Advise Needed

[glbreil]

I am cutting shapes out of 3/4 thick mild steel using a MillPort Rhino 40B bed mill. One pass around my shape is about 40".

My question is your recommendation on tooling, cutting speed and feed, etc?

My last I have cut with a 3/8 carbide end mill in 6 passes 1/8" deep each. It is slow and I have broken some end mills as well.

What can I do to speed up the process?

Thanks in advance! Gary

[lakeside]

CARDIBE WILL BREAK VERY EASY YOU MAY WANT TO FIRST USE A RUFFING MILL LEAVE .03 ON SIDE FEEDS AND SPEEDS WITHOUT KNOWN SETUP AND MACHINE RPMS IS JUST GOING TO BE A GUESS I CAN GIVE YOU THE DEFUALT VAULS BUT ITS A STARTING PIONT HERE A LIKE LOOK FOR RUFFING MILLS IN THIS SITE WWW.MSCDIRECT.COM BALL PARK 500 RPMS 4IPM FLOOD COOLANT

[Ken_Shea]

Gary,
What speed and feed, number flutes, coolant were you using?

Breakage does not necessarily mean you are feeding to fast, but that RPM may be set too slow for that feed.

Also carbide can take quite a bit of heat but will trashed quickly if suddenly cooled while hot.



Ken

[One of Many]

One option. Send them out and have the shapes plasma, laser or water jet cut if this is cut all the way through your plate. The cost is nothing compared to the time spent turning it into chips that could be used more wisely. Have them cut oversize if a machined edge is required. Finish them off with a larger cutter.

Rough guess for a 3/8" 4flute endmill. 800-1100rpm at .002 chip load feeding at 4-8 in/min(my experience says 2-4in/min would be more realistic for a full width cut at .125). Flood coolant you might be able to push it twice as fast on rpm so that feed rate would be likewise.

DC

[dertsap]

do you have an insert mill to do the roughing then use your carb. em to finish , i would never recommend hss cutter on steel
verimill makes some tough carbide endmills you can run them much faster and harder, try high helix ,

[glbreil]

I was using a .375" 2 flute mill at 900 rpm and 1.7 feed with mist oolant to help blow chips away.

I may have made it sound as if breakage was a real problem. Not really to bad it is just not very forgiving. If anything goes wrong it breaks.

I thought I might be able to move faster by using a larger size mill that could be pushed a little harder. Just not sure of the best option.

"One of Many" may be right on sending them out, but then I wouldn't be making them and thats what it is all about. Right?

Thanks Gary

[Ken_Shea]

From my what I am seeing on speed and feed specs you should be able to double the RPM and feed, You are correct, as a rule of thumb always use the largest cutter you can, also a 4 flute will give better performance on steel. Check to be sure the cutting edges are still sharp.

but then I wouldn't be making them and thats what it is all about. Right? Well, that does seems right but does not always offer the best return of time / money, but that is what it is all about to most of us most of the time.
It goes against the grain to purchase all that equipment just to have someone else make something, I agree.

[glbreil]

You mentioned speed and feed spec's, where can you find some rules to govern your settings. For instance I have a publication that says for mild steel to operate at approx 90 sfm which is what I was shooting for. But as for the depth of cut (.125) it was just a guess. Is there something out there that puts all that information in one place?

Thanks Again Gary

[Ken_Shea]

Gary,
For me MEPro has been one of my most used tools.
There is also a lot more to this software then feeds and speeds.
It is usually on the conservative side with regards to feed and speed results, which I like, keeps me out of trouble while I gain experience

http://www.cncci.com/products/cncmepro.htm


Ken

[One of Many]

Originally Posted by Ken_Shea but then I wouldn't be making them and thats what it is all about. Right? Well, that does seems right but does not always offer the best return of time / money, but that is what it is all about to most of us most of the time. It goes against the grain to purchase all that equipment just to have someone else make something, I agree.

Yes, I would also agree that it is questionable to send them out, but the idea was to save cycle time. At 1.7in/min the cycle time 20+ minutes per pass times what 7-8 passes? That is better than 160min/part. The cost of outside time would be 30 min/part or less on more suitable equipment.

With material removal rates, it does not always pay to use a larger cutter on 2D profile cuts. When the cutter diameter goes up the surface speed does too. If the RPM must go down to maintain relative SFM, the feed rate may not compensate to make up for the loss in RPM. Besides the fact that you are also taking more material out to make the same part. It sure wouldn't hurt to try a 1/2" 4flute just to see how hard you can push it.

I do not think a mist coolant to be thick enough for cutting steel or carry away enough heat to be very effective if you expect better efficiency.

DC

[dertsap]

http://www.hanita.com/us/HAN03040B-Varimill.pdf

check these out they will by far out perform most endmills out there , we use them on some ugly materials and they hold their own ,