ductile cast iron

[sureline67]

any tips on machining ductile cast iron from gray cast iron relating to speeds and feeds and chip load

 

 

[crazy^millman]

Follow what the Tool manufactures give you for speeds and feeds. Every manufacture has these charts. Take the time to familiarize yourself with them. 

[JoshC]

2 hours ago, sureline67 said:

any tips on machining ductile cast iron from gray cast iron relating to speeds and feeds and chip load

 

 

what kind of Lathe are you working with? just kidding, its a mill right? but seriously with a question this vague how can we help. We dont know if your on a lathe or a mill, if its a rigid setup or not, if tooling is insert-able or solid carbide, if you want to dynamic mill or traditional mill. Therese just too many unanswered questions to give you any advice but your tool vendor as ron mentioned is the best source for this data because an endmill from one tool vendor uses different SFM and FTP than the exact size tool from another. two identically sized tools could cut completely differently from 2 different tooling vendors, one might be double the cost and might perform twice as efficient  as another vendors tooling depending on coatings and the tooling geometry (like chip breakers, variable helixes, variable pitched flutes, etc.). some of the proprietary coatings they put on tooling also make a Huge difference in price and performance and a tools coating can really set one tool apart from another. another obvious factor in SFM and FPT or RPM and IPM is fixture/tooling rigidity, tooling and fixture rigidity is always a big concern when deciding on speeds and feeds because some of us push the limits of machining when it comes to work holding, for example i have held parts in vices with as little as .03" of material in the vice and on that job i was running a small fraction of recommended speeds and feeds to prevent the part from pulling out.

 so ultimately we are happy to help if you have questions but its a bit too vague to answer yet.

[JoshC]

also if it is a mill, and if it is a solid carbide tool, I would dynamic mill it and would be looking somewhere in the ball park of what i show below for Speeds/feeds/stepover/depth of cut.

disclaimer: i made a few of assumptions for the calculation below so these may not apply to your application.

[jeff]

Ductile sucks because it has some serious stank to it when you machine it.

Other than that, it's gravy.

[Wargo]

I'm in the same boat here. The shop I'm at cuts mostly cast iron with conventional methods. Since we're pretty old school we use ALL cast parts. Not a single part is made from bar stock.

 

We run a variety of parts through some HAAS VF-2's, VF-4's, VF-6's, a few large Mitsubishi HMC's, and and large MAZAK HMC. Because we're a production facility and work solely from castings we have an extensive inventory of fixtures. This means that essentially every part requires a full change over. 

 

In my opinion, the change overs and setup time could be reduced by swapping a lot of our parts over to bar stock. My boss doesn't seem too on board with this idea, solely because it will increase machining time. He also has never used Mastercam or dynamic milling. He calls a dynamic toolpath a circle thingy.

 

In order to woo the crowd, I need to find the most efficient way of removing massive amount of stock. There a lot of parts that wouldn't require this, but one of our large parts would need up to a 14" X 6" X 4" area cleared out.

 

It has a "leg" that sticks out 4" and can't be welded on or fastened. It currently goes through a registration operation on a VMC, and then two pallets on one of the HMC's.  Because these parts have to be machined in pairs (left and right hand symmetrically opposite) it takes 10 setups through the process. If I do this from stock I could do it all on one pallet without the pre-machining on the VMC. But, they're still skeptical since it'll add overall machining time. 

 

Can you guys weigh in on this?

[crazy^millman]

Look into probing and using a fixture that allows you to machine as many features at one time as possible. With the HMC you should be able to make match pairs in 2 setups. Will take some work up front coming up with a standard process to match, but you should have enough history to make that happen on these parts. You know what your key features are so make that the starting point for your revamping of the process. Might consider going back to the foundry and asking them to leave stock in the difficult or more free areas that allow you the ability to make them match sets. Sorry, but I am going to agree with your boss the why you thinking seems logical and keep thinking the way your thinking.

However to that lets open the thought to a different direction all together. I have cut castings that were originally designed in the 1850's and for 50 years they had a problem with one set of shaker boxes over heating. I was not aware of that when I questioned the machining process back in 1994 at a place I worked. I was converting the manual machining of the shaker crank to a CNC machining process. I was checking the journal tolerances to the specifications called out by the bearing manufacture and it was wrong. The print made in 1928 called out for journal size that was .0013 bigger than the high tolerance for the bearing. After some arguing and being called stupid the owner of the shop he finally called the customer to teach me a lesson. The customer was his a company his son was working in and he came along with their President. The son start ripping into me about how they have made these parts since 1850 and this print was from 1928 and how dare I question it. My owner is laughing and drawing up my pink slip. The President of the company we were doing work for just looked at me and said that explains why this unit has been over heating some times for the last 50 years. My owner and his son both had nothing to say and I explained to everyone what the specification of the bearing manufacturer called out and how it looked like to me someone transposed the number the wrong way at some point as the low number was the high and the high number was the exact opposite of what should be the low number. If someone had made them at the prints low the bearings were tight, but within the specification of the bearing manufacture so probably over the years the tribal knowledge was keep it to the low side of the print of even couple tenths under and all is good. The President called one of their Draftsmen and had him work on a new drawing to send over and I kept my job. My point is I have never been afraid to do the right thing and you thinking correctly to do the right thing so I applaud that. Many factors have to be cosndiered going from a casting to a billet. Yes it would be fun to program and fun to machine, but many other things have to go into the equation. Weight of the billet. The chips, the base material and other things that have to be considered. By thinking about how to machine them smarter you might accomplish what your after and revamp the process without having to make them out of billet.

[Wargo]

Thank you for the response. It's encouraging to hear someone have courage in what they believe is right, regardless of what the outcome is. 

 

I agree that billet may not be the right choice, and altering the casting could prove successful. I'll keep brain storming. I'm all about continued education and I never plan to stop learning and pushing myself.

[crazy^millman]

On 1/22/2020 at 11:49 AM, Wargo said:

Thank you for the response. It's encouraging to hear someone have courage in what they believe is right, regardless of what the outcome is. 

 

I agree that billet may not be the right choice, and altering the casting could prove successful. I'll keep brain storming. I'm all about continued education and I never plan to stop learning and pushing myself.

That is kind of my attitude I am always learning and trying new things. Don't be afraid to make mistakes and fail. Edison learned many ways not to make a light bulb before he got it correct. Had he quit like a majority of people do after he didn't get it right the first time who would have been the person to figure it out and have their name be known as the one who created the light bulb? We are not changing the world with what we do, but sometimes when you figure out or do that one thing no one thought was possible it is rewarding.

I did broaching on a Vertical Mill/Turn last year for a Major Aerospace Company. I had many different ones telling me it wasn't possible and it took 3 different tools before we got it dialed in. The Verification software wasn't supporting the process correctly and I had to keep working my way through different issues, but once it was all said and done that part was beautiful and to the print. I showed them that 50 years of doing something could be improved. What I showed them has now becomes the new de-facto standard for doing the broaching.

I did a project for a different Aerospace Company about 5 years ago that took a part that was taking over a 100 hours and needed 5 different machines down to one machine and no outside process to grind in the 4-8 um areas on the part. That one part was a $2.3 million ROI over 5 years verses the methods they were using before I did that work.  Same company I took the roughing of a part and reduced it from 100 hours down to 40 hours. I am thankful to have been given the talent and ability the Lord has blessed me with. My advise to you is keep trying and exploring better ways in the long run you will grow in doing so.