Problem- Real stumper

[ben_heinman]

We have a brand new vertical CNC with an Oi-MC control. We had a workpiece set in G54 with a Z0.7940" work offset. We had to do another quick production job of 20 or so parts. So using G55 the work offset was Z1.0132". The first part ran without any problem, but when we put a new piece of material in and started the program the first tool crashed. Put a new drill in, started again. First piece no problem, second piece tool crashed. When we started to investigate we found it went .2192" deeper when it rapided in the Z axis. So with a reference height of only .100" above the work it was doing a rapid movement .1192" into the top of the workpiece. We relized that the .2192" was the exact difference between the G55 work offset and G54 work offset. Since the machine is brand new and under warranty, we have had a FANUC tech. here for three days and he's stumped too. What we did find out was that it would not happen if you used single block or pressed feed hold before the first negative Z axis movement or if the first tool of the program was already in the spindle. We tried many different work offsets for G54 and G55, if G54 was a bigger number than G55 then the tool would stay up and if G54 was smaller it would come down to far. The amount was always the difference between the two offsets. This will only happen on the first tool in the program, the 2nd and 3rd would go to the proper depth. We have tried numerous ladder diagrams and different edits of these ladders from machines that work fine and have compared the parameters to many working machines. I've checked all I have also contacted the MTB and they are baffled also. Has anyone ever heard of anything like this or have any suggestion what to try to fix it.

[chucker]

Try using G55 and G56 I have seen some machines have a problem using G54 because it is the default value when the machine comes up so I make it a habit not to use G54 I cant explaine why but I have seen simalar things like it before

Good Luck

[xavierdemoura]

Ben,

I dont know, but you have put G55 in the start of te program. Some G-Codes are reset if you press reset key. You need cusomize your machine to this G-Codes don[t can be reset press reset key

Daniel

[dcoupar]

Why not post your program here so we can peruse it?

[springlakecnc]

I sold "a particular brand" of cnc controls for a good 10 years.

I would waist my time, trying to fix a customers machine, and after several calls, the manufacture would admit, “some people have that problem, just upgrade the software”. I would always comeback with “right! You mean everyone has that problem, just some people found it, right?”……..no answer!

You better believe that’s true! It would piss me off because I’m trying to fix their controls, and the manufacture wouldn’t even be up front with me, and tell me there was a problem! Only one time they recalled a software version, because it was so bad, it was wrecking machines! In my heart, i believe their policy is: If we admit we have a problem, it opens us up for a law suit! but I can't prove that.

I solved my problems by always loading in an older version of software, in the customers machines, that I knew didn’t have problems!

Some versions didn’t last a week! STRIKE THAT, some versions didn’t last 3 days!

BTW, it’s not that brand of control that you have, and I’m not naming any names, I don’t rep them anymore, and as with computers, things change so fast, today one brand can be the best, and tomorrow it could be the worst, and next week, back to the best.

I’m not saying that’s your problem, its just a thought.

Even though your probably a nice guy, I think you have to get tuff and say: If you don't get this machine fixed, get it out of here! Everyone has problems, even my friend, who bought a new mill for $200,000.00 to cut areospace parts, it took 10 service calls (i wasn't involved in that) to get it running right, but oh what a sweet machine after they got it fixed!

[f-bu]

I would also check the tool change macro, if it exist. Usually for tool change it is necessary to change to G53, then return back to previously used coordinate system.

[timlkallam]

Heres my 2 cents .I bought a new sharp mini mill with a o-i mc control . When the machine does a tool change it switchs to G91 mode and it stays in that mode unless you write it in the next line of code.It stumped me for a while . At the end of the tool change program i put in a G90 and a G49.

[ben_heinman]

Here is the program that we are running to try and figure this problem out. Some things to note are the problem will occur even if reset has not been pressed since power up; even if the G54 work offset is not set (Z=0.0000") it will still cause the problem; tool change macro is not used in this machine, it is written directly into the ladder; we have changed the software to older editions from older Oi-MC controls that we know work and lastly only the first tool is affected the 2nd and 3rd will run at the proper set height.
%
O0100
(PROGRAM NAME - TAP-1-4 )
(DATE=DD-MM-YY - 14-08-08 TIME=HH:MM - 07:47 )
G20
G0 G17 G40 G49 G80 G90
( TOOL - 1 DIA. OFF. - 1 LEN. - 1 DIA. - .201 )
( DRILL HOLES )
T1
G91 G28 Z0
M6 T5
G0 G90 G55 X.5 Y-.312 S850 M3
G43 H1 Z2. M8
G08 P1
G98 G73 Z-.74 R.02 Q.125 F3.4
X2.
G80
M5
G08 P0
G91 G28 Z0. M9
/ G28 X0. Y0.
M01
( TOOL - 5 DIA. OFF. - 5 LEN. - 5 DIA. - .5 )
( SPOT DRILL HOLES )
G91 G28 Z0
M6 T4
G0 G90 G55 X.5 Y-.312 S1600 M3
G43 H5 Z2. M8
G08 P1
G98 G73 Z-.13 R.02 Q.075 F2.
X2.
G80
M5
G08 P0
G91 G28 Z0. M9
/ G28 X0. Y0.
M01
( TOOL - 4 DIA. OFF. - 4 LEN. - 4 DIA. - .25 )
G91 G28 Z0
M6 T1
G0 G90 G55 X.5 Y-.312 S400 M3
G43 H4 Z2. M8
G08 P1
G98 G84 Z-.75 R.3 F20.
X2.
G80
M5
G08 P0
G91 G28 Z0. M9
G28 Y0.
M30
%

Thanks for the input and suggestions so far guys.

[extanker59]

I have no answers but one question. How come the T# doesn't match the H# or at least be a predictable # (like T1 would be H51, adding 50 to all H offsets). I realize this is not the problem. Just curious.

[dcoupar]

The only thing I see is there's a G49 before the 1st tool, and not before the 2nd and 3rd tools. Try taking it out altogether.

[beege]

Do you touch your tool ALWAYS in G54? or G55? If some of your tools are touched off the G54 fixture and some in the G55 fixture, and you are in G54 by default when the machine turns on, something's bound to go wrong. Always touch off on the same thing in the machine, and in the same Coordinate system... rambling on....
Not too coherent, but how are the tools touched off?

[ben_heinman]

Sorry, that was an edited version of the program which was missing the proper tool changes. Beege, tool heights were set off the top of the vise for G54 & G55. It is the work offsets that are different. I'll try taking the G49 out.