Siemens System 8 (G53, G40?)

[RLMTS]

FM100 Fleximatic. Siemens System 8 Sprint.
KTM Panel 45054. Diagram 454254.

Hello,

I am currently working on a KTM machining centre that 'screws up' during tool-change.

The 1st tool change is always ok, but subsequent tool-changes send the Z-axis into + overtravel.

The problem seems to relate to commands in the sub that send the Z (Z carries the work on this m/c) to a safe position for tool changing. Z is sent to +500mm which is away from the spindle and 1mm short of s/ware + o/travel.

During this tool change cycle, the axis position displayed is updated to take into account the inserted tool length. (eg. if tool length is 100mm then axis position display now shows Z at only +400 from spindle (tool tip) The actual position of the axis in the m/c coordinate display (Test "eyeball" N812) is still +500 and has not moved since being put at this 'safe' position.

On the next tool-change, the Z-axis is again requested to move to the safe position of +500, but this time goes into overtravel (+501)

The problem can be simulated in MDA (when a tool length offset is active) by programming a move in absolute m/c coordinate mode "G60 G0 G90 G80 G53 Z 500" where I would expect the axis to move to +500 with respect to MACHINE REF COORDINATES, but the axis wants to go more! and O/Ts.

I have proved by experimentation that the axis is trying to move to the commanded position including the tool length offset, hence O/T at +501 !

I believe that the active tool offset should be ignored when L959 moves the Z axis to the safe position of +500.

What G Code is used to move an axis with resect to m/c coordinate system (with respect to REF point) ? is it G53? if so, this is not working.

What on earth is going on, I am very confused?

Any help, pointers, jokes! would be appreciated.

If necessary, I will list the Lprog here.

Oh, forgot to mention the m/c was recently moved, it lost it's memory, and all had to be reloaded. I have checked the parameter listing against a print-out of what I am told should be in there and it is correct?!

There is heavy use of @ functions in the tool-change sub-routine (L959)

Do you have any knowledge of System 8 "@" commands?
Can I view/download a list from anywhere?

I hope you can help, or point me to someone who can.

Regards Richard.
rlmts@controlit.fsbusiness.co.uk.

[RLMTS]

UPDATE.......

The problem seems to be related to the system ignoring G40 (I believe)

I am told (and it makes sense) that G53, when used, only disables the Zero Offsets, (G54-57)

Problem Example.......

Status before move.

Z-axis is at +400 (m/c coordinate system, reading shown at Test N812)

The operator display is showing +350 (50mm Tool Length Offset active)

Then the following MDI Auto command was executed...

G0 G53 G90 G40 Z 410.000

(Move Z in rapid (G0), use m/c coordinates (G53), use absolute moves (G90), cancel tool offsets (G40) Move to +410, a +10mm move)

I believe the axis should have moved 10mm in the +ve direction BUT it moved 60mm +ve!

Final axis readings were...
N812 = +460
Op display = +410

So, am I right in assuming G40 (& G53) should have set the position register to m/c coordinate values, then moved +10mm (showing 410mm in N812)?

You think you're confused! It's taken me 20 minutes to type this!

Please comment on this, if it's only to say "good luck mate! (just nice to know someone actually reads my post!)

Have a nice day,
Richard.
rlmts@controlit.fsbusiness.co.uk

[HuFlungDung]

Hi RLMTS,

What happens if you simply cancel the tool offset before you attempt the return to home?

This could be a parameter option, whether the current tool offset is cancelled when a new tool change is commanded. If the parameter is "Off" then this might explain what is happening.

Also, check that your softlimits are set properly for the tool extremes, presumably to allow the tool that has to move the fartherest, to be able to complete its move without hitting the soft limit.

[wms]

Good Luck Mate!

[RLMTS]

Hi Huflungdung and WMS!

Thanks for taking the time to reply.

If you see my 2nd post, you'll see that cancelling the tool offset (G40?) seems to do nothing.

The Software limits are as they have always been.

Depending on the move (direction) the S/Ware O/T may not necessarily operate, but position seems wrong.

The main point seems to be the G40 ? (see L959 Listing and my 'manual data input' code)

I can clear the offset by programming D0 in the move block, but this was never in the original code?

Have a nice day!
Richard.

[HuFlungDung]

RLMTS,

Cancel a tool offset with T0. You should try this in addition to the cancelling of the work offset G40.

[RLMTS]

Hi Everyone,

Thanks for your posts!

The preparity command 'G40' does not seem universal/standard for cancellling a 'tool offset' so I am looking into the possibility that when the memory was lost, and subsequently reloaded, they did not 'tell' the control what it was, or selected the wrong description of control.

With Siemens System 8, after clearing all memory, amongst many other things you have to 'boot up' holding the 'input' button and a numerical button from 1 to 5. This tells the processor what type of System 8 control it is.

eg.
'input + 2' = "8M Sprint"
'input + 5' = "8M"
and there are others for 8T, 8MC etc....

The reason I am 'down this road' is because of a simple comment I read on one of many photocopies of G Codes for Sys 8.

One copy (but not others) said.....
"G40 = Cancel Tool Offset" (8M Only)"

I have to hold on to the fact that the L.progs and P.Progs have not been changed.

Regards, Richard