Newbie- possible to use 4th axis this way?

[landslide]

I would like to find out if it is feasible to use a rotary table to create a part that is otherwise too large for a small mills Y-axis movement.

can MACH3 control a rotary table to cut a 2D star shape with rounded apex's?

[neilw20]

A lot of things are possible, but I need to upgrade my imagination before I can be of assistance.

[landslide]

lol yeah it is a bit hard to describe and I'd have to draw up some diagrams.

[landslide]

any tips on uploading a image? I tried creating an album in my profile but I can even get a tiny black and white image, you can see, to meet the file size restrictions. for some reason I only have 1kb of space but the image size can be 90odd kb.

[doorknob]

How about using a service such as photobucket instead?

(that's the way that I've always embedded photos into my threads, anyway)

[landslide]

ok. this is just a made up shape to try and explain the concept. the over all geometry may not allow for the process in all situation's but helpfully it is enough to explain what I have dreamt up.



assume that I want to make a shape with convex and concave curves all at tangents to each other so it is smooth. the item would be made out of 10-20mm plate. It could be water cut to shape and just a clean up milling step or a full milling out of the shape from a square plate.

assume that the plates dimensions just exceed the Y axis capabilities of the mill no matter what way you mount the plate to the table. you could make it by repositioning the job in a 2 step milling process.

however I would like to see if you could utilise a rotary table to make it in one fixture.

mount the rotary table so the axis is along the Z and offset on X to one side of center. the plate would rotate on top of the table. Only half the diameter of movement would be needed out of the x axis and minor movement in the Y axis to cut the curves.

you wouldn't want a shape that hit the column or would require the table to reverse rotation at any point.

I guess you would need a fancy cam package to program the tool paths if at all possible?

[neilw20]

I have machined a 40" diameter 3" plate on a 20" Y travel machine. (X=48, Z= 20)
I just rotated it manually, indexed on pre made marks.

Big (well it was for me) wood chipper disk.

It was on a tilt table to boot, so made angled cavities for knife blades.
We did 4 or 5 of these. 2 days machining, each. 12 blade slots.

Sure you could do it with a rotary table, but stability on the unsupported areas needs some clamping, or Z chatter will become very apparent.

[landslide]

well that's encouraging.

I wouldn't be expecting miracles in terms of finish. I'm really only considering this as I can only justify purchasing a small machine for hobby use, that would be 20mm to small on the Y for a couple of designs I currently get water cut then finish on a manual mill.

in terms of programing is it feasible for a MACH3 stepper motor mini mill or impossible unless I have a cam package worth 3-5 times the mill?

[ger21]

Originally Posted by landslide any tips on uploading a image? I tried creating an album in my profile but I can even get a tiny black and white image, you can see, to meet the file size restrictions. for some reason I only have 1kb of space but the image size can be 90odd kb.

Use the "Go Advanced" reply option, and then the "Manage Attachments" button, and you can upload images into the post.

[Torsten]

Originally Posted by landslide well that's encouraging. I wouldn't be expecting miracles in terms of finish. I'm really only considering this as I can only justify purchasing a small machine for hobby use, that would be 20mm to small on the Y for a couple of designs I currently get water cut then finish on a manual mill. in terms of programing is it feasible for a MACH3 stepper motor mini mill or impossible unless I have a cam package worth 3-5 times the mill?

Possible Yes, Mach3 should have no problem with this.
As you expect finish would suffer a bit.
Problem is the Postprocessor for such a Machine configuration.
I have seen Industrial prototype Machines with just a X,Z and B Axes.
Where any shape of contour could be machined by sliding the x-axes and B-Rotational Axes in sync.
Usually the Programs will be a bit longer because of the many Blocks required to describe the path.
Programming this by hand would be very difficult.
And a custom Postprocessor is likely not cheap.