Coolant, or dry in 15-5?

Machinerer · Nov 17, 2021

I'm machining some 15-5, H900. HSM toolpath, 485SFM, 8% WOC, varying DOC, from .5 to 2.0, and .002"ipt. Will I have better luck running this with coolant, or air blast? Running on an HMC, so chip evac is no issue.

BTW, it's this endmill -----> Helical Tool

Orange Vise · Nov 17, 2021

Dry with air blast.

Machinerer · Nov 17, 2021

I've already upped it quite a bit from the recommended cutting parameters on Helical's MAP tool, but it still sounds like it could be pushed more. Any suggestions on where to push this tool?

Orange Vise · Nov 17, 2021

485 SFM is pretty decent for H900 material.

You can experiment, but expect tool life to drop off quickly past a certain point - most likely not too far off from where you're already at.

boosted · Nov 17, 2021

About all you can do is add feed at this point.

At a certain point it may start to chip pack, which will limit your feed. Coolant helps stop the chips from sticking, but reduces your tool life dramatically.

I sometimes just increase the feed until it chip packs, then back off 25%. Recently had a program where I swapped out the 7 flutes for 5 flutes (both that same helical design), and I got better roughing life out of the 5 flute running at the same IPM as the 7.

Machinerer · Nov 18, 2021

Orange Vise said:
485 SFM is pretty decent for H900 material.

You can experiment, but expect tool life to drop off quickly past a certain point - most likely not too far off from where you're already at.

Part ran good with no coolant, however it looks like I may be forced to use coolant, as I think it may have put too much heat into the part. I roughed the part, leaving .005" and when I ran the finish pass, it left witnedd of the roughing toolpath in the center. It's a long skinny part, held down at the ends (not my fixture design) and I suspect the part bowed as it heated, then flattened back out once it cooled during finishing. I'll have to do some checking once it's off the machine.

I wonder if cutting a larger chip, to pull more heat away would help any...8% already seems pretty healthy for this material.

boosted said:
About all you can do is add feed at this point.

At a certain point it may start to chip pack, which will limit your feed. Coolant helps stop the chips from sticking, but reduces your tool life dramatically.

I sometimes just increase the feed until it chip packs, then back off 25%. Recently had a program where I swapped out the 7 flutes for 5 flutes (both that same helical design), and I got better roughing life out of the 5 flute running at the same IPM as the 7.

What do you mean by chip-packing? Probably just a different term of something I'm familiar with.

dandrummerman21 · Nov 18, 2021

JBethell said:
Part ran good with no coolant, however it looks like I may be forced to use coolant, as I think it may have put too much heat into the part. I roughed the part, leaving .005" and when I ran the finish pass, it left witnedd of the roughing toolpath in the center. It's a long skinny part, held down at the ends (not my fixture design) and I suspect the part bowed as it heated, then flattened back out once it cooled during finishing. I'll have to do some checking once it's off the machine.

I wonder if cutting a larger chip, to pull more heat away would help any...8% already seems pretty healthy for this material.

What do you mean by chip-packing? Probably just a different term of something I'm familiar with.

I would simply leave more than .005 as finish stock. Try .020 to be a bit more safe.

I'd also turn the coolant on the part after you are done roughing (change tools first! don't let the hot tool cool off with coolant) and let the coolant hit the part for a few seconds before starting finishing (rather than immediately start cutting the warm part).

Chip packing is when the flutes fill with chips and they don't easily fly away from the tool while milling. Chips will pack easier when the flutes are narrowly spaced (7 flutes has less room for the chip than a 5 flute)

Machinerer · Nov 18, 2021

At .020" the finish facing wasn't great. The material wanted to "lean" the endmill, which left a very slight step between passes. I may just have to do a semi-finish cut before finishing. As far as the chip-packing, this is a chipbreaker style endmill, so I would think that would be less of a problem? I'll keep my eye on it and see if I notice anything.

Pfmarkeytoolguy · Nov 20, 2021

Maybe a touch more feed but really your parameters and radial are pretty good. All the tooling manufacturers are pushing dry with air blast for stainless with a HSM tool path (and I get it send the heat into the chip not the tool or part), however in the field I have always had the best luck running a quality coolant, tick up in concentration, and make sure it’s well flooded or even better a coolant blast holder.

mmurray70 · Nov 20, 2021

I understand the theory and have tried both but I've never ever got better results dry with stainless. Pretty sure Sandviks calculator says coolant all the time with stainless too.

Your feed seems low for 8% stepover. Whats the point of doing light stepovers if your not increasing feed?

Machinerer · Nov 22, 2021

I started with Helical's MAP parameters, and I've doubled the ipt and the woc from their parameters, so I have in fact upped the feed quite a bit. Keep in mind, this is H900 treated material, so about 44hrc, which isn't crazy hard, but enough to make a difference, from my experience.

boosted · Nov 22, 2021

Chip breaker endmills will pack chips between the gullets too. We use those exact same Helical endmills, and do have problems with chip packing when we get really aggressive with the feed. If you're not having that issue, then you must have room for more flutes and more feed.

boosted · Nov 22, 2021

mmurray70 said:
I understand the theory and have tried both but I've never ever got better results dry with stainless. Pretty sure Sandviks calculator says coolant all the time with stainless too.

Air lets you run much higher SFM with the right coating. There is no doubt about it. I have run some parts where the tool is glowing orange/red for the entire 30 minute cycle, and somehow makes it through a dozen parts. Turn the coolant on, and it breaks after a few minutes.

Stainless is tricky though, because sometimes it's gummy, and basically requires coolant. I don't have a hard rule about milling with air vs. coolant in stainless. Seems like every new part is an experiment.

Machinerer · Nov 22, 2021

boosted said:
Chip breaker endmills will pack chips between the gullets too. We use those exact same Helical endmills, and do have problems with chip packing when we get really aggressive with the feed. If you're not having that issue, then you must have room for more flutes and more feed.

Is there an easy way to tell if your chips are packing in the flutes? I mean, obviously if the tool breaks and there's a bunch of chips in the flutes...but how else can you tell? Visually, it appears to be throwing a good "rooster tail" of chips. Sorry for all the questions. When, and how to push a tool harder is one of my weaker areas when it comes to machining.

boosted · Nov 22, 2021

It will be obvious when it starts to chip pack. Lots of noise and material welded to the workpiece. Usually means failure of the tool.

When I’m roughing stainless, I typically post at about double the feedrate that it should run. Then I creep up the feed in small increments until it starts complaining via chatter, harmonics, packing, etc. Then just back it off 10% - 25%

BROTHERFRANK · Nov 22, 2021

Dry with air blast for roughing. I like a 5 flute or 4 if I don't have a five. I run a 3/8", 5% step over, 10k rpm, 350 ipm. This part was 14" by 7", H900, roughed in 13 minutes. Made 10 parts and tool was still going strong.

https://youtu.be/G8byzRQPn9s

What blew me away was a 17-4 H900 part, similar size, Iscar all in one 3/8 5 flute. Dynamic milling said run at 14,500 rpm at 650 ipm with 5% step over dry. Ran great.

Machinerer · Dec 1, 2021

BROTHERFRANK said:
Dry with air blast for roughing. I like a 5 flute or 4 if I don't have a five. I run a 3/8", 5% step over, 10k rpm, 350 ipm. This part was 14" by 7", H900, roughed in 13 minutes. Made 10 parts and tool was still going strong.

https://youtu.be/G8byzRQPn9s

What blew me away was a 17-4 H900 part, similar size, Iscar all in one 3/8 5 flute. Dynamic milling said run at 14,500 rpm at 650 ipm with 5% step over dry. Ran great.

View attachment 335153

WOW! Do you think that Iscar endmill is a special case, or would you expect to be able to achieve similar numbers with a different endmill from a reputable vendor? Do you recall what the flute length was on either of those cuts?

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Coolant, or dry in 15-5?

Machinerer

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Orange Vise

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boosted

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dandrummerman21

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Pfmarkeytoolguy

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mmurray70

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boosted

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BROTHERFRANK

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