Tool Changing Problem - Important

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Georgi Baltov
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Tool Changing Problem - Important

Postby Georgi Baltov » Mon, Aug 13 2007, 5:19PM

Well we've had our 3 axis Therwood machine for about 6 months now and so far everything has been ok. Today I was cutting some dovetail drawer boxes and I switched tool #7 with the dovetail bit, measured it and went in controll nesting to load the boxes. I wrote the CNC code and started the program. At this point tool #7 (3/8 dovetail bit) was in the spindle and I didnt really see if the machine tried to release it and go to get tool #3 (3/8\" dado bit), all I know is that the machine went to grab the tool in position 3 with the dovetail bit not realeased and still in the spindle. You can figure out what happened later.

Now the thing I dont understand is what happened, how did it happen?Would it happen again? A moment later I ran the rebuilt program to get rid of the #3 tool and then run the Tool lenght program. EVERYTHING RAN PERFECTLY!!! I didnt change f*** all. What messed up?

I ended up with one broken diamond bit and one holder broken as well. Let's exclude the emotional side of the problem.

Anyways any responce and feed back will be greatly appreciated.

Thank you guys

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Postby Mark Taylor » Mon, Aug 13 2007, 6:49PM

Hey Georgi...welcome to the club! Heart was racing a bit eh? I know the feeling all too well!

At one point or another, everyone will make a mistake like that. The last time I didn't pay attention to what I was doing, I slammed a 1/2\" end mill into the #1 position with another bit already in the holder and snapped the aluminum tool holder plate. Next thing I knew...almost before I could even react, the first three tool holders (still attached to the aluminum plate) were lying on the floor. Expensive lesson, but the machine's still running!

While it doesn't sound like you made a mistake in tooling, you obviously did because the machine just simply doesn't make a mistake like that.

Whenever changing tools, I always run the rebuild program and place the tools into the holder I've specified in controller. Be sure you remove the #1 tool and put it into the spindle. If you force yourself to make this a habit, you won't make that same mistake again.

It's also a very good habit, every time beforeyou run a program to look at the spindle and determine what bit is in the machine and then check the controller to see if the bit listed is the same as what's in the spindle....

Mark

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Postby Rob Davis » Tue, Aug 14 2007, 6:07AM

Georgi,
Been there, done that.
We have to verify that the tool number on the screen is the same as the EMPTY slot on the tool bar. We did it when we lost air pressure during a tool change We put back to where we thought we were but the machine had already changed tools so we crashed. We learned the number showing on the screen that the machine thinks it has loaded is the critical one, not what we think the machine should have.

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Postby Rob Davis » Tue, Aug 14 2007, 6:08AM

Georgi,
Been there, done that.
We have to verify that the tool number on the screen is the same as the EMPTY slot on the tool bar. We did it when we lost air pressure during a tool change We put back to where we thought we were but the machine had already changed tools so we crashed. We learned the number showing on the screen that the machine thinks it has loaded is the critical one, not what we think the machine should have.

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Postby Bill Rutherford » Tue, Aug 14 2007, 6:28AM

Did you change the tool position for the bit that was in the machine in the course of getting set up. If the machine has a tool that came from position 4 (or any other position) and you change the position of the tool while it is in the head it will try to put it down into the new position resulting in a crash. Not sure if this is what caused your problem but it is one possibility
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Georgi Baltov
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Postby Georgi Baltov » Tue, Aug 14 2007, 6:33AM

It's kind of funny because guys from Therwood said the machine just doesn't do that. And then I come to the forum and I see all these \"tool release\" problems. All I know is that I didn't change anything when I went to run the rebuilt program and the machine released and measured every tool corectly. And tell me how after a tool lenght operation on the #7 tool, job loading and cnc code writing the machine will crash. It knew what tool was in the spindle it just didnt release it and went to grab another tool. If there was a mistake from my side it wasn't in Tool Manager or Controll Nesting. The only mistake I made was that I din't look at the machine to prevent that. I knew perfectly what tool it uses first to start cutting the boxes. Well the lesson is learned but I just hate when something around me goes wrong.

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Georgi Baltov
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Re:

Postby Georgi Baltov » Tue, Aug 14 2007, 6:46AM

Bill Rutherford wrote:Did you change the tool position for the bit that was in the machine in the course of getting set up. If the machine has a tool that came from position 4 (or any other position) and you change the position of the tool while it is in the head it will try to put it down into the new position resulting in a crash. Not sure if this is what caused your problem but it is one possibility


Let me explain more thoroughly. Just before I ran the dove tails I was cutting a small cabinet job. I had a .2953" drill bit at #7. So I went to change it with the dove tail bit when the cabinets were done - preparing for the drawer boxes. I didnt get the tool from the spindle. The 1/2" bit was in the spindle at that moment. The #7 bit was free in it's position. I shanged it. put it back in position #7. I went in tool manager and the only thing I changed was the diameter. Then I went in Control Nesting Tooling to change the specs from drill bit to dado/rout bit. Then I went to run the tool lenght program. It did measure the tool and I went again in tool manager to add .015 to the daylight to make sure I get tight joints in the boxes. I went back to the Control nesting to load the program. It loaded and wrote the code. Then you know what happened. And just to prove myself right I run the tool lenght program afterwards to make sure there wasnt a mistake with two bits at the same location. The machine measured every tool. Well except for the 3/8" at #3 because the holder broke. So you tell me where I messed up so I don't do it again. I cant see my mistake. May be you can help

Pete Riddle

Postby Pete Riddle » Tue, Aug 14 2007, 9:07AM

Georgi,

From your decription it sounds as though it's possible that the drawer bar down sensor in the router motor may need a slight adjustment. Let me explain.

When the machine performs a toolchange it moves to the drop off position at which point the drawer bar solenoid is fired to release the tool. The control then waits for the drawer bar down sensor to make (indicating the release of the tool) before coninuing to the new tool position. If the sensor is out of adjustment it may be possible for the sensor to make even though the tool is still in the head. The Service dept. can go through the steps to make the adjusment, but there is something that you can do to prevent this from ever being a problem in the first place.

Make sure your tool holders and the taper inside the router spindle are clean, shiny and free of build up. The compressed air used to purge debri during a toolchange almost always contains moisture of some kind. Combine that with dust and wood chips then, the heat transfer from a tool, and you get a film of debri on the taper of the toolholder and insode the spindle. When the machine picks up this dirty tool and pulls it up into the head, then gets warm from the heat transfer of cutting it can get wedged into the head pretty tight. By keeping the toolholder and the router taper polished and dry (never use a lubricant) the toolholder should easily release from the head during a toolchange. I recommend using a dry red or green Scotchbrite pad to clean with.

Hope this helps.

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Georgi Baltov
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Postby Georgi Baltov » Tue, Aug 14 2007, 10:05AM

A technician is coming today to replace the broken holder. I will ask him to check any possible sensors that might have caused that. Thanks for the feed back guys. I appreciate it.


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