Hi all, joined up and been lurking for a few days, thought I'd best say hi and thanks for all the great postings. And sketch out my plans so far in case anyone has some feedback.
Been thinking of a CNC mill for a while now and almost ended up with one of the Denford Novamills off Ebay recently but luckily sanity prevailed because I really and truly have nowhere to put it!
So Plan B is to add a removable CNC sub-table (X-Y) to my existing milling machine, a Deckel FP1. The CNC table would simply be clamped to the existing worktable. As the vertical head is easily removable on this machine I plan to make a new head which will incorporate the Z axis slide.
Beauty of this plan is that there is no need to create floor or bench space for a new machine and in a few minutes of heavy lifting (ideally crane assisted) the mill can be back to its normal manual use, and the CNC bits tucked under a bench. Or for simple profiling I could just use the X-Y CNC subtable with manual Z and existing machine spindle if I can't be bothered changing over the vertical head.
As the mill also has a DRO, this can effectively be used to add travel i.e. if I have a Y axis travel of 150mm on my CNC subtable then that can be effectively doubled (at least some of the time depending on the part) by CNCing the frist half, then using the milling machine's original Y slide to move exactly 150.000mm via the DRO and then do the rest on CNC, no reclamping required. Assuming that it's all aligned perfectly... which may not be entirely trivial.
If it doesn't work out as an add-on (I suspect it may just be too much hassle changing it over and aligning it each time) all I have to do is clear some space (ha!), make up a beefy frame, and bolt on all the bits to make a stand-alone CNC mill.
Will be machining mainly lumps of alloy I think, plus doing random bits of engraving.
Anyway what started me actually getting on with it was more or less impulse-buying this on ebay:
Slide/ballscrew assembly on Ebay
Got it a few days ago and looks pretty good, slides are in great shape. Ballscrew (16 x 5) is rolled and has a few tiny bits of pitting but it'll serve for now.
Current plan is to use that as an X axis. It will sit on 400 mm slides (just bought from Ebay USA - he's got some more BTW:
Slides on US Ebay
(Cheaper than any UK ones I could find, and even 15mm Hiwin stuff new is almost twice the price. Incidentally German Ebay also has loads of slides which seem often cheaper than UK - search for "Linearführung". Also some cheap alu profile e.g. this seller)
Anyway those NB slides will sit under the X axis Airy points on a 20mm+ thick alu plate which will be the machine baseplate (approx 350 x 450). Will be trying to find an affordable bit of flat tooling plate type alloy for this as my milling machine only has 250mm or so of travel so I can't easily accurately machine flat the 400 mm Y slide bases.
Ballscrews for Y and Z are yet to acquire. Z slide blocks (or may use 25 mm rails) also still to acquire. Not sure either yet what sort of spindle to use - will probably build one around a straight shank ER32 collet chuck. Not sure re spindle motor either - will see what comes along.
As for the electronics I'm planning on getting the 3Nm/5A system from www.diycnc.co.uk as everything I've read has been super positive about his stuff and I'd rather spend a few quid extra and get the UK support than buy drivers etc from China.
Power supply will be three 350W computer power supplies (free from a mate) in series for 36V, 20ish A :-). More than required most likely... but price is right. Will build in some nice analogue panel meters to show output.
All of the electrical connections (steppers, limits, e-stop, spindle) will be plug-in via XLR or similar plugs so once unplugged, the control box and computer can just sit under the bench too. Have yet to decide on controller software and CAD/CAM options.
Will use belts to gear down the motors by 2:1 or so (assuming other ballscrews also end up 5 mm pitch). Looking like 220 mm X travel and 200mm or so Y travel currently.
That all sound reasonable? It is all getting bigger/heavier than I'd originally envisaged as a lift-on, lift-off device but it should also be more capable :-)
:feedback:Main outstanding question at this stage is swarf guarding. Bellows like the 5Bears build used would be ideal - anyone found an affordable UK supplier for off-the-shelf ones, or have any hints on DIY bellows? Or other alternatives?
Will start a build log once a few more bits turn up!
Never had any experience in using PC power supply's to run CNC and I am not saying that they wont work but the quality of some of them is piss poor from past experience with PC's. May be worth while looking at one from Roy for how much he is selling them at.
I bought all my electronics from him which included the following -
3 x 5A Driver cards
1 x Uniport BOB
1 x 36v PSU
3 x 3.1Nm Stepper motors
Because I bought everything from him he did do me a good deal, worth asking him before you shop around too much.
Thanks - good to hear another vote for diycnc.
A 'proper' PSU might be an idea as you say but I think I'll have a go with the free computer ones first. If they do fail, I'm hoping any failure mode would just result in lack of power, not frying all the stuff they're connected to...:cry:
That system you ordered looks very much like what I was thinking. Odd that his 'standard system' with the 5A driver cards uses the 24V supply - higher is better within reason as I understand it. Maybe it's to avoid needing the 'high voltage' option on the PBB20.
Another thing to bare in mind is that he makes the boards up to order so don't expect next day delivery. Worth the wait though!
Another quick thought, I have designed and made a bespoke enclosure to suit Roy's boards which you could use for yours.
It will hold 4 x DRV50's, 1 x Uniport card and a 24v or 36v PSU.
Takes a lot of the hassle out of mounting cards etc and looks really nice, I will post some pics later.
That sounds interesting.
I was thinking of using a big old PC server-type tower case with a new aluminium front plate (making a nice engraved one might be the machine's first job) to hold all the drive electrics. Has several cooling fans already mounted which is handy, and plenty of space (if I go with my PC PSU power supply it will be bulkier than Roy's). But the internal dividers/drive trays etc in some PC cases can be a bugger to cut out/work around.
I've used this type of box before for VFD installations etc:
Enclosure on Ebay
and that's another option.
Sorry, did not get time to do the photo's last night, I went in the workshop and said to missus "I will only be an hour.." four hours later I was still going..!
Anyway. here are the photo's -
Powder coated finish, the colour was what he was painting at the time and actually I quite like it!
The spare XLR connector holes are for limit switch's and 4th axis. Power connector on front is the in/out for the spindle motor, power in is on the rear. 80mm fans front and rear for cooling, sucks the air in at the front and exhausts at the rear.
I have put 10mm standoffs in were all the boards fit so its just a case of screwing them in and wiring up, dead easy!
Looks like an excellent job, very tidy and well laid out. Colour looks good too.
Did you use your machine to do the cut-outs?
Chicken and egg scenario...!
But the front panel is stainless or could be made out of aluminium in which case I can make new ones on my machine once I do get it running which should be tonight... Just got to mount my ballnuts and stepper motors, everything made so should be a case of drilling and tapping a few holes, fingers crossed.
Last edited by HiltonSteve; 28-07-2009 at 11:57 AM.
Very tidy job! Good luck with the finishing touches!
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