I've done some exploration of the MP Select Mini in the past 24 hrs. Nothing is perfected yet and this is just a "notes" entry as my thoughts and findings coalesce.

Electrical & Electronics end:

• The "12V 10A" power brick measures 12.3 V nominal at the control board. Measured with a UT171C.
• Standby current with the printer powered on and idle is ~140 mA. In-rush current is > 1 amp as the steppers kick when the board powers up. Measured with UT210E multiple times.
• Power lines are 16 AWG and with up to 10 A of current draw, will drop to no lower than ~12.25V.
• Upon using the "Home Axis" function to bring the printer to 0, 0, 0 while maintaining a hotend temp of 210 °C & bed temp of 60 °C, I measured no more than ~6.6 amps using the UT210E.
• The power transistors for the hotend and heated bed are AOD484, 30V N-Channel MOSFETS with 15 mOhm RDSon resistance.
  • Despite the lower current draw of ~2-2.25 amps of the hotend and bed, individually and not cumulative, these still warm up a bit.
  • I'm curious how the NXP PSMNR90-30BL will behave in place ot the AOD484.
• The display/LCD is a TM032PD204 and apparently a fairly common part.
• The USB-A to Micro-B cable provided is *unshielded*. Replace as soon as possible with a sheilded one. A house fan I used for temperature PID testing clued me into this detail.
• The thermistors are naturally noisy with a +/-0.5 °C spread at room temperature.
• Repetier-Host has no problem connecting and talking at 1,500,000 baud
  • The stock 256 MB card tops out at 40.87 KB/sec for writing files to the SD card via Repetier-Host, regardless of the connection baud rate.
  • Using an 8 GB SanDisk Ultra microSD card
• The updated M301 PID settings of P=10, I=0.02, D=304.5 work okay and do produce a stable temp, but when observing warmup, it is apparent that I is too low as the temperature undershoots.
  • Given that there is a temperature gradient, between the element and the nozzle and the thermistor, I'd advise an initial temperature overshoot to ensure everything got up to temp appropriately and quickly.
  • Adapted settings I've tested, but still take too long to stabilize, ~60 seconds, for my tastes are P=23, I=0.04, D=1500.
  • However, the aforementioned settings take ~120 seconds to stabilize.

Mechanical end:

• The 10, M3x0.5mm, stainless button head screws that hold the side panels on are olvaled for thread forming. This means that despite the tapped threads in the sheet steel, the screws then roll the rest of the thread when they are installed.
  • This is extremely beneficial for the "fine" pitch, though it is considered the standard pitch for this size shank.
• The Phillips screws are a #2 size and have a bolstered head to accommodate higher fastening torque.
  • These are a triagle shapped shank for rolled thread forming as well
  • A small split-lock washer accopanies each of these
• The set screws for the hotend are 1.5 mm hex
• The allen key provided is a 2 mm hex
• The additional support screws for the 5 mm shafts on the z-axis are a 2.5 mm hex fitting and are also M3.
• The hotend has the following details
  
  • The hex fitting on the nozzle is 7 mm with a M6x1.25 mm thread.
    • The ID of the nozzle is ~1.9 mm.
    • The nozzle is made of brass.
  • The guide tube is also threaded M6x1.25mm
    • The opened is flared to 4.75 mm and constricts down to ~2.25 mm
    • The bottom end *is* lined with PTFE for about the last centimeter and this further constructs to a 2.05-2.1 mm ID.
    • It is lightly magnetic and is stainless steel.
  • Together, the threaded sections amount to ~1 cm, which is also the thickness of the heater block.
  • The heatsink has a 1/4" ID bore for the guide tube.
  • There is a 6 mm OD x 4 mm ID x 8.5 mm tall PTFE bushing between the push-to-connect bowden tube coupling and the guide tube.
    • The coupling is just a smidge under 3 mm ID, ~2.95-2.98 mm,
• The bowden tube is 29 cm, end to end. You can trim this to 28 cm, 27.5 cm minimum is you really want to, though I wouldn't recommend it.
  • It is ~4 mm OD nominal and 2.1-2.25 mm ID.
• My hotend clogged once already and did so in the guide tube at the PTFE transition. Analysis of this failure mode suggested 2 things.
  • Prolonged temperatures of ~210 °C for PLA with the stock fan are too high as a thermal equilibrium will make the PLA too soft.
  • The heatsink for cooling the guide pipe is insufficient. Duh.
  • Instead of threading in the nozzle and guide tube equidistant into the heater block, the nozzle should be threaded deeper and the guide tube thereafter to reduce thermal transfer.