Thread: QT20 Tplus stays in single block while running a program

This is my first cnc lathe program. When in auto mode no combination of button press will get out of single block mode. It will go through the program even display its operations on screen , but continues to halt at the end of each block. the LED on the single block button blinks as it runs through program
HELP ! What am I doing wrong ? ?

David Lawrence

could be a coolant pump or some other "non-fatal" thermal trip

When you get a themal trip it throws it into single block. But you should get somekind of "error msg on the screen " though.

Some door interlock feature or a waylube alarm maybe? Key switch in setup, test, mode? ballscrew lube alarm?

Had the same problem a couple of days ago with a QT8 T32 and it turned out to be the coolant pump relay thermal tripped just a wippin boy mentioned. What was odd about it was that you could run the pump in manual which may bypass the thermal relay but would alarm in auto and single block only. The pump was warm to the touch (which would be expected for running for several hours) and the relay was ambient temp. Haven't had the problem since then.

It appears that any one of the items previously mentioned items will keep it in single block ops. It may just be a process of elimination till you find the culprit.

Yup. . . . there is a lube pump failure alarm active.

I connected the two wires from the pressure switch above the clear plastic container (which I take to be ball screw etc lube) That didn't make it go away. Well there are several things to do now to track it down

Thanks guys for all the insights

David Lawrence

first would be little motor in lube is dead
another common is a broken lube line somewhere that won't let system build pressure
does it clear if you pump it up by hand?

What was odd about it was that you could run the pump in manual which may bypass the thermal relay but would alarm in auto and single block only

had the same kinda thing on a old qt8 once
machine won't "bypass thermal" but what i decided it was was one of the little ice cube relays was acting up giving false alarm,never was sure it just quit doing it after a few weeks (fixed itself ...my favorite)

No the alarm doesn't clear with hand pumping . . . . .I'll get a piece of wood to push with , the manual pump is awkward to get to . Perhaps I wasn''t pumping long and hard enough.

But, since the wires are now jumpered together at the pressure switch it woud seem that would generate an alarm clear condition.

Would be great to have a measurable setup like pressurizing an oil vessel with air above the oil , the oil exit in the botton and then determine the volume of oil discharged in a specified time frame pressurized at a known pressure.

The ballscrew looks wet with oil however oil level in the clear plastic tank hasn't dropped noticably. What would be a typical usage rate ?

David Lawrence

on old machines it wasn't a jumper thing
it was a disconnect the wire and leave it dangle thing
at some point they went to software that had see the pressure switch go high and then low (to stop guys like me from jumping out alarm)

What would be a typical usage rate ?

somewhere between an inch, to half a tank over a day depending on who set the flow rate

Had a little trouble getting on but another new member has arrived.

Stuck in single block normally means you have the door interlock active.
I suggest you adjust or replace broken door switches. You can also bypass the the interlock by setting the machine in test operation via changing a parameter. This will allow you to open the door when the machine is running.

Checking further showed the lube switch operates on 24 volts DC , also that it is a normally closed switch and that consistantly opens up with a couple pumps of the hand pump . By hand pumping at startup and occasionaly later it now stays out of single block and runs fine. I'v left the voltmeter on it in parallel with the switch to see what its doing when it opens 24 VDC appears on the meter and all is well.

The motor is not running there is 96 volts AC to the motor is this correct ?

THANKS

David Lawrence

If you have 96 VAC 'to the motor', it should be turning! If it's not turning, you will not make your pressure switch which drops the 24 VDC off the alarm timer, which resets the alarm from turning on.
Lee

An important detail about "manually pumping" the lube pump is to NEVER force the plunger down! Only pull the plunger up, and let it fall on it's own.

Forcing it down can damage the tiny gears inside the lube unit.

And, the motor should be turning constantly. It drives the gear train that raises the plunger every so often. If the motor ain't turnin', it is either not getting proper voltage, or it's bad.

Also, my QT15's only use about 1/2" of lube per 8 hours running. Miserly little bastards with the Vactra #2.

Greg

Greg is correct in lifting and not forcing the handle down. I thought mine was bad but after taking it apart and cleaning, added a couple if test leads and found that the motor was working but it turns so slow that I had to have it apart to notice. The handle only comes up once every 5-10 minutes or so and then lowers very slowly as the lube is pushed thru.

If the tank has been run empty it can be a real bear to get it working again. Ask me how I know!

if it has sat awhile there is a tiny ball check in the bottom that gets stuck
the felt also loads up with sludge
i've also had a couple that wore out the casting that the worm screw rides in alowing lose of contact between worm and wheel, i bushe those with a piece of brass and got them up
if you machine has a "Lube" in it there in one of the carolinas for parts and support
google Lube USA