View Full Version : uni-directional mold machining

05-25-2003, 04:56 PM
I'd like to know if, on "real good" cnc machine tools, is it common to have to mill in one direction for acceptable results? I am referring to planar type finish paths, using ballnose cutters, in complex 3d paths.

Even if your machine had near zero backlash, would servo lag still cause a slight drag effect which effectively doubles the displacement between adjacent passes, were you to simply mill back and forth?

How good are present day tools? (I run older stuff).


05-25-2003, 07:09 PM
the rule of tumb I have been using is:
to go clockwise(G2) if you are cutting outside (like outside walls)and counterclockwise(G3) if you are cutting inside(like in a cavitie or hole,circular or rectangular, actually any shape). This applies for finishing cuts, for roughing you can go any way that save time; as long as you have coolant at all times.
Best regards,

05-25-2003, 07:18 PM
When cutting cavity I use use both Zigzag and oneway maters on the shape.

with there being severail typs of surface paths to choose along with diffrent options to make for a real good finish in the mold cavity or core.

some time a simple Paralle path cut in say 45 deg the first and coming back at say 125 deg will give good results.

05-27-2003, 08:56 PM
For speedy metal removal and no concern on tool life use zig-zag cuts.

Make sure on a conventional cut that you stay away from your finish dimensions. Conventional cutting pulls the tool into the work.

But finishing: climb cut. And all cuts going in one direction for the cutter. Whether you use circular or linear paths to do your shape.

If you zig-zag on a finish cut, it will look like the step over was twice as much as what was used. So if that was acceptable, use half as many paths and go in one direction anyway. Takes half as long and looks better or as good.

05-27-2003, 09:51 PM
is cool but if at all possible you alway want to climb cut.
Most times its just a matter of what the model will allow
you to do. But there is certainly nothing wrong with
zig-zag toolpath. I have actually acheived better surface
finish with some toolpaths by zig-zag'n.

Good tools,good holders and machine make all the

05-28-2003, 12:11 AM
like I alwas say the shape makes a big diffrence on how I cut the shape.
I do anywere from Plastic,wax investment & die cast molds.

05-28-2003, 11:54 AM
Thank you all for your input. I guess I knew that climb milling was better, but I hated to waste all that time and wear rapiding back to the same end all the time. However, in machining in zigzag, I was always surprised by how much difference there was between the X position of the zig as compared to the zag (if the primary direction is X). Most likely it is just the somewhat slow processing power of my controller causing that "little extra" servo lag.