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Review: Cheap CNC Mill

October 18, 2019


Hello and welcome back to Switch and Lever! In the beginning Earth was without form and
void, then a whole bunch of stuff happened, and then CNC was invented. CNC mills are freakin’ amazing, but unfortunately
tend to be very expensive. I mean, what does a Modern 57 axis, plutonium
powered, lightsaber CNC mill cost anyway? An arm and a leg? Is one kidney enough or do you need to sell
both? Even the mid level CNC mills, like Tormach,
are still comparatively expensive, but the question is can you go even cheaper? Yes, yes you can, if you skimp on quality
and are up for doing some assembly yourself. I have explored CNC milling in the past, and
I’ve wanted to get back to doing more in that field for some time. When Gearbest reached out recently, offering
to send me one of their low cost CNC mills for review, I jumped at the opportunity. Even though I said I won’t do reviews of cheap
Chinese knockoffs any more, I hope you will see past that and follow along when I put
one of these reasonably cheap CNC mills to the test. Full disclosure, I was paid nothing for this
video, and I gain nothing if you spend money on the Gearbest website or not. This video is entirely for the review, and
I will highlight both the good and the bad points, to ultimately answer the question,
“Would I buy it?” if I had to put down my own money. Though, you’re going to have to wait to the
end of the video for the answer to that question. The mill in question is the 2020B Mini Engraving
Machine PVC Mill Engraver, wow that’s a mouthful. It’s a plastic frame CNC mill, capable of
milling foam, wood, plastics, wax and even softer metals such as aluminium and brass. It comes delivered in a reasonably small,
albeit heavy, box. While the parts are packed somewhat neatly,
most of it is not wrapped or protected from shipping damage as it’s mostly just free floating
in the box. For some reason everything in the box feels
rather dirty, covered in this fine oily grit, not what I expected when opening the box. Some of the parts, as you can see, are pre-assembled,
like some parts have nuts already fitted, and the linear bearings have already been
press fit into some of the plastic pieces. Don’t forget all the sale advertisements,
who wouldn’t like 1.2 kilos of Gold Cake, whatever that is? It’s probably only usable in Shenzen, China,
though. Maybe next time they could ship a cake with
the mill, as a little added benefit to offset the dirtyness? The electronics comes at least packaged in
their own box, but even so the plastic bags are also dirty. I don’t understand what could’ve caused this. While I don’t expect clean room handling,
it’s still as if this was packaged by a car mechanic after he’s been working on replacing
oil pans all day long. Also, I’m not sure if I should be worried
that the power supply warranty seal came pre-broken? Hopefully we’ll be fine! The software to control the CNC mill comes
on this burnt DVD-R, which I suggest you immediately get rid of, once you copied over the contents
to a USB flash drive. Who even uses disc based media any more? On the disc there is also a bunch of PDF and
DOC files, which I suggest you print out, as they will be needed during the assembly
of the CNC mill. The assembly of the CNC mill is in itself
fairly uncomplicated, and even though the assembly instructions contain a lot of text
it’s obviously Google Translated Chinese of the worst kind, and most of it makes zero
sense. Luckily enough the pictures are for the most
part enough to understand how everything goes together, even though I managed to put a few
things on backwards, which needed to be taken apart and reassembled. One thing I did not expect though was breaking
one of the very first parts I assembled. The plastic which the frame of the mill is
made from is extremely stiff, but also extremely brittle. I overtightened a pair of bolts and snapped
a piece in two. Unfortunately there was no other way out of
that than to make a new piece, which I ended up fabricating out of aluminium. If you get this mill it’s something to be
aware of though, as if you break something there is really no going back, and the Engrish
instructions don’t really warn for this either. The leadscrews are just regular threaded rod,
and the piece I broke was a part of an anti-backlash mechanism. The leadscrews could probably do with a bit
of a straightening as well. While they’re reasonably straight anything
but perfect will have a negative impact on machine operation. Ideally I’d want to replace the leadscrews
with acme thread screws instead, for somewhat smoother operation, and faster movement. The table that comes with the machine is also
made from the same brittle plastic, and since I already easily broke a piece I did not quite
trust the table to do what I wanted. Instead I found some scrap aluminium extrusions
with slots which can accomodate screws so things can be tightened down more securely
to the table. At least when machining metal you really want
your material as rigid as humanly possible. While the table turned out a little heavier
than the original table, the machine seems to operate just fine with it. However, due to the increased height I’m losing
about thirty millimeters of machining height, leaving only about fourty millimeters of height. Since I don’t plan on using this machine for
very tall objects that’s just fine with me, but again something to be aware of if you’re
planning on getting this yourself. At least, the least dramatic thing to assemble
was the spindle, which slid in without any issues at all, though with some hesitation
how tight it should be fastened due to the earlier plastic breakage. With all the moving parts assembled, and the
easy stuff out of the way, let’s move onto the slightly more complicated electronics. First things first, if you are uncomfortable
playing around with AC power, do not build this mill. Connecting the electronics will require you
to strip and connect 110 or 220 volt cables to both the power supply and the transformer
for the spindle. Annoyingly, no such cables are supplied in
the box, so you have to provide your own. Since there is no obvious place to put the
electronics for the mill I ended up building a box for the mill to sit on, with space underneat
for the electronics, spending some time to plan out how to place the individual components
most logically, and then screwed down to a scrap board which slides into the box. The cables provided for the NEMA 17 stepper
motors are just too short to reach the electronics, any way you put them, so you will need to
extend those cables with new cables. I simply soldered on a piece of ribbon cable
and connected them to the screw sockets that fits into the stepper driver board. The same thing unfortunately goes for the
spindle motor, but as it carries more current make sure you use thicker cables. Instead of soldering these on I connected
the extension cables with screw terminals. With many of these connections, especially
with the power supply, transformer and the rectifier, adding spade connectors to the
cables is a good idea, rather than just the bare wires. Even though crimping them in should technically
be enough, I would still recommend adding a bit of solder to further secure them in
place. It never hurts to be doubly secure when playing
around with high voltage. It’s also a good idea to start up each component
one after another to make sure everything works properly, instead of putting everything
together and not knowing where the error is if something is not working. All of these issues, non existing cables,
too short, no obvious place to mount electronics, exposed wires, and so forth, almost makes
me believe that the electronics were an afterthought. I understand that small mistakes can be made,
but with so many of them there just doesn’t seem to be any reasoning behind it. Since the instructions were somewhat lacking
a multimeter can come in quite handy as well, to figure out which connectors to use to get
the right voltage out of the transformer to power the spindle. The instructions that came with the mill was
not correct compared to the actual measured voltages. I was truly hoping not to have to use any
hotglue in this build, but unfortunately there was one piece where it was simply the right
choice. All components, even the rectifier, could
be screwed into the board, but the relay that turns on and off the spindle, simply didn’t
have any mounts, so hotglue was the way out. This CNC mill uses ER11 collets to hold the
tools, which coincidentally is the second smallest ER-collet available on the market. While the mill ships with a collet which holds
a 1/8″ tool, it will readily accomodate a 3mm tool as well. Since the machine doesn’t have a Z sensor
you’re going to have to set the Z-zero manually, and design your CAM programs accordingly. Alright, to the point you’ve no doubt been
waiting for, can it mill!? The software that the mill ships with is fairly
self explanatory, if you’ve done any CNC and CAM work before. It’s probably not something you would find
easy if you have no experience before, or at least haven’t spent some time educating
yourself how CAM systems work, what G-code is and how to operate a CNC mill. Bear in mind that the mill will need to be
calibrated using the supplied software as well, so don’t expect it to work and be accurate
right out of the box. I generated all the G-code needed from Autodesk
Fusion 360, and therefore chose the iconic Fusion F to do my tests with. The first test, beyond basic movements, was
done in a somewhat soft modeling foam, and as you can see it’s not giving the intended
results. This is partially down to me being too optimistic
of taking too deep cuts, and partially the stepper motors skipping steps, and cutting
where it’s not supposed to. Due to that the mill crashed into the workpiece
and knocked it loose from the double sided sticky tape. The likely reasons behind this was operator
error, being a bit too gung ho with the depth of cut, as well as using a bit too high feedrate. So let’s correct those and try again! The second attempt already looked a lot better,
but eventually similar errors started showing up, where the motors skipped steps and started
milling where it shouldn’t. I noticed a lot of squeaking while milling
though, which was coming from the leadscrews and the nuts which were riding on them. Therefore all the leadscrews, and the linear
rails and bearings, were oiled up with sewing machine oil, which is a light oil which should
with ease creep in where it’s needed without gumming up the works. Lo and behold, even though I didn’t manage
to get any footage of it (forgot to hit record, doh!) the third attempt was far more successful
with smooth surfaces and seemingly accurate dimensions. Now, I know what you’re going to ask, what
about metal? Can it mill metal? Show it milling metal! Okay okay, hold on to your horses! Here we go, milling a small brass Fusion F,
at slow feedrate, with hardly any depth of cut, and…well…judge for yourself. It’s not doing too good of a job I’m afraid. I’m sure it could engrave metal just fine,
with a very small tool engagement, but using this ball ended endmill seems like it simply
was too much. Even though the plastic the frame is made
from is very stiff, it simply isn’t stiff enough, and the frame bends ever so slightly
which causes the tool to ride more on the surface of the brass rather than cutting into
it. After a few minutes of this torture, I simply
had to turn it off. However, if you look close enough, you can
kind of make out the F. In the end, the question still remains, would
I buy this CNC mill if I had to open up my own wallet? The answer is…possibly. It’s not so clear cut. It’s reasonably cheap, coming in at around
$400, so even with the downsides it may be at a price point which could justify it. Considering that you could use it as a platform
to learn CNC, especially coupled with Fusion 360, it could be seen as a rather attractive
little mill. It will require a fair amount of tinkering
to get working though, and being somewhat comfortable with electronics, but once you
get it running it’s pretty capable. I even ended up writing a small program which
will convert a photo into G-code to be used with a home made pen-holder for the mill. It may not be Leonardo da Vinci, but it’s
at least fun to build a ridiculously overcomplicated printer! In conclusion, get it if you want something
to tinker with, but don’t get it if you’re looking for a production machine. Though, because it is so simple it could easily
be used as a start for building your own CNC mill, replacing the plastic parts with aluminium
plate. I don’t know if it would be cheaper than simply
buying the parts separately, but it is at least something worth exploring. If you are interested at lookig closer at
this CNC mill, look at the links in the description. I hope you enjoyed this video, and while you’re
waiting for your own Mona Lisa portrait, why don’t you take a look at one of the other
videos from Switch & Lever. Also remember to head over to instagram, for
more non sequitur material! Until next time!

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