[CROSSHATCH]

Hello All,

Had really an awful day machining yesterday. Long story short, I was running an HSM toolpath; 1/2 Carbide 3-Flute; .5" DOC, .075" WOC, 50 ipm (I forgot what I calculated, so i'm off on this particular feed). Beautiful chips, low noise...great material removal rate. That is until I made an error in the amount of stock and forgot about the last depth of pass when the end-mill drove the 6000 Carbide Endmill into at least 1/2 of stock, full slot.

Needless to say, the Spindle bogged down, and before the tool broke in half...the Servo driven table continued moving to the point where my Spindle Head shifted due to the force.

If the Head didn't rotate, maybe something else would have broke.


My question, is anyone using a specific torque for the two bolts that hold the Spindle Head Assembly to the Z-axis column. If something like this happens again, I would ideally like for the Head to rotate in such a situation (which it did) though I am surprised my x-axis servo did not overload and trigger the E-Stop.

Was a bad day, but could have been worse.

Regards,

-Jason

[hjl4]

Seems to me the table should of stopped moving as soon as the spindle stalled.
That type of safety protocol has been implemented for well over 30 yrs on CNC's.
Does Novakon not have this built in?
Even Larken Viper drives have this feature built in.

[AUSTINMACHINING]

Been there, done that, so I feel your pain. I just tightened mine as hard as I could with an adjustable wrench. Not sure my torque wrench would fit in that space anyway. It's a pain to re-tram when it get bumped, but somethings gotta give. I kind of wish it were just a direct mount as I can't imagine an application where I would rotate the head.

[BTP]

Depending on what VFD it has, you can sometimes simulate a fault to test to make sure all the safety interlocks are working properly. For instance on my machine I have a few output relays on the VFD which can be programmed to be triggered when a certain event takes place i.e. a fault. I have one of the relays close to a pin on the BOB and then my macro pump see's that input is active and it e-stops the machine. There is a very small amount of programming needed to be done for the macro pump, but it's pretty basic stuff. I would definitely look into though. Doesn't sound like they have any kind of safety interlock for the spindle faulting.

[engnerdan]

I changed the 2 head stock bolt out for studs from Mc Master Carr, which are capable of higher clamping forces.

These are the items I ordered for the 2 large bolts.
91005A039 2 Each Metric Black-oxide Steel Flange Hex Nut, M16 Screw Size, 2mm Pitch, 24mm W, 21mm H O'all
98040A109 1 Pack Metric Extra-thk Black Oxide Stl Flat Washer, M16 Screw Size, 32mm Od, 4.5mm-5.4mm Thick
98867A515 2 Each Metric Black Class 8.8 Steel Spacing Stud, M16x2mm Sz, 70mm Lg O'all, 38mm&17.5mm Lg Thrd

Then to Replace the 4 M10 bolts holding the rotation plate to the other piece of cast iron I used
98040A106 1 Pack Metric Extra-thk Black Oxide Stl Flat Washer, M10 Screw Size, 23mm Od, 4.5mm-5.4mm Thick
93275A040 4 Each Black-oxide Steel Spacing Stud, M10x1.5mm Sz, 65mm L, 20mm & 20mm Thread Lengths
91005A037 4 Each Metric Black-oxide Steel Flange Hex Nut, M10 Screw Size, 1.5mm Pitch, 17mm W, 13mm H O'all

[rlockwood]

There's probably a parameter for excess on the spindle drive, which could be used to throw a fault in such a case..

Easy mistake to make; even easier when the job comes back around and the material is 1/4" longer.. Just gotta get in the habit of making sure the actual stock matches the programmed stock.