 5 parts:  The 3 OpenBuilds C-Beam style extruded arms that connect to the top/bottom plates.  Everything was cut to the same length, and it was square immediately after bolting it together with no adjustments.
  • Integrated BLTouch in the delta effector.  Docs here.
  • 120v AC bed with SSR: ‘Nuff said.
  • Elegant electronics boxes and power cabling.
  • A ‘hanging bowden’ style extruder:  Keeps the mass directly off the delta effector, and decreases the bowden tube length significantly.  Based on experience, I dislike bowden’s and the blobs they produce.

TLM Cons:

  • MKS SBase V1.3 : While it runs Smoothieware and comes with a small touchscreen, I’ve heard quite a few problems from people running this knockoff Smoothieboard.  It also uses integrated DRV8825 steppers, which historically aren’t the best choice for 3D printers (needing separate ‘TL Smoothers’ to help remove artifacting).
  • Knock-off hotend and extruder:  While these are based on the E3D-v6 hotend and Titan extruder, they’re complete knockoffs.  And they gave me more grief than anything else stock on the bot:
    • The knockoff Titan extruder started squeaking in the first month.
    • The PTF fitting in the knockoff heatbreak disintegrated, dropping metal chunks into my filament path.  I didn’t realize this until taking the whole thing apart and shinging a light in there, and seeing stuff reflect back.
    • I didn’t realize it at the time, but it appears that the heatbreak isn’t all metal (like a standard E3D) : It had some sort of plastic liner.  Later, that liner failed, and completely jammed it.
    • I’m not sure the ‘.4mm nozzle’ was really .4mm at all.  After swapping to a legit .4mm volcano nozzle, I noticed an improvemnt in print quality.
    • Basically, ditch that entire hotend for the real thing and save yourself a bunch of pain.
  • The bed isn’t removable. However, you have plenty of access to it, so I don’t feel removing prints from it should be an issue.  And since it’s mounted directly to the base of the machine, I don’t see any calibration issues if I have to really pull on the print to get it off.

Upgrades:

First thing, the knock-0ff Smoothieboard had to go.  My C-Bot has been running RepRap Firmware on a RADDS setup for some time, so for this bot, it was time to get the real deal:  A Duet Ethernet with touchscreen.

Installed:

Future:

  • Remaining parts of a real E3D-v6 Volcano Hotend (hotblock, heater cartridge, and thermistor)

Duet Pros

I can’t say enough good things about the Duet ecosystem.

  • 32 bit processor, no delta computation speed issues.
  • Live tuning of nearly every value:  Via the Duet Web Interface (or any connected gcode sender) you can live tune nearly ever firmware setting.
  • Updating firmware is as easy as uploading a single file.  No pre-compile (or Arduino IDE) necessary.
  • Integrated steppers + 1/256 silence : The integrated TMC2660 drivers, when driven at 1/16 microstepping uses their ‘microPlyer’ tech to interpolate to 1/256 : The loudest thing on the machine is the PSU’s fan.  Creepy quiet.  you can check out their pdf datasheet here for more techy-info, or this forum post.
  • RepRap Firmware : Having used Marlin, Repetier, and Sailfish firmwares in the past, RRF is hands down my favorite.  Super easy to edit, and create custom macros.
  • Duet Web Control (DWC) : Comes with its own web-server, similar to Octoprint, but specifically for the Duet hardware.
  • Actively developed, active community/forum.

Duet Links

RepRap Firmware Links

Assembly Notes

The assembly of the TLM took a little under three hours with the help of a friend, following the printer instructions that came with it.  Nothing was missing, nothing went wrong.  The only think that took a chunk of time was rewiring the electronics to plug into the Duet.

  • For setting up the TLM with the Duet, this is the assembly guide I used: https://www.thingiverse.com/thing:2355136 : This was a lifesaver!  Used all their firmware configurations by default.  There’s also a forum post here that discusses this conversion.
  • Had to rewire the endstops:  The order of the wires that plug into the Duet are a very different order from the wires that plugged into the MKS SBase, and are an even different order than how they plug into the endstops themselves.  Tracking this order is (obviously) really importing when rewiring them!
  • All the other connectors that plugged into the MKS SBase plugged directly into the Duet, except I had to cut off the side-clips so they could slide into the Dupont conectors correctly.  A combo of side-cutters and exacto-knive
  • BLTouch :
    • Had two sets of wires:  One needed entirely rewired to plug into the Duet expansion pin, while the other needed trimmed & rewired to a single plug, since the other wires weren’t needed.
    • Had to cut the trace on the board (after removing from the delta effector) to switch it from 12 to 24v.
  • I needed to switch the PSU from 220v to 110v, based on where I live.
  • As it turns out, the thermistor for the heated bed was bad: I kept getting 9000 deg reading from the firmware.  However, and somewhat coincidentally, they shipped with an extra thermistor;  I taped it to the bottom of the silicon heater, and it was up and running.
  • The top of each of the tower carriages has a small set-screw that is what trips the optical endstops.  I hadn’t done any adjustments to these:  They ‘looked’ ok.  A few weeks of printing later I checked them with my calipers, and they were up to 1.5mm off from each other, and felt loose in their threads:  I removed them all, applied blue threadlocker, and  screwed them in so a consistent amount was sticking out the top (6mm seemed like a good number).

Slicer Configuration

I use Simplify3D as my primary slicer :  It actually has a built-in preset for the TLM : Help -> Configuration Assistant -> Select Printer -> Tevo Little Monster.

I only had to modify a few things to start:

  • In RRF’s config.g, you need to set ‘M555 P2’ : This ‘sets compatibility’ to look like Marlin, which appears only to matter when trying to communicate with host software like Simplify3D, Octoprint, etc.  Up until then I had it set to P0 (RepRap Firmware), and I couldn’t get S3D to connect.  What’s interesting is that the baud rate seems to not matter:  I’ve had a number of different values and it connects fine.  RADDS, on the other hand, needs 115200.
  • Created a new ‘Tools -> Firmware Configuration’ setup for all the appropriate RepRap Firmware G & M codes.  It’s also important in the ‘Communication’ tab to set ‘Flow Control’ to ‘Hardware Flow Control’.
  • The above Duet assembly guide Thingiverse link comes with all the needed configuration .g files to get things working properly.  To support them, here’s my start/end scripts.  Obviously, you need to ‘Run Mesh Grid Compensation’ (G32) to store out the heightmap.csv that the G29 reads before print.  But you really only need to do this once in a great while.
; starting script
G32 ; Run the bed.g macro which homes and auto-calibrates the machine - also loads the last mesh grid
G92 E0 ; zero extruder
M98 PpurgeBeforePrint.g ; Purge the extruder along the front of the printer
; ending script
G1 E-10 F900 ; Retract 10mm at 15 mm/sec of filament to clean the nozzle.
M106 P1 S0 ; turn off filament cooler fan
M104 S0 ; turn off extruder
M140 S0 ; turn off bed
G28 ; Home all
M98 PplaySong.g ; play song when print ends
  • The purgeBeforePrint.g has the below code.  I found that printing small items, even with multiple skirts, didn’t always purge enough based on all the ‘pre-drool’ that came out of the head.  This lays down a fat line across the front.  A lot like my old Makerbot used to do.
G1 X-60 Y-150 Z.4 F3600
G1 X60 Y-150 Z.4 F1200 E30
  • In the G-Code tab, make sure to:
    • Set “Relative Extrusion Distances”.
    • Set the “Firmware Configuration Type” to the custom firmware I made above.
  • In the Temperatures tab, I always uncheck “Wait for  temperature controller to stabilize before beginning build”, since RRF will become non-responsive until that temp is hit.  I manage my own temps manually.
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    • Alex
    • January 18th, 2018 9:39am

    Hi,
    what is inside of the playSong.g file?

    Thanks for this great overview.

  1. Just a series of M300’s (play beep at a certain Hz/duration) and G4 (dwell) after each for the same amount of time. I found if I didn’t put a G4 after each M300, it would try and play all the beeps at once. I found the Hz rates for different keys online, and made a little song 😉

    https://duet3d.com/wiki/G-code#G4:_Dwell
    https://duet3d.com/wiki/G-code#M300:_Play_beep_sound

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