Fanuc G70 canned cycle

[MarcusCNC]

I am looking for some clues on a problem with a Daewoo 8UHS lathe fitted with a Fanuc OTC-B. Machine works perfectly and is accurate, until canned cycle G70 is called.

If G71(stock removal) is called with 1mm finishing allowance, then part is cut to size + 1mm in diameter and length, which is correct.

If G70 (finishing cycle) is called with 0.5mm finishing allowance, then diameter is to finished size, not to+0.5, and length can be +0.8-1.8.
In summary, G70 does not recognise any U(dia) finishing allowance,always setting it to 0, and always puts in a W(length) finishing allowance, which is random.

Fanuc are working on the problem, but so far no joy. Anybody seen anything like this?

 

[rhodie]

No, but I program an ONA wire EDM machine, and everytime I program a M00 command, all offsets and tapers are lost and remain so for the remainder of the program.

It seems M00 = E-Stop to the ONA engineers. They told me I was pretty much "S.O.L.", so be thankful that at least Fanuc is working on it.

 

[grinderguy]

I have a similar control. I cancel every tool offset in mdi when I stop the program for any reason. I very rarely get g41, g42 to work. I have heard that g0 cancels g41 just like g40. I am glad to hear other people have problems and what they are doing.

Robert Setree

http://www.advanced-grinding.com

 

[MarcusCNC]

Thanks for the replies guys, will post the diagnosis when we get there. So far Fanuc have not shed any light on the matter, still charging my customer $140 per hour to do it.

 

[twinny]

g70 does not support g41/g42 offsets

Make sure you have enough stock on the roughing cycle so that the finish cycle can remove it all.
Especially on tapers and circle moves.

The bigger the tool rad the more stock needed.

 

[MarcusCNC]

Thanks for your posts, it appears that the finishing allowance in the X axis is a TYPO in the Fanuc Manual. There should be NO finishing allowance in X for G70. The Z axis problem is still unclear, Fanuc are still puzzled by this.

 

[Russel]

Marcus The G70 is for finishing no offsets required you program the finish dimensions. If you want the size up 0.5mm just offset using the g xoffsets and adding 0.5 or the w xoffset and add 0.5mm to it. In 24 years of programming Ive never come across the need to put u or w values into a G70 and dont believe Fanuc or any other controller maker would recomend that way of programing. You can use different offsets for diferent parts of the same job if you need to change things as you go by calling the next offset with the right x and z values to give the right results. I personally edit the program to get what I want as it is so quick and easy to do and see where you are.
Regards Russel P

 

[MarcusCNC]

Thanks Russel,

The point of this post is that I did want to use offsets for this program, in order to fault find the system, and they do not work as described in the Fanuc manual.
There is a fault in this Fanuc system as it does put a variable offset into the Z axis, regardless of whether you program one or not.
The Fanuc manual does describe this method of programming.

Marcus

 

[Russel]

Russel Hi Marcus Im with you now. I use a Deawoo 10HC with the same controller. I just add 1mm x to the od tool wear offsetts which are at 0 after setting the tools the same for all id tools and -1mm x on id tools except drills and may or may not add to the z offset After runnuing thru you adjust these offsets to hopefully get a good component 1st time and not waste material. Note to improve your sucess rate stroke the machine in x and z a few times when you have stopped for more the 5 mins as the oil pump pushes out oil every 10 mins and this will affect your sizing when you are working to less than 0.01mm. Good luck.

 

[Mechineer]

I WILL NEVER BUY A DEAWOO MACHINE!

 

[bob1371]

I have to agree with Russel on cycling the machine a few times after it is stopped for a short period. We are making a small part that will always be out of tolerance when the operators come back from thier 10 min breaks. We just finished adding a Macro that will check start/stop times and if more than 5 mins the machine will cycle the warm up program X number of times then finish the part. Works great.

Bob