We are machining stress relieved gray iron plates 28" x 34". Using a Doosan 750/50 II 8K with a 4" facing cutter head and are removing approximately .125" per side in two passes running dry, no coolant. The plates finish at 1.000" +/- .0025, flat .005", Par .002". We are getting a fair amount of movement of the plates when released from the magnetic table.
Anyone in the Titan Brain Trust have any suggestions? Thanks.
@ScottDennison if the plates are not flat to begin with the magnit will pull the plate in a bow. You can take the raw stock to a surface plate and shim it until it is flat mark were shims are then transfer it to machine. If the plate has .005 bow use .005 .003.001 as they fit. You may have to repeat the process after taking a skim cut.
So after taking the first skim cut put that side down and shim it and cut the back side. It usually takes 3 cuts to get something flat.
Thank you, Sir. That is what we are having to do. The material is very inconsistent before we even start. Our plan is to use the Doosan for roughing and then finish in a Blanchard. We are just getting more movement and inconsistency in the raw material than we anticipated. Do you think we are imparting any stresses by using the mill? We were roughing in a Blanchard but need greater through put.
@ScottDennison short answer is yes.
Anytime you introduce Heat to a part you can create or relieve stress.
I feel as though I have cut my share of cast iron don’t wish to cut any more. My question to you is why are you not using coolant? This can help keep the stress down. I assume you have coolant in your Blanchard. I understand that with cast it can make a muddy mess. While the majority of the cast iron I have cut was on manual machines like a large duplex Milling machines we cut it dry. But for the lucky folks that got to operate the CNC machines they had some coolant. Granted you have to have the proper coolant for cast iron. My comments are only relative to my past circumstances. I do not know what your setup is specifically.
Thank you. We are a Blanchard grinding shop with 10 machines from 42" chuck diameter to our monster 200" machine, the largest in North America. We primarily grind A36, tool steels, and cast iron. One of our top customers has a foundry cast these plates in a few different sizes and our thought was to dedicate two machines to them because of the quantities run. The decision was made to purchase the Doosan milling center for roughing the plates and then pair the Doosan with a CNC modified 48" Blanchard. The thought was to rough mill in a more efficient manner than roughing on another Blanchard and reduce the finish stock to a minimum for the finish grind. With the Doosan and the new Blanchard we could also attract operators that were CNC qualified and not manual Blanchard operators…a dwindling work force.
I guess I do not know enough but have been told coolant with machining cast iron causes thermal shock cracks and running dry does not. Most of the insert reps reiterate that and recommend their specific inserts designed to be run dry. Even Titan’s video of face milling cast iron shows running without coolant. So the bottom line is we are open to all input and the reason I reached out to the forum and people with more experience for advice.
My cast iron expens is from 25 years ago so that being sed, how they did things then is not how it’s done now.
I always ran cast iron and graphite with no coolant. I did use an air blast coolant system when I was machining deep pockets in cast iron, for chip removal.
We run the spindle air along with air through the adjustable coolant tubes for clearing chips.