CNC Tooling

[sanddrag]

On our router at ~20,000 RPM, we've had a lot of trouble cutting aluminum with a standard 1/4" 3 flute carbide variable helix endmill we use with great results at 6,000 RPM with coolant on the mill. On the router, it just wants to load up and melt/weld chips. I'm thinking a 2-flute would give better chip evacuation.

Currently, our coolant system on the router is a student and a spray bottle of WD40.

[R.C.]

Originally Posted by AdamHeard

I'll leave others to comment on tooling, but I will say we run a mister nonstop during cutting. It greatly increases cutting speed and reduces failures. This doesn't create a lot of liquid per hour, so we don't have any method of collecting or reuse for it.

Originally Posted by sanddrag

On our router at ~20,000 RPM, we've had a lot of trouble cutting aluminum with a standard 1/4" 3 flute carbide variable helix endmill we use with great results at 6,000 RPM with coolant on the mill. On the router, it just wants to load up and melt/weld chips. I'm thinking a 2-flute would give better chip evacuation.

Currently, our coolant system on the router is a student and a spray bottle of WD40.

David,

Like Adam we also use a mister non stop. Your issue is using the WD-40 squirt bottle. Its a waste of time, we did that for a few weeks until we got tired of endmills gumming up and wasting our money.

What we also do is a run 2 airlines + the mister. So two airlines are blowing away the chips so your not recutting chips. The mister keeps the endmill from gumming up.

http://littlemachineshop.com/product...y=212208195 9

This is the one we have, bought it off of ebay for ~$40 bucks.

-RC

[DampRobot]

We use a mister too. I'm not sure of the model. It does help a significant amount, we've been able to cut faster after starting using it (I think we started out at like 2 in/min with a 1/4" cutter in 1/4" alu before, now we set it to 6 ipm fairly regularly). In my experience, mist coolant helps most with cutters in the 1/4" to 1/2" range, where heating tends to slow down your cutting speed. With very small cutters (1/8" or smaller) I've seen them break more because of their small diameter than whether or not coolant was used.

Like others have said, collection or recycling isn't really an issue as the mister doesn't put out much fluid. However, it's very important to clean up properly after using the coolant. A lot of our steel tool holders have noticeable rusting in small spots from the mist, and after some pooled under our vise, it left a mark on the machine's table. I recommend wiping down the machine well every day, and taking up any fixtures on the table every week or so. On the other hand, it's a good idea to do this anyways.

8000 is extremely fast for tools in the 1/4" or 1/2" range, in my experience. With coolant, I believe we typically set 1/4" two flute cutters at 2000 rpm or so in 1/4" aluminium at a feed rate of about 5 ipm. Our mill only goes to 3600 rpm, and we only really use it that high for very small tooling.

[Cory]

Originally Posted by DampRobot

8000 is extremely fast for tools in the 1/4" or 1/2" range, in my experience. With coolant, I believe we typically set 1/4" two flute cutters at 2000 rpm or so in 1/4" aluminium at a feed rate of about 5 ipm. Our mill only goes to 3600 rpm, and we only really use it that high for very small tooling.

A 1/4" diameter carbide end mill under ideal conditions wants to be run between 12,000 and 36,000 RPM (750-2000 SFM).

At 2000 RPM you're at 125 SFM which is fine for HSS but doesn't take advantage of carbide's benefits.

[scottandme]

Don,

Look at the Onsrud catalog - the 63-600 product line is probably what you want to pick up. McMaster sells them if you search for "Router Bits for Aluminum" - "Grooving and Slotting". They're 1 flute solid carbide. The biggest issues with routers are going to be chip evacuation and and getting lubrication on the tool.

The 1-flute tools are nice because they give plenty of space to evacuate chips, and you don't have to run them at a high feed rate to maintain a proper chip load on the cutter to prevent it from rubbing. Depending on the construction (ball screws? rack and pinion?), your machine will probably be happier at lower feed rates and acceleration rates.

You'll definitely need something to get evacuate chips and provide a little lubrication on the tool. Otherwise you'll be re-cutting chips and getting a built up edge on the cutting tool - leading it to load up with aluminum and come to an untimely end. We're picking up a micro-drop coolant system (Trico Md-1200), which is like a mister, but instead of a constant stream of mist, it shoots small droplets of lubricant along with an air blast. They're more expensive than mist systems, but seem to clear chips better and don't make as big of a mess. Regular misting systems tend to linger in the air, and breathing that stuff isn't the greatest. At the very least look into a Fogbuster system to minimize that, or good ventilation.

[Mr. Lim]

Originally Posted by scottandme

Don,

Look at the Onsrud catalog - the 63-600 product line is probably what you want to pick up. McMaster sells them if you search for "Router Bits for Aluminum" - "Grooving and Slotting". They're 1 flute solid carbide. The biggest issues with routers are going to be chip evacuation and and getting lubrication on the tool.

The 1-flute tools are nice because they give plenty of space to evacuate chips, and you don't have to run them at a high feed rate to maintain a proper chip load on the cutter to prevent it from rubbing. Depending on the construction (ball screws? rack and pinion?), your machine will probably be happier at lower feed rates and acceleration rates.

You'll definitely need something to get evacuate chips and provide a little lubrication on the tool. Otherwise you'll be re-cutting chips and getting a built up edge on the cutting tool - leading it to load up with aluminum and come to an untimely end. We're picking up a micro-drop coolant system (Trico Md-1200), which is like a mister, but instead of a constant stream of mist, it shoots small droplets of lubricant along with an air blast. They're more expensive than mist systems, but seem to clear chips better and don't make as big of a mess. Regular misting systems tend to linger in the air, and breathing that stuff isn't the greatest. At the very least look into a Fogbuster system to minimize that, or good ventilation.

Second the Onsrud single flute cutters. They have been life-changers for our CNC Router. We run our spindle at 18,00 RPM with these same 63-XXX series Onsrud cutters, and they are incredible. Chip clearing performance was key in getting nice finishes on our cuts - and the feed rates we can run with these cutters are pretty aggressive too.

Our CNC Router came with a Unist Mister as an option, and we consider it a must when cutting aluminum. Mr. Stehlik here at 610 has been a big fan of the mist coolant approach and Unist misters in general, and has outfitted our metal chop saw, mill and lathe all with similar Unist misters. I don't think we've used a bottle of coolant all year long, clean-up has been easier, less machine corrosion, and the cut qualities have probably been better overall.

Here's a link to our Canadian supplier for the Onsrud cutters:
http://www.cncroutershop.com/ca/inde...us-metals.html

A not very useful picture and description of our router's mister setup from the manufacturer:
http://www.axyz.com/us/secondary-options/
...but if you read between the lines, it setup not as a continuous mister, but as in the post above it periodically dispenses droplets of coolant through a pulse generator.

A link to Unist's line-up of misters:
http://unist.com/solutions/machining-cutting.html

[apples000]

We got a box of roughly 100 1/8" bits for our 4' by 4' cnc router to cut sheet aluminum. Our sponsor gave us the box several years ago, and we've only broken a few and we've cut a TON of sheet metal. The bits are similar to 3317A21 from mcmaster, but they are a little different, and the writing on the box is in Chinese. The trick is to get the feed rate correct, and have an air line always pointing at the bit.

[DonRotolo]

Originally Posted by DampRobot

now we set it to 6 ipm fairly regularly

Like others have said, collection or recycling isn't really an issue as the mister doesn't put out much fluid.

Our mill only goes to 3600 rpm, and we only really use it that high for very small tooling.

Thanks for all that info, especially the mister and lack of need for fluid collection - it seems that's the way to go.

6 IPM? gee, that's really quite slow. I expect to be cutting several tens of inches per minute. Maybe my mileage will vary...

The minimum speed I can get is 8000 RPM.

Originally Posted by scottandme

Look at the Onsrud catalog - the 63-600 product line is probably what you want to pick up.

Depending on the construction (ball screws? rack and pinion?), your machine will probably be happier at lower feed rates and acceleration rates.

You'll definitely need something to get evacuate chips and provide a little lubrication on the tool.

OK on Omsrud, I have heard this from others as well.

It is a Rack & Pinion machine, with an integrated dust (chip) collection system and safety shield (using a 2-1/2" vacuum hose), which I hope will deal with both the mist vapors and chips. And dust, when I cut anything not metal.

Any comments on which cooling fluid you use? There are so many choices...

[scottandme]

Have you checked out the math for calculating speeds and feeds? 2000RPM and 6IPM is way too slow, that's only 0.001 in/tooth. Way too low for a 1/4" end mill.

Spindle Speed is roughly the surface speed (in feet/min) * 4 divided by cutter diameter. Carbide in aluminum numbers can exceed 1000 SFPM, so you can run up to at least 16,000 RPM with a 1/4" cutter. You can run slower with no ill effects here, might want to check out where the peak torque or efficiency is on your router.

Feed rate is the chip load * #teeth * spindle speed. Here's the link to the Onsrud specs. They don't provide a SFPM rating which is odd, they just list 16,000 RPM.

http://www.onsrud.com/files/pdf/2012...20Aluminum.pdf

They list 0.003-0.006 in/tooth for 1/4", you don't want to have this drop too low or the cutter will just be rubbing as opposed to taking a clean chip. Plugging those in gives you 16,000 RPM and between 48 inches/min and 96 inches/min as your feed. If your machine is unhappy accelerating that fast - just drop the spindle down to 8,000 RPM and feed between 24 in/min and 48 in/min.

I like the calculators at this site - they have one for HP/Torque requirements also that will let you get a feel for how heavy your cuts are.

http://www.custompartnet.com/calcula...speed-and-feed

G-Wizard is another nice (pay) piece of software that gives some good suggestions and does fancier stuff like calculating tool deflection on smaller cutters.

http://www.cnccookbook.com/CCGWizard.html

We use KoolMist 77 as flood for our mill (McM 11365K61), but it obviously works as mist as well. It's probably not the ideal coolant for aluminum, but it's one of the safer ones to work with. The MSDS sheet is pretty tame, it doesn't go rancid in the tank, water soluble, no skin reactions, biodegradable, etc.

I would just take the dust-shoe off when you're cutting aluminum, it'll get in the way of the coolant system and you won't be able to see the cut. Bump up the pressure in the mister so that it clears chips from the slot, or mount up an air blast. A lot of milling in steel and hard alloys is now done without coolant, just a heavy air blast to clear chips and prevent recutting. Aluminum needs the lubrication though.

[DampRobot]

Originally Posted by DonRotolo

Thanks for all that info, especially the mister and lack of need for fluid collection - it seems that's the way to go.

6 IPM? gee, that's really quite slow. I expect to be cutting several tens of inches per minute. Maybe my mileage will vary...

The minimum speed I can get is 8000 RPM.

Yes, 6 IMP. We do throw a good chip though, nice little curls. It is quite slow, mostly because we have a mill mentor who is, shall we say, conservative, with his machine's speed. He is right to go slow, though, the chips look good and we have had problems with breaking tools in the past (and crashing into clamps, but that's another story).

I'm sure with those router speeds, you'll be able to go faster. We're running a very different type of mill (a HAAS toolroom mill), so take my cutting speed experience with a grain of salt.

Perhaps we do cut too slow, but since the chip looks good and our part tends to vibrate excessively if we push it much faster, I'm inclined to stick with what we have now.

[Mk.32]

Originally Posted by DampRobot

Yes, 6 IMP. We do throw a good chip though, nice little curls. It is quite slow, mostly because we have a mill mentor who is, shall we say, conservative, with his machine's speed. He is right to go slow, though, the chips look good and we have had problems with breaking tools in the past (and crashing into clamps, but that's another story).

I'm sure with those router speeds, you'll be able to go faster. We're running a very different type of mill (a HAAS toolroom mill), so take my cutting speed experience with a grain of salt.

Perhaps we do cut too slow, but since the chip looks good and our part tends to vibrate excessively if we push it much faster, I'm inclined to stick with what we have now.

A HAAS TM should be able to go faster.......... we were cutting up to 30IPM on ours in Alum with no problem.

What kind of spindle speeds are you spinning at?

[DampRobot]

Originally Posted by Mk.32

A HAAS TM should be able to go faster.......... we were cutting up to 30IPM on ours in Alum with no problem.

What kind of spindle speeds are you spinning at?

Like I said, somewhere in the 2000-3000 rpm range.

[Cory]

Originally Posted by DampRobot

Yes, 6 IMP. We do throw a good chip though, nice little curls. It is quite slow, mostly because we have a mill mentor who is, shall we say, conservative, with his machine's speed. He is right to go slow, though, the chips look good and we have had problems with breaking tools in the past (and crashing into clamps, but that's another story).

I'm sure with those router speeds, you'll be able to go faster. We're running a very different type of mill (a HAAS toolroom mill), so take my cutting speed experience with a grain of salt.

Perhaps we do cut too slow, but since the chip looks good and our part tends to vibrate excessively if we push it much faster, I'm inclined to stick with what we have now.

Are you using carbide or HSS? With HSS I could see 6 IPM being reasonable, but you should be running at about 0.003 IPT or more with a good carbide end mill, which would be a baseline of double what you're currently running. With a cutter that small and a top speed of 3600 RPM I would never run slower than max speed. We were forced to run our machine no faster than 2500 RPM recently and were slotting 1/4" plate at 23 IPM with a 3 flute end mill. You have a less rigid machine, but 1/4" Al plate isn't very taxing and I would expect similar performance.

As Scott mentioned, with a chip load of 0.0015 IPT you're coming closer to smearing material off as opposed to shearing, which will dull your tool and cause premature breakage. This will be a bigger problem if you're conventional instead of climb milling as chip formation begins with zero thickness and increased rubbing.

If you find that you're breaking tools it's almost certainly a chip evacuation problem. We can slot 1/4" plate with a 3 flute aluminum specific end mill indefinitely as long as the chips are cleared out of the path of the tool. As soon as you start re-cutting chips you run the risk of dulling/snapping the tool or welding the chips to the flutes.

[DampRobot]

Originally Posted by Cory

Are you using carbide or HSS? With HSS I could see 6 IPM being reasonable, but you should be running at about 0.003 IPT or more with a good carbide end mill, which would be a baseline of double what you're currently running. With a cutter that small and a top speed of 3600 RPM I would never run slower than max speed. We were forced to run our machine no faster than 2500 RPM recently and were slotting 1/4" plate at 23 IPM with a 3 flute end mill. You have a less rigid machine, but 1/4" Al plate isn't very taxing and I would expect similar performance.

As Scott mentioned, with a chip load of 0.0015 IPT you're coming closer to smearing material off as opposed to shearing, which will dull your tool and cause premature breakage. This will be a bigger problem if you're conventional instead of climb milling as chip formation begins with zero thickness and increased rubbing.

If you find that you're breaking tools it's almost certainly a chip evacuation problem. We can slot 1/4" plate with a 3 flute aluminum specific end mill indefinitely as long as the chips are cleared out of the path of the tool. As soon as you start re-cutting chips you run the risk of dulling/snapping the tool or welding the chips to the flutes.

Most of our cutters are HSS, but I believe we have a few carbide tools. We tend to really only push up to that 3600 limit when using 3/16" end mills or smaller and small diameter number drills.

This whole discussion of our cutting rate leaves me rather wondering if our mill has been incorrectly displaying units for cutting or something... I was always told that the units for the feed rate readout were in inches per minute. Like I said, we usually cut with that in the 2-6 range. I think we've pushed it up to 10 or 12 in the past, but that introduced some very serious vibration, and I believe even some tool deflection. Cory, maybe you're right, maybe this is all caused by a less rigid table, and our low cutting feed rate is just a product of vibrations occurring when we get near "normal" cutting speeds.

We have experienced some dulling and tool wear. Perhaps this is due to the lower cutting speeds we use wearing instead of cutting. When we increase spindle speed and cutting speed, though, we tend to start melting chips onto the tool. I always attributed this to poor cooling (even with the mist coolant) rather than chip evacuation or low cutting speed. We always (well, except for a few special cases) climb mill.

Granted, when I'm talking about tools breaking, I'm talking about a couple of 3/16" or smaller endmills breaking when they took too deep a cut at too high a feedrate.

[Cory]

Originally Posted by DampRobot

This whole discussion of our cutting rate leaves me rather wondering if our mill has been incorrectly displaying units for cutting or something... I was always told that the units for the feed rate readout were in inches per minute.

Feed on a mill is displayed in inches per minute, but it doesn't mean much without knowing the chip load which is in inches per tooth. Chip load is independent of number of flutes, which makes it easier to talk about as a comparison.