Series 3 upgrade - mixed so far...

[philbur]

Generic quote:

"Always operated the equipment in accordance with these instructions, failure to do so can result in damage to the equipment and serious injury to the operator."

Phil

[dbrija]

Generic quote:

"Always operated the equipment in accordance with these instructions, failure to do so can result in damage to the equipment and serious injury to the operator."

Phil

I see what you are trying to get at. I can follow the recommended procedure (and usually do). Its the unknowns that bother me (as others have posted, like PC power failure, etc...). I won't be any too happy with a ruined part, tool, spindle bearing set, etc... because the brake lets the Z fall. No instructions or even disclaimers can cover every scenario, but this issue is a potential problem, and safety issue.

[TXFred]

"Always operated the equipment in accordance with these instructions, failure to do so can result in damage to the equipment and serious injury to the operator."

This isn't a case of obvious misuse leading to damage. This is a case where normal use can lead to damage.

Imagine your car. You park. You shut off the engine. You then shut off the headlights. All is well.

But suppose that you park, shut off the headlights, and then shut off the engine? And suppose that a feature of the car is that, as soon as the headlights are off, the car begins to move under its own power, with no way for you to stop it?

Is that a design flaw, or is it operator error?

Frederic

[Scott_M]

The Z axis brake is just a safety device to prevent the head from drifting down IF the gibs go out of adjustment. On a properly adjusted and maintained machine the shutdown procedure is irrelevant. It is just another layer of protection for those who do not keep up on machine adjustments.

Scott

[dbrija]

The Z axis brake is just a safety device to prevent the head from drifting down IF the gibs go out of adjustment. On a properly adjusted and maintained machine the shutdown procedure is irrelevant. It is just another layer of protection for those who do not keep up on machine adjustments.

Scott

Not exactly true now with Series 3 IMO. If you re-read the reply that compunerdy posted from Tormach, the new motors don't have the same static hold force. My machine got correctly adjusted at the time I installed them, and it still falls. It is now a potential safety issue. Unlikely, but now possible where it was not before. Not a show stopper as far as I am concerned, I just do the proper sequence. Others have a different comfort level with the issue.

[David Bord]

Isn't that a philosophy applied by all of us many times every day. There are many things we do every day, that if we do them in the wrong sequence we are in trouble. Do I need to give examples?

Phil

Red lights come to mind

David

[compunerdy]

I do not understand the engineering behind it all but if there is a brake installed on the machine then it should be a dead man switch setup.

Since we are talking about the brake have you ever seen anyone setup a direct drive rotary table using a brake for the holding power?

[TXFred]

I do not understand the engineering behind it all but if there is a brake installed on the machine then it should be a dead man switch setup.

Since we are talking about the brake have you ever seen anyone setup a direct drive rotary table using a brake for the holding power?

Going off topic for a moment...

I'm told that larger rotary tables have a drag brake on them to resist machining forces. The table's motor has enough power to overcome this, creating a very rigid arrangement.

The VF-2 that I ran at the last job had an air brake on the table. You could hear it unlock before a move, and then lock again after it had moved. That provided additional rigidity when doing simple indexing. But it didn't contribute any to the rigidity of the system when doing rotary machining.

I don't think direct drive would work. The motor wouldn't have enough power to overcome the brake. But since the drag brake is holding the table in place during machining, backlash in the drivetrain isn't a problem anymore, and you can afford to gear the motor down.

Besides, a direct drive rotary table would only be able to move in increments of 1.8 degrees (Full step, no microsteps). A worm gear arrangement gives the table more power and more precision.

Frederic

[Don Clement]

Going off topic for a moment...

I don't think direct drive would work. The motor wouldn't have enough power to overcome the brake. But since the drag brake is holding the table in place during machining, backlash in the drivetrain isn't a problem anymore, and you can afford to gear the motor down.

Besides, a direct drive rotary table would only be able to move in increments of 1.8 degrees (Full step, no microsteps). A worm gear arrangement gives the table more power and more precision.

Frederic

The Contraves-Goerz direct drive rate tables we used back in the ‘80s were accurate to sub arc-sec. Also I have used linear stepper direct drive wafer probers with micron accuracy http://www.electrolab.com/html/wafer_prober.html Micro steps and compensation mapping using a laser interferometer can increase the step resolution.

In addition there are alternatives to using worm gears for the final drive as shown in this telescope drive I built years ago. http://www.clementfocuser.com/images...rive_Print.pdf

Don

[compunerdy]

Sorry I meant in combination with a harmonic drive gear setup.

[philbur]

What would be the situation if no brake was fitted?

The brake greatly reduces the possibility of uncontrolled downward movement of the head during a shut down. It currently doesn't totally eliminate the possibility. But then a number of electronic failures will also result in a crash. Tormach would probably have done things differently had it been a simple fix, they do indicate that a fix is on the way.

I suggest that those of nervous disposition stay in bed until the fix arrives.

Phil

[MFchief]

A couple of notes on the upgrade progress.

I started my Series II machine upgrade this morning, and it started off well, the first thing, related to the earlier discussion, when I disconnected my Z axis coupling nut, the head did not drop at all, it stayed exactly where it was shut down, even when I hand rotated it to re-install the coupling nut, it did not drop.

That's the good news.

The bad is that even though my machine's serial number is over 1700, and therfore I ordered the kit without the DC Bus board, my board turned out to be one of the old ones (P/N 30600), so now I am stuck with an inoperable machine until I can contact Tormach on Monday and get a Bus board shipped out. That's rather frustrating!

One other minor thing, for people who plan to do the upgrade, on my machine at least, the Z axis cable is not a continous cable, but has splices inside the vertical column, so just be careful pulling the wire out of the hole in the column, it's very easy for the splices to catch. I found that it works much better on all the cables if you loosen the cable nuts on both ends and remove any cable clamps holding the cables and then push one the old cable, pull some, then alternate pushing and pulling a few inches, until the cable clears the hole in the column.

Terry