DIY CNC machine for steel?

[Neale]

Interesting, but personally I wouldn't touch them for a mill conversion. I'm using something similar (although home-built) on my current CNC router. They've been working reasonably well, but only because the router is an MDF structure that can't manage anything like reasonable speeds or cuts. For a mill - no way! There's a reason why people say "use ballscrews"..

[JohnHaine]

I got a Novamill without its electronics off eBay for £610, built the electronics for less than £200 using 2m542 drivers, BoB and PSU from China. The Novamill is about X1 size but a different league for quality.


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[Davek0974]

I have a feeling your budget is way too low, even for decent work in aluminium, the likes of the 3040 on eBay will do very light cuts on ally, not steel, but will push your budget and fail after a short time. I had thought of getting a 6040 from eBay but after research I decided to build one better, the budget went out of the window, from £400 to over £1500 now but I am far more confident of results and life expectancy.

The Proxxon is a mini drill really, don't class it as a mill, for watchmaking maybe yes but anything bigger no. If looking at other smaller mills to convert, try not to look at those with swivel heads - these are very weak (i had one).

As said, what is your target project, if we know the subject we could guide a bit more :)

[JohnHaine]

The SX2 from Arc looks quite nice. It has a better table than the standard X2, basically the same as they supply on their version of the X1. You can also get it with an R8 spindle, R8 collets are economical, grip very well, and don't incur the overhang of an ER type collet chuck. And they don't get stuck! I think quite a few people have done CNC conversions of this class of mill including fitting ball screws. Another point about CNC is that since you don't have to stand around twiddling feed screws, the computer can take multiple smaller cuts so machine rigidity isn't maybe quite so important.

I started off a conversion of an X1 with this table, in the end the Novamill came up so I sold the X1 to a friend in manual version. It was clear that one could fit ballscrews, but you need to design the bits carefully so you can make them on the manual mill then just fit them whilst it's in bits. Also be prepared to at least fettle and possibly replace the gib strips, I made new ones from brass.


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[JohnHaine]

Loads of model engineers are using machines like the X1 and X2 and the WM series for doing good work in CI and MS. What you don't want for steel is a gantry style router, a standard vertical mill format is much better, but of course you pay in reduced work area. I agree about swivel heads, they are not worth it, there are very few jobs where they can be used and the reduction in rigidity for everything else is a pain. What you can do with the X Series mills is fill the column and base with epoxy/granite chips which increases the mass a lot. The Arc SX2P doesn't have any swivels.


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[lukeleb2010]

My budget ~£700 is for the machine prior to cnc conversion.

I'd like to be able to make aluminium parts and make some small steel cuts. The steel objects might be clamps for the mill itself or small hobby items (dice, keys little projects) I wouldn't cut deep or fast or with a large cutter in steel!

I am very tempted by the SX2. Is this likely to do the job?

Luke

[JohnHaine]

I would think it would be fine, Arc have a good reputation and Ketan the owner is well respected. If you can, go along to their showroom and have a look at the machine and talk to him about what you want to do. There's a very capable engineer called John Stevenson who works with Arc and has a lot of input to the machines they sell, they have a number of improvements compared to the generic X series. As I said above, if you went for this I'd get one with R8 spindle, the collets are cheap, hold well, don't get stuck, and with the cutter in a collet direct in the spindle you get more headroom and better rigidity.


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[Davek0974]

X2 looks ok, there is even a conversion kit for it...

http://www.cadcamcadcam.com/cncretro...illseigx2.aspx

[JohnHaine]

Indeed, but in the USA, out of stock, designed for the standard X2 rather than Arc's improved version, and using trapezoidal rather than ball screws.

[JohnHaine]

The Sx2p table has anti backlash nuts which are made of cast iron with a longitudinal slit, and an adjusting screw to take up the backlash. The threads are trapezoidal IIRC, and there is a common technique to make delrin nuts by heat moulding the material around the screw, so you could perhaps do your own. The advantages of ball screws are low backlash, near zero if you use double nuts, and low friction, I'd recommend them if possible. A good strategy would be to try the standard nuts and adjust the backlash as small as possible, try delrin if that isn't satisfactory, and ultimately if you need to, upgrade to ballscrews.


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