Endmills snapping at holder nose tip

[Stirling]

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

that vid IS the part im making last time ran it. was a 0.05" stepover and a 4 deg ramp on the bore. only getting 5-7 of that op done before the tool breaks tho
I have 10 of that op2 to run tomorrow, gonna drill out the center hole clearence this time. but need to see better tool life on the parts, it would be nice to at least run op1 and op2, 10 full parts with one endmill. honestly that even seems like bad tool life to me?

 

[plastikdreams]

a ramp tool path huh? never though to use that here. ive only ever ramped to dive into pockets.
what would that look like? big indexable ramping down the outside profile?

No you could use the .375 endmill

 

[Stirling]

No you could use the .375 endmill

and ramp straight down the side of the profile? would that not leave large chunks hanging off the edge? or am i missing something? that would def interfere with the soft jaws holding op2. I guess that could be worked around tho.

is the advantage to mill less material and just break off the excess sides?

 

[cameraman]

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

Jumped down the rabbit hole (In English and German) on Schunk tool holders and other related products,

very interesting indeed,

but haven't as yet found specific statement on what the actual clamping pressure and forces actually are ?

One thing that was interesting in the manual , was to say that don't tighten the tool holder without a tool (shank) being in the holder, (they don't say why) but presumably if you do then that has the capability to permanently deform the interior walls of the gripping part of the "Bore".

Gives an idea as to the forces involved,

I'm not familiar with the chemical composition and structure and (treatments thereof) of the Harvey (Kennametal) end mills [proprietary] but presumably some flavor / grain structure of cemented carbide ? ~ Being quite brittle. no free lunch for increased hardness in spite of some increased core "toughness".

^^^ The venerable "Bob" of the man of carbide - knows a lot about that.

I'm not sure if mechanically massive compressive forces acting radially inward on the shank would cause it to fail while the other end is being flexed and mechanically knocked about. *?

Couldn't find anything yet on temperature versus clamping pressure "Metrics" either ???? What happens if a Schunk hydraulic tool holder reaches 220 degrees Fahrenheit rather than 120 degrees Fahrenheit stated absolute maximum ? .


Interesting what MILLAND was saying about good for "Finishing" for hydraulics but Schunk Catalog all 790 pages + say it's good for everything lol (naturally) - some interesting stuff about calculating tool imbalances towards the end (around page 756 ) in a really easy way and exhaustively illustrated different scenarios that are worked through with their products yet nothing about clamping pressure and temperature issues. [Could act as very good reference for technical German vs. English ; bi-lingual document.].

Add links in a Mo'

Data sheets

Schunk data sheets on tool holders various + catalogs

Operating manuals

Schunk "Operating manuals" for tool holders etc.
_______________________________________________________________________________________________

* this might not be the mechanism ~ but imagine if an end mill was made of glass, (precision ground rod) and you put it into a schunk (or other) tool holder and really amped up the hydraulic pressure and knocked the end about a lot vs. having an identical glass rod that is gripped only with sufficient pressure and then knocked about... Which one will fail first ? Sort of an exaggerated concept for illustrative purposes of a severe concentration of stresses at the juncture of the tool holder versus the rod - but not unlike pre-stressed glass like materials ((Prince ?) - Rupert's glass exploding tear drops ). - Googling about there is this idea of brittleness and premature failure - for 'Solid" carbide endmills.

OTOH you mention slippage and fretting on the tool itself - suggesting insufficient grip ? ---> ? (will re-read thread)

The Schunk tool pressure test with the test bar seems 'Odd" as it there's no actual gradated measurement taking place ? Does the test bar slip with two finger pulling on it, but doesn't measure how much force can be applied under different conditions the other way i.e. tooooo much force ? ???

Schunk stuff seems really really nice,

Maybe you can call tech support at Schunk ? and then maybe Kennametal ?????

 

[Stirling]

Jumped down the rabbit hole (In English and German) on Schunk tool holders and other related products,

very interesting indeed,

but haven't as yet found specific statement on what the actual clamping pressure and forces actually are ?

One thing that was interesting in the manual , was to say that don't tighten the tool holder without a tool (shank) being in the holder, (they don't say why) but presumably if you do then that has the capability to permanently deform the interior walls of the gripping part of the "Bore".

Gives an idea as to the forces involved,

I'm not familiar with the chemical composition and structure and (treatments thereof) of the Harvey (Kennametal) end mills [proprietary] but presumably some flavor / grain structure of cemented carbide ? ~ Being quite brittle. no free lunch for increased hardness in spite of some increased core "toughness".

I'm not sure if mechanically massive compressive forces acting radially inward on the shank would cause it fail while the other end is being flexed and mechanically knocked about. *?

Couldn't find anything yet on temperature versus clamping pressure "Metrics"

_______________________________________________________________________________________________

* this might not be the mechanism ~ but imagine if an end mill was made of glass, (precision ground rod) and you put it into a schunk tool holder and amped up the hydraulic pressure and knocked the end about a lot vs. having an identical glass rod that is gripped only with sufficient pressure and then knocked about... Which one will fail first ? Sort of an exaggerated concept for illustrative purposes but not unlike pre-stressed glass like materials ((King ?) - Rupert's glass exploding tear drops ).

OTOH you mention slippage and fretting on the tool itself - suggesting insufficient grip ? ---> ?

The Schunk tool pressure test with the test bar seems 'Odd" as it there's no actual gradated measurement taking place ? Does the test bar slip with two finger pulling on it, but doesn't measure how much force can be applied under different conditions the other way i.e. tooooo much force ? ???

Schunk stuff seems really really nice,

Maybe you can call tech support at Schunk ?

fretting looked to be at the points of contact, inside the tool holder bore, on the outside and inside of the reducer sleeve and on the endmill at the point i assume the flexture makes contact. patchs of discolouration.
considering its a floating flexture i assume there are hard locating points (tool holder nose) and the upper is "floating" however many microns the fluid/steel flexture allows. theoretically as you apply side load and rotate you may be able to move the fluid side to side in the system, rocking the endmill back and forth as the pressure angle changes during rotation? even a micron a million times would assumably show up like this imo.
perhaps its breaking becouse the front nd bck of the endmill is povoting like a sesaw and breaking at the ridged noise point.
the fit feels good when putting a 0.75" solid endmill in. you can leave it in for days and still need to watch out, the air thats compressed into the bore when putting in the endmill will pop it out when the pressure is released.

i wish the milling chuck had not made it scream bloody murder tryig the same cut. crap milling chuck maybe?

ill see how it holds up tomorrow by taking the radial from 0.05" 200ipm to 0.01875" 400ipm (ill turn on hsm look ahead too).

maybe i rubbing it to death and its not the holder?
need to get this learning under my belt so i can stop going through so many tools!

 

[Milland]

Interesting what MILLAND was saying about good for "Finishing" for hydraulics but Schunk Catalog all 790 pages + say it's good for everything lol (naturally) - some interesting stuff about calculating tool imbalances towards the end (around page 756 ) in a really easy way and exhaustively illustrated different scenarios that are worked through with their products yet nothing about clamping pressure and temperature issues. [Could act as very good reference for technical German vs. English ; bi-lingual document.].

It's what I've read/inferred from various comments here over the years. And from the following "Thought Experiment", it seems reasonable:

If we presume the hydraulic chambers are contiguous (not isolated by (say) longitudinal quadrants), then the fluid within the chambers must be able to flow to any area. Since there's only one clamp screw, we can go with all fluid communicates with all of the chamber.

Since we know there's elastic deformation of the interior clamping areas allowing the process to work, that means that any "tipping force" on the endmill will allow a (near) constant volume of the chamber to be conserved, so the function of a perfect hydraulic systems incomprehensibility doesn't come into play (the fluid flows).

Now, we know there HAS to be clearance for a random tool shank to fit, both above and below the clamping chamber. This clearance means that forces tipping the tool can do so up until the shank "uses up" the available clearance, then you have metal-on-metal contact.

We know the metal of the clamping chamber itself has it's own static stiffness, and it's this stiffness that locates the tool shank up until forces are applied sufficient to deform the chamber and lead to the M-on-M contact.

The inherent chamber stiffness is high, but clearly not infinite, so from that we could say that "finishing forces" are unlikely to tip the shank, but high roughing forces conceivably could.

So from this reasoning I accept the idea that hydraulics are great for finishing, but I would use shrink or other holding systems for roughing.

The above is my TE/opinion, others may have come to their own conclusions.

[Edit: post #25 anticipates some of my reasoning]

 

[mhajicek]

I've also heard that hydraulics aren't the best for roughing, because the fluid can move around from one side to the other under load and let the cutter move a small amount. I'd go shrink fit (you can use a torch if you don't have an induction machine) or sidelock. I'd regularly get 5 hours of life from a Helical 1/2", dynamic roughing in Ti on a Haas, using shrink fits.

 

[cameraman]

fretting looked to be at the points of contact, inside the tool holder bore, on the outside and inside of the reducer sleeve and on the endmill at the point i assume the flexture makes contact. patchs of discolouration.
considering its a floating flexture i assume there are hard locating points (tool holder nose) and the upper is "floating" however many microns the fluid/steel flexture allows. theoretically as you apply side load and rotate you may be able to move the fluid side to side in the system, rocking the endmill back and forth as the pressure angle changes during rotation? even a micron a million times would assumably show up like this imo.
perhaps its breaking becouse the front nd bck of the endmill is povoting like a sesaw and breaking at the ridged noise point.
the fit feels good when putting a 0.75" solid endmill in. you can leave it in for days and still need to watch out, the air thats compressed into the bore when putting in the endmill will pop it out when the pressure is released.

i wish the milling chuck had not made it scream bloody murder tryig the same cut. crap milling chuck maybe?

ill see how it holds up tomorrow by taking the radial from 0.05" 200ipm to 0.01875" 400ipm (ill turn on hsm look ahead too).

maybe i rubbing it to death and its not the holder?
need to get this learning under my belt so i can stop going through so many tools!

For your 0.75" my understanding is that the central portion of the cylinder of the holder bulges out to grip, but everything fore and aft of that is pretty close indeed and rigid ? . We're talking massive forces here and pretty rigid effective geometry. - hydraulic fluid and even water is basically incompressible whereas the metal will flex but be extremely rigid

Your spindle runout will be of the order of 3 to 6 micron,

The tool holder itself is rated to about 3 micron + length of tool projected out. (that all adds up).

I don't have a feel for that sleeve like "colletty" thingy.. :-) but I suspect it's rigid both ends / minimal tool pivotting / "see sawing" in a fluid / metal composite ~ scenario you mention.

I think Schunk have been at this a long time and are certainly not dummies. (that would seem like an obvious problem that could be fixed in development years and years ago (maybe) ? ).

The tool holders seems to be mainly warent-eed for 36 months but if there are problems you can send them back ?

____________________

The regular weldon type shank (accepting) version of these look pretty good ? I don't know if they are cost effective or not ?

Seems you don't have to use end mills etc. that have continuous cylindrical shanks. They allow for two or three different types + whatever tool balancing might be necessary for higher rpms.

~ The fine adjust set screws for correcting runout seems like a nice feature on some of their holders towards the machine interface / connection.


<-- Klikenverblowenupft

^^^ shanks that can be used (broad strokes) - not sure if this is universally applicable across the range.

AND,

<--- Click to blow up.

^^^ Some I guess have the set screws to adjust runout but doesn't work for the sleeves .

 

[plastikdreams]

I agree with a sidelock cutter. You have a hydraulic holder with a reducer. Unghetto things then dive in.

 

[metalmadness]

Shrink Fit for days..funny enough I was talking with a seasoned veteran of aerospace alloys and he said "no we don't use shrink fit it just doesn't perform as good as sidelock for harder metals" and in my head I am like...wtf are you talking about. They ONLY use sidelock for roughing and never use shrink fit for anything. I chuckled. I can see how you might be concerned about pullout from a shrink fit but if you are pulling a tool out then you got some other issues methinks. Technically a sidelock will never pullout but I have never seen a shrinker pull out like that unless your slotting titanium 3x deep (why?).

I rough stainless with shrink fit holders all day long.

 

[cameraman]

Shrink Fit for days..funny enough I was talking with a seasoned veteran of aerospace alloys and he said "no we don't use shrink fit it just doesn't perform as good as sidelock for harder metals" and in my head I am like...wtf are you talking about. They ONLY use sidelock for roughing and never use shrink fit for anything. I chuckled. I can see how you might be concerned about pullout from a shrink fit but if you are pulling a tool out then you got some other issues methinks. Technically a sidelock will never pullout but I have never seen a shrinker pull out like that unless your slotting titanium 3x deep (why?).

I rough stainless with shrink fit holders all day long.

Yeah, I think OP's reduction sleeve is slipping (fretting and appearance of wear / discoloration and excessive heat) and maybe be (being) pulled out even a very very small amount before failure , be interesting to see if there are any welded chips etc. [A good case for a high speed camera in a machine.].

Without the reduction sleeve / collet the Schunk hydraulic system for their Tendo compact tool holders is "allegedly" good to 900 NM torque (roughly 660 ftlbs torque) .

So ^^^ about two minutes in (has English sub-titles) they get a little more to the nitty grittty (ish) - although I don't really agree with their "graphical" representations for how the system really works. Like what @Milland was saying - they seem to be keen to dispel pre-conceived notions of a hydraulic tool holder being actually capable for roughing in tough materials as well as HSS type strategies. + attempt to dispel the idea of excessive angular deviation of the tool axially. [longer tools and or long ADOC ?]

Haimer with a competing Lambda non- pull out system with some sort of helix/key at the end of the shank.

I dunno with grease, and coolant and what not (Europeans seem more keen on (minimum quantity lubrication ~ air brush with olive oil ) + massive cutting forces pullout/ failure seems to be an issue.

I think @Jashley had an idea about simultaneously left and right handed (helices) - cut - end mill (maybe with variable pitch) to balance out pull out problems. I guess like a giant version of a hand held high speed router tool ?


The schunk principal is very interesting to me for other applications. I originally visualized the thinner cross sectioned walls of the hydraulic (cyclidrical) flexture* as a bit like "Wiggle bars" on a regular 2d flexture and the thicker parts of the walls being what is moved. It's a bit like a flexture mechanism (profile) revolved around a longitudinal axis - hydraulically actuated like an old school breaking system on a car i.e. potentially massive forces exerted over a very small distance and massive mechanical advantage (force wise). I guess it would be easy to map out how the contact surfaces actually grip the tool. The inner surface has rings or spiral groove for grease or dirt or lubricants to be squeezed into along the length of the inside "bore" as the walls expand to grip the tool. The animation seems to indicate that the tool is gripped fore and aft and the middle sections creates a relief along most of the length of the tool (not sure that that is really how it goes vis a vis the animation in the video ?).


__________________________________________________ __________________________________


* Building Prototypes Dan Gelbart part 10 of 18 Flexures - YouTube

^^^ The venerable Dan Gelbart explaining flextures...

 

[Stirling]

ill take some time tonight and dig out some photos of previous failgures for you

 

[cameraman]

ill take some time tonight and dig out some photos of previous failgures for you

That would be cool as a lot of folks / "Peeps" on this forum would be able to help you better to find the "Smoking gun"

~ "Ahhhaaa classic ... "

 

[CAMasochism]

That would be cool as a lot of folks / "Peeps" on this forum would be able to help you better to find the "Smoking gun"

~ "Ahhhaaa classic ... "

Operator error.

 

[Stirling]

That would be cool as a lot of folks / "Peeps" on this forum would be able to help you better to find the "Smoking gun"

~ "Ahhhaaa classic ... "

here are some photos of the fretting

changed settings to 500ipm 10000rpm 0.75doc 0.01875woc and ran a few parts today, so far all good, but the mmr sucks at those settings.
if thats all a 3/8 can take reliably so be it lesson learned, but is it????

 

[Milland]

View attachment 327248View attachment 327249

here are some photos of the fretting

changed settings to 500ipm 10000rpm 0.75doc 0.01875woc and ran a few parts today, so far all good, but the mmr sucks at those settings.
if thats all a 3/8 can take reliably so be it lesson learned, but is it????

Try a few using a shrink holder, or go with sidelocks. That fretting is a good clue that there's too much movement in the current holder for reliable rough cutting tool life, in my opinion.

 

[D Nelson]

I think 10 k is to much rippems I would run it 5 k .02 step over 1 1/2 ramp angle 70 inches per minute 400 ipm backfeed and cut all the parts no problem
Don


Sent from my iPhone using Tapatalk Pro

 

[primeholy]

Here is what I would run at. I don't run production, so we dont go balls to the wall, and we like to keep our makino f5 spindles happy.

4 flute
RPM 10701
FR IPM 154
I'd probably do .01-.015 stepover. I run coolant and air blast with 1018 and 4140HT, any of the other tool steels just air blast.

These are my base line numbers for trochoidal high feed milling. My ramp is 2 degrees or less. on ramp in I cut my rpm and feedrate in half approximately


Volumill surface feet

Take recommended surface feet and chip load x3
Surface feet Chip Load (tool diameter x .0032)

D2/M2 260 x 3 x 3
H13 230 x 3
4140 300 x 3
1018 350 x 3
A2 250 X 3
FORGE DIES 200 X 3
S7 215 X 3

4140 (.5) 6879 rpm 160 ipm
1018 (.5) 8025 rpm 190 ipm (.75) 5350 rpm 150 ipm
H13 (.5) 5274 rpm 125 ipm
D2 (.5) 5962 rpm 140 ipm
FX (.5) 4586 rpm 110 ipm
Standard milling
1018 350 sf (.625) 2140 rpm

 

[fmari --MariTool-]

Fretting on the front of the shank and collet is because of movement. Hydraulics do not clamp until at least 3/8-1/2" in the bore socket. Front of the tool holder bore is brazed to the outer nose, so it cannot move or clamp.

This is where shrink win. With shrink you have 100% clamping the entire bore length and 100% all around. The very extreme front of the tool holder is clamping just as hard as the back of the tool holder. Maybe just a little less depending on the thickness at the nose.

 

[zero_divide]

One curious thing I noticed about hydraulic holders is they are not very stiff. I used 2 or 3 different types and they all seemed to allow for a lot more tool deflection. I think this could be due to the fact that while the liquid pressing against the inside of the bore is incompressible, the bore itself is actually rather thin piece of steel tube. So this allows some movement of the shank deep inside the bore.

I find those only good at light to medium roughing. At heavy loads I have seen pull outs.

So either shrink fit, or side lock for heavy stuff.