Homing Problem on Triac

[benners]

Problem with Denford Triac PC circa 2001no ATC.

We are currently having a problem whereby the PC connects to the triac but is unable to get a response to home all. We are using VR Milling 2.25.3.917 via an RS232 cable.

When trying to home the machine the co-ordinates on screen move as normal but the machine doesn't respond by moving on any axis. Eventually the PC responds with Major time out problem sending - MB61(MB). This occurs on each axis individually and also on the home all command.

I have tried to get a response from the machine by starting the spindle. The machine tries to respond and it sounds as though the motor is trying to spin without moving and fuse F8 blows which is puzzling as this according to the schematic is for the work light. (I have just replaced the fuse and tried again with the light switched off - similar result however this time fuse F8 failed to blow and the 7seg display on the motion controller flashes 0 and then returns to L with decimal point flashing).

Inside the black control box the motion controller has an 8 showing on start up. After trying to start the spindle the 7seg display changes to L and the decimal point flashes.

I have had a look at the spindle and it rotates freely. The belt that drives the spindle is located on the motor and the armature of the motor seems to rotate freely. I am also able to rotate the pulley system that drives the Z axis to manually lower or raise the machine head.

Any help of ideas as to how to narrow down the problem would be greatly appreciated.

[angel-tech]

are you sure it's F8, as that's normally for the coolant pump.

You may have the axis drive psu down which is fed from F4.

[Martin]

Is the emeregengy stop relay powered up?

It may just be on a axis limit switch. Try pressing & holding in the "Axis Limit Overide Switch" while homing the machine.

[Denford Admin]

The initial problem sounds like the drives aren't powered up or enabled - check this first.
The fact that you get a timeout (MB) message could mean that the control card is resetting - indicating a problem with the power supply, something taking too much current etc...

[benners]

Many thanks for the responses. I didn't realise that receiving emails up responses was unchecked by default!

Denford Admin - how do I go about checking that the drives are powered up? I have tried pressing the Axis Limit Switch whilst trying to home the machine without success. I have also checked the fuse F4 which is fine.

[Denford Admin]

I didn't realise that receiving emails up responses was unchecked by default!

I know - it really bugs me that the default is to NOT notify you of replies to something you posted.

With the machine off you should be able to rotate one of the axes ballscrews by hand (The Z might be easiest to get to but I'm not sure if it has a brake on it?)
With the machine on, if the drives are energised then the ballscrews will be held in place and you won't be able to turn the screws.
You could also check to see if the motors warm up after being powered on (they are holding position all the time)

[benners]

Thanks for the really prompt reply.

I have removed the stepper motor from the x axis and have been able to rotate screw on that axis without a problem. I have tried the z axis but as you say I think that has a brake applied. The motor doesn't get hot as such but when I rotate the spindle on the motor i have removed whilst the machine is powered up the relay for the door lock switches (perhaps indicating there is some power going to the motor?).

[Denford Admin]

Just to determine if the steppers were powering up, you should be able to turn the stepper motors when the power is off.
When it's powered on,estop is out and you're connected to VR milling, you will not be able to spin the stepper motors by hand.

If the steppers are active, the axis displays count up when homing, but the axes don't actually move, it sounds like the step/direction commands to the drives are being generated but not getting to the drives.
The timeout is probably because the homing sequence never finishes.
Is this a rack system ? (is the Baldor card with the red 7-segment LED slid into a rack on the left hand side?)

[benners]

When it's powered on,estop is out and you're connected to VR milling, you will not be able to spin the stepper motors by hand.

I have just checked the stepper motors and they can be spun when the machine is powered, the e stop button is not active and the machine is connected to VR Milling. I guess there is an issue with these not receiving power hence the not homing. I assume that all three steppers for each axis are supplied by the same power source.

Is this a rack system ? (is the Baldor card with the red 7-segment LED slid into a rack on the left hand side?)

It is a rack system. I have checked the seating of all the cards and these seem fine. I have also attached a photo of what I am seeing when the machine is powered and connected to VR milling. On start up the card shows a L then the decimal point LED flashes and it then displays 8

[blatter]

there are 3 fuses located on the rack base plate, just to the left of the orange stepper connectors. i have had these blow on one occasion causing the steppers to fail. the cause in my case was powering up the machine with one of the steppers disconnected and the driver board still in the rack

[Martin]

I agree, The power LED on the Sprint 1200 spindle drive is on so the E-Stop relay must be enabled.

[benners]

Thanks for your suggestions. I guess there is an issue with the stepper motors not receiving any power hence being unable to home.

there are 3 fuses located on the rack base plate, just to the left of the orange stepper connectors

I have checked the three fuses as suggested by blatter and all three appear to be fine. Is there anything else to check to perhaps narrow the problem down further.

I have taken a video of what happens when I try to start the spindle manually and the error this generates. I would be really grateful of any thoughts.
The video can be seen at this link:-

http://dl.dropbox.com/u/14360805/CNC%20 ... ressed.mov

Thanks again.

[Denford Admin]

I'm pretty sure now that there is a wiring fault or the spindle drive is faulty.
When you do the M03 it looks like the main power is dipping so the rack is losing it's DC supply.
Check the spindle run relay - it may be possible to press it in by hand - if so does the same reset happen ?
If not then it could be an issue with the spindle run relay or the output from the control/rack

[Martin]

Has the machine been moved?

Check the pins in the harting plug on the connector on the back of the machine.

From the video it looks as though the 24volts DC (wires 60 & 61) is being pulled down when you start the spindle which will shut down the motion control card.

[benners]

Has the machine been moved?

Yes it has and hasn't worked since it has been re-sited.

Check the pins in the harting plug on the connector on the back of the machine.

I have checked what I think is the harting plug (the large interconnect between the rack/power supply and the Triac) and have reseated the plug with similar results. What should I be looking for. None of the pins on the Triac (the male parts of the connector) look bent or damaged.

From the video it looks as though the 24volts DC (wires 60 & 61) is being pulled down when you start the spindle which will shut down the motion control card.

That is exactly what is happening. I checked with a multimeter and the power on these wires is definitely being pulled down. Do you have any ideas what this could this indicate? The relays marked SGR and GIR are also switching at this point.

[Denford Admin]

You need to disconnect things related to the SGR(spindle go relay?) and GIR(Guard Interlock Relay?) bit by bit, until you find what is dropping/shorting the supply.
Try taking the fuse out of the spindle drive supply, or take the mains wires off it and try the SGR again - maybe the +24 will stay up this time...

[benners]

I tried removing the spindle drive supply fuse (F1) with no joy. I did notice though that when measuring the voltage the drop occurred across the ESR along with the SGR and GIR not sure if this is significant?

[Denford Admin]

Take a decent photo or make notes then remove the wires to the relay contacts, ie, remove whatever the sgr and gir are switching on to try narrow it down.

[benners]

Thanks for your help so far. I have had a look at what could be causing the shorting out of the SGR SRR and through a bit of trial an error I have narrowed it down to wire 31 that comes out of the SGR. Without this connected the machine will connect with VR Milling and on M3 (Spindle Forward) wires 60 and 61 do not drop to 0V. The SGR switches but nothing happens due to this wire being connected. VR Milling stays stable and responsive. What I haven't been able to determine from the wiring diagrams is what wire 31 connects to. I have attached a copy of the wiring diagram that indicates it may be the lube pump but have not been able to locate any other instances of wire 31 in the cabinet. Any ideas on how to go forward from here? Thanks again.

[Martin]

Wire 31 would normally be part of the 100volt line which as you say would power the lube pump. It would also power any solenoids fitted, the fan in the cabinet & also the 24volt DC which is what is dropping off.

It may be worth testing the continuity of wire 31 from the SGR to the lube pump on the back of the machine.