David Falkner
01-27-2020, 11:07 PM
This may be common knowledge amongst you CNC guru's but I just figured it out today. I don't research cutting profiles and tips often - ok, rarely - and it would probably be in my best interest to do so from time to time.
However, assuming this little issue is one you've encountered or not thought of then this little tip will save you a bunch of time and a fair amount of sanding.
My normal cutting profile on 1/2" BB (12mm) for Longworth chucks is to cut the slots in a rough pass climb cut leaving 0.007" on the side walls (radial) and 0.020" on the bottom (axial). Then I come back and clean up each slot with a conventional cut at full depth and that has left a very clean slot. Except for the bottom face veneer sitting on the spoilboard. That has splinters/fibers/fuzz and I have to hand sand those. All this is at 175 ipm and 18k rpm.
Now this may not be a big deal if you're cutting one Longworth chuck. But on days like today, where we had a 16" going to the UK and three 12" sets for the States, then that adds up to 64 slots! That's way more hand sanding than I want to be doing on these given the low cost we charge and I don't want to increase the cost just because I feel the need to do some sanding to make a better product.
However, time is money and as I was cutting the plates today I began to finally think about how I can eliminate the fuzz. It dawned on me before I cut the final of eight plates that I need to cut the full depth in one pass rather than leave 0.020" because what's happening is there's nothing to support the upcut of the compression bit in that final 0.020". So I quickly modified the cutting profile in Fusion 360 and cut the final plate.
Turns out my thinking was correct, albeit 7-8 months late (we've cut over 270 Longworth chucks and I've had to sand slots on most of these). So now I can't wait to cut more chucks and NOT sand slots! LOL! In thinking about why this worked I realize it's something that just makes sense and I should have thought about this a long time ago.
Leaving 0.020" for final pass -
424674
Cutting to full depth in one pass -
424675
David
However, assuming this little issue is one you've encountered or not thought of then this little tip will save you a bunch of time and a fair amount of sanding.
My normal cutting profile on 1/2" BB (12mm) for Longworth chucks is to cut the slots in a rough pass climb cut leaving 0.007" on the side walls (radial) and 0.020" on the bottom (axial). Then I come back and clean up each slot with a conventional cut at full depth and that has left a very clean slot. Except for the bottom face veneer sitting on the spoilboard. That has splinters/fibers/fuzz and I have to hand sand those. All this is at 175 ipm and 18k rpm.
Now this may not be a big deal if you're cutting one Longworth chuck. But on days like today, where we had a 16" going to the UK and three 12" sets for the States, then that adds up to 64 slots! That's way more hand sanding than I want to be doing on these given the low cost we charge and I don't want to increase the cost just because I feel the need to do some sanding to make a better product.
However, time is money and as I was cutting the plates today I began to finally think about how I can eliminate the fuzz. It dawned on me before I cut the final of eight plates that I need to cut the full depth in one pass rather than leave 0.020" because what's happening is there's nothing to support the upcut of the compression bit in that final 0.020". So I quickly modified the cutting profile in Fusion 360 and cut the final plate.
Turns out my thinking was correct, albeit 7-8 months late (we've cut over 270 Longworth chucks and I've had to sand slots on most of these). So now I can't wait to cut more chucks and NOT sand slots! LOL! In thinking about why this worked I realize it's something that just makes sense and I should have thought about this a long time ago.
Leaving 0.020" for final pass -
424674
Cutting to full depth in one pass -
424675
David