Machine Crashes and Tool Explosions

[AssassinXCV]

Well, i decided to take a look at some youtube videos of industrial cnc machines crashing. You see the tool break in half and fly across the room. Would we have to worry about that with machines at the low rpms that we have? And if we try cutting 1" deep on one pass using an endmill that only has 1/2" of cutters, would the tool snap? (I'm talking about solid carbide endmills)

Enjoy:

Bad programming:

Dont crash your machine infront of the customer:

BTW, anyone here ever get to use one of these 5-axis machines? Looks alot more complicated programming that our 3-axis routers.

[JC50]

I watch American Chopper a lot. They have some of the latest CNC equipment out, and apparently since they are on TV, a lot of it is given to them just for mentioning their name and showing what the machines will do. The Flowjet does some amazing 2D work, and they got a 5 axis machine where they could actually cut design, logos, etc into preformed motorcycle fenders and gas tanks. They dont' mention the CNC programming, other than showing a few snippets of parts being designed, but I remember seeing a MasterCam sign in their shop, (which was also probably given to them). They do some elaborate 3D parts with 3 and 5 axis machines. And yes, they did show a couple of breakdowns where tools and parts were flying around the room. And I normally DVR it, so I can just fly past the heated arguments between Jr and Sr.

[louieatienza]

Well, i decided to take a look at some youtube videos of industrial cnc machines crashing. You see the tool break in half and fly across the room. Would we have to worry about that with machines at the low rpms that we have? And if we try cutting 1" deep on one pass using an endmill that only has 1/2" of cutters, would the tool snap? (I'm talking about solid carbide endmills)

Enjoy:

Bad programming:

Dont crash your machine infront of the customer:

BTW, anyone here ever get to use one of these 5-axis machines? Looks alot more complicated programming that our 3-axis routers.

10 times more people watched the video with the crash than the one he got right?! Funny though...

I actually crashed my machine recently. I made a few BMX chain sprockets out of 6061. Instead of using a ball end mill to bevel the edge of the teeth, I thought it would be easier and faster to iuse a 150 degree v-bit. Thing is, when I cut the sprockets, I had my origin at the center, and for the bevel toolpath, I used a different program, with the origin at the bottom left corner! Needless to say, the first sprocket was ruined!

I haven't but would love to someday, use a 5-axis! I believe the CAM has a simulated model of the machine and its toolholders, and can detect a crash in simulation. It's one thing for a 2HP router, totally different when it's a 40HP spindle!

I've snapped 1/4" endmills clean off when I first started (ran into a fixture bolt on my table at rapids speed.) What makes carbide extremely hard also makes it brittle! And that's with my 2HP router and puny 450in-oz steppers. I can't imagine what 40HP spindle and 2000 watt servos would do!

[AssassinXCV]

Take a look at this 5-axis:

Only $25,000

Started drawing up a similar one in sketchup, maybe make one. You can get those cheap TB6560 5-Axis boards off ebay, but the real issue is some how getting your hands on 5-axis software that doesn't cost a fortune.

[ger21]

If you're cutting wood, broken tools will tend to stay in the wood.

Whether or not the tool will break depends on a lot of things.

I've seen a 1/2" bit push a 4x8 sheet off the table.

I've seen bits still cut while spinning backwards.

If the spindle doesn't stall, a bit can burn it's way through wood. (literally)

If the steppers don't have enough power, they'll stall before a bit may break.

Keep in mind than a 1/8" bit will break a lot easier than a 1/2" bit.

A few weeks ago, I had a 1/2" bit literally disintegrate when trying to cut at 700ipm and 1300 rpm (typo on the rpm). It got less than an inch before it broke into about 20 pieces.

[mlabruyere]

I broke a 1/4 bit into 5 pieces ( I was suprised by this) when I had my safe height set wrong and drug the bit through some MDF at 400IPM rapid....sounded like a gun shot....

[william1384]

I have a small gantry style CNC Router, 12" x 17" cutting area, made from
MDF and Lexan, using small stepper motors coupled to all-thread with
rubber hose, I like using the rubber hose, because if there is a problem
the stepper motor will just spin until the rubber hose lets go, a few times
when cutting, there would be some screw-up and the Z axis would rise to
far, that would cause the rubber hose to let lose, and then Z axis just drops,
and now the router burns into what ever material I am cutting, and now
the X and Y axis are stuck so the rubber hose lets lose on them to, and
shortly there after I have a nice fire.

I do have limit switches, and they work, but at the time I was getting
interference and that was causing me to lose control of one of the Axis,
suddenly and out of the blue, Right and Left or Up and Down are suddenly
only one direction, for example, if the Computer tells the CNC to go
Left it may go Right, and when the Computer tells the CNC to go Right
it still goes Right, so you get Right and Right instead of Right and
Left, it could also be Left and Left, Up and Up or Down and Down.

Turned out to be a USB hub I had next to some unshielded motor
wires.

Fun times

I am now more careful, have my wires sorted a little better, and
even watch my CNC router threw a Web cam, when I have to step
away for a short time