Drilling force monitering/chipped drill detection/1000's of holes in SS

[PatK]

Hi Folks wonder if anyone can help with this is in relation to something we do at work.

We drill 1000's of through holes about 3-4mm in dia in cast stainless steel about 6mm deep with carbide drills, we get drill life of perhaps 1800 holes but tool life can be quite unpredictable and some of the castings can have defects which drastically reduces tool life.

sometimes the drills break (surprise surprise) and can be quite a pain to remove from the job although its generally possible using hard cut drills.

however IF we could FAIRLY cheaply monitor the drilling force and detect chipped/blunt drills we could save ourselves a good deal of pain.

o.k that was perhaps a bit lengthly.. if you're still with me what about a wireless force sensor above the tool holder??

anyone know of anything? I've tried searching the web but no joy yet!

regards,

Pat

[John S]

Monitor the spindle motor amperage, if it goes up you have a chipped or blunted tool, simples.

Also change to 4 facet ground drills, they last far longer before the web degrades.
I do roughly the same job 1,000's of 2.5mm to 3mm holes in 4mm and 6mm steel, not stainless so i use cobalt drills as they are more forgiving.

[PatK]

Thanks John, sorry to be slow replying! I wonder just how easy it would be to monitor the current on our mills, a clamp type meter would be simple?

Pat


Monitor the spindle motor amperage, if it goes up you have a chipped or blunted tool, simples.

Also change to 4 facet ground drills, they last far longer before the web degrades.
I do roughly the same job 1,000's of 2.5mm to 3mm holes in 4mm and 6mm steel, not stainless so i use cobalt drills as they are more forgiving.

[m_c]

Easy way, but not automated would be a clamp type meter, or add an ammeter.

More automated way would be to install a current transducer (http://uk.rs-online.com/web/c/process-control/sensors-transducers/current-transducers/), then depending on how automated you want, some simple electronics could provide you with a warning light, or could be interfaced to whatever controller is driving the machine to signal a drill change is needed.