Don't you just love CNC?

[imagineering]

Don't you just love CNC and the way the Machine does everything that you tell it?

Don't you just hate CNC and the way the Machine does everything that you tell it?

 

[doc1955]

:big: :big:
You have to take the bad with the good.

 

[1hand]

yup i hear ya. For some reason my poster was making the gcode perfect for the part till the second to last line. Where it decided to plunge into my vise, before it returned to the start postion. Now I know how to edit gcode, and look at the second to last line. Sometimes it does it sometimes it don't, but experience makes me check everytime.

Matt

 

[kvom]

On of my vises has just such a blemish (not made by me); luckily not a critical location.

 

[shred]

I've got an old vise that's pretty much swiss cheese on the bottom from all the drill-thrus. I don't think it was CNC mostly though, just people stopped caring after the first six or seven.

 

[Deanofid]

Thank goodness I don't use CNC, so I don't have those problems. :big:

 

[Swede]

That sort of stuff is why CNC scares me, but I'm still plugging away at it.

While holes in vises and tables are NOT good, what scares me more is the thought of damage to the machine itself if a powerful servo drives a ball screw to the limits and keeps on going... Or the spindle itself crashes into a vise during some rapid movement. Broken cutters are no fun, but that'd be worse. The stresses are massive. Something has to give, and it is usually expensive.

 

[FIXIT]

Bin there!!!

just a tip from another newbie to cnc if you are using Mach3 you can do a trial run in the toolpath screen and it has a panel marked absolute limits which tells you the max movements/limits the machine is going(or try) to go to


Steve

 

[Tin Falcon]

To err is human to really mess things up requires a computer
Tin

 

[seagar]

Tin,I have no trouble really messing things up without a computor but I have a lot of fun doing it.lol

Ian(seagar)

 

[imagineering]

Bin there!!!

just a tip from another newbie to cnc if you are using Mach3 you can do a trial run in the toolpath screen and it has a panel marked absolute limits which tells you the max movements/limits the machine is going(or try) to go to
Steve

Did all of that - just forgot to set Z origin. Machine did what it was told & Drilled to Z-14. Unfortunately the base of the Vice was about Z-12.

.

 

[BillC]

And why do those Z axis mistakes become much more likely when you have a brand new carbide end mill in the collet ??!! ;D

BillC

 

[schmetty]

Well it happens i wish i had a picture of the kurt vise someone plowed the cutting head right into it.

On a Haas mill it shows work offset position for x,y, and z but because it uses tool length offset to guage where the part is in relation to the cutter you never need to change that z unless you have a special setup.

With that being said one of the hotshot students that really didnt know what he was doing changed that z coordinate to the parts zero BIG MISTAKE.

Now the machine thinks that zero is about 5 inches lower than it should be and all of his tool length offsets were set before he changed that z coordinate. So the machine starts changes to 1.25 inch flat endmill carbide mind you and then proceeds to move over to the part and plow at rapid through an inch of 7075 aluminum and about .125 into the brand new vise.

Ruined everything the whole machined had to be realigned and serviced the vise was toast and that piece of aluminum was beyond repair. Worst part is none of that belonged to the student so about 3k later everything is fixed and back to spec. What grinds my gear is he didn't shell out a dime nor did he show any concern that it left the machine out of commission for 3months. I got dicked out of what it cost to fix the machine because i was no longer able to mill my paintball gun trigger frames nor any of the other parts i made and had sold already. So a simple ignorant mistake cost me a fortune even though i was completley uninvolved in the destruction when it took place.

Lesson learned never allow a student to work without supervision. He claimed he didn't know how it could have happened and his program was written proper. No one was able to place any blame until i showed up and had them look at the offset settings and it became blatantly obvious what happened and who was to blame. Not the instructor but the STUDENT who didn't listen to the numerous statement made by the professor to leave work offset z alone.

The instructor is acutally my father whos been in the Machining industry for about 45+ yrs and about 30 of those spent teaching other how to machine. He has bundles of experience and while sometimes i surprise him with something new 9 out of 10 times he makes it clear how much more knowledge and experience he really has.

 

[Ken I]

Years ago the company I worked for installed a brand new Jig-Borer in a specially constructed air conditioned room in their toolroom.
The toolmaker who had been specifically recruited to run this machine accidentally drilled a hole in the machine's bed on his first day.
Fearing he would lose his job over this he fretted about it and came up with a classic solution - he counterbored the hole, tapped it, inserted an oiling nipple and carefully stamped on the word "OIL" next to the hole.
Until his retirement some 20 years later, nobody (not even the machine's agents and service personnel) noticed the deception and the lubrication Wallah dutifully pumped oil into the nipple at each service (it ran to waste into the machine bed area).

At his retirement some 20 years later he told this story - we all went to look - and yes there was the nipple and it led precisely nowhere.

Necessity is the mother of invention.

Regards.
Ken

 

[coopertje]

I think that all that use CNC had this experience (at least all the people I know). Since it happened to me more than once (some learn slower than others ) I carefully check my G-code before starting the machine.

First step is to simulate the code in NCEdit. If you google on NCedit you will find a free download. I especially watch the Z-axis movement in this simulation. When I cannot see anything strange in the simulation I load the code in my machine and let the code run with the spindle stopped, no material in the clamp and with my hand at the E-stop. Try to keep the concentration and watch carefully for collisions with clamps, vises etc. Also I try to watch if the Z-axis is not "forgetting" to retract before reposition.

Since I followed above I did not have any damage to my tools and machine anymore.

Have fun, regards Jeroen

 

[kvom]

On my mill, when I set the tool height, I set Z0 to 1" above the work, and then run the program cutting air with the spindle stopped. When I'm confident, I raise the spindle to Z0 and reset Z to 1.00. Even then I usually will single step the program for the first steps, mainly to listen to the cutter and to adjust the feed&speed if necessary.

 

[shred]

I was running some code at a friends shop on his Haas machines. First run of everything is always dialed way back and with a finger hooked over the 'feed hold' button housing for instant pressing. I do that with Mach at home as well.

Another guy with a Fanuc was joking that you had to stick the stop button up where the sun don't shine 'cause that's the only muscle that can react fast enough when something goes wrong on one of those....

 

[steamer]

;D

Good.....I'm glad because now I'm not the only one!... :big:
Sorry about the divit....mine's worse though.....I'm trying to forget....

Dave

 

[bezalel2000]

Another guy with a Fanuc was joking that you had to stick the stop button up where the sun don't shine 'cause that's the only muscle that can react fast enough when something goes wrong on one of those....

Rof} you've gotta put that in the humour thread Rof}

Now my stomach muscles are aching :big:

Bez

 

[moanaman]

Unfortunately, or fortunately not sure which, but the only electronic devise in my workshop is an old radio and a new digital read out 150mm caliper. Nothing to automatically produce unnecessary scrap metal. I have the skills to make heaps of rubbish without having to resort to electronic aids.