First time 304 on PCNC 770. Any good tips?

Like the title says, I am about to cut some 304 stainless with my PCNC 770. I have a 1/2" 4 flute carbide endmill with a TiN coating, and full flood coolant. I am a manual machinist by trade so I am used to being able to feel what I am doing, so I am still trying to learn how to translate that into PathPilot and just my coding in general.

Are there any tips I need when CNC milling stainless with carbide that are different from doing it manually?

First off I would say that unless you are only facing, you will probably find that 1/2" diameter is a bit optimistic for a 770. 1/4" would be a more realistic size if you have the option to change out. One of the benefits of CNC over manual is the machine can move more than one axis at a time reliably. Are you only hand coding or are you able to utilize either the conversational in pathpilot or a cam software? Computer generated code will make creation of toolpaths that utilize the benefits of CNC much easier.

That being said, generally you are either going to be taking large radial cut and shallow axial cut or the reverse. The great thing about CNC is if it takes 25 minutes to run the tool path, you can do something else instead of turning wheels the whole time.

That is already helpful. Yes I do have 1/4" carbide i can use as well. The reason I went to the 1/2" is because the part is 6"x4"x1.5" with a lot to come off to get to size, and coming from a traditional manual machining background, I can just hear my old boss in the back of my head saying “what the F are you using such a small GD end mill for!?” so I am still trying to get out of that head space.

Well, you tell him you are not working with a 20 hp 8000# machine, so you need to use appropriate tooling. Plus 1/4" endmills are a lot less expensive so you can afford the learning curve better.

Are you going to be hand coding your tool path or are you using a computer to help you?

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I will be using PathPilot for my coding for this particular part. I have also started to learn Fusion360 as well.

PathPilot conversation, to be specific.

Oh good. Hand coding would be no fun. The toolpaths available in Conversational should utilize strategies familiar to manual machinists. Fusion has many more toolpaths, but you will need to learn a lot more before you can start making your part. If you don’t have the manual you should be able to find it on Tormach’s website.

I’ve become fairly proficient with conversational machining with PathPilot, using pockets and profiles to get things into the shape I want, but that has all been aluminum with HSS. very very forgiving stuff. this 304 is a new beast so whatever recommendations you have are greatly appreciated. I Have already faced one side and found out that a stepover of 80% made the 1/2" endmill squeel, so I changed to 50% and it liked that a lot more. I am thinking lowering stepover more and increasing the depth of cut to maybe .1" or .125"

I’d recommend checking out ProvenCut or at least check out Library - NYC CNC

SS really wants lots of coolant during cutting.

If you are still runnning the 1/2 em you may want to go down to like .06" stepover. Besides the resources Mike suggested, I have found the IMCO toolbot to be pretty good. If you select their E14 series endmill (general purpose endmill) I have found their speeds and feeds to be fairly reliable . For your machine tell the toolbot you have a 1hp motor. In stainless I ended up using lower rpm to get rid of the squealing.

Luckily I have full flood coolant right on the tool tip, so I am keeping things frosty there. I will for sure check out the pinks you provided! Thank you for the suggestions!

These machines are gonna want to work in WOC of about 10% of tool diameter. If youre using the TTS tooling, long axial cuts will result in tool pullout with larger EM. Your available hp is low even compared to your typ J head kneemill. In 304 i like to use 5 flute stuff when i can. The Kyocera SSG series is very formidable. I would recommend getting used to calculating your feeds and speed kinda backward. It is very important to consider the hp. At work, I will run a 1/2" 6flute SSG at 330sfpm and .003" pet flute at 1.5x diameter axial depth and .05 WOC. That would be pulling 98% of availible hp. Thats not a good place to be. This would definitely result in pulling the TTS out of the collet Also. Reduce the depth to .5" and WOC .04" while leaving RPM and Chip load the same and your more like 52% hp usage. I like to be maxed at 80%. IMO, 1/2" is too big for even the 1100 machines in stainless. My 1100 loves 3/8 EM. Ultimately, youll have yo make some cuts on some scraps and take notes to get it primo.

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