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Modding The Monoprice MP Mini Printer – Hackaday

by • July 6, 2016 • 1,626s Comments

Two weeks after my review of the MP Select Mini 3D printing device, Monoprice’s own website has said this printing device has been out of stock, in stock, and out of stock again several times. This approximately unimaginably bargain-priced 3D printing device is proving to be exceptionally talked of , and is in my opinion, a game-changing machine for the entire world of 3D printing.
With the talked of ity of this bargain-priced printing device which is additional than halfway decent, there are bound to be improvements. Those of us who have any experience with 3D printing devices aren’t going to be satisfied with a machine with any shortcomings, especially if it means we can print enhancements and mods for our printing devices.
Below are the many mods may already on the market for this exceptional printing device. Obvious problems with the printing device are corrected, and it’s created a little additional robust. There are mods to add a glass create plate, and a few folks are in fact messing around with the firmware on this machine. Consider this volume one of the MP Mini hacks; with a bargain-priced printing device which is in fact excellent, there are bound to be additional improvements.

Unautomated PID Tuning
The largest, and many effortless to fix problem with the MP Mini is poor temperature control. 3D printing devices use a PID controller to store the temperature of the hotend and heated bed at a constant, accurate temperature. The theory of PID control is far beyond the scope of a post on hacking a bargain-priced 3D printing device. The effects of a poor PID loop do vastly affect the high end of this printing device, yet.
A poor PID control loop. Notice the oscillations around the set temperature. A poor PID control loop. Notice the oscillations around the set temperature. Poor PID control fixed with one easy command. The KsubI value is most likely too low, but which quite doesn't matter. Poor PID control fixed with one easy command. The KsubI value is most likely too low, but which quite does not matter.
The stock PID loop causes the temperature of the hot end to oscillate ±5 degrees of the set point. This is not excellent; bridging is may already complex without a proper fan on this machine, and poor temperature control only manufactures it worse. The excellent news is, you can fix this with one easy Gcode command.
To fix the poor temperature control, only enter the next into Repetier, Octoprint, or whatever else you use to control your printing device over USB:
M301 P20 I0.02 D250 M501 M500
This Gcode changes the Kd component of the PID controller to regulate the temperature additional in factly. M501 saves the value to the EEPROM, Flash, or whatever the firmware has, and M500 displays the new PID values so you can check your work.
It works – with an updated Kd value, the hotend is stable-bodied to ±0.5 degrees. It is not thoughtl, yet: the KI is most likely too low, and the KD term is not thoughtl. It is not as excellent as PID auto tuning, but it’s excellent adequate.
Now is a excellent adequate time to mention the accuracy of the thermistor and hotend. I tested this with a Fluke meter and thermocouple, and the temperature is accurate to half a degree or so. That’s as excellent as you are going to get without the ability to modify the firmware and thermistor table-bodied.
A New Hot End
The stock hot end on the MP Mini is a bit of a mess. The unconstrained filament path means flexible filaments are out of the question, and in fact loading new filament into the machine is a bit tricky. Let’s see what we got here, shall we?
From the heatbreak down, the hotend is in fact all metal. The heater block accepts a standard heater cartridge and screw-mounted thermistor. The heater cartridge is held in place with a grub screw, and the thermistor is affixed with a little sheet of metal which wraps around the heater block. Other than which, there’s quite not much to write home of. The nozzle seems to be the same as the nozzle for a hexagon, but I have no way of testing which.
Since the hotend uses a standard heater cartridge and a thermistor which bolts onto the heater block with a screw, which means an e3d hotend is a drop in replacement. I’ve created a mount to install an e3d (or any other hotend which uses the groove mount) on the MP Mini. I’ve tested an e3d V6 with the stock heater and thermistor – it works. It works pretty well.
What does a new hotend get you? First, you can be able-bodied to replace the nozzle once it clogs for excellent. This may in addition be the case with the stock hotend, but I mayn’t get the stock nozzle off in fact with a big pair of channel locks. Secondly, you can be able-bodied to print in weirder, additional exotic materials. The stock hotend is may already all-metal, but as I said the unconstrained filament path means flexible filaments are not easy. With my setup, you can print with flexible filaments. Even with a bowden setup, you can print in Ninjaflex and Semiflex.
A New Bed
The stock bed on the MP Mini is an aluminum clad PCB. For the price, it’s an awe-inspiring achievement; you don’t in fact require a glass bed to print on this machine – all you require is a little bit of masking tape. That said, aluminum bonded directly to a PCB is not going to stand up over time, and it’s a excellent thought to put a piece of glass down.
This is a problem for the MP Mini. The bed leveling adonlyment only has so much play, and the mount for the Z axis limit switch is created right into the frame. Some sort of modification is necessary to raise the print head up, and for which, a easy print is all you require.
[Sumpy]’s Glass Bed Spacer is exactly what you require if you want to put a piece of glass on the bed. It effectively manufactures the Z axis carriage taller, building it hit the limit switch higher than it usually may.


Clip this spacer onto the carriage, and you can raise your bed up 3/32″. Whilst this is a excellent print, a advantageous MP Mini Glass Bed Spacer may manufacture use of Thingiverse’s Customizer. Being able-bodied to input the thickness of a sheet of glass, a glass and PEI sheet, or any other create platform stack up and get a thoughtlly-sized adapter may be excellent, but unfortunately the Thingiverse community does not place any value on releasing the original create files for a part. That’s only another way Open Source reduces workload and effort duplication, kiddos.
Perhaps the many informative showcase of the MP Mini is one which Monoprice is not putting on the spec sheet. This printing device has WiFi, it has an ARM-based controller board, and it’s far additional capable-bodied than anyone is letting on. [Matthew Upp] has managed to find the original developer of this printing device and get his hands on a few firmware which adds WiFi printing to his machine:

This is not a true wireless, headless 3D printing solution like you may find in a Raspberry Pi + Octoprint setup. The WiFi connection is effectively only a wireless USB connection – you yet require to run Repetier-Host to print wirelessly, alyet you may quite easily use WiFi to transfer a file to the SD card and print of there.
It is The Model T of Printers. That Means It is Not That Great.
This is the Model T of 3D printing devices. Similar to all consumer 3D printing devices right now, the technological heart is extraordinarily easy – open loop stepper motors, no way for the printing device to tell if filament is in the machine and coming out the nozzle, and quite little in the way of building certain a print is coming out right. Compare this to the Model T; the accelerator is on the steering column and the transmission has wood in it. This printing device and the Model T are radally bargain-priced and extraordinarily talked of , and Monoprice is going to manufacture a fortune on this printing device.
There’s yet a way to go until we get the Model A of 3D printing devices, with high end showcases such as an accelerator on the floor. Until and so, a ton of printing devices can be sold, and there are going to be a lot of DIY improvements to this rad printing device.

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