johnm
09-05-2006, 11:18 PM
Folks -
Okay, we broke our first router bit yesterday. Bang! - The gantry lifted up about an inch and the machine had our complete and undivided attention. Man, what a racket!
Here's what we were doing, what I think happened, and our unsolved issues.
We were cutting six pieces, small pedestal legs out of maple using a 1/4" Onsrud Spiral Bit in a 3 hp Colombo on our PRT Alpha. We had just finished cutting the first six. We moved the gantry to the location we wanted to start cutting the next six, 35" down the board and used the "2D offset" to cut out another half-dozen. Rose got her instructions on 2D offset from Bill Young, and we followed them to the letter. We didn't re Z zero before we started the file in 2D offset, but we *MAY* have moved it from its normal "Z" safe start point of .500
So, we were wondering if in 2D offset if it takes the "Z" from whereever "Z" happens to be when you start the file?
If the above is true, this is really stupid on the part of the software. When you run a file from 0,0,0, it runs "home" and from safe Z, regardless of where the cutter actually is. Why would this be different in a 2D offset?
The cuts started okay, but sounded "heavy"... We were taking 5 passes of approx .16 depth each, plus a final finishing pass of .020. Our feed rate was 1.3 IPS
The first few legs all cut, except for the final pass, but then the bit snapped on the first pass of a new leg. The bit broke off right at the collet and was very hot. Two legs were damaged when the bit gave way.
The loose parts made it apparent that the bit had eaten up most of the heigth of the bridges and ~1/8" into the spoilboard, even though according to the file, it still had it's finishing pass yet to do.
Initially, we thought that the bit had slipped out of the collet - fair enough, it has happened before. But, this was a "down cut" bit, so if anything it would have been forced back into the collet. Also, the cut into the spoilboard was flat - not like the bit had slipped, but rather was just too deep.
The only thing we can think of is that the kerf still had a significant amount of wood waste in it, so on the final pass it's like it was making a full depth cut.
On our cuts today, using a straight bit, I tried to clear out as much waste as I could, and we slowed the feed rate down as the bit went deeper. We ran the final pass as a separate file after we cleared all of the waste out of the kerf. We got MUCH better cut quality, with less fretting.
So, the questions remain - Why did the machine introduce nearly 1/4" additional depth in the "Z" cut using 2D offset? We had just finished running the file with no problems, didn't shut down the machine, etc...
And finally, why did the bit break during the first pass of a cut, rather than when it was at an apparent full depth cut.
What do y'all make of this?
John & Rose
Okay, we broke our first router bit yesterday. Bang! - The gantry lifted up about an inch and the machine had our complete and undivided attention. Man, what a racket!
Here's what we were doing, what I think happened, and our unsolved issues.
We were cutting six pieces, small pedestal legs out of maple using a 1/4" Onsrud Spiral Bit in a 3 hp Colombo on our PRT Alpha. We had just finished cutting the first six. We moved the gantry to the location we wanted to start cutting the next six, 35" down the board and used the "2D offset" to cut out another half-dozen. Rose got her instructions on 2D offset from Bill Young, and we followed them to the letter. We didn't re Z zero before we started the file in 2D offset, but we *MAY* have moved it from its normal "Z" safe start point of .500
So, we were wondering if in 2D offset if it takes the "Z" from whereever "Z" happens to be when you start the file?
If the above is true, this is really stupid on the part of the software. When you run a file from 0,0,0, it runs "home" and from safe Z, regardless of where the cutter actually is. Why would this be different in a 2D offset?
The cuts started okay, but sounded "heavy"... We were taking 5 passes of approx .16 depth each, plus a final finishing pass of .020. Our feed rate was 1.3 IPS
The first few legs all cut, except for the final pass, but then the bit snapped on the first pass of a new leg. The bit broke off right at the collet and was very hot. Two legs were damaged when the bit gave way.
The loose parts made it apparent that the bit had eaten up most of the heigth of the bridges and ~1/8" into the spoilboard, even though according to the file, it still had it's finishing pass yet to do.
Initially, we thought that the bit had slipped out of the collet - fair enough, it has happened before. But, this was a "down cut" bit, so if anything it would have been forced back into the collet. Also, the cut into the spoilboard was flat - not like the bit had slipped, but rather was just too deep.
The only thing we can think of is that the kerf still had a significant amount of wood waste in it, so on the final pass it's like it was making a full depth cut.
On our cuts today, using a straight bit, I tried to clear out as much waste as I could, and we slowed the feed rate down as the bit went deeper. We ran the final pass as a separate file after we cleared all of the waste out of the kerf. We got MUCH better cut quality, with less fretting.
So, the questions remain - Why did the machine introduce nearly 1/4" additional depth in the "Z" cut using 2D offset? We had just finished running the file with no problems, didn't shut down the machine, etc...
And finally, why did the bit break during the first pass of a cut, rather than when it was at an apparent full depth cut.
What do y'all make of this?
John & Rose