Carbide inserts vs. Ceramic

[nitro]

Hello,
I'm presently trying to do a tool study for a company which makes cast
iron flywheels. The castings come in from the foundry in very
irregular shapes and sizes. The previous engineers started using
ceramic inserts (silicone nitride) for the cnc turning operations. The
problem is, these inserts give no warning when they are failing and
when the break, you not only lose the tool but we have had 150 lbs
casting fly out of the jaws!!!! Every salesman I talk to has a
different approach to using these inserts and I can't seem to get a
straight answer. Are these inserts for roughing or finishing? Does
anyone out there have any experience using these type of inserts for
cast iron turning applications? Any help would be appreciated.
Thanks

[Ed Huntress]

Post by nitro
Hello,
I'm presently trying to do a tool study for a company which makes cast
iron flywheels. The castings come in from the foundry in very
irregular shapes and sizes. The previous engineers started using
ceramic inserts (silicone nitride) for the cnc turning operations. The
problem is, these inserts give no warning when they are failing and
when the break, you not only lose the tool but we have had 150 lbs
casting fly out of the jaws!!!! Every salesman I talk to has a
different approach to using these inserts and I can't seem to get a
straight answer. Are these inserts for roughing or finishing? Does
anyone out there have any experience using these type of inserts for
cast iron turning applications? Any help would be appreciated.
Thanks

FWIW, I think that trying to gather info on these inserts by means of
individual examples is a very, very long and hard way to do it.

I'd start at the other end, at the insert manufacturers. After you hear from
them, check with some of their users. And then fish around among other users
on your own, as you're doing here.

I've written many reports on inserts and applications over three decades,
and that's the method I've finally come to use. You're getting into an area
where new developments in both ceramics and in carbides can put a whole new
complexion on things. There are tougher ceramics than there were a few years
ago and there are coated carbides that can stand up to the initial cuts on
cast iron better. You'll find that production turning in cast iron sometimes
is done at upwards of 3,000 sfm today.

Good luck.

Ed Huntress

[Santa Cruz Shop Dog]

On Mon, 19 Apr 2004 04:16:53 GMT, "Ed Huntress"

Post by Ed Huntress

Post by nitro
Hello,
I'm presently trying to do a tool study for a company which makes cast
iron flywheels. The castings come in from the foundry in very
irregular shapes and sizes. The previous engineers started using
ceramic inserts (silicone nitride) for the cnc turning operations. The
problem is, these inserts give no warning when they are failing and
when the break, you not only lose the tool but we have had 150 lbs
casting fly out of the jaws!!!! Every salesman I talk to has a
different approach to using these inserts and I can't seem to get a
straight answer. Are these inserts for roughing or finishing? Does
anyone out there have any experience using these type of inserts for
cast iron turning applications? Any help would be appreciated.
Thanks

FWIW, I think that trying to gather info on these inserts by means of
individual examples is a very, very long and hard way to do it.
I'd start at the other end, at the insert manufacturers. After you hear from
them, check with some of their users. And then fish around among other users
on your own, as you're doing here.
I've written many reports on inserts and applications over three decades,
and that's the method I've finally come to use. You're getting into an area
where new developments in both ceramics and in carbides can put a whole new
complexion on things. There are tougher ceramics than there were a few years
ago and there are coated carbides that can stand up to the initial cuts on
cast iron better. You'll find that production turning in cast iron sometimes
is done at upwards of 3,000 sfm today.
Good luck.
Ed Huntress

Are the problems documented so far as run time, failure, etc etc..
casting lot number, operator, etc... machine...

If the tooling reps can't give you the right answer change reps?

Are the castings consistent in quality?

Are each model and variation of the casting consistent?

Are the casting runners and sprues sawcut of machined off and
consistent in size?

Are we talking sand castings?

Using ceramic inserts requires a high quality consistent casting.

Are the inserts changed on a regular schedule? Or are they changed
when the cutting load increases? etc etc..

Is the machine tool and chuck rigid enough for ceramic?

Is the turret still on center after all the crashes?


Are you using low pressure coolant, high pressure or dry?

It was a long time ago.. and ceramic inserts are much better now.. but
at Baker Oil International we roughed with coated inserts with a
carbide substrate for toughness, and finished with ceramic. A lot fo
the castings interrupted cuts, and were meehanite. The machines were
light JBL 312 and 412 Combi's etc..

Do the casting need to be stress relieved or annealed before you
machine them?

Do the castings have foreign objects inserted to chill certain areas
for detail, filling etc ... where you are machining?

Mike

[Lewis Taylor]

Post by nitro
Hello,
I'm presently trying to do a tool study for a company which makes cast
iron flywheels. The castings come in from the foundry in very
irregular shapes and sizes. The previous engineers started using
ceramic inserts (silicone nitride) for the cnc turning operations. The
problem is, these inserts give no warning when they are failing and
when the break, you not only lose the tool but we have had 150 lbs
casting fly out of the jaws!!!! Every salesman I talk to has a
different approach to using these inserts and I can't seem to get a
straight answer. Are these inserts for roughing or finishing? Does
anyone out there have any experience using these type of inserts for
cast iron turning applications? Any help would be appreciated.
Thanks

Ceramic inserts can handle the extreme temps of turning cast iron
without thermal deformation occurring , which is a property of ceramic .
The other property of ceramic is that it has almost no impact resistance ,
and thus when the insert comes to an intermittent cut it shatters .

Carbide has a greater impact resistance but has a much lower thermal
deformation resistance . So when the carbide gets hot , thermal deformation
causes the insert to fail .

Your tool reps should be helping here , this is not the type of shit you
just guess at .
Possibly try rough turning the profile first , paying close attention to
amount of stock
left on diameter and in shoulders . Believe me , taking that little bit more
time to program
a kick ass roughing cycle will help you a lot . To much stock in the
shoulder will cause the finish
insert to bite in and move , plus a plethora of other probs .

Number one issue is does the workpiece have intermittent sections , such as
cross holes , hex profile ,
etc ? If so , then when your ceramic finisher comes to these sections it
will shatter !!!!!

Coolant is another concern . Intermittent supply of coolant to the workpiece
causes massive rises and
falls in insert temp , are you using oil or water soluble ?


Lewis

[Michael Rainey]

Post by nitro
Hello,
I'm presently trying to do a tool study for a company which makes cast
iron flywheels. The castings come in from the foundry in very
irregular shapes and sizes. The previous engineers started using
ceramic inserts (silicone nitride) for the cnc turning operations. The
problem is, these inserts give no warning when they are failing and
when the break, you not only lose the tool but we have had 150 lbs
casting fly out of the jaws!!!! Every salesman I talk to has a
different approach to using these inserts and I can't seem to get a
straight answer. Are these inserts for roughing or finishing? Does
anyone out there have any experience using these type of inserts for
cast iron turning applications? Any help would be appreciated.
Thanks

Look into Kennametal's Kyon line of inserts to get the high SFM advantages
of ceramic along with greatly increased impact resistance. They can really
work well, within reason, for interrupted cuts in cast iron.

[john]

Post by nitro
Hello,
I'm presently trying to do a tool study for a company which makes cast
iron flywheels. The castings come in from the foundry in very
irregular shapes and sizes. The previous engineers started using
ceramic inserts (silicone nitride) for the cnc turning operations. The
problem is, these inserts give no warning when they are failing and
when the break, you not only lose the tool but we have had 150 lbs
casting fly out of the jaws!!!!

they must not be clamping it right. when they fail the usually just
start to run hot and make an ungodly noise rather than a nice hissing sound.


Every salesman I talk to has a

Post by nitro
different approach to using these inserts and I can't seem to get a
straight answer. Are these inserts for roughing or finishing? Does
anyone out there have any experience using these type of inserts for
cast iron turning applications? Any help would be appreciated.
Thanks

IF you got intermittent cuts and got hard cast you might spring for a
solid round cbn coated insert. Borizone is what i would use... start
with a low speed of 100 sfm and work up if you got a lot of
intermittent cuts you got to go slow. Also pregrind the starting edge
of the intermittent cuts if it is allowed so the insert sneaks up to a
full cut and doesn't hit solid ....all depends on how much crap is in
the casting. The inserts are pricey 150.00 but they will hold up
better.


John

[Kirk Gordon]

The best results I've had in a similar situation involved using BOTH
kinds of tools. I had to turn a nasty casting to some close tolerances,
and with some very demanding surface finishes. I used the biggest,
thickest carbide insert I could find, with the biggest nose radius
available, and made a first cut on the part just to clean off the skin,
knock down the bumps, and make the work fit to turn with ceramics.
Then, having prepped the castings that way, I did all the rest of the
work with ceramic inserts at super high speeds. The key to this plan
was that the carbide inserts did only one cut around the work. They
didn't last very long (in terms of total minutes or inches of cutting);
but they paid for themselves many times by letting me get good quality
and quick cycle times from ceramics that didn't get powdered by the cast
surfaces. And, because the carbides only had limited work to do, and no
tolerances or finishes to worry about, they lasted plenty long enough in
terms of the number of parts they'd make.

KG
--
I'm sick of spam.
The 2 in my address doesn't belong there.

Post by nitro
Hello,
I'm presently trying to do a tool study for a company which makes cast
iron flywheels. The castings come in from the foundry in very
irregular shapes and sizes. The previous engineers started using
ceramic inserts (silicone nitride) for the cnc turning operations. The
problem is, these inserts give no warning when they are failing and
when the break, you not only lose the tool but we have had 150 lbs
casting fly out of the jaws!!!! Every salesman I talk to has a
different approach to using these inserts and I can't seem to get a
straight answer. Are these inserts for roughing or finishing? Does
anyone out there have any experience using these type of inserts for
cast iron turning applications? Any help would be appreciated.
Thanks

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[PrecisionMachinisT]

Post by Kirk Gordon

Post by nitro
Hello,
I'm presently trying to do a tool study for a company which makes cast
iron flywheels. The castings come in from the foundry in very
irregular shapes and sizes. The previous engineers started using
ceramic inserts (silicone nitride) for the cnc turning operations. The
problem is, these inserts give no warning when they are failing and
when the break, you not only lose the tool but we have had 150 lbs
casting fly out of the jaws!!!! Every salesman I talk to has a
different approach to using these inserts and I can't seem to get a
straight answer. Are these inserts for roughing or finishing? Does
anyone out there have any experience using these type of inserts for
cast iron turning applications? Any help would be appreciated.
Thanks

The best results I've had in a similar situation involved using BOTH
kinds of tools. I had to turn a nasty casting to some close tolerances,
and with some very demanding surface finishes. I used the biggest,
thickest carbide insert I could find, with the biggest nose radius
available, and made a first cut on the part just to clean off the skin,
knock down the bumps, and make the work fit to turn with ceramics.
Then, having prepped the castings that way, I did all the rest of the
work with ceramic inserts at super high speeds. The key to this plan
was that the carbide inserts did only one cut around the work. They
didn't last very long (in terms of total minutes or inches of cutting);
but they paid for themselves many times by letting me get good quality
and quick cycle times from ceramics that didn't get powdered by the cast
surfaces. And, because the carbides only had limited work to do, and no
tolerances or finishes to worry about, they lasted plenty long enough in
terms of the number of parts they'd make.

Hi, Kirk....

Daww gone it, I love you and yer posts, but you ever think about maybe not
always top-posting sometimes?

Use a fricking c2 grade carbide to get through the skin.

Tougher than nails.

If ya want to see whats going on, then get a coated grade, that way when the
coating wears thin, ya know its not gonna last much longer. And in
production it will almost certainly get more parts per edge.

If ya can chamfer the work first with a tough grade, and then get under the
scale with a ceramic, and without an interrupted cut, then more power to
you.

Still, I prefer to send the stuff to a competitor shop, or to some third
wirl country, it makes such a mess, and the wife simply dont like it when
THAT happens.

[Cliff Huprich]

Post by nitro
I'm presently trying to do a tool study for a company which makes cast
iron flywheels. The castings come in from the foundry in very
irregular shapes and sizes.

First gain control of the castings, IMHO.

You may then wish to do a slight roughing operation with (C2?)
Carbide
before doing much more processing.

[Michael]

Post by nitro
The castings come in from the foundry in very
irregular shapes and sizes.

This can be caused by a few things, check the integrity of the tooling
first. Check with the foundry to see if the sand mold has adequate
squeeze pressure to form a sound sand mold. If the tooling is bad it
should be repaired or replaced, repair is usually all it takes vs buying
all new tooling. If there are molding sand problems some type squeeze
pressure feature can be added to the existing patterns to create a
firmer sand mold. If you pour molten iron into a sand mold that is not
firm enough, the sand can wash out and/or "give" to allow what appears
to be swollen or sunken irregularities in the finished casting.

Post by nitro
The previous engineers started using
ceramic inserts (silicone nitride) for the cnc turning operations. The
problem is, these inserts give no warning when they are failing and
when the break, you not only lose the tool but we have had 150 lbs
casting fly out of the jaws!!!! Every salesman I talk to has a
different approach to using these inserts and I can't seem to get a
straight answer. Are these inserts for roughing or finishing? Does
anyone out there have any experience using these type of inserts for
cast iron turning applications? Any help would be appreciated.
Thanks

At our gray iron foundry, our machining operations tested ceramic after
ceramic insert. Ceramics always do well right up until they break, ugh.
Then add tool holder cost to the ceramic insert cost. We eventually quit
with ceramic and stayed with carbide using a "flood" coolant to avoid
thermal shock. I prefer carbide tools any day over ceramic. Remember,
the sales guys "wish" to sell ceramic for a rea$on.
As for machining cast iron successfully, bury the carbide insert tip,
skimming along through the crust is a tool killer no matter what kind of
insert you are using.
Michael