Please Help - In depth technical advice requested. Longish read

Mostly Printed CNC - MPCNC Advice
21

Im also running a lowrider and an MPCNC
MPCNC is 395x395mm (about 15 inches square) that I run aluminum and acrylic on.
Timber is done on a lowrider2 thats 1.3m (x) and 2.5m (y) (4.2 feet by 8.5 feet)
I use the 2 machines for different things, the lowrider has VAC, while the MPCNC is enclosed and has air blast.

As so many others have stated here, rigidity is king when cutting metals.

Answers on your comments.

  1. Dimensional accuracy, both my machines are running to under 0.1mm per 100mm, so its 0.1%
    be prepared to spend some time getting them dialed in to get it to that point though, i am running duel end stops on both, is very important to make sure its square and this can take some time.
    Also i had to use non integer values in the firmware for my steps per mm and let GRBL do the math, cause I was not running small enough microsteps on the lowrider to make it a whole number and not get any drift.

  2. For Aluminum rigidity is king, and smaller is better in that respect, timber not so important.

  3. My machines have been very reliable, i blew a stepper motor driver today but that was my own fault and was a 2min fix. Mechanically i have never had an issue, and most of the electrical problems have been cause I did something dumb (shorted something with a screwdriver, unplugged a stepper while it was live, etc etc)

Im also running a Makita, and they are great.

Stepper motors, Ryan sells nice ones, but so do a ton of other places, im running 2 amp ones from stepper motors online. (sorry Ryan but Australia is expensive to get stuff to)

Main board, its much easier to get support around here if you use the ramps boards Ryan sells, however I am using GT2560 controllers for both my machines, use what you know if you can, it makes trouble shooting much much easier.

Firmware, again use what you know (or are willing to learn) im running GRBL on the boards, but again personal preference, for software I am using ESTLCAM for the cam work, and bCNC on the laptop to drive the machine. I am a linux tech by trade and like open source where I can get it.
ESTLCAM is cheap and i have found it to be reliable and easy to use
GRBL, because its open source, and there is a TON of gcode streaming packages that work with it (although the same can be said of most firmware packages now)
bCNC, cause I was having stability issues with openbuilds control running at high feed rates and nodeJS running out of CPU cycles, bCNC is python and so does not break the cpu in the old laptop i run for machine control.

Printed parts, PLA, cheep, easy to print with, and nice and stiff which is what these machines need.

In terms of cost, my total spend on both my machines is a little over 2k
of which $500 was in routers, and another $1000 was in timber / screws for the lowrider2’s table cause its huge. (yes timber is expensive in Australia for some reason)

If you really want 30inch square on aluminum, and timber, and only want to build 1 machine, i would be taking a look at the lowrider2 rather then the MPCNC, as so many others have stated the MPCNC starts running into stiffness problems in aluminum if you make it much larger then I did (even mine is pushing it if you want to run fast in aluminum with no flex)

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22

also while i remember.

Z axis height shorter the better, but the MPCNC is MUCH more sensitive.
the MPCNC works from the top down, so the longer the Z axis the more flex at the bottom of the travel
the lowrider works from the bottom up, so it gets more flex at the TOP of its travel.
my MPCNC is 80mm on the Z, and i normally run it with a thick spoil board to reduce it to 40-50mm (about 1.5-2 inches) to get some extra stiffness

my lowrider has 250mm worth of Z travel, but because it gets stiffer near the bottom of the travel, it does not really matter, i normally only use the bottom 50-75mm (2-3 inches) of travel anyway but the extra is there if I need it

finally, end mills, use good ones, you will save SOOO much time its not funny, for aluminum this is really important, for perspective, $1 Chinese end mill vs $15 end mill from Adams bits (Australia again sorry Ryan)

i found the $1 ones that I have will clog in Al if driven at more then 0.5mm depth of cut at 1000mm / min
the $15 one runs fine and makes nice chips at 3mm depth of cut and 2000mm / min
(both using toroidal milling and all other settings / air blast flows etc being identical)
basically turns a 6 hour machine job into 1 hour, and i reckon i could run it faster / deeper but I am happy where it is for now.
if your using these machines to make money, machine time = money, and good bits are totally worth it.
they also last much longer so you have to change them less, and are much harder to break.

23

Welcome to the forum, and everyone has so far given great advice.

I was like you, a novice when I started my First MPCNC, and new to the 3D printing scene too. Now a veteran of 3 Builds, each to improve on the previous build as well as the improvements made by Ryan.

Only advice I can give is -

  • Just do it!

  • Use what you are comfortable with. If you have a SKR Mini and comfortable on how to program it, use it. It will do the job.

  • 100% infill. Always, forget saving material. Strength before economy

  • Makita, Elu, they all will work. I love my Makita, I have 3 of them now as I grab them when ever I see one at a Cash Converters. Imported a 3mm collet from Australia.

  • Don’t forget to enjoy the journey, its not just about the destination. You are going to learn so much from doing the build. and bonus over buying one, when things go wrong you can fix it yourself. If you get stuck, there are so many really clever knowledgeable people on this forum who will bend over backwards to help you.

  • Stay with the forum and pay it forward to the next Newbie where you can.

The satisfaction of using something that you build will far outway any time savings of buying something prebuild and I still do not believe you will get anything close to the same features of an MPCNC for the meagre investment.

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