z-truck, how tight?

[badger2424]

tried the springscrew adjustment, doesnt work and gets errors, how do you tell the exact tension you need on the belt?

[fwharris]

From the instructions for the Z truck replacement:


Re-tension the Z-truck belt:

In order to keep the truck in place while you tighten it,

replace the Z-truck motor pack tensioning shoulder screw and spring with the 4mm
Allen wrench (See Figure 10). This screw and spring set the tension on the belt to
the correct level. Tighten the shoulder screw all the way down.


4.


Tighten the two screws holding the Z-truck motor pack: Tighten these two

screws as tight as possible by hand. Check again and make sure that the Z-truck
motor pack tensioning shoulder screw and spring are in place and tight before
tightening these screws. Failing to tighten these screws after the Z-truck motor pack
tensioning shoulder screw and spring will result in an incorrect belt tension. Also
make sure that all wires are clear of the area. It is possible to pinch the wires
coming up from the board sensor when this interface is tightened. Move the Z-truck

up and down its entire travel feeling for jerky or noisy motion. If the motion is not
smooth the belt is not tensioned correctly or the motor pack gears may need to be
adjusted.
5. Tighten the adjustable roller bearings: This is the most important step in the
replacement process. First using the 12mm flat wrench to hold the roller stud,
tighten the roller screw so that the face of the hex stud is snug against the back of
the casting. Do this for both rollers but do not fully tighten the screws. The problem
that must be avoided is creating a cant to the truck by not having the face of the
roller stud flush with the Z-truck casting. See Figure 14 and 15 for a comparison of a
properly and improperly assembled roller.


What kind of Z errors are you getting and what is the machine doing when you get them?

[badger2424]

FW I can find the insturctions, but the guys that use the machine give better info than some person that are reading a list. Sorry to be blunt.

[fwharris]

FW I can find the insturctions, but the guys that use the machine give better info than some person that are reading a list. Sorry to be blunt.

Badger,

No problem on being blunt and I agree that sometimes a little insight to the insrtuctions goes a long way for getting the job done! I am getting ready to install the rubber belts so Im guessing I might be in the same situation as I've read that others have had issues with the instructions on that one..

The couple of times that I've had to remove and install the Z truck/motor I just followed the instructions as written with no issues. I think the important part is getting the tensioning shoulder screw tightened down all of the way as this does set the proper belt tension.

You did state that you were getting Z errors. What kind and when are you getting these? It might not even be and issue with the belt tension. It could be something with the z bearings.

[Digitalwoodshop]

Searching "Z Stall" would have you come up with a long list of what can cause it... Not sure when you mention the spring loaded screw on the top of the Truck... It is a shoulder Screw and can only be tight... and the spring provides some movement.

If your talking about Tight as is Bearings.... There is Tight as in Closed or Cam position on the rails or squeeze the rails.... I can only be max cam position and nothing more.... Never too tight....

As for the screws holding the Cam Bearings.... I recommend painting the flat of the Cam Bearing with nail polish that will be facing out when the cam is fully closed or squeezing the rails. Use the wrench to locate that position then snug the Philip screws. Then back off the Cam Wrench 1/8 a turn and re snug the screw... Not tighten the wrench 1/8 turn. TOO Tight you SNAP the screw... TOO Loose and the Cam Turns later...

AL

[badger2424]

How stupid am I, I ment the belt on the y motor. No wonder I couldn't make heads or tails of what you guys were saying. Sorry fwharris!! Sometimes my brain doesn't show up till the next day. When I tighten to the end of the spring loaded screw opposite the menu buttons and tighten the set screw, I get Z errors. Tightened a little tighter by forcing the wheel plate and tightening, then I get a humming noise from the Y motor. I can't find a happy medium between fixing the Z errors and the humming I know isn't suppose to be there. Thanks guys, bear with me.

[Digitalwoodshop]

Since we are talking about the Y Axis or Left Right....

Things that can cause this problem....

The Y Gear Box Bearings are shot in the gearbox. Easily replaceable but if you have worn the Y big plastic shaft gear then you need a new gear or gearbox or Y motor with gearbox. A OLD Z gearbox will work too....

OR one or more Y Rail Bearings have Frozen.

OR The Y Gearbox sits in a U Shaped area of the frame of the machine. If the Big Plastic Gear is rubbing on the frame it will cause this.... Either the Motor is mounted too close to the Center of the machine on the U Shaped opening or the bearings are BAD.

TO make it easier to tighten the screw on the Y Idle plate on the cut motor I drilled a hole in the top cover to let a long screwdriver reach it easy.

If you have over 450 Cut Hours then it could be the Y gear box bearings.

The Belt will never stretch so if it is loose then the bearings have worn.

3 Clicks at the Bit Plate = worn bearings too....

AL

[badger2424]

Sorry about not responding sooner, had to work my real job, and thanks Al for the info. I know its not the Y large motor gear or the gear wearing in the u gap because I just took the y motor off and cleaned and lubed the gear, neither is it the y bearings-checked those. I'll have to check into how to get to the y gearbox bearings and also check to see what a y idle plate is. I only get the humming when the z truck is all the way to the menu side, and it doesn't do it all the time while it is there. I'll check the y gearbox bearings and the y idle plate and let you know. Thanks

[Dan-Woodman]

I have had that same Humming for years. It only does it after measuring, when the z-truck is all the way to the keypad side. Sometimes lasts for 2-3 seconds.
later Daniel

[Digitalwoodshop]

Humming when the machine is cold is almost normal.... But I am not there to listen... It is the vibration of the wire coils in the motor... I would look for a loose wire on the Y motor plug too.... Servo Motors are a balance system with electronic pushing in both directions to hold the motor to the ordered position of to push and pull it through a cut... Could be a bad Y Motor.... Shorted winding.... messing up the ballance... I have a bad motor here... But it happened when the FFC Cable snagged and pulled out under power and shorted the motor... I forgot to put the little black cap on the FFC cable at the Z Motor and the cable snagged when it drooped.... Remember that cap....

Good Luck,

AL