Calypso CNC User Forums

I am not sure if it has anything to do with the software update or not. After the update I decided to reset all my tool library Tool Length Offsets. I am using a probe as master tool. In the past I have not used the auto TLO since I am using all repeatable height tools. I am trying to set up my tools and get a message ERROR: PTL measurement Negative! I have measured the PTL of the master tool and entered it into the tool library. It has an offset of 0 which makes sense to me. I have set the MC Z using the probe touch off of the touch plate, making the top of the touch plate MC Z 0. When I enter the next tool, which is shorter than the master tool and measure it using a touch plate. I get the error.

Program Startup
Sun - 11:41:10 ---MachStdMill Initialized
Sun - 11:43:16 ---Tool Change...Press CycleStart to continue.
Sun - 11:43:17 ---Moving To TC Position...
Sun - 11:43:17 ---Press CycleStart after Tool Change
Sun - 11:44:02 ---Tool Change Complete.
Sun - 11:44:05 ---Tool Change Complete.
Sun - 11:44:17 ---
Sun - 11:44:18 ---Op with Mounted Probe Ignoring Gage Block=TP (not sure what ignoring Gage Block=TP is?)
Sun - 11:44:21 ---Surface Found...
Sun - 11:44:22 ---Z axis zeroed to edge
Sun - 11:44:47 ---Tool Change...Press CycleStart to continue.
Sun - 11:44:47 ---Moving To TC Position...
Sun - 11:44:49 ---Press CycleStart after Tool Change
Sun - 11:45:36 ---Tool Change Complete.
Sun - 11:45:39 ---Tool Change Complete.
Sun - 11:45:56 ---
Sun - 11:45:57 ---Probe T# not mounted (Not sure what this is. I mounted a new tool #72)
Sun - 11:45:58 ---Probing to TCP TP along Z-...
Sun - 11:46:18 ---TCP Touch Plate Found...
Sun - 11:46:18 ---ERROR: PTL measurement Negative!
Sun - 12:34:51 ---Tool Change...Press CycleStart to continue.
Sun - 12:34:51 ---Moving To TC Position...
Sun - 12:34:51 ---Press CycleStart after Tool Change
Sun - 12:34:56 ---Moving To TC Position...

Hi,

thomsl wrote:... I have set the MC Z using the probe touch off of the touch plate, making the top of the touch plate MC Z 0. When I enter the next tool, which is shorter than the master tool and measure it using a touch plate. I get the error.

OK, so you made the top if the TCP touch plate be = MC Z0?
That is a bit of an unusual setup.... Since MCZ is set my mach when the axis is homed, I am not sure how you would arrange for MCZ0 to be at the top of the TCP TP....

Here is the normal setup:
Normally on a vertical mill, the top of travel on Z (head all the way up at the home switch) is MC Z0.
This is what you get after you home the Z axis to the home switch - mach sets the MC 0 to where it found the home switch.

Then to use the TCP TP, you first have to teach the system where the top of that plate is in MCZ. Since MCZ0 is at the top of the z axis travel, the TCP TP surface is going to be at some negative MCZ level. The way the system learns where the TCP TP is, is by using the "Set TCP MCz" button on the settings page, common tab.

What that button does is as you for the PTL of whatever tool is in the spindle when the button was clicked. Knowing that value, it then causes teh tool to probe downward to find the TCP TP. When it finds the TCP TP, it knows how far it traveled in the -MCZ direction, adjusts for the PTL of the tool and calculates the physical location of the top of the TCP TP in MCz. That value is stored for later use when using the TCP TP to measure tools. This is covered in section 7.1.4 of the user manual.
Note that it is only necessary to use a tool if the spindle nose will not reach the TCP TP surface. If you do not need to use a tool, then just tell the calibration process that the PTL of the moutned tool is 0.

Once the TCP TP is calibrated, the system measures PTL to tools by:
a) probing from the TCP, downward in MCz until the tool touches the TCP TP. We know know where the spindle was when the TCP TP was touched.
b) we also know the absolute level in MCZ of the TCP TP.
c) the difference between a) and b) gives us the PTL of the tool.

The error you are seeing is because the difference endedup with the calculated PTL being < 0..... which is a physical impossibility (at least for all the tools I have). Thus the system says, Hey, something is wrong here.... Let's tell the operator so he can fix this.

The most common reason for the calc to come out negative is that the PTL of the tool used to find the TCP TP for calibration was a bad value. That results in the stored TCP SP level being incorrect. That incorrect value is then used in the calculation and the result is a negative PTL value.

Also note that the TCP TP level is stored and used between mach sessions.. this depends on the machine being able to home accurately. If the home switch introduces error, then the effect is to "move" the TCP TP each time the machine is homed... and that can also result is errors in PTL measurement (including a negative PTL calculation).

A PTL (not a TLO) Should never be a negative value.

I suggest that you check out the calibrated level if the TCP TP - Confirm if it is correct or not. I suspect that the stored value is not the real physical level of the TCP TP.

Note that the Probe is not used to locate the TCP TP for calibration. Use a fixed length tool. Once the TCP TP is calibrated, you can THEN use the TCP TP to measure the Probe PTL (which by the way is the physical length of the probe when it triggers - not when it is at rest).

Dave