I got a CNC3040 from eBay member zlx108108108
It came in about 2 weeks, but it was not packed well enough and a couple of bits were damaged.
The seller has actually been helpful and has good communication, they just should have packed it better. Talk to Michelle and say Simon (eBayer: ssashton) told you to talk to them. Tell them to pack the Y axis assembly separately from the main table, and remove the spindle motor from the bracket to reduce the weight hanging on it. Remind them you will want replacement parts if it arrives with damage.
Oh, they only listed its value as £100 for VAT ;)
Personally I feel the electronics is the least of the worries. For what you pay for a machine that cost alone is worth the machine if you reckon material and time up.
Personally I'd be happier with a control box I threw together myselfJohn S -
I've machined one manufacturers’ HDPE that would only give nice finish if cut at high feeds but when tried same setup on another manufactures HDPE at same feeds/speeds it goes into melt down or produces long curly wurly chips which strangle everything. . . . Don't figure.?? Not done much with Acrylic but from what I know and have read it too prefers high feeds.!(often the cure as not been feeds & speeds but blown air.?) . . . .Thou to be honest what concerns me is that even the melt downs have needed to be cut around this machines Max.!
My personal view on this machine is that it will be ok initially but fail quickly if pushed too hard.!!. . . It's cheap price dictates cheap components have to be used.
It's compromised in several key area's like unsupported rails and acme screws, probably both very cheap quality. The electrics are basic and again questionable regards quality and I've seen several mentions of issue's with them in various places.
I would say for a first time machine then Ok Maybe because it's cheap-ish.? . . But for special project and where it would need to shine in both quality and performance not mention longevity then I'm sorry but I'd be giving it a wide berth.!!
Camhgu I can appreciate your urgency and need for it now, but you have to ask your self can you afford for it not to perform as you might like or hoped it would.? Or the down time if unreliable.?
Buying ready made plug n play packages can be a good quick start-up if they are good quality but equally can be a right expensive time eating night mare if cheap and nasty.!!!. . . . The saying " You get what you pay for" apply's at this level I believe.
That said I wish you good luck.
Last edited by JAZZCNC; 29-01-2012 at 06:40 PM.
Thank you and thanks once again to all who responded, this forum is certainly a wonderful resource in all things cnc related!
I will let you know how we get on in due course :)
This, for example, would be a good start:
(Not suggesting you should buy any of these parts yet, clearly you will want to first draw the whole machine to work out exact sizes)
That's a bit bigger than you're after however you can ask the seller for different lengths if that's a problem.
Add to that 3Nm stepper motors, drivers, breakout board, PSU, wire and 50V drivers and you'll easily get good feedrates fort around £210 in total as long as you don't get all that from England. Once you add on the price of a spindle and the frame it's over £700 and probably more like £1000. However since the machine has supported rails, ballscrews and a good control system so it will be out perform the CNC3040 by much more than that price difference implies. Plus from making the machine yourself you will learn, as I did, a lot more about how it works and be able to troubleshoot it much more easily.
I have cut acrylic on a similarly small low power machine and obtained a good finish. So long as the chipload is correct and the depth of cut is not so high as to cause significant tool deflection the finish should be good.
One thing that helps here is single flute tools:
(That's just the first one I found, shop around for the cheapest and get the smallest flute length you can safely use as that reduces the tool deflection, resulting in a better finish.)
Since the feedrate is proportional to the number of flutes on the tool, the rpm, diameter and chipload, if you use a single flute tool the feedrate is proportionately lower than with 2 or more flutes. Similarly if the rpm is low, which it has to be as your spindle on that machine says it only goes up to 9500rpm the feedrate is also low. The relatevely low rpm is not so bad as the surface speed is lower, causing the cutter to heat less reducing the chance of melting the acrylic. Chipload is the 'width' of the chips, or put another way the distance the tool moves per revolution divided by the number of teeth.
According to Gwizard feedrate calculator (google it) the chipload for a single flute carbide tool in acrylic is about 0.1mm for 6mm tool and 0.06mm for a 3mm tool when limited to 9500rpm. That gives 600mm/min for 3mm or 1000mm/min for a 6mm tool. If you got a better spindle and used a 6mm tool at the reccomended rpm (12700rpm) the feedrate is 1400mm/min, still well within the 2500mm/min reccomended in the eBay listing, assuming that rating can be trusted!
So in conclusion I'm confident the machine is capable of cutting acrylic with a good finish, but still I would not let that persuade you the machine will do you need. You will have to take shallow cuts, so the overall time to cut a given thickness will be greater than for a more rigid machine. If you really want a good finish on acrylic then get a laser cutter, but that'll cost a teensy bit more than £700 and is not as versatile! Alternatively look into other ways of finishing, such as buffing the edges to get an optically clear finish.
It would cut aluminium, but nowhere near fast enough for it to be worthwhile so it's hardly worth mentioning. Similarly I cut titanium sheet on the router at school (roland camm PNC2300A, probably weaker than the CNC3040) and yes it worked, but prematurely wore out the machine and took forever! It was worth it as a one off as I really wanted the part but it would be foolish to try it regularly.
Saying 'the machine can cut material x' isn't saying much, whatever the material is unless you know how fast it can cut it (i.e. material removal rate, often measured in cm^3/min).
Last edited by Jonathan; 30-01-2012 at 06:02 PM. Reason: Deterioration of grammar
A bit selfish Jonathan making a school loose there cnc machine because you WANTED a part made
Shame on youIf the nagging gets really bad......Get a bigger shed:naughty:
Interestingly the machine is 'cable driven'. There's steel wire/rope wrapped round drums and attached to the gantry, so no backlash (I think). After dismantling it some time later and adjusting the belts it was OK.
Last edited by Jonathan; 30-01-2012 at 09:03 PM.
By adamh in forum Marketplace DiscussionReplies: 4Last Post: 06-12-2013, 11:24 AM
By craigrobbo in forum Milling Machines, Builds & ConversionsReplies: 11Last Post: 03-05-2012, 04:55 PM
By jimbocafe in forum New Member IntroductionsReplies: 1Last Post: 19-12-2010, 01:45 PM
By CraftyGeek in forum General DiscussionReplies: 1Last Post: 17-07-2010, 11:37 AM
By alan2525 in forum Marketplace DiscussionReplies: 10Last Post: 16-04-2010, 09:53 AM