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QSIMDO
08-27-2017, 10:43 AM
Been watching some CNC end milling videos of late and noticed that they all seem to climb mill.
Is that how it's done for CNC?

DEVILHUNTER
08-27-2017, 10:49 AM
Not always, but mostly. Climb milling usually have a lot of benefits.

Bob La Londe
08-27-2017, 11:23 AM
Climbing milling gives a nicer surface finish and seems to be easier on the tool IF you have a machine with little or no backlash. My CNC mills all have .003 or less. (much less) It seems to work particularly well with aluminum. I often use climb milling just because I like the sound of the cutter. The same cut in conventional will make the hair on the back of my neck stand on end. Often when using mixed milling for roughing the sound is like really interesting.

On manual machines you quite often choose conventional because it pushes the cutter back against the slop (backlash) on the machine. If you use climb it pulls the cutter ahead and causes unpredictable over cutting.

I'm no expert CNC operator, but I've spent about ten years learning what works for me.

Dan Dubeau
08-27-2017, 11:33 AM
Yes, 99.9% of cnc milling is done climbing. Cutter life, surface finish, chip thinning feed rates are all positives afforded by climb milling.

DR
08-27-2017, 12:11 PM
I'm a big fan of climb milling.......

One thing puzzles me though, why is conventional milling the default in CAM programs so often? You always have the option of climb milling,but generally if you don't notice they don't do it.

Bob La Londe
08-27-2017, 12:25 PM
Some CAM programs give you the option of changing the defaults.

I think the reason is climb is good if your machine is tight, but conventional is passable whether it is or not.

Rich Carlstedt
08-27-2017, 12:52 PM
Most all CNC Mills have Ball Screws for lead screws and this means no ( or almost no) backlash is present. This is ideal for climb milling which produces a superior finish and lower heat . You can see this in action with a wood plane and a board of oak (ie.) Set the plane down about 2 inches from the end of the board and try to plane to the edge of the board (2" travel) and note the chip !. Now reverse the process and approach the board from the end and you will note several things . a bigger chip , less force to get started , and a slight shock at the start. The shock is easily absorbed by ball screws and the freer cutting action means more productivity. Light machines and regular lead screws do not like the shock part and will vibrate violently at times, which could damage the part or cutter or both as well as hammer the leadscrew nut.

In the old days, machinists would increased the drag on the table by tightening the gibs or putting the table clamps on ( Bad idea !) while feeding !
Even seen a cable fastened to the table then to a wall pulley and a counter weight to keep tension on the table nut during climb mill moves as well as more accurate dial readings

Rich

pinstripe
08-28-2017, 02:56 AM
I often use climb milling just because I like the sound of the cutter.

Seeing as most work is done on CNC these days, I wonder if the latest cutter geometries are optimised for climb milling. Any cutter behaves differently in climb/conventional, but they might design cutters to work better in one or the other.

Bob La Londe
08-28-2017, 11:18 AM
Seeing as most work is done on CNC these days, I wonder if the latest cutter geometries are optimised for climb milling. Any cutter behaves differently in climb/conventional, but they might design cutters to work better in one or the other.

Well I do a lot of aluminum, and I buy high helix (40ish degree) mills when I can for aluminum. For steel I tend towards high flute count variable helix cutters.

gbritnell
08-29-2017, 07:48 AM
I worked in a pattern shop making patterns and core boxes on CNC machines. 99% of our machining was climb cutting. If you went into a pocket with a long ball end mill using a conventional cut it would whip around and gouge the walls. Not good!
gbritnell