Hi from rainy York - build plans/questions

[bikepete]

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!