Broke a bit, have a question

[mblackwell1002]

I broke the .125 straight bit that came in the desktop starter bit kit. I carved the sign below with the v-carve bit first. I made the profile of the plaque by having the v-bit cut @ .5 depth "on the line" and then switching to the .125 straight bit "outside the line" to do the through cut.

I broke the bit during the bit change routine. When the v-bit was finished I was prompted to change the tool. Using the keyboard, I raised the Z axis to accommodate the tool change. Then I followed the prompt to re-zero the z axis. When the zero-z routine finished, the machine traveled to the profile cut, and plunged the bit into the work, shattering the bit. It then gave me the prompt to start the router...

I think this happened because the .125 straight bit is longer than the v-bit. But I am not sure.

So, my question is... is there a way to change the code in the tool-change routine so that It does not plunge prior at the end of the the routine? If not, how do I avoid this in the future?

I have attached the picture of the plaque, but the spb file was too big.

What are your thoughts?

-Matt

[kurt_rose]

Check you step down for the endmill in the tool data base. Sounds like it may have plunged to far before it started it's travel. An straight bit shouldn't exceed it's diameter or even half it's diameter in the stepdown box depending on the material your cutting. Keep in mind I'm still considered new in the Shopbot CNC world, but I have a bachelors in bit breaking!

[myxpykalix]

So the prompt to START the router came AFTER you started the toolpath in motion?
I would not have used the 1/8th" bit for the cutout. I would use a .25 bit for cutout especially on mdf. Also your feeds and speeds would be a factor along with cut depth.

It almost sounds like you maybe didn't get a good "RE Z'ing" of your smaller bit because it went down too far according to your explaination. Like he said check the cut depth in the tool menu to see what it was set at. Maybe a combo of a couple things caused this.

But don't worry, you're not the first guy to break a bit, and won't be the last. It's almost considered a badge of honor to break a bit here. You're truly not considered a Shopbotter till you break your first bit:rolleyes:

[gc3]

ck your clearance heights in the material set up box rapid z gaps clearance z1 plunge z2

[Joe Porter]

In your profile toolpath, did you figure a "Lead In" or "Ramp" to lower the bit into the material? This is in the PartWorks porogram down at the bottom right before you hit "Calculate"....joe

[adrianm]

See my reply in this thread - http://www.talkshopbot.com/forum/showthread.php?t=16596