[Andre' B]

Even with a proven program you still need to make sure your work offsets and tool comps are good the next time you set the job up or even change a tool while running.

I rarely use jog for the Z axis and never for a minus Z move, always use the MPG for that. Have even considered removing that button from the panel.

[bremenrules]

Always do a simulation beforehand, especially if the offsets have been changed. I note the min/max Z-height on each tool (the simulator tells that) and jog each individually to see if everything looks clear. It's prevented dozens of crashes. My advice:

-- Keep those rapids and feed overides SLOW the first time you do a part or change a tool.
-- Don't work with interruptions. No conversations...no radio blasting books-on-tape, etc. I nearly lost my hand on a surface grinder because I was too busy chatting with a buddy about something to pay attention.
-- Trust your instincts.
-- TAKE YOUR TIME. If you don't have the time to do it right in the first place, where will you get the time to do it again because something was overlooked?
-- Don't give up. You're asking for advice, which makes you a better craftsman than most.

[bookwurm99]

one good idea is to let somebody who knows what they are doing check the program and watch what you are doing. they can also help you get in to a routine of what to do when you start to set up a part. also works when you get a little more experienced and are running more expensive parts and/or programs that you are unsure of or towards the end of the shift or when you are the most tired.

in my operation of turning centers and machining centers classes my teacher would zero all of the offsets for every tool and we had to reset them every time. took for ever but we were always right with tools. we also had two other classes that used the machines earlier in the day and on other days of the week. i think my teacher also gave us a test setting the tools and having it in distance to go and stopping at least 2" above the part.

bookwurm99

[neilw20]

You cant be a machinest without scrapped parts here, and broken tools there. My first few months in my newest job I scrapped a $600 z setter, $300 octamill, countless collet holders and collets, over 100 E/Ms and drills, and alot of parts. This was just in my first few months. Now my numbers are down, but you gotta realize that there are hundreds or thousands of characters in programs. A zero here or a decimal there can be the difference from .05" and 5" deep. Proof slowly at slow rapids, dont use live parts (make a test piece out of aluminium), and always double or tripple check everything you do. Remember that 300ipm is a blink of an eye away from a trashed part.

Do your first run with a chunk of wood.
More speed, less haste.
Do the ABC.
Accept nothing
Believe Nothing
Check Everything.
Measure twice. Cut once.
I've only kill three cutters all under 1/4" in 3 months on a new machine.

[M-man]

I did mess up a live tool holder in the lathe, cost of $3600 and two of the jaws were nocket out, safety glass got a crack and the main spindle had to be aligned..the tool that collided were the tool positioned next to the tool that were cutting. I knew that it were some risks with the interferance, I had the hand on the feed control and were ready to slow it down if I heard any noise from holder contacting the jaws, but in on mili sec, the chuck took the toolpost from x250 ro x0 and I almost did it in my pants. I am a trained cnc-operator with experience, so there not only new guys crasching stuff. But luckely for me I live in swe and there are no way to get fired or something like that.

[Geof]

Reading through all these posts I have not seen anyone suggest using graphics to find out where the machine is moving to. Maybe on most machines this is not possible but I do know on a Haas it is possible to step through a program in graphics and have the machine coordinates displayed. It is a simple matter to write these down for the moves that take the tool close to the chuck, or a vise or fixture. Then using handle jog with the spindle stationary move the machine carefully to these coordinates and make sure nothing is going to hit before getting there. It is a hell of a lot better to rotate the chuck by hand and find it is going to hit a tool holder than it is to ram the toolholder in to a rotating chuck no matter how slow you have the rapids. If a machine can do a graphic display with machine coordinates there is absolutely no excuse for crashing anything.

[neilw20]

After loading a program in Mach 3 you can display the minimum and maximum of each axis in one of the screens. Check that for unexpected silly numbers.
Zooming back on the graphics view (use ortho graphic display so silly Z moves are displayed) will show wild vectors. Combination of double clicks and the scroll mouse wheel will eventuall display the lot. Makes sure you have a scroll mouse.
Single stepping through the code, using the down arrow in the scroll bar, shows each move hilighted on the graphics. Look especially for long/unexpected ones.
G0 rapids are a different color to G1 programmed feed ones.
This is a quick and easy first check of a program. Also easily picks up crop-circles cause by selecting wrong circle direction for an arc.

[MASTERCAMMASTER]

Good thing you are not an electrician, you would be electrocuted by now, or the place would be burned down.
If you crash any machine you don't belong on it, without training.
Did I hear the word dry run in other posts?
Good luck
P.S. Don't leave the vise handle on machines with 2700 ipm rapids.
(not a crash but made a loud noise, only once)