Turret problem after crash on Hitachi Seiki HT20-SII

[Driftwood]

Well, this just made my weekend... If anyone is familiar with this machine or similar and can offer any advice, it would be much appreciated. Here's my problem:

The machine is a 2 axis CNC lathe, a Hitachi Seiki Ht20-SII. I accidently loaded a boring bar into one of the tool slots that was sticking out the back of the holder a little too far and it caught on a bolt when the turret was rotating.

So I hit the E-stop, noticed an alarm saying something like "turret indexing fault". But once I removed the boring bar and did a tool change, the turret slowly moved to the next position and seemed to find its correct position. The alarm vanished and everything seemed to be fine.

Well, its not fine. Manually, the turret only turns one way but when running a program, the turret turns both ways, taking the shortest distance to its next tool.

So when the turret rotates clockwise (in both automatic and manual mode) it seems to work fine, but when it turns counter clockwise, it goes slightly beyond the correct position and the tool doesn't lock in place. And when the tool is in this position, I can rotate the turret by hand without too much force!!

Whats more is, now that I've pushed the turret a couple times, the tool positions no longer match the machine. ie: I call tool 8 in a program, and it give me tool 6!


So thats the scoop... any thoughts?
Anyone know how to reset the tool positions so that a program tool call matches the correct tool position? (Other than pushing the turret all the way around by hand the way I screwed it up in the first place...)

Anyone offer some info as to how the whole turret system works, and how/why the turret seems to turn just fine in one direction, but not in the other?

Anyone suggest where to get some tech support for this machine? I'll be trying Mori Seiki tech support today, cross your fingers for me...

[jp41558]

I have found that Mori "inherited" Hitachi some time back and many of their service personal don't have a great handle on them. It all depends on the location, some of the local tech centers have a little more knowledge then others. good luck and keep up posted on the outcome.

jp

[Driftwood]

Fixed it...

Contacted Mori, but the only thing they were able to help me with was resetting the tool positions, so tool call commands now called the correct tool. But they were pretty stumped as to the rest of the problem, and in fact, were having problems finding info for me because the serial number on my machine didn't have enough digits...


The rest we solved with a little intuition and luck. We found that the turret is driven by a stepped motor, which drives a large sprocket half a turn for each tool change. A sensor on this sprocket detects its position and dictates whether the machine thinks a tool is correctly selected or not. This sprocket, however, is perpendicular to the plane of the turret and the gears that transmit its rotation to the turret rotation is all enclosed and hard to get at.

The beauty of it is that as the sprocket turns continuously, the turret does not; the turret slowly accelerates then moves to the next tool position, decelerates and even stops while the sprocket is still turning. In fact, there is a small range of about 1/5 of a revolution of the large sprocket which causes no movement of the turret. The center of this range appears to be the correct tool selection position.

The sprocket is seated on a shaft and held in place by means of a ring inside it, which is compressed around the shaft by means to several bolts. So when the machine crashed, the sprocket slipped on its shaft and hence, resulted in a misalignment between the turret position and where the machined believed the correct tool position to be.

Beautiful design, this was obviously supposed to happen in the event of a turret crash and is easy enough to fix without any replacement parts needed. Glad there were no solid keys on the shafts of anything, that would have sucked.

So looks like we got lucky...

[Hidemi Fujimori]

Dear,

Did you receive my message. I still confuse to use this site.
Do you have other E-Mail option.
Thanks, Fuji
My E mail is hitecno@gmail.com

[Ghoten]

Do you know if this turret has on the servo motor a one encoder, o tell me how determinate when de machine know has tool number one, because I think the encoder should be make this work.

[Driftwood]

I don't know if it has an encoder.

There is a procedure to reset Tool 1 if the machine loses its position. This can happen if there is a turret crash or if you lose power during a tool change. You rotate the turret until you get the tool you want as Tool 1 and then press 3 buttons together, but I can't remember which buttons. If you have a manual, it will be in there, or you can contact Mori Seiki, they had it last time when I needed it.

Good luck...

[Ghoten]

Originally Posted by Driftwood I don't know if it has an encoder. There is a procedure to reset Tool 1 if the machine loses its position. This can happen if there is a turret crash or if you lose power during a tool change. You rotate the turret until you get the tool you want as Tool 1 and then press 3 buttons together, but I can't remember which buttons. If you have a manual, it will be in there, or you can contact Mori Seiki, they had it last time when I needed it. Good luck...

thanks.
in fact if there is a procedure that I have according to the sequence is TAPE STOP. to remove the clamp. then the three buttons to rotate, ok, when pressed turns and never stops. sources to check it necessary to skip a parameter, but everything indicates that the amplifier is damaged. is asked if he knew why the encoder. Greetings.
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