More Adventures in cheap 3D printing

In this second installment, I wanted to delve deeper into my experiences working with my Monoprice Mini Delta 3D printer. After printing three maneki-neko cats which came bundled on the included 128MB micro SD card, it was time to print a design of my choosing. To set the printer loose on the wide world of 3D models and see what it could produce. But first…

Finding a 3D Model

Where do you find ready made 3D models for printing? Well you can always head over to Google if there’s something specific you’re hoping to find, but there are some great communities for sharing 3D models. I got started with Thingiverse but there is also Cults3D and many more. Both have countless free models available for download. You want to get your hands on an STL file, which stands for Stereolithography which you don’t really need to know but now you do. I started with the Benchy model, a popular print of a cartoony boat for putting the machine through its paces.

Screen Shot 2018-03-12 at 11.51.12 PM
Benchy, a popular 3D model, loaded in Cura

Slicing Software

How do you go about picking your model slicing software? Well, I wanted to start with something free, that worked on a mac, and was good. I chose the open source Ultimaker Cura as my first pick, Repetier is another good choice and plays nicer with this particular printer over USB if you prefer to have your printer hard wired.

Using the software is pretty straightforward, just load a model, select your printing options, prepare and export the .gcode file. This file can then be put on the MicroSD card, sent to the printer via it’s slow but functional Wi-Fi connection, or printed directly over USB.

The hard part is configuring the software for your particular printer. As of now, Cura or Repetier do not come with built in printer profiles for the Delta Mini, meaning you’ll have to set one up yourself. Not the most straightforward task for a beginner, but absolutely achievable with a little patience. There are amazing resources published by a great community of Mini Delta users both on the Mini Delta Owners Facebook Group and the Monoprice Mini Delta Wiki.

Screen Shot 2018-03-12 at 11.52.41 PM
Benchy, sliced into G-Code instructions and visualized in Cura

Printer Calibration

Ok so here’s the fun part, setting up Cura so that it knows the constraints of your particular printer. There are plenty of docs available detailing the correct settings for your printer, things such as the bed dimensions, whether or not it’s heated, number of extruders, etc. The part that may require some trial and error is when you enter the Start and Ending G-Codes. These are the commands that are prepended and appended to the main model printing commands.

You have to be careful about not blinding executing commands you find on the internet as I quickly found out. I grabbed some starting codes from a community thread that resulted in my printhead being commanded to dig itself deep into the aluminum printing bed all but destroying the low quality coating on it. So take it slow, understand what you’re commanding the printer to do and be ready to cancel if anything goes awry.

Here are my starting and ending codes that I landed on for the MonoPrice Mini Delta:

Starting codes, executed at the beginning of every print…

M92 X57.14 Y57.14 Z57.14 ; Fix issues with scaling
M500 ; Save to printer
M190 S60 ; Pre-heat bed and wait
M109 S210 ; Pre-heat extruder and wait
G21 ; metric values
G90 ; absolute positioning
M107 ; fan off
G28 ; home
G29 P5 C-2.0 Z0.36 ; Bed calibration
G1 Z15.0 F4800 ; move down 15mm
G92 E0 ; reset filament location
G1 F200 E5.0 ; extrude 5mm of filament
G92 E0 ; reset filament location
G1 F4800
M117 Printing...

At the Ending Codes that execute at the end of every print…

M104 S0 ; turn off hotend heater
M140 S0 ; turn off bed heater
G91 ; Use Relative Coordinates
G1 E-3 F700 ; Retract the filament a bit before lifting the nozzle to release some of the pressure
G1 Z2 F1000 ; Raise 2mm from current position
G1 E-2 F700 ; Retract filament even more
G90 ; Use absolute coordinates
G28 X ; Return to home position. Without an X Y or Z after G28 the print completion time will not be displayed on the Mini Delta's display.
M84 ; Disable motors
G4 S360 ; Pause for 360 seconds to keep fan running to cool hotend and allow the fan to be turned off
M107 ; Turn off fan.


Now that the slicing/printing software is configured, it’s time to send the .gcode file to the printer. The Mini Delta has no less than 3 options for doing this. Wi-Fi, a MicroSD card, and direct via USB. I tried all three but for the first print I would recommend going with the MicroSD card. USB requires a constant direct connection to the printer, while Wi-Fi requires a long slow upload… as in several minutes for a couple megabyte file.

While the MicroSD card is the most reliable method for printing, it isn’t necessarily the most convenient. The card slot is tiny and the card itself is easily dropped, or inserted backwards. I think Monoprice did a disservice by not going with a full-size SD card here, but this can be easily overcome with a Micro SD TO SD Card Extension Cable Adapter. Then you can use full size SD cards and put the slot in a more convenient location.

My printed Benchy, pretty nice I’d say

Which leads us to the next adventure… customizing the printer’s hardware, more about that coming soon.

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