Machine continues to run when spindle cover is opened

[TMashino]

Hi everyone,

I was wondering what would happen if the spindle cover was opened while a program was running, so I tried it. Much to my suprise, the machine continues to run while the spindle shuts down! I find this pretty alarming that this is allowed to happen. Has anyone else noticed this? Is there a fix for this problem?

Thanks in advance,
Tom

[LeeWay]

I don't have one, but I would expect it to create an estop, rather than an M5.

[justgary]

Tom -

Yes, the mill will run with the door open. I found this out last week when I *thought* I had closed the door, but I had mis-latched it.

Lucky for me, the program I was running started with a very slow plunge, and I noticed that the spindle wasn't turning just before the tool touched the work. It took me several minutes to diagnose the problem.

The door switch is a safety interlock only (to keep you out of trouble when you change tools or belt speeds), not an e-stop for the whole mill.

The fix? As for me, I chalked it up to experience, thankful that I didn't wreck the tool or the work. It definitely falls into the "Doctor, it hurts when I do that" category. Just follow the doctor's advice, and "don't do that."

Regards,

- Just Gary

P.S. You may find a time when locking the spindle and running the mill is exactly what you want to do. My sons and I made a "reflector" for a street sign by using a 1/4" punch in the spindle and programming a rectangular grid of "holes" that were 1/32" deep.

By clamping a sheet of aluminum flashing over plywood, the mill proceeded to make a great textured finish. We flipped the sheet, offset the holes, and did it again on the other side. If we had used a shaped punch (square, triangle, etc), I would have locked the spindle to keep it from arbitrarily rotating. Since you can't close the door with the spindle lock in place, that approach wouldn't work.

[fastlanecafe]

Originally Posted by LeeWay I don't have one, but I would expect it to create an estop, rather than an M5.

Sounds like the design came from the ever-paranoid legal department rather than from an operator. Stopping the spindle only may keep someone's lawsuit prone fingers out of the moving parts, but its a sure recipe for broken tools, bent spindles and ruined parts.

[Al_The_Man]

Rather than an E-stop, which is normally a coast stop, a better idea may be an M5 and a feed hold, both would be not possible at E-stop.
This should be easier on both spindle and tooling.
Al.

[saabaero]

Just a side note on not having the spindle turning when the tool contacts the work...

The spindle motor drive is activated by it's own latching relay. The first time the spindle is started, or if an Estop occurs, or spindle door open LS is activated, the relay needs to be latched again and the drive powered up. There is a longer delay when the spindle drive is first powered up vs when just a start signal is sent to it from the controller after it is already powered up.

Consequently, in those situations when the distance of the cutter to the workpiece is short I have to hold my breath and hope that the spindle gets to speed before the cutter contacts the workpiece and causes a crash.

Because of this it seems to be a good idea to start a program with the cutter a distance from the work or to start the spindle manually first to give the drive time to power up.

[Al_The_Man]

This is where an Up-to-Speed signal from the spindle controller is important and a nice feature.
Al.

[HMB3000]

you could try what I did on my Tormach....Duck Tape the switch closed

[BlueFin]

I was across the room during a long cut with an expensive end mill, I heard the spindle slowing down and thought it was strange to be done already. When I looked I saw the cutter at full depth just before it snapped off. I used a file to remove burrs from the latch and get it to rotate more. I also filed some of the paint and burrs off the housing that it latches into. But I still check the latch constantly for fear it might vibrate open again.

[justgary]

Eeeeeks! I never thought about the latch vibrating open. That's baaaaad.

I haven't had that happen yet, just the one time that I didn't get it closed properly. I'm better at visualizing the door when I shut it so it won't happen again.

But as soon as I do like HMB3000 did and jumper the switch, I'll leave the spindle lock on and smoke the motor and controller. You'll tell me the fuses will blow, but I too have stalled the spindle on a plunge (the "wizards" helped me and changed the Z offset) and they didn't blow. Maybe the controller knows I'm an idiot and backed off the current when the spindle stopped turning. Maybe I hit e-stop fast enough. By now I'm sure that the controller knows I'm an idiot anyway.

One thing about computers: They will always do exactly what you told them to do. You might not have told them what you thought you told them, but they obligingly do what you did tell them. In that regard, I can swallow my mistakes about leaving the door open or the spindle lock on, or even letting a "wizard" change a Z offset without noticing in time, but if I shut the door it should stay shut.

By the way, Bluefin, to me every end mill is an expensive one. I'm too dumb to order them in quantity, and when I break one it means I go without that size or shape until somebody has a sale on them again. If I actually made any money with them, it would be very different. Besides, I have only broken them because I'm an idiot, and I figure I just *have* to outgrow that some day...

Regards,

- Just Gary

P.S. [off topic] Is it the use of subroutines that changes the position offsets in "wizard" code? I think it only happens when I dry run one and stop it before it completes. I tend to do that often, and have toasted myself several times because of it. I'm now very leery about using a "wizard" at all.

[BlueFin]

Originally Posted by justgary By the way, Bluefin, to me every end mill is an expensive one. I'm too dumb to order them in quantity, and when I break one it means I go without that size or shape until somebody has a sale on them again. If I actually made any money with them, it would be very different. Besides, I have only broken them because I'm an idiot, and I figure I just *have* to outgrow that some day...

Well, to me I figure I could go to CNC school for two years and after being taught I would probably crash "less" tools than I do by tearing the wrapping paper off the new machine and hitting the ON button. So you either pay tuition to a school, or to Enco and MSC. So far I have learned a LOT in just a few weeks and the "tuition" has not been as much as what the school would have been (so far)

So, a .125" Atrax single end mill on sale for $5.00 getting broke off (did that) is not expensive to me. But last month I did not set a safe rapid Z height high enough to clear the head of a allen head screw and when I hit cycle start it tried to mill it off with a brand new $50.00 three flute aluminum finisher. That new end mill never even touched a piece of aluminum before it's teeth were ripped off by the bolt head.

[300sniper]

Originally Posted by justgary P.S. [off topic] Is it the use of subroutines that changes the position offsets in "wizard" code? I think it only happens when I dry run one and stop it before it completes. I tend to do that often, and have toasted myself several times because of it. I'm now very leery about using a "wizard" at all.

i can't remember what the code is off the top of my head but look for the "cancel tool height offset" code in your wizard program. i was fighting one of the wizards for a while trying to figure out what was going on as it kept trying to bury my cutter at the start of the program. it was putting that code in there for some reason.