Triac PC Homing Issue

All info relating to the Denford Triac series of CNC milling machines

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AntCox
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Triac PC Homing Issue

Post by AntCox » Mon 24 Aug , 2020 19:59 pm

I have a Denford Triac PC that I am not able to home.
Pressing the home button causes the axis to move in the opposite direction. I am under the impression the Z axis homes up, Y to the front and X to the left. However on pressing the home button, the axis move in the opposite direction until they hit the travel limit switches.
Any suggestions?

TDIPower
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Re: Triac PC Homing Issue

Post by TDIPower » Tue 25 Aug , 2020 19:15 pm

sounds like there is an issue with the home position switch. Im not familiar with the triac but on other machines when you hit the home button the machine sends itself to the home location switches and presses on them then it slowly winds away until the switch changes state again. So if you machine is moving away from the home location switch it sounds like it has failed and thinks it is pressed so is trying to move away waiting for the switch to change state.

Pete

DavidB
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Re: Triac PC Homing Issue

Post by DavidB » Tue 25 Aug , 2020 22:02 pm

My Triac PC uses NAMUR inductive proximity sensors for the home sensing rather than switches, they're 2 wire and there is circuitry on the auxilliary card to convert the changing resistance to an open collector signal for the main Denstep card home inputs. I don't know if they're susceptible to ferrous debris effecting the signal but it might be worth checking they're clean. The Z one is visible when the head is down near the top of the column in the centre, I've not looked for the other 2. The signals are available on one of the ribbon cables and the connection details are in the circuit diagrams. Normally a NAMUR sensor runs with 8.2V supplied to it and a sensing circuit used to sense the change in resistance, the Triac supplies 12V and a higher load resistance buts works the same. It may be possible to get a meter on the signals where they come in from the machine connection loom and check to see what the voltages are and if they change when the home position is approached.

AntCox
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Re: Triac PC Homing Issue

Post by AntCox » Tue 25 Aug , 2020 22:10 pm

Yes mine has the same sensors. However when I press home, the axis go in the opposite direction and as such it doesn’t come into contact with the proximity sensors.

DavidB
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Re: Triac PC Homing Issue

Post by DavidB » Tue 25 Aug , 2020 22:37 pm

I was thinking from Pete's description of the homing process that if the NAMUR sensor was contaminated or failed then the control card may thinks it's at home already and moving away to detect the transition but no change found so an indication of some issue hence the suggestion to try and check the sensor output voltage to see what level it's at and whether it changes, can you use the software to drive the axis towards home. My Triac is in the process of conversion to LinuxCNC.

TDIPower
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Re: Triac PC Homing Issue

Post by TDIPower » Thu 27 Aug , 2020 17:13 pm

is this on all axis or just one? if all that would be a bit odd unless say they sensors are all powered from the same source and that supply has failed. On the switch type I'm not sure if they are normally open or normally closed and if they connect high or low +v or 0v.
I would be looking to the sensors and supply lines be them +v or 0v in which ever case


Pete

Martin
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Re: Triac PC Homing Issue

Post by Martin » Sun 30 Aug , 2020 14:13 pm

If the Triac has been upgraded then you need to change type to Triac VME.

I presume you are running VRMilling version 5.

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