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Endmills snapping at holder nose tip

Stirling

Cast Iron
Joined
Dec 11, 2013
Location
Alberta canada
Firstly I’m no CNC mill master.

So I’m running these kennimetals endmills that where on sale. The harvi te 4 and 6 flute endmills.
Cold rolled mild steel square stock
0.375 endmill. 1” doc 0.05”woc 200ipm 8000rpm
Held in Schunk tendo e hyd. Cat 40 holder with a 0.75” to 0.375 reduced.
Coolant or air last used to test. Seems to be the same problem
Haas vf-2

I’m milling less than 40 cubic inches before the endmill shears at the collet tip.
Sometimes a single break. Other times it breaks in 3 lengths. One break at the collet nose. Another 0.25”ish in side the collet
Tool is deep into the holder with 1.2” projection

Cut sounds fantastic. I only know it’s broke when I don’t hear the cutting anymore.

It does not seem like I’m pushing it hard at all. Spindle loads low. Looking at the broken endmills the flutes are perfect, tips are good (except the ones that contact/grab once broken)

What gives?
I’ve run these several times now and am getting the same result over several jobs.
Gone as hard as 0.075woc 1”doc 10,000rpm 400ipm (air blast) in 1045steel
Seems no matter how hard or soft I run it’s the same’ish metal removal before breaking.
I mean mr titan runs the same endmill at one million Ipm and rpm right?? :)

Run the kor5 aluminum cutters way harder and they won’t die. Same tool holder and mill.


Tips, advice?
Grew up on old school manual equipment, self taught CNC. And the learning gets $$$$ some times
 

pato

Plastic
Joined
May 22, 2021
Location
Colorado
In mild steel you should be measuring tool life in hours of cut time, not minutes if I'm understanding the 40 cubic inches before destruction right. I've always started under 10% radial on hsm cuts personally. Last time I had a production run on steel I used their 6 flute 1/2" and I think I got about 3-4 hours of cutter life at 9000 rpm and 560 ipm running air blast. I was at .050 radial(but with a 1/2" endmill and on an m560 not a vf2) and 1.15-.75 axial. Did you try less radial and more chipload? Another thing to consider is that you need to maintain feedrate and if you do not have highspeed machining on your vf-2 and/or if your cam smoothing/arc filtering/tolerance/ ect.. settings are not ideal you may be running well under posted feedrates. If you choke a haas on code you will rub your tooling to death quickly at 800+sfm.
 

Stirling

Cast Iron
Joined
Dec 11, 2013
Location
Alberta canada
You may be right about boosting the feeds. I did not time it, but I feel I got more life when it was fed faster.
“High speed machining” look ahead is not activated, in fusion360 my tolorance is set to 0.006” and smoothing is activated and set to 0.006” and the haas controller is set to p1 (loose and fast)

I got one endmill left I’ll turn on hsm and drop the radial to 5% and feed at 4-500ipm 10,000rpm and see I guess.

Here’s a vid of a few months ago when i ran it.
Got better endmill life but not wild. Hsm was activated for this vid, the haas has a 200hour trial I can toggle on or off.
Haas VF-2 HSM in mild steel (VOLUME WARNING) - YouTube
 

Stirling

Cast Iron
Joined
Dec 11, 2013
Location
Alberta canada
That sounds like a big cut for a 3/8 Endmill
Don


Sent from my iPhone using Tapatalk Pro

What parameter do you think is to big? I can play around with the numbers and see what works

The next job is in 4140htsr and I don’t wanna replay this $$ job.
I could switch to 0.5” endmills if the tool life goes up too. 3/8 is just a nice price point and has juuust enough flute to get the job done
 

Stirling

Cast Iron
Joined
Dec 11, 2013
Location
Alberta canada
About .02 step over are the chips coming off dark blue?
Don


Sent from my iPhone using Tapatalk Pro

In the vid posted it was 1.06doc 0.05” woc, 300ipm 10,000 rpm, air blast

Chips came off “straw” and turned blue ish after they hit the table.
I have not trued 0.02” woc.
I’ll give it a go tomorrow
I’ll go 5% so 0.01875woc. 1.06 doc 10,000 rpm 400ipm.
Sound like good settings?

Any recommendations?
Love to know your mild steel and 4140htsr setting for .375 and .5” cutters :)
Got a couple more of the harvi te cutters left 4 flute and 6 flute in those 2 diameters
 

Stirling

Cast Iron
Joined
Dec 11, 2013
Location
Alberta canada
I think your helix in was also too steep maybe try 1.5 degree
Don


Sent from my iPhone using Tapatalk Pro

The endmill is supposed to be able to cut 45deg plunge says kennemetals …?
But that doesn’t mean i should not back off a bit I suppose. I know it puts on a light show when it breaks through! I think it was 3-4deg helix
Maybe I should just pre drill it.
Got a 1” indexable coming tomorrow. Would eliminate the need the helix in
 

zero_divide

Stainless
Joined
Feb 2, 2012
Location
Toronto
Edit: I misread something.
I would start from something like this:Screenshot_2021-08-15-10-50-51.jpg which is almost exactly what you are doing.
But the fact that the endmill is breaking after just 40cub.in tells that the radial engagement is too large. I would drop it to 10% - 0.037in

Edit: It does not really seem too aggressive. Other reasons for it could be holder slipping. Are you seeing any pullout? Try to run it in a sidelock.
 

cameraman

Diamond
Joined
Nov 24, 2014
Firstly I’m no CNC mill master.

So I’m running these kennimetals endmills that where on sale. The harvi te 4 and 6 flute endmills.
Cold rolled mild steel square stock
0.375 endmill. 1” doc 0.05”woc 200ipm 8000rpm

Held in Schunk tendo e hyd. Cat 40 holder with a 0.75” to 0.375 reduced.


Coolant or air last used to test. Seems to be the same problem
Haas vf-2

I’m milling less than 40 cubic inches before the endmill shears at the collet tip.
Sometimes a single break. Other times it breaks in 3 lengths. One break at the collet nose. Another 0.25”ish in side the collet
Tool is deep into the holder with 1.2” projection

Cut sounds fantastic. I only know it’s broke when I don’t hear the cutting anymore.

It does not seem like I’m pushing it hard at all. Spindle loads low. Looking at the broken endmills the flutes are perfect, tips are good (except the ones that contact/grab once broken)

What gives?
I’ve run these several times now and am getting the same result over several jobs.
Gone as hard as 0.075woc 1”doc 10,000rpm 400ipm (air blast) in 1045steel
Seems no matter how hard or soft I run it’s the same’ish metal removal before breaking.
I mean mr titan runs the same endmill at one million Ipm and rpm right?? :)

Run the kor5 aluminum cutters way harder and they won’t die. Same tool holder and mill.


Tips, advice?
Grew up on old school manual equipment, self taught CNC. And the learning gets $$$$ some times

I'm wondering if there's some sort of "Thermal shock" situation...

Not sure where or how you are directing air or for that matter coolant - (I thought coolant was a bit of no-no ... No ? :-) )

Heat will build up in the hydraulic tool holder and shank of the tool with potential built up stresses and compression.

Question is are there any "pinch points" from excessive stresses / thermal shock. (Whilst the tool is mechanically loaded/ deflected continuously in cut + whatever oddities from more modern tool paths.).

Titan (Gilroy) "theory" is that more engagement creates better stability in the cut - but seems in your case (perhaps) there's some thermal condition that eventually builds to failure. A form of compressive shrinkage relative to the tool holder versus how the tool expands.

Maybe I scratch about to "Gauge" tolerances for hydraulic tool holder and quality (and basic fudgeable latitude) versus assumed composition of the Harvey 1 etc.

I think @CarbideBob would have some good ideas on this...

@Stirling how are you directing or controlling air or coolant through the whole process ?
 

cameraman

Diamond
Joined
Nov 24, 2014
I haven't gotten into hydraulic tool holders 'proper",

Just scratching the surface of top level Schunk technical info-ish...

Schunk hydraulic actuation.jpg < --- click to Blowup.

So interesting working principal; the hydraulic fluid being monstrously incompressible and tool holder mechanism essentially being a hydraulically actuated cylindrical "flexture" (sp) but the shank of the tool being accurately aligned before clamping ( i.e. being close fitting to begin with.). [no torque wrench and just whatever someone is naturally inclined to do with an Allen wrench to tighten against a small hydraulic piston in the body of the toolholder + whatever depth-set-plunger is set to ?].

schunk hydraulic features cont.jpg <--- click,

^^^ More enumerated labeling of first diagram.

.

Schunk clamping force test.jpg <--- click,

So ^^^ somehow this precision ground test bar or something can verify clamping force / pressure within the hydraulic tool holder itself ?

.

And

schunk tendo e temperature range.jpg <--- click.


^^^ Somewhere there is a bunch of information that explains in much greater detail what is actually going on here with range of temperatures from tool holder / shank all the way to end of tool / work piece in cut ? (for this tool holder and end mill combo kinda claims " 20-25 degrees Celsius working range up to 50 degrees Celsius ( 122 degrees Fahrenheit ) - seems rather conservative or states other working temperatures are available on demand ? When the hydraulic fluid expands (incompressibly due to heat build up - what pressure is being exerted on the tool shank ? ).

+ complication of a step down sleeve ?

Held in Schunk tendo e hyd. Cat 40 holder with a 0.75” to 0.375 reduced.
____________________


How does this all go with a more "Normal" tool holder ?


What clamping pressure is too much for some sintered tools and how little clamping force can cause a smooth bore sleeve (i.e. not keyed) to slip rotationally beyond a certain torque ? [Op's constant spindle load seemed interesting. ].

This may all be completely irrelevant but - selfishly interested in these tooling systems as they seem to be "pimped" a lot by various vendors and MTBs.
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
Two things:

1) I've read of hydraulic chucks being very nice for finish ops, but perhaps not stiff enough for roughing. If there's excessive sideward force on the chuck, causing the endmills to "wobble" a bit (even if it's not showing signs of pulling out of the chuck) then that could easily cause premature cutter breakage. So I'm with those saying try a (very good) sidelock holder out for test purposes.

2) If this is an older VF with miles on the belleville washers, you may have too low toolholder retention force, allowing the holder itself to pull from the spindle a bit and leading to the same failure mechanics as "1".

So, how old is the machine, what condition is the spindle and drawbar, do you see any fretting or wear rings on the toolholder tapers, etc. Maybe some pics of these areas and the broken tools themselves will give us more clues.
 

Mechanola

Stainless
Joined
Mar 21, 2011
Location
Äsch
Stirling, I’m taking some resistance with the volume you cut off. Why so complicated? Make one form and have the parts cast. To be frank, I have something against the worldwide CNC craze, too much hogging around takes place as if the owners and machinists get satisfaction from watching. Together with those who do not think of how to make something, the mouse clickers, the industry has become less efficient than it was half a century ago.

You could first mill away half the height on the left (video) with a sturdy facing head. Then you plunge with the end mill. Besides that you better install a second cooling pipe because (video) the tool is not reached behind the part.

Some thoughts of mine
 

cameraman

Diamond
Joined
Nov 24, 2014

^^^ Just for sh*ts and grins how they run the Harvey 1 TE (four flute) at KENNAMETAL*'s test lab* - not so much hustle (feedrate) comparatively ...

the thin but quite broad chips (slotting) @ 2 mins 20 seconds in - seem super interesting.

|< 525 sfm, (4000 rpm), 0.002 ipt, 100 % radial engagement , DOC 1" ) [1/2 " endmill [the blah blah blah ] 4 flute ] >|

Seems to take pretty much anything you throw at with a decent chip load ?


__________________________________________________ ___________________________


* No affiliation.


_____


Schunk reduction sleeve 1.jpg <-- Clickable

Rando - reduction sleeve ^^^


schunk tendo E test bar 1.jpg < --- click / enlarge

^^^ test bar - so if you tighten the hydraulic screw and you can pull the test bar out with your fingers pretty easily then your holder is not clamping properly , so I guess it's judiciously tolerance under-sized , so presumably properly sized tool shanks would still grip pretty firmly and yet fail the test bar "Test".

Not sure how that would translate to an intermediate reduction sleeve ? + complications of being coolant (TSC) compatible.

Seems pretty involved but they have nice accessories and cleaning tools and all manner of schtufff :)
 

Stirling

Cast Iron
Joined
Dec 11, 2013
Location
Alberta canada
I'm wondering if there's some sort of "Thermal shock" situation...

Not sure where or how you are directing air or for that matter coolant - (I thought coolant was a bit of no-no ... No ? :-) )

Heat will build up in the hydraulic tool holder and shank of the tool with potential built up stresses and compression.

Question is are there any "pinch points" from excessive stresses / thermal shock. (Whilst the tool is mechanically loaded/ deflected continuously in cut + whatever oddities from more modern tool paths.).

Titan (Gilroy) "theory" is that more engagement creates better stability in the cut - but seems in your case (perhaps) there's some thermal condition that eventually builds to failure. A form of compressive shrinkage relative to the tool holder versus how the tool expands.

Maybe I scratch about to "Gauge" tolerances for hydraulic tool holder and quality (and basic fudgeable latitude) versus assumed composition of the Harvey 1 etc.

I think @CarbideBob would have some good ideas on this...

@Stirling how are you directing or controlling air or coolant through the whole process ?

the attempts where done with coolant, or airblast, seperate to avoid any drops of coolant to contact the cutter when dry. application of airblast was done by dissconnecting the coolant to the lockline manifold and apllying air. so 3 points of angle, tool holder did not have a significant rise in temp as i ade sure one of the blasts biasd the tool holder.

I did try a milling chuck (GS brand) with a reducer sleeve, mchined about 3 inches and shut it down due to the chatter death howel that came from it. i would like to try a side lock but alas the endmills are straight shank, not sure how i feel about angle grinding a flat when im lready breaking them! haha.

the hyd. tool holders are pretty neat and seem great besides the obvious breakage issues. definatly seem to dampen the cutting as advertized, good wall finishes and tolorance/runnout. there is no pull out as the depths have always remained good, but I do notice what i would describe as fretting on the endmill and sleeve, leading me to belive the flexture effect is struggling. of course the tooling rep said its the perfect holder for the job tho :p one aspect i do not like is that the actual clamping zone is (imo) far from the tool holder nose, 1/4" or more maybe wheras a collet is right at the tip.
you comments on "too much" clamping pressure is interesting, i could be curious what the pressure increase is from 25-50C working temp

MILLAND
as for the machine it is a 2009 vf2, but ony has 450 hours on it as i that in a university looking nice until i got it under a year ago. spindle runs true, drawbar seems way srtronger than the tm series i replaced it with. tapper is OK. i have noticed some lines on my tool holders comming doen the taper verticaly.

you comments on "too much" clamping pressure is interesting, i could be curious what the pressure increase is from 25-50C working temp
 

Stirling

Cast Iron
Joined
Dec 11, 2013
Location
Alberta canada
Stirling, I’m taking some resistance with the volume you cut off. Why so complicated? Make one form and have the parts cast. To be frank, I have something against the worldwide CNC craze, too much hogging around takes place as if the owners and machinists get satisfaction from watching. Together with those who do not think of how to make something, the mouse clickers, the industry has become less efficient than it was half a century ago.

You could first mill away half the height on the left (video) with a sturdy facing head. Then you plunge with the end mill. Besides that you better install a second cooling pipe because (video) the tool is not reached behind the part.

Some thoughts of mine

these parts should be cast and finish machines ideally, but the neice i fill is so low volume it is not practical (i think). i may sell 20-30 of this part a year for the industrial equipment it goes on. steel is cheap just mill it out. some of the larger aluminum casted parts i replace i feel guilty about milling so much off. but again, 5 of them a year.... lack of casting knowledge, lack of any foundry in remote northern canada. truck in some steel, machine ans shelf the parts untill they trickle out the door.
im a one man band in a garage work with the tools i have i guess

there are rubber compenents i would like to have made if you know any domestic shops, or beter yet direction to get me going making my own!
 

D Nelson

Stainless
Joined
Jan 7, 2015
Location
Missouri Ida
That video showed 2xdeep and 5 percent step over and about 1 1/2 degree ramp in angle should make the 3/8 Endmill sing right along that’s about what I run and get good tool life
Don


Sent from my iPhone using Tapatalk Pro
 








 
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