Planing a small cnc milling machine

[stefang]

Hi Folks,

At the moment I dont have too much time to continue working on my 3 Zylinder Radial Engine, but I had time to do a bit of development work leading to a small cnc milling machine...I dont know if it will be built some day, but who knows...

It will look like the famous (at least, they are here in germany...) Deckel Fp toolroom mills ( http://www.lathes.co.uk/deckel/index.html ), milling table moving up/down and sideways, the milling spindle moving forward/backward.

The guideways will be Size 15 linear rails, and the leadscrews are planed as 16mm ballscrews with 4mm pitch.
Steppers are 4A Sanyo Denki in a size of Nema56, I think, they are powerfull enough.

The milling spindle is self contained and can be mounted horizontaly or verticaly, the milling table can be removed, to mount big workpieces, a 4th axis, an universal swiveling table, etc.

A Work in Progress picture is attached to this post..

greetings
Stefan

 

[jimmybondi]

Hi Stefan,

my opinion:

the ballscrew for Z travel in such a project has to be more than 16mm diameter

i'm using 35mm ballscrew in Z (ok - thats oversized ) and the spindle heads weight is 100kg.
Your table looks to have not much less than 100kg

The steppers may be ok for X and Y - but only the Nema-size and the power consumption are not a indication of their maximum torque.

you have to take a look to the datasheet of the steppers about rising/falling torque-curve on dependence of the speed.

i'm using nanotec-steppers on X / Y with a given max. torque 2.5Nm and a torque of 1Nm at a speed of 1000revs/min
my ballscrews have 4mm pitch too and i drive them direct.
calculating the maximum force: on 4mm pitch with ballscrews (efficience 90% or more) you get nearly 140kgf (eq. roundabout 1400N) per Nm torque
Thats enough for my XY table - but not on my Z-axis.
I can use it up to 10m/min (and a little bit more) but thats really to fast for my mill (i think my mill is comparable to a Sieg X-3)

you can travel a little bit faster because of the linear guides you planning to use - my mill has conventional dovetails


Frank (i will contact you next days direct)

 

[applescotty]

The Aciera F1 seems along the same lines as what you're building. It may be a bit smaller than what you're proposing. Anyway, it's spindle could be mounted horizontally or vertically. Thought I'd pass along the link in case you're unaware of it. Good for inspiration, perhaps.

http://www.lathes.co.uk/aciera/index.html

Scott

 

[stefang]

Hi,

Yeah Scott, the Aciera F1 is also a guide for me in designing this small milling machine

Frank: Thank you for your detailed answer

The complete Z/X axis with the table has arround 45kg, the steppers i plan to use have a maximum current of 4A, maximum torque of 1,5Nm, and at 1000 rpm 1,1Nm (Datasheet: http://www.einfach-cnc.de/download/index.php?Shop/103-H7126-1740.jpg )

This mill will be much smaller than your F45...

Are you shure with the 16mm ballscrew? The ballscrew for the Z-axis has a length of 300mm..are you concerned, it will bend sideways?

greetings
Stefan