Now here's a real End Mill Flute design I've never seen before - outside of some off-the-wall router bits. It's for cutting composites. A lot of times when cutting composites they tend to delaminate, what we did is sandwich them between a couple of layers of sacrificial material. Time consuming since the clamping would have to be moved from one side to the other. For drilling we made sure they were sitting on a scrap subplate for bottom support. Anyway here's a different solution from an article in Modern Machine Shop Online. Excerpts from the article follow:
Cutters Compress To Effectively Machine Composites:
This cutter has both up-cut and down-cut spiral flutes that compress the layers of composite materials during milling operations, preventing delamination at the outermost layers and also between inner layers. Machinists, on the other hand, sometimes struggle to effectively mill and drill composites because the materials possess atypical properties that require special machining practices.
Onsrud Cutter, a member of the LMT Group, offers six-flute composites cutting tools with specific geometries and coatings to overcome these machining challenges. The company?s ?compression cutters? have intersecting up-cut and down-cut spiral flutes that push individual composite layers together during machining to prevent the layers from separating from each other. This action prevents delamination from occurring at the outermost material layers. It also averts delamination of inner layers, which can be a less noticeable workpiece imperfection.
The company currently offers these tools as customs, but a standard product line will be available in 2010. ==================================================================
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Interesting. Does it really "compress", or does it just alternate between lifting and pushing down? I wonder how it compares to a fine- pitch rougher?
It actually compresses , that is cuts simultaneously up and down . At least the solid carbide two-flute type we use in the CNC router at the cabinet shop do . I suspect the six flute is a bit more difficult to make . I use the cast-offs (they can only grind 'em so small , then the geometry of the edge doesn't cut wood so well) from work in my mill-drill . They do a pretty decent job in aluminum and mild steel . Prolly better if I used coolant ...
40,000 RPM routers aren't exactly the same thing as a 7,500 RPM Haas.
Didn't I suggest you call some tooling manufacturers to see if they recommended using router bits in VMC's or HMC's the last time you suggested this? Have you since done so?
I've found that 3 flute end mills give a better finish than 2 flute end mills at the same feed rate in aluminum. Now to go from 3 flutes to 1 flute seems to be going in the wrong direction to me. But if you've got some data that supports this idea, I'd be willing to listen to it.
We already went over the increased scallop height issue & chip load comparison of running a one flute end mill vs. a three flute end mill at the same feed rate.
It's not the aluminum that's the concern (alum. seems to have a very high SFPM limit - I'm not even sure we even know what that limit is). What's of concern is the most efficient end mill for the machine tool in question.
No. Why would *I* call Onsrud? You're the one making the suggestion/claim. Do you have any support for this suggestion backed up by end mill manufacturer's suggestions? Plus, a router bit would only be useful in soft material like aluminum or magnesium, whereas three flute end mills could be used in a variety of materials. Why tie up a shop's resources for tooling by buying end mills for just one material, and just roughing at that, if they aren't likely to improve material removal rates? And another factor is that most heavy material removal is done now-a-days by inserted end mills.
For the same material removal rate at the same RPM and Feedrate a one flute cutter would have to have three times the chip load. Have you seen how flimsy router bits look compared to 3 flute end mills?
Let's stay focused here. You're suggesting/claiming that router bits would be better for VMC's or HMC's. I haven't seen any evidence of that.
I'm NOT certain. Router bits *might* remover material faster. I've yet to see any evidence of this. But anything is possible.
Here is some info on Onsrud's 2 & 3 flute cutters with a coolant through feature, that THEY recommend for aluminum. Roughing AND finishing.
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They're not exactly pushing router bits in their ad.
That's unsupported speculation. Evidence, evidence, my kingdom for some evidence.
HSS? You're kidding, right? Inserts are cheaper than End Mills.
Push them too hard and you'll see what aluminum can do to HSS or Carbide.
Let me just summarize some of the reasons why I didn't think following up on your suggestion was such a hot idea.
Poor finish - One tool cannot be used for rough & finish passes.
Greater tool wear - One flute doing all the work would likely have greater wear on it than if the work was spread between 3 flutes.
Limited to soft materials like plastics, Alum. & Mag. Ties up shop resources.
Inserted End Mills have coolant through holes that are able to blast the chips away with coolant in pockets.
Inserts are cheaper to change than whole End Mills.
Hard to measure the diameter of router bits, especially if they've been reground.
The chance of a router bit deflecting and gouging is probably greater than a 3 flute End Mill or inserted End Mill since they don't seem to have the body strength that regular End Mills do, or especially that inserted End Mills do.
They look funny. Just kidding, I wouldn't care what they looked like if they worked and lasted. But that's the crucial question - DO they work? You can see from Onsrud's own ad for cutters for aluminum I listed above, that they were pushing 2 & 3 flute End Mills NOT router bits. But hey, if you can dig up some data to support your router bit theory, or if someone posts about using router bits in their VMC at higher removal rates than 3 flute End Mills - I'll be more than willing to listen. Until then, it's just so much unsupported speculation and not worth spending much more time on.
Just a little addendum here while I have a few spare minutes.
Horsepower rating is determined by the MMR X Unit Horsepower
MMR = DOC X WOC X Feedrate (number of flutes or RPM doesn't matter)
HP = MMR X Unit HP (.25 for aluminum)
So calculating the horsepower difference between a one flute router bit as opposed to a 3 flute end mill is inconsequential.
The limiting factor for feedrate is the amount of back clearance on your flutes. If you feed faster than the amount of clearance you have you'll hit the backside of your cutter and just rub and possibly deflect it and maybe even snap it off.
Now a rule of thumb is that you can safely feed your End Mill with a chip load of 1.5 to 3% of the diameter per flute. So lets take the lower limit to give the router bits their best shot. On a 1/2" three flute end mill that would be 1.5% of .500 or .0075" chip load per flute for a total of .0225" forward movement per revolution.
Now from the Osrud site on speeds and feeds:
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We'll pick the largest recommended chip load for a one flute router bit in aluminum, in the 1/2" column. We'll pick the column for cutter
63-000 which is a one flute router bit with a recommended chip load of .011 - the other ones with .015 chip load are for 2 flute end mills. That chip load of .011 is per revolution since it's ONE flute. That is 1/2 the amount of feed of the 3 flute End Mill we just calculated for, that moves .0225 per revolution. So the conclusion I draw from these calculations is that a router bit can only be feed at 1/2 the feed rate of a 3 flute end mill.
Now, that's just theoretical calculations, if someone can produce some verifiable evidence that router bits are more productive than 3 flute end mills - I'll be more than interested in seeing it.
"When pocketing or contour machining we generally recommend using a single flute end mill for optimum feed rates and material removal. Because of the high rate of material removal, the surface finish sometimes is compromised. Therefore sometimes a finish cut is required with the single flute. If surface finish is critical and not speed, we recommend using a double fluted end mill at a lower RPM and feed rates."
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"High Speed Roughing 6061 T6 Aliminum"
Do you want to remove stock or not? Do you have jb's confusion about VMCs & HMCs?
It's partly in the gullet I think. And such tools are claimed to be a bit stronger.
Not for 2 & 3 flute cutters.
Do the calculations.
Do a total cost calculation.
So getting the chip out might be important.
So what, even in cases where true? Ever heard of a "toolchanger"? Or of not over-finishing?
Would it? For the total production cost dollar?
I did say Aluminum IIRC.
Or tumble them back in?
Shut own machine & change inserts or just call for a toolchange?
Easy to test on the machine if you have some stock to touch. IF it matters all that much (roughing).
Not if you can change cutting parameters such a DOC & IPR.
There are other limitations. Remember that the task is material removal.
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.050 IPR, 20,000 RPM, 10 mm diameter cutter. 1,000 IPM. DOC probably .5 to 1 diameter.
That chart seems unclear. For Aluminum. For single-pass & roughing. Someplace they list tools by material. For Aluminum roughing only single-fluters were suggested IIRC.
Well I'll have to admit that .050" sure sounds like a healthy chip load alright. I wonder if they are actually achieving that in their #1 video. If their machine had a 1G acceleration I figure it would take like... (32 feet per sec. = 384 inches per sec., 1000"/384" = 2.6 sec. to get to full speed) and the tool has to decelerate at the same rate since they are stopping at the top to stepover in Y. But it's big chip load in any case. I've never heard of this Rocky Mountain Tool Co. Perusing their web-site, they seem to be a distributor for some more recognizable brand name tools, and they appear to do resharpening. I find it odd that Onsrud (Which IS a well known and respected tool manufacturer) doesn't recommend anywhere near a .050" chip load for ANY of their router bits. In fact the most they recommend is .020 and that's for a 3/4 dia. cutter. On a 3/8" dia. router bit (closest to
10mm) they only recommend an .008-.010 chip load.
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Also in the #1 Rocky Mountain Video it looks like the tool is going no deeper than about half the tool diameter, or about .2 deep.
Here's some info about a 2 flute end mill from Helical Solutions.
Crafted of certified premium sub-micron grain carbide, the H35AL-2R is ideal for roughing and slotting applications and is available in stub and regular lengths. In testing with tool path optimizing software cutting 6061-T6 aluminum, this end mill achieved 1,000 ipm, compared to the 300 ipm for aluminum cutting tool designs previously available in the marketplace.
The test conditions were 1 in depth of cut, ½ in width of cut, 12,000 rpm and .0277 in chip load per tooth. This 100 cu ipm metal removal rate was achieved with a mere 10 percent load on a 20 hp (14.9 kW) vertical machining center. Over time, putting less stress on the machine results in longer machine life and longer tool life. ========================================================
So if the claims for this "Helical Solutions" 2 flute end mill are valid, it seems to be cutting approx 5 times the depth of the Rocky Mountain router bit, and with the .0277 chip load times 2 it would be a .0554 chip load per revolution or 10% more than the single flute router bit.
I don't see any speed or feed data at the above site you listed.
I don't see any specific feedrate data at this site either.
Ahh, now this one has some data. 15,000 RPM and 500 IPM gives a .033" chip load per revolution for one flute. Pretty speedy, but still not up to the "Helical Solutions" 2 flute end mill with .0554 per revolution.
So far it looks like the 2 flute end mill is in the lead.
Actually, my first choice would probably be a 3 flute end mill with a .010 chip load per flute and at least twice the depth of cut as the router bit. It seems even that would end up with a higher material removal rate.
Opps sorry, wrong bait to catch a BB-halibut.
IMO, attempted insults & appeals to emotion aren't constructive in an objective evaluation of cutting tool properties.
From the pictures at the Rocky Mountain site (side view and the one at the upper left of the site), with the deep gullet the cutter "looks" pretty wimpy. Maybe that's why they were only taking about half the diameter for a DOC in their 1000 IPM video. Plus it has to have a back relief of AT LEAST .050" so the back of the cutter doesn't drag. But a cross-section end view of the different cutters would sure be helpful to estimate relative core strengths, between the 1, 2, and 3 flute tools.
But they make router bits as well, and they didn't suggest using them in their ad.
Like I said, it seems like the end mills are in the lead in this horse race.
I don't know, the router bits "look" weak from the pictures, and that .050 chip load slamming into the part like a hammer just seems like it would be deflection city.
Well, if someone sent me a couple I'd sure go to the shop and give them a test run. I LOVE testing stuff to destruction. LOL
I thought that sounded a little odd at the time. I figured the they must have made a misprint on the HP percentage. But let's do a little rough horsepower calculation:
MRR = DOC X WOC X Feedrate (number of flutes or RPM doesn't matter)
HP = MRR X Unit HP (.25 for aluminum)
Using their above "Test Conditions" from the article:
1" DOC X .5" WOC X 1,000 IPM = A MRR of 500 cu. in. per minute.
500 MRR X .25 = 125 HP Yikes! THAT's unlikely.
The article itself says it was a MRR of 100 cu. in. /minute - so there is a discrepancy right there.
So much for truth in advertising, eh. LOL
There needs to be some independent verification of all these advertising claims.
Yeah, you're slackin' dude. You'll never get above 250 political troll posts in this weeks statistics at this rate.
My original point being, the HP difference should be inconsequential if the DOC, WOC, or Feedrate remain similar between a 1 flute end mill or a 3 flute end mill.
Sure, what particular limitations are you thinking of?
The above is a video of a regular end mill milling away on a part. I'm not sure what relevance that has toward your contention that 1 flute router bits make better roughing CNC roughing tools than end mills.
Yeah, the DOC "appears" to be about 1/2 of the diameter. But I'm still not positive they actually reach their full programmed 1000 IPM feedrate. Perhaps they should have done a spiral out instead of stopping X movement at the top of the circle to stepover in Y on every revolution.
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I don't know. Seems pretty straightforward to me. It's a chart of their recommended chip load per flute in cutting aluminum for their their single flute cutters. Only single flute cutters were listed because that's what the chart was about.
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