eBay CNC machines… yay or nay? - Page 1
Forum section: electronics / general

author: David Aurora
author_rank: Frequent Contributor
timestamp: June 15, 2021, 12:51:26 am
content: I’ve been umming and ahhing about buying one of those cheap-ish small CNC machines on eBay for years (not 100% sure on size yet, most likely the 3040 though). It would literally have one job and one job only- engraving labels into aluminium panels (mostly small Hammond boxes). If it can also make the control holes that’s a bonus, but not required.Anyone got any input on whether or not they’re actually worth buying for something like this? I can’t stress enough that I’m really not after a new hobby. I don’t want to spend 6 months playing with drivers and aligning the damn thing, I’m after a tool I can actually use to do small batches of enclosures. In the past I did a lot of chemical etching for these and it worked fine, but was way too laborious to be financially worthwhile.

author: PlainName
author_rank: Super Contributor
timestamp: June 15, 2021, 05:57:09 pm
content: I acquired a Sable 2015 some time back to engrave PCBs. Similar style to the 3040. It does the job OK, albeit not very quickly. It is accurate (and repeatable) enough in both depth and x/y axes to do 0.5mm pitch SMD and I've done LGA28 (LSM330DL) on it. It drills the holes (component and fixing) beforehand then mills ou the board afterwards, so I'd say it would be easily able to engrave aluminium given an appropriate bit.Anything at this level is going to need a bit of setup and some tuning as you do the first few jobs, but my setup hasn't changed in quite some time.

author: Reminx123
author_rank: Contributor
timestamp: June 15, 2021, 09:44:41 pm
content: Hi David,I regularly follow this lady on Youtube, have a look to this episode:https://youtu.be/znZgT3Zmf5Yyou may find some suggestions about what not to buy.CiaoReminx

author: PlainName
author_rank: Super Contributor
timestamp: June 15, 2021, 10:19:44 pm
content: She speaks good stuffBut it's a drag watching a talking hand

author: Brumby
author_rank: Unknown
timestamp: June 16, 2021, 02:59:15 am
content: When the hand is showing you information about what the presenter is talking about, I don't have a problem in the world.Seeing flapping lips doesn't help you visualise anywhere nearly as well as actually looking at the things being discussed.

author: David Aurora
author_rank: Frequent Contributor
timestamp: June 16, 2021, 07:15:35 am
content: Quote from: dunkemhigh on June 15, 2021, 05:57:09 pmThanks for the info! Speed isn't really an issue, I work about a thousand hours a day already so I can easily throw enclosures in through the day and get on with other things. And yeah, I definitely expect a bit of screwing around at first as well as occasional maintenance, I just don't want a full time hobby getting the thing to work right

author: David Aurora
author_rank: Frequent Contributor
timestamp: June 16, 2021, 07:18:50 am
content: Quote from: Reminx123 on June 15, 2021, 09:44:41 pmThanksI'm talking about CNC routers though, not lathes

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 16, 2021, 08:20:20 am
content: I have a 3040 which gets mostly used for cutting prototype PCB outlines and drilling for test jigs etc., for which it works very well.I did try engraving brass once, which didn't work due to poorly controlled z-height. Aluminium might be easier but you may need to do some research on cutters - ali. has a habit of binding to the curtter.One thing I'd strongly recommend is a standalone offline controller with MPG.However if all you're doing is cutting the same thing into labels or boxes it may save you a lot of hassle subbing this who does it all the time, or getting boxes pre cut & printed. UV printing can be a good option for labelling

author: langwadt
author_rank: Super Contributor
timestamp: June 16, 2021, 08:30:43 am
content: Quote from: mikeselectricstuff on June 16, 2021, 08:20:20 amadd a few drops of alcohol, it works like magic keeping the aluminium from welding itself to tools and it doesnt' leave a mess like oil

author: kosine
author_rank: Regular Contributor
timestamp: June 16, 2021, 08:31:02 am
content: I do a lot of work on a slightly larger machine (a retro-fitted Axminster ZX30), but I did play with a "3040" type machine a few years ago. It was functional, though like all machines, you will need a bit of experience to get the best out of it.Most important things I've learned that improved my results:1. make sure there's no runout in the bit. I get up close with a jewelers loupe and keep reseating the bit if it's not spinning perfectly straight. (You'll see a blurred shadow around it if it's not true.)2. map out and correct for any backlash. Fit the sharpest bit you can find and jog back and forth in XYZ. You can see 0.1mm offsets easily with a loupe.3. try to get the bed as flat as possible. You can see very small Z offsets by putting a light behind the machine and looking at the cutter tip with a loupe.4. cut at a very slow feed rate. Going too fast introduces a slight deflection into the system and you get wonky cuts. These table-top machines are not all that rigid. Cutting circles is a good way to test things.5. when using small cutters on aluminium, I have to keep clearing the swarf with a squirt of soluble oil - otherwise I get rough cuts and broken bits. So you'll probably need to cover any exposed electrics and put a drip tray under the machine. (Mine is set at a very slight angle so the oil pools in a corner. I then suck it out with a squeezy eye-wash bottle and reuse it.)I'd also suggest getting some carbide dental burrs. You may need a suitable collet (usually 1.6mm), but they're pretty cheap and come in a wide range of shapes and sizes. I've found the plain cylinder type cut aluminium very well, though the ball-nose ones do wear out fairly quickly. (For ball-nose cuts I use standard carbide BN slot drills.)Not sure how well those pointy engraving bits will work on a 3040. I've never had much luck with them on aluminium (keep breaking the tips), but they do work well for making circuit boards. In aluminium, I tend to engrave with a 1mm ball nose at about 0.2mm depth of cut.

author: PlainName
author_rank: Super Contributor
timestamp: June 16, 2021, 11:51:18 am
content: QuoteYes, that would be cool. But 95% of the time the hand is flapping up and down on something which may or may not be relevant, just keeping time with the voice.I appreciate that there is not a lot to show, and a static shot of whatever for the several minutes it takes to talk about could be, er, less interesting.Perhaps I am overly susceptible after exposure to the BBC's American financial respondent whose hand gestures during her reports have only one syllable yet manage to express the exact opposite of whatever she is talking about. Mind, by 'hand' in her case I actually mean 'hands, elbows, shoulders'.