need more efficiency on CNC lathe

[GITRDUN]

Our job shop is about 80% cnc lathe work and i am always looking for more efficiency in turning and boring. After 15 years of programming and operating cnc lathes and mills i feel i have a good amount of experience but i am always up for suggestions from other machinists.

Most of our lathe parts are around 1" to 3" diameter. In turning the OD i always use G96 mode and try to run about 500 to 600SFM. At that speed i always end up around .150 to .2 depth of cut in diameter or .075" to .1" true tool depth on the side. We use mostly coated carbide TNMG 432 inserts for turning. I find that a DOC around .25" diameter value will greatly shorten the life of the inserts. Increasing SFM means you need to decrease DOC and vise versa to keep the tool tip from overheating. So the limitation really is heat generated from what i figure.

So i guess my question is, what would you advise for more efficiency in turning work? What kind of wonder tooling is out there nowadays that can exceed the performance of the old TNMG inserts?

The lathes we run are Okuma 8" chuck with 2 speed gear boxes. They have a ton of torque, especially in low range. A .25" DOC on a TNMG insert will almost peg the meter to max levels.

[Shane123]

have you tried running your roughing inserts dry? i used to cold shock my roughing inserts till i started running dry with pvd coating. i use wnmg 432 inserts, sandvik 1125 grade on stainless & whatever, they kick major butt!

also, have you noticed that your turret waits for the spindle speed to drop when changing tools? call out a g97 and speed close to what your next approaching speed is, then return the turret, tool change, bring tool in, and call up your new g96 command. you can easily shave a second off per tool change......

[txcncman]

Make tool changes as close to the work as is reasonable and save about 2-4 seconds (or more). Writing macros to read your longest tool lengths can help with this.

Referencing what Shane mentioned, most machines have a programmable option to turn off the "Wait for spindle" command. Use it if you feel comfortable doing so. Will save a few more seconds on each tool change.

What lead-in angle is your tool? Positive? Negative? Neutral? Negative lead-in is less tool push off. Positive is less horsepower. Most run negative because they have to run against a shoulder. Should be able to run positive with at least insert thickness DOC. Rough with positive and finish with negative if needed.

Also use negative rake if they will hold up to heat.

C series inserts will be stronger and probably not break down from heat as easily.

W series inserts might also help.

[Shane123]

also, if you can build gang tooling blocks, you can save time from not having to tool change. and aligning your tools in order so your turret dont have to rotate as much... simple things like this can shave time, and when your doing big runs, time adds up!

[djr76]

Ive found the Kennametal Beyond and/or the Seco Duratomic grades really do what they advertise, they've outperformed my older grades significantly.

[txcncman]

Oh crap! I was not even thinking. The biggest time waster of all is almost always set up time. Anything you can do to reduce set up time is a big savings. Have material already cut and waiting on a cart or pallet near the machine. Have tooling pulled and waiting with material. Have programming finished with detailed set up sheets waiting with material. Have programmer working closely with set up machinist of first time run to make corrections immediately. Have inspector stay on top of 1st article inspections. Scrap and rework are huge time and money wasters. Do in-process inspections to keep tabs on operators.

If you do one set up per day per machine and cut down from say 1 hour to 30 minutes per set up on an 8 hour shift, that is a 6% increase right there.