Auto retract on CNC before drill burns up

[cncguy]

Is there any way to write a macro that would make a drill automatically retract to the r-plane and stop with a message if it reaches a certain HP? I'm trying to save drills from burning up.

The macros would be Custom Macro B language, as we have fanucs, mitusbishi and mazak controls. I met a programmer awhile ago who said he wrote something for his machines like this, I never looked into it until now. How do you even get the information needed to write something like this?

Any help would be appreciated...

[angelw]

Originally Posted by cncguy

Is there any way to write a macro that would make a drill automatically retract to the r-plane and stop with a message if it reaches a certain HP? I'm trying to save drills from burning up.
The macros would be Custom Macro B language, as we have fanucs, mitusbishi and mazak controls. I met a programmer awhile ago who said he wrote something for his machines like this, I never looked into it until now. How do you even get the information needed to write something like this?

Any help would be appreciated...

Is that you Paul?

There are no Standard System Variables supplied by Fanuc to alloy Polling for Spindle or Axis load. Some MTBs supply additional System variables, but their supply is infrequent. Nakamura is one maker that I've seen supply System Variables for Axis Load.

What you want to do is possible by calling a Macro Program via an Interrupt Signal (UINT). When a tool abnormality is detected, processing to handle the abnormality is started by an external signal. To achieve this, you would have to add some hardware to monitor the load on the machining system. Axis load would be my choice, not Spindle load. If your machine has a Z axis load metre, it would be possible to tap into that circuit to trigger the Interrupt Signal.

An interruption type Custom Macro Function can be applied partway through a block. When the interrupt signal (UINT) is input, any movement or dwell being performed is stopped immediately and the interrupt program is executed.

Regards,

Bill

[cncguy]

Hey there Bill! Yes it is me, I was posting to the three forums at the same time, figuring I'd be reaching more people. These things are awesome, I just really starting to use them regularly. Maybe I don't need to post on so many though lol ... & also, hopefully someday I'll be able to help other folks .. all I can do now is post the results on all the forums to help others...

Anyway, thanks again...

[Stevo]

Hey Paul,
Just asking questions and getting answers always helps others. I read many threads that I am not involved in just to learn more. As I am sure you have realized by now there are many of use that float between forums, helping and learning where we can.

I thought that I read some time back in one of the manuals that there were parameters for setting load sensing. I will have to do some digging around. Although I am sure if Bill has not used it then I am probably mistaken that it exists. None then less it gives me another reason to read the Fanuc manuals right Bill?? I told my wife about you mentioning reading the manuals for recreation and she about peed herself.

Steve

[angelw]

Originally Posted by Stevo

Hey Paul,
None then less it gives me another reason to read the Fanuc manuals right Bill??
Steve

We're peas in a pop Steve. LOL
The print may have worn off the pages in my manual, and therefore I've missed the reference to this issue in recent times. I'm sure there are many, as I am, interested in what you might find. I'll look again also, but what Paul wants to do would be possible via an Interrupt Signal Called Macro.

Regards,

Bill

[Stevo]

Yes Bill it most certainly is possible with an interrupt signal. I will be sure to dig up what I can find as I am now interested to see if my mind was playing tricks or if I actually did see this.

The print is wore off most of my manuals as well. Even though I have most Fanuc manuals on PDF there is nothing like the good old fashion hard copy. It seems to take me longer to find what I need when reading it thru a PDF.

Steve

[sinha_nsit]

G83 can be used for a similar process on machines equipped with overload torque detection signal (skip signal). An M-code specified in parameter 5163 selects this mode for G83. Retraction is, however, not up to the R-plane. Drilling is resumed with reduced feedrate and increased rpm. On the other hand, feedrate is increased and rpm reduced in the next peck (Q), if overload signal is not detected. Thus, this G83 mode ensures fastest yet safe drilling speed. This was discussed in a previous thread.

[Guren]

I have a side question, why dont the machine makers add temperature detectors that would enable the worker to see how hot is the drill getting?

No really, how hard can it be?

On my machine I have encountered an error message when the drill overheated once. But it was an extreme case, where the head of the drill was as black as the night.

I assume the whole tool changer head got really hot & this was the trigger. I think it was some servo overheat error or something, I cant quite recall.

But this tells us that it already has heat detectors built in. Check your error manual, maybe you have something similar.

If you do, then, in theory, it might be possible to simply reduce the temp number in the machine to a lower value & then you should be able to figure out, with trial & error, at what speeds the error will be displayed, so you can reduce speeds.

That is, I assume, that this value, is somewhere in the machine config.

[Stevo]

Originally Posted by Guren

I have a side question, why dont the machine makers add temperature detectors that would enable the worker to see how hot is the drill getting?

Guren,
It is a good question in theory but very hard to do. Well at least IMOH as I am not a MTB.

The thing you have to take in account is the fact that if the tool is going to be hot enough to transfer the heat from the tool tip, to the insert holder, thru the tool holder and up the spindle then I think the tool tip would be gone before that actually happens. The only way to detect that sooner would be to have sensors in the actual tool itself. But then you would have to find a way to read them thru the spindle

The spindle is going to run warm even with a chiller on it. The problem I think would be that it would take too long for any heat variation to reach a sensor pertaining to the tool tip.

I think the load monitoring is still the best way to go as most machines can read pretty accurately what the load is and any signs of a tool break will immediately show on the load.

Yes some machines have sensors in the spindle to detect heat but this is mainly for detecting heat before burning up the spindle.

Stevo

[angelw]

Originally Posted by Stevo

Guren,
It is a good question in theory but very hard to do. Well at least IMOH as I am not a MTB.

The thing you have to take in account is the fact that if the tool is going to be hot enough to transfer the heat from the tool tip, to the insert holder, thru the tool holder and up the spindle then I think the tool tip would be gone before that actually happens. The only way to detect that sooner would be to have sensors in the actual tool itself. But then you would have to find a way to read them thru the spindle

The spindle is going to run warm even with a chiller on it. The problem I think would be that it would take too long for any heat variation to reach a sensor pertaining to the tool tip.

I think the load monitoring is still the best way to go as most machines can read pretty accurately what the load is and any signs of a tool break will immediately show on the load.

Yes some machines have sensors in the spindle to detect heat but this is mainly for detecting heat before burning up the spindle.

Stevo

Hi Steve,
You're quite correct on all points.

Originally Posted by Guren

I assume the whole tool changer head got really hot & this was the trigger. I think it was some servo overheat error or something, I cant quite recall.

If the error message was in fact related to the servo overheating, the overheating was not due to the transfer of heat from the drill to the Servo Motor, but, I suspect, to the Servo overheating due to the unreasonable and sustained load placed upon it by the failing drill.

One catastrophe I saw the result of, which I considered quite remarkable, both from extreme operator ignorance, and the fact the control didn't alarm, involved machining a dia20.0 x 25 deep bore in cast iron. This part of the program used three tools, an 18.0 U/Drill, and two dia12.0 boring bars (rough and finish).

1. The U/Drill had obviously failed within the first 1 or 2 mm of penetration, and then had been melted and mushroomed for the remaining 23 or 24mm of travel.

2. The roughing boring bar then came in to complete it's operation, only to have approximately 24mm melted and mushroomed off of its length.

3. If 1 and 2 weren't bad enough, in terms of operator incompetence or lack of suitable training, the finishing operation was allowed to proceed and have its length reduced by 24mm. Fortunately, these were the final three tools in the program, otherwise I fear that other tools would have been destroyed.

4. The operator was at the machine throughout the whole process.

Regards,

Bill

[Guren]

Maybe this will be useful information:

The reason my drill was burning, was because it was not centered. The tool holder head has been damaged once & after that no drills were in the center.

Of course I tried to center them by moving the center by X, but it was still way off, about 1,2 mm off even after that.

Drill Diameter was 20mm & hole length was 60 mm

So hire is a thought, maybe that is the cause of your problem? But of course if u have hard material there is really nothing else to do but to lower the feedrate & maybe spindle speed also, & make sure the coolant gets in.


I have also had issues with small drills, especially Diameter 4 drills when Im drilling 40 mm long holes, not enough coolant is getting in.

I solved this issue by moving the tool back to Z+50 & then if i have really bad material I add a 500 millisecond dwell, so that the coolant can cool off the drill.

G1 Z-10 F0.05 M9
G0 Z50
G4 P500
Z-9.8
G1 Z-20
...etc

If this does not help I reduce drilling distance from 10mm to 5mm

But then again, it all depends, if the drill is not in the center, each time you move your drill back & forward, it will increase the hole.

You gotta keep that in mind.

Edit I was thinking later & then it came to me, no mater how you bend this, in order for this to work, you need exact temp reading. But getting that is not possible, so all you are left with is to look at the chips, if they are yellow then think about reducing the speeds, if a bit yellowish, you are good, if they are black, sound the alarm.

[angelw]

Originally Posted by Guren

Maybe this will be useful information:

The reason my drill was burning, was because it was not centered. The tool holder head has been damaged once & after that no drills were in the center.

Of course I tried to center them by moving the center by X, but it was still way off, about 1,2 mm off even after that.

Drill Diameter was 20mm & hole length was 60 mm

So hire is a thought, maybe that is the cause of your problem? But of course if u have hard material there is really nothing else to do but to lower the feedrate & maybe spindle speed also, & make sure the coolant gets in.


I have also had issues with small drills, especially Diameter 4 drills when Im drilling 40 mm long holes, not enough coolant is getting in.

I solved this issue by moving the tool back to Z+50 & then if i have really bad material I add a 500 millisecond dwell, so that the coolant can cool off the drill.

G1 Z-10 F0.05 M9
G0 Z50
G4 P500
Z-9.8
G1 Z-20
...etc

If this does not help I reduce drilling distance from 10mm to 5mm

But then again, it all depends, if the drill is not in the center, each time you move your drill back & forward, it will increase the hole.

You gotta keep that in mind.

Edit I was thinking later & then it came to me, no mater how you bend this, in order for this to work, you need exact temp reading. But getting that is not possible, so all you are left with is to look at the chips, if they are yellow then think about reducing the speeds, if a bit yellowish, you are good, if they are black, sound the alarm.

Guren,
The biggest problem with visual monitoring is that its impractical to be looking at the swarf for colour change all the time, and it would be difficult to automate visual inspection. On the other hand, load monitoring, as was the OP's request, is very doable without too much trouble and is a very accurate method of determining the condition of the cutting tool.

In my opinion, to try and use a drill, other than a U/Drill, not on centre line, or not pointing square with the chuck, is just asking for trouble. Even with the U/Drill, the peripheral insert would have to be on centre height and offset in the direction that will cut the bore larger than the drill. The time and money invested in rectifying whats causing the need to offset the drill is well spent irrespective of how urgent the job may be. Nearly invariably, more time is spent coaxing the less than optimally set tool through production.

Regards,

Bill