If you're like me and have exquisite taste in commoditized Chinese machinery, you might already be familiar with my other thread called Fun with a $200 CNC machine.
In it, I detailed the selection, setup, and use of a Sainsmart Genmitsu 3018 PROver to make some aluminum parts. After a few months of playing with it in the evenings, I'd managed to learn the basics and was confident enough to jump into the deep end of the pool and make some upgrades with the goal of competently making aluminum parts for my race car and for a side project I've been working on called Caliper Garage.
What needed upgrading? Basically everything. Out of the box, the 3018 could make small aluminum parts very slowly. That's fine to learn, but I really wanted a larger work envelope, a more powerful spindle, and a stiffer structure. The reasons why are fairly obvious in the later pages of the $200 CNC thread, but basically the 3018 isn't stiff enough or powerful enough to cut aluminum aggressively enough to keep the tool cool and prevent clogging.
I looked into upgrading the 3018, as there's a huge aftermarket: axis extension kits, metal Z axis parts to replace the factory plastic, spindle upgrades, etc. can all be found with varying levels of English translation in their eBay auction descriptions. But after some research, I realized that I'd be spending $300-$500 on upgrades and still not really have what I wanted. Plus, shopping for machinery is fun!
This thread will be all about my second complicated dangerous machine purchased from China. Will I get lucky twice in a row? Will it end in complete failure and a pile of useless off-brand parts? Follow along to find out!
So, onto the machine I picked. After lots of shopping around and poking/prodding the used market, I decided new and off brand was the best bang for the buck for a hobbyist like me. I'm space limited and was looking for something that would fit in about a three-foot square, which meant spending something like $5000 with a company like Avid CNC. And on the used market, everything was way too big, clearly meant for 4x8' sheets in a real factory.
Fortunately like every drug, this one has a generic equivalent. 
There are about a billion Chinese CNC routers available at various sizes, and one popular variant is the 6040, called that due to its 600x400mm work area. Type "6040 CNC" into eBay or Aliexpress, and you'll find 1,000 listings with varying adjectives photoshopped over the stock image. After reading some reviews and horror stories and watching a few YouTube videos, I decided to give it a try and buy one.
I found prices for the 3-axis versions as low as $900, but decided to splurge on this $1082 option that included a fourth axis, a USB port, and promised to ship from the USA. I wanted local shipping to prevent any weird Covid delays, and the fourth axis mostly for the spare parts. I'm not sure I'll ever do any 4-axis machining, but figured the four-axis controller and it's extra stepper drive, plugs, cables, and motor would be good spares. Plus I can turn the chuck into a weld positioner or something.
And, luckily, it showed up! Before I go any further, though, I should mention that if you do this, you'll be on your own. Here's the seller I sent $1082 of my own hard-earned dollars to:
I've got nothing against, uh, whoever that is, and I ended up having a great experience overall, but between the distance, the language barrier, and the promises on the listing that zero support or software would be provided, it was made clear to me from the start that whatever showed up would be my problem, and I'd be on my own to make it work or not work. And unlike the 3018 or a Miata or my Ender 3, there don't seem to be enough 6040s in hobbyist hands to build a critical mass of online support.
Most of the forum posts I did find were complaining that the seller didn't honor the fake 2-year warranty or saying "I just threw the included controller away and re-powered it with $1000 of new stuff."
Anyway, less than a week after I ordered it, three extremely dense boxes showed up (one not pictured):
Let's get this out on a tray... NICE!
I was worried about shipping damage, and those fears came true... barely. The only issues I could find were one knick in the table and one broken link in a cable chain. I ignored the former and glued the latter: Fixed!
Overall, I'm impressed. It was packed exceedingly well, it's way heavier than I expected (most of this seems to be cast aluminum) and it seems to match the photos in the listing.
It also came with some mostly helpful odds and ends, including a hold down kit and some end mills. It also came with two spare fuses, one of which was already smashed for me.
Assembly took about 20 minutes, and mostly meant bolting the gantry to the base, securing the cable chains, and checking all the hardware.
This spindle is liquid cooled, so I threw the included pond pump into a bucket of water.
All set for its first test!
Look at that Z travel! This thing will jump a coke can!
So... let's talk controllers. By controller, I mean the beige box on the far right of the setup photo with the big red "STOP" button on it. In a perfect world, the basic CNC workflow goes something like this:
- Design your part with CAD (computer aided design) software.
- Turn that part into a toolpath for your machine with CAM (computer aided manufacturing) software. Nowadays CAM is often a module attached to your CAD; I use Fusion 360 for both.
- Upload that toolpath to the CNC controller.
- (Oversimplification) The CNC controller uses amplifiers/drivers to actually move the machine. On my machine, this means stepper drivers for the axes, and a variable frequency drive for the 120VAC spindle.
Sounds great, right? I thought so too, until I set up the machine, plugged it into the computer...and nothing. Zero. It was dead on arrival.
First step of troubleshooting? See if I can operate the spindle manually with the VFD. This is the only thing that can be operated without a computer, so it's the obvious place to start. I flipped the switch to "manual," and couldn't even turn the spindle on. Damn.
To the Google! But I'll tell the rest of that story in the morning; it's time for bed.
Is it the fuse? I hope it's just the fuse.
Well, now we know. Tom fixed the fuse, plugged it in and there has been a terrible, gruesome accident. It's the only explanation.
Sorry about that; got distracted by another new project for that showed up this morning and couldn't really sit outside.
Anyway, the non-functional spindle on the VFD. After a healthy dose of googling the numbers printed on the front, I discovered the variable frequency drive (VFD) needed to be programmed. Naturally there were zero instructions or mention of this when I bought the machine.
Fortunately, some random internet person managed to figure out how to program the VFD, and put everything into a giant unofficial manual that also covers a few other aspects of the average 3040. That's slightly different than my machine, but looks mostly the same:
https://imaginieriecom.files.wordpress.com/2019/04/01.-cnc3040-with-prt-e750-drive-complete-english-documentation.pdf
It's not exactly a Stephen King novel, but this manual proved to be a treasure trove of info. In it, I learned what each of the 180!?!?!?! settings on the VFD did, and how to program them with the tiny keypad to make my spindle work. Here are a few snippets to give you the gist of things:
After programming the VFD, I flipped the switch... and the spindle fired right up! I checked the indicated speed against a handheld tachometer to confirm I'd set everything correctly. Success!
With the VFD programmed and the spindle working, I plugged the 6040 back into the computer to see if I could make the axes move. Had I changed anything to make them suddenly work? No, but I couldn't resist trying anyway. Something something success breeds success something something, right?
Wrong. I now had a working spindle, but still couldn't make the computer talk to the machine. I'll need screenshots to tell that part of the story, though, so we'll end on another cliffhanger for now (sorry!)
I know I know. I've been busy! Working on it!
Yeah, gonna need some more. I wouldn't mind adding something like this to the fleet of 2d/2.5d cnc machines that seem to be multiplying in my shop.
If there is any documentation that isn't translated, Google translate is surprisingly handy.
Okay I guess it has been a month. Let me put the next chapter together this weekend. But I also need to pull the transmission out of the 350Z (again).
