Okuma Lathe questions

[ColemanDonnelly]

Hello,

First let me say that I am not a machinist so I apologize if my question seems unusual.

I am a metrologies working with Machinists and I am trying to better understand the machining process so that I can tailor the inspection process to the machining AND help the machinist optimize their process.

At the moment I am trying to understand the signals that the machine can communicate to the operator. We have an Okuma lathe that can monitor and alarm based on back pressure or load to a given axis or tool. I am trying to identify a way to set an alarm based on load limits that spike up or down in an unusual way which would indicate a "special cause" in the process. This special cause (I believe) would tell us that either the tool chipped/broke (spike down) or the tool picked up a chip wrap and is cutting with the chip (spike up).

The goal is to demonstrate that certain features represent the process and as a result the entire part does not require 100% inspection once it can be determined that the process is in control.

The concern appears to be that we are using a 0.006 radius insert to cut the finishing pass on the part and the little variation in pressure for this tool would not be enough to register on the chart.

My questions are as follows:

1) Is it possible to set the load monitor to units that are tuned to individual tools within a program. Currently the operator is showing me that the load monitors XX% relative to 100% warning limits are set at 50% and 60%. The resolution of 1% is concerning to me because I have no way of knowing or understanding what the 1% means... 1% of what? What if I need to see 0.05% in order to set my alarm that tells me I have a special cause?

2) I have read that when you start making a new program you do a "test cut" and that the 100% load limit is relative to the maximum pressure that it took to make the test cut. Are these 2 things related? How do I tell my machine that I am making a test cut? and how do I tell my machine to use a different 100% for each tool that I am using?

If my roughing tool is hogging out 90% of the material at a fast rate and my finish tool goes in and cleans up the surface delicately then my 100% becomes of little value...

3) Am I chasing a rabbit hole hear and if so can someone please point me in a more productive direction?

Thanks

Coleman

[underthetire]

With the load monitor option, you can set high and low limits for each tool.

There is a teach mode that you turn on for the first cut, it sets a null and you can adjust from there.

Load monitoring usually does not work that well for sharp finishing tools like that. There is almost no extra load on the axis or spindle other than normal slide movement.

Options, in machine part probing, or automatic tool breakage detection.

[fordav11]

You're wasting your time IMO. The kind of things you want to monitor are too miniscule to monitor. The machine axis will exhibit a load based on the slide/turret movement. What you are seeing is servo motor loads.

Under normal machining conditions when cutting the load can change but it tells you nothing really. If loads are monitored on a specific axis its almost always because the operation is doing some heavy work and the monitoring is to protect the tool or job from being damaged if the machine were to continue with a broken tool. Where monitoring is used it's always for roughing operations but there needs to be a realistic tolerance on load from low to high otherwise the machine will be stopping all the time even if not cutting just when moving in rapid. For example I frequently run jobs where some tools can load up to 180% for a few seconds when peck-drilling with very large drills in very deep holes. I run these jobs all day like that and everything is fine. The amount of load added by a finishing tool is almost nothing in comparison. You will only see a load change on heavy roughing cuts.

As for picking up chips or chip-wraps and cutting with them.... the machine has a powerful motor, usually 20-60HP. It can cut high tensile steel and other hardened materials without breaking a sweat. Cutting with a blunt tool won't really affect it much unless the job caught fire and half of the tool is missing. Cutting with a large bundle of swarf wrapped around the part also won't affect it much. Of course it'll affect the size if the tip is blunt but you don't seem to be concerned with size only that the machinists are incompetent to run their machines. Any spike you may see is no guarantee of broken insert/tool or whatever.

Now I'm thinking why can't you ask your machinist buddies? I suspect they couldn't believe what you are trying to do.... and/or your questions or purpose is not very realistic and/or time-wasting B.S.

They probably think you should look for something more constructive to do with your time and let the machinists get on with their work. I'm tending to agree.

[ColemanDonnelly]

I’m not real sure what is to be gained by criticizing my approach. I'm pretty sure that I am not waiting my time in what I am trying to accomplish. There are whole companies that are successfully dedicated to what I am trying to do Caron Engineering comes to mind...
CARON Engineering : Tool Monitor Adaptive Control System (TMAC) protects your CNC machine
The machinist that I am working with is very open and cooperative to what I am trying to do AND feels that the end gain would be very beneficial. I have however learned through my past experience in my current field and others that sometimes you can make big steps forward quickly by reaching out to a community of experts rather than limiting your resources to the ones that are all inside of the same building...

Thanks for the info though - it was very helpful

[fordav11]

load monitoring is pretty standard across newer machines. not sure why or how another company could survive by re-inventing the wheel.

at my work we rarely use it except in specific circumstances on machines that run fully auto with robot loaders.

for inspection we only ever check 10% of our batches. the processes are near perfect and programs are proven 1000's of times over the years so the profiles are always fine. the sizes can vary but are usually within limits. those that are not are tagged and inspection fill out a form. all parts are booked by our machinists at the end of each day and entered into a computer so everything is traceable if necessary. people who scrap items without notifying inspection usually get their ass kicked but that's very rare. it happened only 3 times in my 25 years as a cnc programmer / cnc machinist.

[underthetire]

Nothing really new from Caron. I have done the analysis on light load tools. The machine/axis/spindle etc simply will not pick it up changes in load with those tools. Even Caron is for catastrophic failures in heavier cutting. The only way I was able to get any tool monitoring that was sensitive enough was to put load cells around the tool(lathe) or spindle flange(on a mill). With this I could measure down to 30 LBS of cutting force reliably. The problem with load cells, you need movement in your tool/spindle in order to see any changes. This meant weakening the structure enough so we had tool/spindle deflection at 30-60lbs of force. This also for the most part eliminated any chance of automatic tool change (we don't use automatic tool change on these machines anyway), that would not meet any kind of production machining.

Load monitoring has been around for decades, in one form or another, from Fanuc/Okuma/ and aftermarket.

So, in conclusion, yes you can monitor your roughing tools, and the Okuma load monitoring works well for this. Sharp finishing tools will be a complete waste of time on a large lathe. Now, air bearing, hydrostatic diamond turn machines can monitor loads quite small. They have almost null friction in the spindles and slides.

[ColemanDonnelly]

Load cells sounds like it might be a possibility - where can I go to learn more information about this? Do you have any documentation regarding this approach?

Thanks

[underthetire]

Pressure, Strain and Force

[Algirdas Basher]

it happened only 3 times in my 25 years as a cnc programmer / cnc machinist.

Right!!! I personally have never even seen a scrap part with my own eyes, I have heard stories about them though, and it has been 85 years. Way less than 3%

AB

[fordav11]

WTF ARE YOU TALKING ABOUT SH*T-TALKING MORON WITH ONLY 28 EQUALLY DUMB-ASS POSTS TO YOUR NAME.
I SAID PEOPLE GETTING INTO SERIOUS TROUBLE FOR SCRAPPING PARTS AND TRYING TO HIDE THEM ONLY HAPPENED 3 TIMES AT MY COMPANY. AND YES I'M SHOUTING BECAUSE YOU SEEM TO HAVE TROUBLE HEARING TOO, BAGPIPE BLOWING F*CKWIT.

P.S. I won't be coming back to this thread again so don't bother to post yet another dumb reply because I won't be reading it. Goodbye asswipe

[txcncman]

@ford - No need to feel offended from the offensive. He is from Scotland ya know. And us Scottish people have been known to nip at the bottle sometimes. Maybe the bottle nipped him back. Kills brain cells ya know. And being from Scotland, English is a second language. Give the poor sots a break.

[Algirdas Basher]

people who scrap items without notifying inspection usually get their ass kicked but that's very rare. it happened only 3 times in my 25 years as a cnc programmer / cnc machinist.

So my question to ya lad; is people getting their arses kicked very rare, or scrapping parts very rare? Or people not notifying quality that they scrapped a part very rare?

YOU OBVIOUSLY KNOW EVERYTHING ABOUT THIS INDUSTRY, TELL ME HOW YOU SURVIVED 25 YEARS WITHOUT MAKING JUNK EVER. (or 3 times according to ya). YES I AM YELLING, BECAUSE I AM SCOTTISH.

AB