Tool breakage detection system

Hello
I'm wondering if anyone implemented or tried to implement a tool breakage algorithm based on VFD / Spindle tool load?
Thank you

I haven't heard of anyone doing that.
The difficulty I see is in telling the difference between a broken tool and a non-engaged feed.

If you can see a way round that, then I would consider setting up a "lincurve" HAL component to map the base-line spindle load against spindle speed, and then use a "comp" component to detect when the load is below the curve. The motion type (rapid or feed) is available on a HAL pin.

I guess a 2 minute filter on the low-force signal might work.

Depending on the CAM, you could perhaps filter on program lines, ie if a line of code is a feed and never crosses the threshold then something might be wrong.

Have you tried monitoring spindle load? You might be surprised how little it varies between engaged and unengaged for light cuts and small cutters.

I've always imagined a system that senses vibration and load to keep tabs on whether things are ok. The idea would work best for production, or long running parts. You'd monitor it yourself the first time and tell it "this is the base line". From there, either you set trip points for each tool or cut path, or when something starts loading up due to dulling you flag it so the system knows what's considered "bad".

Extreme deviations would cause an E-stop because it would mean a broken tool or launched part.

This could probably be done with sensitive accelerometers, which can be had inexpensively on a chip.

I've seen some advertisements for such systems. (I'm sure they are quite expensive.) They appear to work like this, you make a known good run and the system records readings from it's sensors (both load and vibration), then compares readings from that good run to subsequent runs watching for readings out of tolerance and stops the machine or takes appropriate action. (too high for a tool that is about to break or is too dull, or too low for a broken tool.)

I have seen one of those systems on a VMC in Germany from a US company.
Unfortunately, after 2 days of testing and adjusting and calibration they where so confident that they would intentionaly ram the tool at fool speed on the stock, well it did not end well at all. It broke the 1 inch tool from the side and continued to ram the spindle down till it tilted the head by at least 20 degrees, al the while sparks flying all over and even the ground shaking. It could have been a glitch, but i was terified watching that happen ( so were some 20 other ), and waisting a perfectly new machine.
Later i went on to discuss the system with the technician, but after he refused to give any info.
Now back on topic.
Anyone have a shock sensors from car alarms??? There are so called dual zone ones that have 2 separayely adjustable sensitiities with 2 outputs, they would do the job quite nicely wired directly to Linuxcnc. Use the high sensitivity one to activate at the lightest cuts, and the low sensitivity one to activate at max load. In Linuxcnc it should be wired so with and feed it should have hisens output on and if the lowsens activates stop the machine and raise Z axis. If there is a feed and none of the outputs are active, the tool is gone ( or stock ) or cutting air so just seting an alarm is enough, the machine can safely continue to work.
I do have some of those sensors around my shop ( i did alarm and security systems instalations for over 15 years ), but i do not have a VMC.
I do not know how much they do cost but a complete cheap car alarm is from 30 euro upwards, so very cheap, and ver effective for that job. Having 4 or 5 of those attached to a machine would work like a charm.

Here is a video.