Before I begin, the machine:
Leadwell MCV1000AP, circa 1996, 40x20x~20 travels. BT40 spindle, 6000rpm, 15HP. Linear ways. Fanuc 0mf control. Drawbar pressure: 1600LB
Trying to make a part (shown below incomplete, about 1/8" material left on the part shown) out of 304 stainless. Programmed the part using Gibbscam with Volumill. My programmed speed is 2800rpm, 120IPM, .05" radially, 1.25" DOC. The endmill is an HTC HotMill, 5/8" Diameter, resharpened.
When cutting the part in the bottom left, top left, and top right (quadrants 1-3), the part runs fine. It takes a nice cut, works well. Spindle load around 50%. However, when externally cutting in the 4th quadrant (bottom right), the machine is never happy (at higher feedrates). See the following pictures:
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Here's a couple photos of where the machine had no troubles:
Top right:
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Bottom left:
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Top left:
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Some backstory:
About a year ago, a new employee was hired, as I was going to school and couldn't be a full time employee (I still am going to school). One of his first tasks was to do some milling on this machine. I wasn't there at the time, but I was told that he used a pretty decent size facemill in steel, and proceeded to feed it pretty aggressively, and "stalled the spindle a few times". From what I gathered, he possibly did more than just stall the spindle, as the problems with volumill on this machine have only started after this occurred.
In addition to this, I've since had issues facemilling, and have also stalled the spindle where I thought my feed was conservative. I attribute that to having the same cause as this.
I want to be clear, this is not chatter like you'd see with a tool spinning too fast. This is more like a shudder. The whole machine shakes VIOLENTLY. When looking at the machine while it happens, it almost looks like the whole head is shaking back and forth. I cannot tell, however, what exactly is moving. It might even be the glass door giving the illusion of the table and/or headstock moving. It is really hard to tell.
In fact, the shudder was violent enough to shatter my first 5/8" endmill I used. If you look at the picture, you can see the scar on the floor of the part from the previous endmill. The shudder pictured is with another endmill that I replaced it with.
There is negligible measurable backlash in all 3 axis, as well as the backlash parameters being pretty small (they are similar values to our other mills). The machine is level and the spindle and headstock are square to the table. All the machine feet are on the ground. Pushing the table and headstock manually shows no movement on a .0005 indicator.
In the pictures where the "chatter" is massive: where the finish is OK, the feedrate was 60IPM (volumill eases the tool into the cut). It is only at elevated speed this happened. It seems to be cut size relevant to a point. I was able to do a few of these parts while running the machine at 50% feed override in that corner.
On another job in the past, the chatter was horrendous until we slowed the feed down to about 60ipm, and had to cut the cut width back to about .03"radially, with a .5" tool, to get rid of this "chatter". When testing on an external circle, it occurs between ~290-330 degrees. Everywhere else on the circle has no issues. Interestingly enough, on an internal bore, there are no issues with this.
The cut is definitely not too big for the machine. I moved the same program and part onto another machine (Leadwell 760CR with same spindle specs) and had no issues completing the program. This is the only machine that has trouble, out of our 7 Leadwell mills.
So, I'm unsure whether I've omitted any details required to give some sort of diagnosis of the problem, but what I want to know is, has anyone had this issue with a similar situation? The ideas at work are revolving around the x and/or y axis thrust bearings (which do NOT sound bad), motor couplings, linear guide bearings and the bolts that hold the table/saddle to them.
Any advice or knowledge of this kind of problem would be appreciated.
Let me know if I seemingly omitted anything.
Leadwell MCV1000AP, circa 1996, 40x20x~20 travels. BT40 spindle, 6000rpm, 15HP. Linear ways. Fanuc 0mf control. Drawbar pressure: 1600LB
Trying to make a part (shown below incomplete, about 1/8" material left on the part shown) out of 304 stainless. Programmed the part using Gibbscam with Volumill. My programmed speed is 2800rpm, 120IPM, .05" radially, 1.25" DOC. The endmill is an HTC HotMill, 5/8" Diameter, resharpened.
When cutting the part in the bottom left, top left, and top right (quadrants 1-3), the part runs fine. It takes a nice cut, works well. Spindle load around 50%. However, when externally cutting in the 4th quadrant (bottom right), the machine is never happy (at higher feedrates). See the following pictures:
Here's a couple photos of where the machine had no troubles:
Top right:
Bottom left:
Top left:
Some backstory:
About a year ago, a new employee was hired, as I was going to school and couldn't be a full time employee (I still am going to school). One of his first tasks was to do some milling on this machine. I wasn't there at the time, but I was told that he used a pretty decent size facemill in steel, and proceeded to feed it pretty aggressively, and "stalled the spindle a few times". From what I gathered, he possibly did more than just stall the spindle, as the problems with volumill on this machine have only started after this occurred.
In addition to this, I've since had issues facemilling, and have also stalled the spindle where I thought my feed was conservative. I attribute that to having the same cause as this.
I want to be clear, this is not chatter like you'd see with a tool spinning too fast. This is more like a shudder. The whole machine shakes VIOLENTLY. When looking at the machine while it happens, it almost looks like the whole head is shaking back and forth. I cannot tell, however, what exactly is moving. It might even be the glass door giving the illusion of the table and/or headstock moving. It is really hard to tell.
In fact, the shudder was violent enough to shatter my first 5/8" endmill I used. If you look at the picture, you can see the scar on the floor of the part from the previous endmill. The shudder pictured is with another endmill that I replaced it with.
There is negligible measurable backlash in all 3 axis, as well as the backlash parameters being pretty small (they are similar values to our other mills). The machine is level and the spindle and headstock are square to the table. All the machine feet are on the ground. Pushing the table and headstock manually shows no movement on a .0005 indicator.
In the pictures where the "chatter" is massive: where the finish is OK, the feedrate was 60IPM (volumill eases the tool into the cut). It is only at elevated speed this happened. It seems to be cut size relevant to a point. I was able to do a few of these parts while running the machine at 50% feed override in that corner.
On another job in the past, the chatter was horrendous until we slowed the feed down to about 60ipm, and had to cut the cut width back to about .03"radially, with a .5" tool, to get rid of this "chatter". When testing on an external circle, it occurs between ~290-330 degrees. Everywhere else on the circle has no issues. Interestingly enough, on an internal bore, there are no issues with this.
The cut is definitely not too big for the machine. I moved the same program and part onto another machine (Leadwell 760CR with same spindle specs) and had no issues completing the program. This is the only machine that has trouble, out of our 7 Leadwell mills.
So, I'm unsure whether I've omitted any details required to give some sort of diagnosis of the problem, but what I want to know is, has anyone had this issue with a similar situation? The ideas at work are revolving around the x and/or y axis thrust bearings (which do NOT sound bad), motor couplings, linear guide bearings and the bolts that hold the table/saddle to them.
Any advice or knowledge of this kind of problem would be appreciated.
Let me know if I seemingly omitted anything.