Build Thread- Slant bed CNC lathe from scratch

[Guldberg]

So it begins...

Im nearing the completion of my cnc router build from scratch from lasercut steel, waterjetcut aluminium, linear bearings and a lot of homemade parts.
I promised myself that i wouldn't undertake any new major projects until it is completly finished, but that doesnt hold me back from designing now.

Here is what we are aiming for:

Slant bed - to allow for cooleant drainage etc. and because it looks cool
Complete enclosed - To allow for heavy flood cooling and to make it look more "pro"
125mm chuck - with possibility to add a 160mm later on
400mm of z travel - properly no tailstock anyway
150-200mm of x travel - Sufficient for that size chuck i guess
Tool turret with 8 positions, room for 4 cutting tools and 4 drills - Will properly be a project in itself later on

And the way to get there:
220Ncm stepper on z - I may change the design to accommodate a 650Ncm
180Ncm stepper on x - Maybe 220Ncm as well
Double nut or zero backlash ballscrews on both axis
Build from scratch of 20mm steel plates - Giving it a weight of +140kg, should provide a very ridig construction
Hiwin linear profiles, 20mm square type for z
20mm flat linear profiles for x - Bought of ebay some time ago

Now for som design pictures. I really hope to get som inputs on the design before i go on with the buildning:







Based on my experience from building the router, im going to build it out for MDF to begin with, there is just to many unknown factors you dont catch in the designing process, hence the idea of doing prototypes.

Thats the beginning, all kinds of input and questions are welcome

[mcwilsonmfg]

wow! sounds like a serious undertaking...I will be watching you...If I see anything where I can help out...would be happy to....

[LeeWay]

I don't know a lot about a slant bed lathe. Not seen many like that. Not seen all that many period. It does look like a great project. I like the amount of steel your putting in it as well. I just have to say it looks unbalanced.
It appears like your turret won't even be on the rails when cutting stuff in the spindle. I like to design the load fully on both rails and use the far ends of travel only for larger parts and extreme cases. For the most part, simply centered where the tool will have the most solid base.
Why not build the whole thing like you have done for the spindle? Then you could spread the lower rail out and down so that it sits under the turret while cutting.
It would seem like a cleaner design without the notched angle of the bed.
Like I said, I don't know that much about these, so take that with a grain of salt. I will follow your thread anyway. Good luck with this as well.

[Guldberg]

I think you are right about it being unbalanced. I'll properly add an extra "leg" on the tailstock end and the whole thing is going to be bolted to a solid tabel of some sort.
With regards to the the turret you are properly right as well, i think i will stick with the idea of having free space beneath the spindle to allow for chips to fall down, but with the rails as close as possible to the center of the spindel

[Guldberg]

From this picture it looks like when turning regular object, the turret will be positioned right above the rails

[LeeWay]

I see why you had the rails off to the side some. To stay out of the chips. In the last drawing, it looks like cutting forces will be right over the blocks on that rail. That should work well. As long as it's not overhanging the end, I think you have it.

[Guldberg]

One of the few parts i already aquired. One of the x-axis rails

[lerman]

I would suggest that you seriously consider using gang tooling instead of a turret. Take a look at http://www.omniturn.com/ for some examples of what can be done.

Adding a turret is essentially adding a rotary axis. Gang tooling provides the same functionality for almost free. The only additional cost is that the X axis must be longer to allow for multiple tools.

Generally, the big downside of gang tooling is that you can't use it with a tail stock; but in your case, you don't support one, anyway.

Ken

[Guldberg]

You are right, gangtooling is easier. There is no reason for the turret except that i would like to make one:-) Until i've made the turret i will properly make a simpel toolplate to accommendate a turning and a parting tool.

[handlewanker]

Hi, Interesting project, I take it your bed design length was determined by the fact that you already have the long linear rails?

Otherwise I would say that the bed/rail length in the x axis is too long.

For bar work, the spindle would probably have a 30mm bore, unless you're only going to machine billets which will be decided by the length of the chuck jaws for the stick out length.

A 160mm 3 jaw chuck has about 40mm of gripping length and this will decide how long the billet material can stick out, given the 4X ratio of diam to length to avoid deflection, a safe stick out would give you 160mm.

The problem with working from billets is the amount of wastage that occurs for the holding length.

The other factor is the spindle bore size which will limit your stick out again to 120mm for a 30mm bore.
A bigger bore size means bigger bearings, but is very desirable.
This will make a good read for many months to come.
Ian.

[Guldberg]

You are right, maybe i'll saw them to size. It can be shorten with 65mm, still maintaining room for the stepper to be mounted below.

The z-rails i haven't bought yet, but i dont think ill make them much longer anyway

Im aiming for around 25-30mm bore, this will go well with the largest ER32 collect

[RotarySMP]

Nice design.

To oppose torsion in the bed, diagonal ribbing would be more rigid. Welding a resonably thin closing sheet to the bottom would also make it stiffer.

If you put a second set of rails bellow parallel to the Z axis, spaced further away from the spindle, you could run a tail stock.

Obviously it intends what you are planning to make on it, but a tail stock adds hugely to a lathes work envelop.