3-D contouring - gouges

[JoBwan]

Good morning everyone out there. I came into work this morning and had an operator come to me with a random problem. Ok, here goes. We are using a 2000 VF-O with (HSM?) option. Randomly, parts are gouging on the roughing and/or finishing pass. It has done both. Example: We have run this 3-D job many times on this machine with no problems. Same (saved) program and type of cutters as always. He ran 4 parts perfect, the 5th is gouged. Ran 3 more good parts, and the next one is gouged in 2 different locations on the part. Ran 1 good and then 1 bad etc.... Gouges are never the same spot on the parts. It could be in the Y or Z axis, but have not tracked down yet. Here is some stats: 1045 merchant grade CRS. T1= TIN coated-carbide inserted ball endmill, .015" DOC, 6000 RPM, and 50 IPM. T2 = another identical endmill, .015" DOC, 6000 RPM, 75 IPM. Questions are: How do I know if it in fact, has HSM option? Has anyone ever seen this type of machine behavior? Can anyone give me a road to the light?
Thanks in advance,

[tobyaxis]

There is the possibility that the Tool is ReCutting Chips. Make sure you have enough Coolant Flushing the Part and enough in the Tank to avoid Zero Coolant Flow. Also watch for the Coolant Foaming. This can lead to uneven Coolant Flow. Chips built up in front of the Way Covers, or Under the way covers. Chips on the Ball Screw.

Many Possibilities.

[extanker59]

I've been noticing that on our VF-2ss too. I'm sure (well, not really sure) it's backlash related. Happens on zig zag paths. Small and easily buffed out, so far, but annoying. We do have the High Speed Machining option and it is turned on. Perhaps my settings are not optimal? I'm at home so I can't see which ones, but I'm talking about the corner rounding and the other related one. What settings would make the most accurate path, regardless of time? We make surgical instruments and prototypes so time is usually not as important as accuracy.


Anybody have a cheap accurate way to adjust back lash? We don't have a ball bar set up. I tried doing what I did on lathes- indicating actual travel with each tick of the handle. But it hasn't really improved anything so I'm sure (this time I am) that I'm not doing it right.

[JoBwan]

Thanks for the posts guys. I ended up calling a technician in and he found that the "Y" axis ballscrew was loose. Tightened up 1 1/2 turns and the machine is running again. This was however, not enough to actually feel it in the table as endplay. Hope this helps someone else out there!

[JoBwan]

To All, an update.
Well the technician didn't dig into this far enough, cause it happened again.
After seeing what was going on, I determined myself that the "X" axis cable had a break in it. After inspection of the cable, I was able to sse the exact spot where the break was. Changed the cable and back to running again. The break was on one of the encoder wires, and with the "Y" axis in a specific area, the encoder was not reading properly. Once the "Y" moved a little the "X" would catch up instantly (Rapid) to where the encoder read that it should be. Hope this helps someone out there in the future.

[tobyaxis]

What did you do to prevent this from happening again??

Glad to hear your back up and running.

[JoBwan]

What did you do to prevent this from happening again??

Toby,
I don't see anything that can be done to prevent this from happening again. As I stated earlier, when the table moves in the "Y" axis, the "X" cable has to follow. There has also got to be enough cable (a loop) for the "X" to follow without it getting torn apart. It's just the nature of the beast. I've seen it on every Haas we own. Does anyone have another solution to prevent this from happening again? Haas HFO only says to replace the cable. Period.
Thanks for asking.

[JoBwan]

Ok Guys, I'm back with the problem happening again. The operator has stated that he doesn't think that the problem has ever been resolved. I know that part of the problem was the "X" cable, cause when I would move the looped "X" cable by hand (under the "Y" way cover), I could get it to jump consistantly. After replacing the cable, I can't get it to jump at all by hand. I also ohmed out the encoder leads on the old cable and did not have continuity on one of the wires all the time. Does this sound like it could be an encoder? Can either a open or shorted cable cause the encoder to react with this type of behavior? Can you buy just the encoder? Our HFO is not very helpful of what can be happening with the machine. They just want me to replace parts and I can't afford to buy parts that aren't fixing the problem. Again, I could use some good advise if anyone has a fix for this. Thanks in advance.

[tobyaxis]

That stinks!! Are you still able to make other types of parts on the machine or is it useless???

[Loose Nut]

If the Z axis and X axis motors are the same, swap them and the drive amps.

If the motor is a Yaskawa Haas does not sell and replacement encoder. Yaskawa does do repairs so you might try giving them a call.

The problem sounds noise related. Try to isolate the X axis cable. Haas uses zip-ties to separate the encoder and motor cables about every foot or so. What they try to do with this is to create some sort of choke for noise. Could be a place to look.


Loose Nut

[JoBwan]

If the Z axis and X axis motors are the same, swap them and the drive amps.

If the motor is a Yaskawa Haas does not sell and replacement encoder. Yaskawa does do repairs so you might try giving them a call.

The problem sounds noise related. Try to isolate the X axis cable. Haas uses zip-ties to separate the encoder and motor cables about every foot or so. What they try to do with this is to create some sort of choke for noise. Could be a place to look.


Loose Nut

Loose Nut,
I finally received an alarm on this machine. "Mocon watchdog Alarm." I replaced the mocon board and will give it another running on some scrapped parts to see if this fixes the jumping problem. If not, thanks for your input. It just might be the culprit.