so i’ve always wanted a cnc mill, arguablymy interest in automated manufacturing in general was what got me into 3d printing inthe first place, since 3d printing is sorta the same thing from a technical standpoint,just way more accessible. but i still wanted something that could machinematerials and not just extrude them, even if it was only for the educational value andless so for actually opening up a job shop
g code for 3d printing, and running the machine 24/7 to produce parts. essentially, it should just augment the 3dprinters i already have and be able to occasionally machine a thing or two from aluminum, acrylicor wood. so i set out to do what i had planned fora long time with the mendelmax 3: i converted
it into a cnc mill. now, even though the mendelmax 3 is a fairlysturdy 3d printer, it’s not quite up to the task of machining materials out of thebox, at least when it comes to my basic understanding of the cutting forces and resonance issuesinvolved with milling. so my padawan and i started replacing a fewessential parts that were originally only made from relatively flimsy 1mm steel - which,surely, sounds like a lot, and actually is the same ballpark thickness that a large partof your car’s chassis is made from, but the geometry plays a huge role, too, in howeasily a part will bend. for a lot of applications, a chunky, 3d printedplastic part can actually be way stiffer than
anything that’s just a flat sheet of metal. so after removing the parts that made thisbeast a 3d printer, we grabbed some aluminum flat stock and replaced the z and y-axis motorholders and the x-axis carriage, since that’s where the new toolhead will go. the great thing with these openbuilds wheelsis that you really don’t have to work precisely at all when it comes to the positions of themounting points for the wheels, since you’ll adjust the pretension of the wheels anyways. we also stiffened up the print bed, since,again, that was simply sheet metal from the factory and didn’t come with any significantstiffness.
to make it less prone to twisting, we spacedout the openbuilds wheels a bit more, which does make the y-axis a bit shorter, but that’sok. what also helped was adding a two-story mdftop-plate. the thicker bottom part was screwed to theoriginal sub-bed and is going to stay there, forever, and the 10mm thick top plate is essentiallya waste plate that will get screwed, milled and drilled into and is just something thatis going to be replaced on a regular basis. electronics-wise, we didn’t change anything. the motors, drivers, control board etc arestill the original parts, but the firmware is now running slightly slower maximum accelerationsand speeds as well as slightly higher current
for the extra weight on the x and y axis aswell the cutting forces themselves. so the original idea was to use this proxxonrotary tool, because it came with a nice mounting flange, has a collet chuck and a wide rangeof adjustable rpms. and it worked great for a while, using thesecheapo 3mm two-flute bits, it milled happily through mdf and even aluminum with, like,super reduced cutting depths and feeds. engraving into acrylic also worked beautifully,but it didn’t last long. the bearing in these tools aren’t great,well, at the very least they’re not made for machining like this, and after replacingthe original proxxon tool with a newer that supposedly had an extra bearing for that exactpurpose and still having it fail in almost
no time, the mendelmax sat unused for quitea while. i was frustrated, after spending so much timeon modifying the machine and buying two of the proxxon tools, it was almost all the wayback to the start. but thanks to the internet, you now have accessto an almost infinite catalogue of parts, and eventually i found this 400w, 48v spindlemotor with an er11 collet. sure, it’s technically only a large-ishbrushed motor with a collet chuck on its shaft, but if it worked, i’d have a more powerfultool, a better chuck and still pay less than buying yet another dremel. so after getting that and a matching 48v powersupply, the machine was back in business really
quickly, and it turned out that the spindlemotor was actually quite solid. i can adjust the rpm by just tweaking theoutput voltage of the power supply, but i still want to add something like this dc motorcontroller to make it a bit more elegant. right now, the surface finish can be tweakedto be, i think, fairly amazing, it definitely needs a finishing pass on any surfaces you’vemachined and tricks like trochoidal milling won’t hurt, either. now, the converted mendelmax isn’t perfectby any means. it’s still a 3d printer frame after all,never intended to be used for these heavier applications.
for example the z-axis nut holder are stillway too weak for this and will be replaced by printed versions, also the electronicsand the y-axis rails for the openbuilds wheels could use some extra protections from thechips, with electronics, obviously, for not shorting stuff out with aluminum flakes, butthe openbuilds wheels are also extremely prone to just picking up chips that sit on the railand then end up rolling everything but smoothly. i also sorta want to replace the regular gt2-2m6mm belts, which are often just called gt2, with something maybe at least a bit widerto make it stiffer, maybe even a leadscrew or a ballscrew if the little mendelmax doesn’tpresent me with any more severe issues. though that would probably also warrant stiffeningup the frame significantly.
and obviously, both 3d printing and cnc machiningare very heavily dependant on what software you use to prepare your jobs, and while cncobviously has a ton of options when it comes to high-end cam packages, the equivalent ofa slicer, there’s not that much great software out there that is somewhat powerful and stilleasy to use. sure, autodesk fusion is an incredibly powerfultoo, but the “free as long as you’re a tiny startup†and the learning curve involvedkept me looking for simpler options. i personally can program something like ahaidenhain cnc controller directly and use a five-axis cam like tebis, but neither ofthem apply here, obviously. what i found to be a nice middleground wasthe shareware-like estlcam, which is a fairly
simple, 2d or 2.5d-centric cam that does justabout enough for me without having to relearn the entire tool whenever i want to machinesomething. it also does picture engraving and 3-axis3d milling, and while that’s good to have, it’s not a major selling point for me. what i want is just a simple, visual tool,estlcam is just about ok enough for this. it even creates marlin-compatible gcode outof the box! so yeah, that’s the first part of my adventurewith turning a 3d printer into a mill. while it’s not perfect and was a lot ofwork, it has most definitely turned out better than i expected.
i mean, it mills aluminum, that’s a successwhichever way you look at it! i’ll definitely be making a few more modsin future, but at this point, it’s already an awesome little conversion, i think. if you want to try something similar, i’velinked the spindle, power supply and milling bits i’m using in the description below. i hope you learned something in this video,if you liked it, give it a thumbs up, consider subscribing to the channel, and because youtubeis still being weird about it, remember to also click that bell next to the subscribebutton or you might end up missing some videos altogether.
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