[jnack95]

I am cutting slots in steel approx 1/8" wide and about 3/8" deep (~1in long). I am using short 4 flute carbide endmills (coated and uncoated) with as little stickout as possible and snap them quite frequently. I am taking as little as 0.030" deep passes at 5 ipm. I was doing this fine on an old bridgeport knockoff cnc machine with meshcam and something seems to be much more difficult using my Tormach 1100 and sprutcam. I seem to remember that Meshcam would take a pass and then go back up and cut off the burr before returning and taking the next deeper pass....I think. It seems that when I snap an endmill it *might* be pulling in part of the bur that was raised during the previous pass (on the surface) and chip welding it, then snapping. Anybody know if there is a way for sprutcam to take a pass and go back up and remove the bur before going deeper? Might just be the machine differences make using 1/8" endmills difficult on the Tormach. Any advice is appreciated. Thanks.

[popspipes]

I am wondering why its pushing up a burr?? Sharp new cutter should not push up a burr of any appreciable size.

You didnt specify all the parameters, rpm? coolant?
You say you are using a short endmill, is the cut deeper than the flutes, if so maybe the shank is rubbing. If a chip can get between the cutter shank and the work it can snap the cutter if the shank is running in the cut itself.......

just a few thoughts...

[jnack95]

I am wondering why its pushing up a burr?? Sharp new cutter should not push up a burr of any appreciable size.

You didnt specify all the parameters, rpm? coolant?
You say you are using a short endmill, is the cut deeper than the flutes, if so maybe the shank is rubbing. If a chip can get between the cutter shank and the work it can snap the cutter if the shank is running in the cut itself.......

just a few thoughts...

It's just a regular upcut em and the depth is not anywhere near the flute length. Most of them were brand new before they snapped. It's also just cheap A36 steel (which seems to easily create burs). Forgot speed 5100rpm and coolant is fogbuster with fine mist to blow out chips (20psi). I also hit it with compressed air to blow out the chips sometimes.

[popspipes]

Maybe try some free machining steel........
lighten the doc to .020 maybe.

I think the problem is the steel, if its pushing up a burr with a new cutter, then thats a red flag. The flutes are easily clogged with a cutter that small.

[jnack95]

Yea, it's just cheap steel and a bit gummy, but it's all I can get locally and the shipping charges for ordering small amounts of steel make it too expensive for me. Seems that the slot is slightly larger than the tool and if I select conventional milling in sprutcam it seems to help. When it cuts the first pass it seems to push up a bit of a burr on the side of the tool that would be climb cutting while the side of the tool that would be conventional milling is much less. If I make sure that the side with the burr is removed during the other pass, the problem seems to be less worse.....maybe. Im still trying to figure out what the z-cleanup options in Sprutcam are for (but I've only spent 10 minutes trying to figure it out too). Also wondering if there is any appreciable difference to using the Waterline vs Pocketing roughing program for cutting a slot (or any pocket for that matter). They seem to do the exact same thing and I never use Pocketing. As far as I can tell, the only difference is that using pocketing doesn't allow you to easily break the depth up into number of passes. Anybody know why I should use Pocket roughing?

[popspipes]

You might check with a local machine shop to get a small piece of steel or scrap for a reasonable price.

[SprutCAM_Videos]

Yea, it's just cheap steel and a bit gummy, but it's all I can get locally and the shipping charges for ordering small amounts of steel make it too expensive for me. Seems that the slot is slightly larger than the tool and if I select conventional milling in sprutcam it seems to help. When it cuts the first pass it seems to push up a bit of a burr on the side of the tool that would be climb cutting while the side of the tool that would be conventional milling is much less. If I make sure that the side with the burr is removed during the other pass, the problem seems to be less worse.....maybe. Im still trying to figure out what the z-cleanup options in Sprutcam are for (but I've only spent 10 minutes trying to figure it out too). Also wondering if there is any appreciable difference to using the Waterline vs Pocketing roughing program for cutting a slot (or any pocket for that matter). They seem to do the exact same thing and I never use Pocketing. As far as I can tell, the only difference is that using pocketing doesn't allow you to easily break the depth up into number of passes. Anybody know why I should use Pocket roughing?

Pocketing is a more efficient tool path that you have some control over. Roughing Waterline, you are at the mercy of the operation with retracts and approaches. I tend to avoid Roughing Waterline as there is usually a more efficient way to go about things, even it takes 4 other operations to replace it. Longer CAM usually means shorter run times in my experience.

[jnack95]

Interesting, I'll check it out more. I'm particularly interested in using it to cut slots so I'll see if I can make use of it there.

[Little_Chips]

A couple of thoughts. Is your spindle pulley really on the high speed position? Is the runout of the spindle excessive? Both of these conditions could cause your problem. The parameters you said you are using come off as conservative in my speeds/feeds calculator and has less than .0002" deflection for .5" stickout. If the stickout is .75" then the deflection increases to .000533". Those are good figures to use even for A36 steel.

[popspipes]

I would try some oil for fluid in the fogbuster, water based coolant is good for heat removal but not so good for cutting or tapping.

[jnack95]

A couple of thoughts. Is your spindle pulley really on the high speed position? Is the runout of the spindle excessive? Both of these conditions could cause your problem. The parameters you said you are using come off as conservative in my speeds/feeds calculator and has less than .0002" deflection for .5" stickout. If the stickout is .75" then the deflection increases to .000533". Those are good figures to use even for A36 steel.

I think I figured out my problem was related to a combination of how I was holding the part in the vice and the part geometry. I changed around the cutting order and fixturing method and it seems to be much better now.