[FuriousGeorge]

I'm running an operation with a slitting saw and my mill keeps stalling. I have no idea why. I'm running a 2.5" D, 0.125" W 28 Tooth HSS slitting saw in aluminum (climb milling) with a 0.15" radial DOC at 17 IPM and 610 RPM. This is only a 0.12 HP cut and the load meter barely moves. I'm running coolant and I keep having instances where the mill just stops spinning. Anyone with slitting saw experience have some insights?

[tmarks11]

What does the VFD display on it readout when the "stall" occurs?

Maybe the spindle door switch is loose (or wiring to it), and it is shutting down the VFD whenever the switch triggers. If that is the case, then you should see the UV warning on the LCD display, followed shortly afterwards by the spindle powering down (since the spindle switch essentially secures power to the C2 contactor, securing power to the VFD).

[Moggot]

I'm running an operation with a slitting saw and my mill keeps stalling. I have no idea why. I'm running a 2.5" D, 0.125" W 28 Tooth HSS slitting saw in aluminum (climb milling) with a 0.15" radial DOC at 17 IPM and 610 RPM. This is only a 0.12 HP cut and the load meter barely moves. I'm running coolant and I keep having instances where the mill just stops spinning. Anyone with slitting saw experience have some insights?

Is it possible that the stock is pinching the blade? Also, what speed range are you in? It's surprisingly easy to stall the spindle at low RPM if you're using the high range pulleys.

[R.DesJardin]

What model PCNC are you using? Low rpm in high range on a PCNC770 this may happen, try low belt.

[Steve Seebold]

Try running your machine liw belt 1500 RPM 15 IPM. I RUN MY 1100 that way and it works just fine.

[SCzEngrgGroup]

It may be only a 0.12HP cut, but at 600 RPM, you don't have a lot of torque. You probably need to reduce the cut width. If you have a two-speed belt drive, use the lower speed pulley.

Regards,
Ray L.

[tmarks11]

Also, what speed range are you in? It's surprisingly easy to stall the spindle at low RPM if you're using the high range pulleys.

+++1

Wish I had thought of that. Yes, 600 rpm in high range is easy to stall.

[mrquacker]

This was happening to me too. You need to use lots of WD40 on the cut. Coolant wont work.

[FuriousGeorge]

Machine is the 1100. My first stall was in the high range, so I switched to low. Surprisingly, I still had one stall and one close call (sounded like it was about to stall, hit feedhold first). I reduced my DOC to 0.1" and haven't had any problems since. I'm making a heatsink with lots of slots, so I'm trying to both reduce the cycle time AND be able to walk away from the machine. Total slot depth is 0.3" so a 0.15" DOC has some nice time savings and I see no reason why I shouldn't be able to achieve that. I'm going to try Steve's advice and kick my speed up to 1500 RPM because it sounds like my issue is not enough torque.

@Steve

Steve, how did you settle on those feeds and speeds? experimentation? I never run my machine in low gear, but in high gear my heavy cuts are always the most successful in the 3000-3500 RPM range, so that 1500 RPM figure makes a lot of sense. A chipload of 0.00035 IPT sounds low to me. I'm curious on why you settled on that.

My plan is to do some more heat sinks tomorrow or Thursday, I'll report back. I'm gonna experiment at Steve's feeds+speeds with a 0.15" radial cut. Depending on how that goes, I'm going to inch my DOC up 0.01" at a time and see if I can cut with a final DOC of 0.28" with a 0.02" finishing pass. I seriously doubt I will able to do this as my heat sink is being held in a fixture with a single Mitee-bite pitbull clamp. It seems that should be my weakest link, not the machine.

[R.DesJardin]

I did GWizard 688rpm @ 10.66ipm chip load is .0006 IPT. There isn't much extra clearance for chips so this sounds reasonable to me. It should run in high range, I tap at 750rpm usually without issues.

[keen]

If your slitting saw is worn tapered the wrong way it will jam up all right.

Are the corners dull? I sometimes touch them up with a thin wheel in the bench grinder.

Or try a new slitting saw. Keen

[CadRhino]

I have been running my 1100 on the high belt only for over a year and have never had a stall. I do slitting too but only in aluminum or Delrin.

I did GWizard 688rpm @ 10.66ipm chip load is .0006 IPT. There isn't much extra clearance for chips so this sounds reasonable to me. It should run in high range, I tap at 750rpm usually without issues.

[FuriousGeorge]

Ended up settling on 0.01 radial DOC, 610 RPM and 17 IPM. I tried kicking it up to 1500 RPM and 1000 RPM, but it just didn't sound right. Or maybe I'm just a baby. Either way, I haven't had any problems since reducing my radial DOC. It'd be nice to shave 5 minutes off my run time, but oh well. Sometimes if it ain't broke, don't fix it.

[mrquacker]

Use WD40 on the cut instead of coolant. It lubricates the blade so the chips don't stick to it.

[Steve Seebold]

Just to prove myself right I did some doodling yesterday.

I cut a slot .250 deep with a 2,5 diameter, 3/16 wide wheel cutter with side chip clearance.

I ran it like I said at 1500 RPM and 15 IPM. I cut .50 deep in 2 passes (.125 each pass and it worked just fine. Oh yeah, and I was using flood coolant. I have a Fog Buster, but it doesn't work good for this application.

[brucec12]

I have seen a couple of times where my 770 spindle stalled/turned off and I wasn't even cutting yet (with an end mill) and rpms were about 2K. I'll have to try checking the door switch but it's only happened a couple of times and then has been fine??

Bruce

[tmarks11]

I cut a slot .250 deep with a 2,5 diameter, 3/16 wide wheel cutter with side chip clearance.

How many teeth on the wheel?

Maybe the side chip clearance is making a difference. Here is what Steve is talking about:

Attachment 301320

That looks great, the slitting saws I have used in the past just looked like miniature saw blades. Those look like they would work better, and would be less likely to bind in the slot.