Struggling to break chips while turning 4130.

[rbeachner]

We’ve had a job in our shop for the last twenty years that requires turning 4130 tubes. (ID and OD) Our surface finishes and tolerances are acceptable, however we’re now adding robotic loading/unloading to a few of our machines, and this job is an excellent candidate for it, provided we can solve our chip (or lack thereof) problem.

We get long, stringy chips that are turning into a rats nest and require manually removing from tools or the workpiece at the end of every cycle. It renders the chip conveyors useless, and we end up having to routinely remove a giant razor sharp tumbleweed from the machine door. I’ve played with the speeds and feeds and achieved tight coils, but can’t seem to get them to just break into a damn chip.

Our setup is as follows;
Haas SL-20

For ID roughing, we have a .750 shank boring bar with a Korloy DCMT32.52-MP (32 nose radius) (NC3225 Grade). Depth of cut is .050”, 480 SFM, Feed Rate is 0.018”, Cut is continuous.

For ID Finishing we have a .625 shank boring bar with a Korloy CCMT32.51-MP (15 nose radius) (NC3225 Grade). Depth of cut is .020”, 550 SFM, Feed Rate is .006”, cut is continuous.

For OD Roughing we’re using a Korloy DNMG432-VM (32 Nose Radius) (NC3225 Grade). Depth of cut is .050”, 800 SFM (Have tried as low as 400, and as much as 1000), Feed rate is .013”, cut is continuous.

For OD Finishing we’re using a Korloy VNMG331-VL (15 Nose Radius) (NC3215 Grade). Depth of cut is .020”, 1000 SFM (Have tried from 600-1300 as suggested by Korloy) Feed rate is currently .005”, (anything over .006” and the finish turns into a record player) cut is continuous.

For the workpiece, raw stock is a 3” long, 1.875” Diameter, and .200 wall thickness. The material is normalized, and has not undergone any hardening/heat treating process.

I’m not married to any specific brand tooling or geometry of insert. I just need to figure out how to make this damn thing make chips so we can run it unmanned. I’m open to any/all guidance, I’ve been banging my head against the wall on this for the last three days, and it’s driving me nuts.

Our Korloy representative has sent us a DCMT with a different chip breaker arrangement, with a NC 3215 grade which he thinks will do a little better, however given the fact that our inserts have all different chip breaker arrangements (MP, VL, VM) I’m thinking that I’m overlooking something here. To make things worse, I am by no means a machinist, a week ago I had no idea what any of the above meant, and I didn’t even know how to modify a program on the control. I’m just the one getting thrown at the challenge as everyone else in the shop is busy with the more immediate money making projects. So, if anyone out there can lend a hand, I’d be very grateful.

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[machinehop5]

...Is the 4130 Steel Certified material? Different supplier?

[rbeachner]

...Is the 4130 Steel Certified material? Different supplier?

Yes it is. US origin, and from the same vendor/mill as always. The chips not breaking is not a new problem, it’s simply just now become a priority to solve the problem. (which, is somewhat embarrassing to admit)

[deadlykitten]

hy, i have solved chip breaking, for some parts, and also handled other machining aspects

i am at work now, will be back 2 u later, tomorow at most

i only replied, as to assure you that i can help, in case you struggle too much with this task, cant sleep haha, is ok

[rbeachner]

hy, i have solved chip breaking, for some parts, and also handled other machining aspects

i am at work now, will be back 2 u later, tomorow at most

i only replied, as to assure you that i can help, in case you struggle too much with this task, cant sleep haha, is ok

Sounds great, I look forward to it!

[machinehop5]

...when you say depth of cut ....is that diameter or per side (radius)?

A good depth is .040/side rough and finish pass....if, machine and tooling geo can handle it..... and a chip load of .010 -.012 rough and .006 finish. SFPM seems a bit high try 400-600

DJ

[deadlykitten]

hy rbeachner medium rpm, and high feed as possible; play with cutting specs for a while, but sometimes, some materials, will only make long chips, and if you push, then insert will break

such situations can be solved with custom turning program, kind of like peck drilling, so contact between insert and material will be intermitent; i can help with programing, generating different codes pretty fast

i dumped into such a thing 2-3 years ago, on okuma machine, for a looooong shaft, where it was not possible to increase the doc, so chips where long and thin ... they would wrap arround the tool like crazy, it was needed to feed hold and clean, like such a waste of time so i coded it differently, and can adapt the result for whatever machine is there, thus there is fast customizable postprocess

how you consider to run that on a robot, means that there are some parts, so you may test and tune to find the best combo; when you only do a part, is enough if it works, but for many, you may adjust for productivity ( day shift ), or longer insert life ( night shift ), etc

please feel free to ask anything recently i did a similar thing for someone else, but implementation was different, not through code, but machine function, like please youtube search "citizen lfv"

[ToolHIT]

That peck turning programming from DeadlyKitten would be ideal, I know many Swiss Machines now offer this and it does work great to break the chips!

That chip wrap is a pain, I always find tubing to be softer and harder to break a chip than solid rounds and there is a huge variance from lot to lot. Your speeds and feeds are right in line with what we would be at, you are definitely pushing the feed rate to help break the chip which is good but your material is just too soft. Here are our suggestions:

-Does your machine have coolant thru and are the boring bar holders sealed on the backside for a coolant thru bar? A Coolant Thru Boring Bar as well as OD Turning Holder will help break the chips. If you don't then here are ways to plum it in from the external coolant ports on the turret. I can send more info on the fittings needed to port it if you like.

-Your Chipbreakers and grades are usually really good choices for 4130 Steels but this lot of steel is too soft and there are series of chipbreakers designed for soft steels with a sharp serrated edge to help break the chips. Many manufacturers offer this (the VL you have coming in is a good option, also see if Korloy has the VB or VC Chipbreaker for the DNMG & VNMG Inserts). If they don't work then here are my top choices to help with chip control that has wrorked well in soft steels):
https://www.toolhit.com/products/tac01866
https://www.toolhit.com/products/tab02211
https://www.toolhit.com/products/tab07650

Hopefully this helps!

Mike

[deadlykitten]

That peck turning programming from DeadlyKitten would be ideal, I know many Swiss Machines now offer this and it does work great to break the chips!

hello thank you ... yes, indeed; is not only gang lathes that do it, but mostly the citizen function is reffered by many as a good example

a bit of trials are required, because too low settings may lead to increased cycle time .... is something like G01 Z10 vs G01 Z0.01 x 1000 times; at such small limits, the cnc machine may succumb, thus real feed is <<< program feed

such motion decay appears at small steps, especially when steps are a fraction of feed/revolution .... however, it can be solved, and is not only good for turning, but good also for deep drilling, as long as the tool won't deviate too much

for some setups, is important to back away the tool more than it advances, like cut 0.15, then back 0.50, etc, thus soft metals/plastics need bigger clearance, otherwise the chip sticks to the tool

anyway, it can be done / kindly

ps : have good sales ToolHit

[John-cbn]

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I am John from China, we are manufacturer of cbn and pcd insert.
If you need any help, maybe we can give you advice.
Contact us at Whatsapp: +86-18282557341
or E-mail: john@meruitools.com