Z Truck Problem

[scw]

Has anyone experienced this?

I had to replace the Z Truck. The one I received from LHR was "rebuilt".
Installed it, with new roller bearings, everything is tight, no play in the truck or belt.

Problem immediately after installing: assume you are cutting a simple vector line, a rectangle, .125 depth with a 1/4 bullnose- to help you visualize this, the cut is a juice channel in the top of a cutting board.

Everything begins normally smooth, the first cut is along the length, seems smooth and easy, then it takes a clean 90 degree turn and begins to cut across the width- AT THIS POINT the machine sounds labored and the flex cable begins to shake violently, at the end of the width before taking a 90 coming back across the length, the cut overshoots it end point about 1/4 " then comes back into line and cuts the length, at its end it makes a good 90 turn and finishes the 2nd width cut and meets the starting point accurately.
The violent shaking of the flex cable continues throughout the cut once it begins.
Also, the cut depth is wrong, about an 1/16" too deep.

Talked with LHR tech...did many tests, looked at X,Y movement, Z movement up and down, flipped the flex cable, checked for play in the truck and its bearing adjustment on the rails. Everything checked out good.
They suspect the Z Truck to be defective, want me to pay shipping to return their new defective part before sending another replacement.
My frustration is beyond words!
The reason the Z Truck was replaced to begin with was I stripped out the original trying to get that #$%! QC loose. I had to bite the bullet and change the whole assembly. The QC broke when a bit slipped in its bit adaptor and cracked off a piece of the chuck inside as it plunged at an angle into the wood.
Before that, everything was great.
I am running the software version 1.126
I'm up against the clock with Christmas around the corner.
Any suggestions before I loose more time in shipping?

[Digitalwoodshop]

Been there Done that....

I got a rebuilt Z last summer and had the same problem. The rebuild tech did not tighten the screws on the back of the Z truck holding the Z belt. So that could be your problem.

Second thing is the bit. If you used it right out of the box without removing the screws and putting lock tite on the screws. The bit can slip up into the bit holder.

Third is dust on your Z Encoder.

and last but not least.... Using a bit like that can place much stress on the flex. I would make 2 or 3 files of the same cut and change the depth in 1/3's down to make is less stressful on the machine.

You could break the Z truck when it is stressing like that.

Remember it is a HOBBY machine. You can cut the groove in hard wood, making it in 3 passes is easier on the machine.

AL

[Amonaug]

Been there Done that....

I got a rebuilt Z last summer and had the same problem. The rebuild tech did not tighten the screws on the back of the Z truck holding the Z belt. So that could be your problem.

Second thing is the bit. If you used it right out of the box without removing the screws and putting lock tite on the screws. The bit can slip up into the bit holder.

Third is dust on your Z Encoder.

and last but not least.... Using a bit like that can place much stress on the flex. I would make 2 or 3 files of the same cut and change the depth in 1/3's down to make is less stressful on the machine.

You could break the Z truck when it is stressing like that.

Remember it is a HOBBY machine. You can cut the groove in hard wood, making it in 3 passes is easier on the machine.

AL

It would be better to upgrade to 1.31 and use the multi-pass option for the path.

[twinpeaksenterprises, LLC]

Another thing you might check is while doing the sensor check on the Z-axis is to lightly tap the z pack motor to see if the reading on the sensor is still active. A problem I had was a short in the solder joint on the optical sensor which attaches to the encoder. With the short the sensor would cut off and on making the machine do crazy things. Also like Al said. Dirty encoder is also a problem. Even though it is enclosed it still has a tendency to accumulate small particles and dust. Be very careful when cleaning as the encoder is extremely fragile. Matt.

[Digitalwoodshop]

I think everyone should upgrade to 1.131. Having the option to do multi passes was something I and others complained about for a very long time. I am grateful for the option.

Getting the Z fixed first is top of the list. A cracked solder joint in the encoder plug will cause this problem too. It will skip seeing a count of the encoder and keep moving. This is what causes the Z to cut at a new incorrect level.

AL

[ChrisAlb]

Also, whenever the flex starts shaking on mine it means it's time to lube. Without fail, when I lube it, 15 to 30 seconds after starting it up again, the shaking goes away.

Use Crane Cam's assembly lube. The ONLY lube for the shaft in my opinion. Goes 40 or more hours between lubes and stays cool to the touch.

[Digitalwoodshop]

I was thinking cross grain and a big bit was causing the problem. Lube is good too.

AL

[ChrisAlb]

Funny thing is for me, with my cut bit at least, cross grain cuts are usually smoother and easier on the CW than cuts with the grain.

The type of wood plays a part but I've cut with my 1/4" bull-nose and all other shaping bits at 3/8" deep in one pass a lot with no troubles.

Type of wood, clean/sharp bits, CW working correctly, it all plays a part.

[scw]

Thanks for all the suggestions everyone.
The thing is, I've made that cut dozens of times with no problem.
Anyway, I look at the encoder and do the lube.

By the way, LHR is sending a new unit, no charge.
I'm in the service biz too, and I understand the tech on the other end having to tow the company line. But in a situation like this, which was just plain unfortunate, I had to insist on going over the techs head to get a fair deal.
Michelle Cantu. Thats all I need to say.
Some of you probably know her. She's a great help.

[scw]

I'm still trying to isolate the shaking flex cable problem.
I was advised to "clean the z encoder"
I need help finding exactly where that is...

also, I once found a .pdf here online that had a complete breakdown exploded view of every single piece of the machine. I dont remember what it was titled, but I searched the pdf section of the forum and haven't found it.
Anyone have a copy of that still? if so, could you post it?

[ChrisAlb]

I'm still trying to isolate the shaking flex cable problem.
I was advised to "clean the z encoder"
I need help finding exactly where that is...

also, I once found a .pdf here online that had a complete breakdown exploded view of every single piece of the machine. I dont remember what it was titled, but I searched the pdf section of the forum and haven't found it.
Anyone have a copy of that still? if so, could you post it?


SCW,

just go to CareWrights site. All the PDF's are there under downloads. I believe Michael has them on his site as well.

[scw]

still trying to work this problem out.

with the z truck, I also got the roller bearings adjustable assy (part 39)
and the flex shaft pivot assy with its screws(141).

However there are two black washers included.
I've looked at the drawings...I dont see any washers associated with the z truck rollers...but on my old truck, it looks as though these washers are on the
fixed rollers.
I dont see that in the drawings. Plus the fixed rollers came already assembled to the truck, apparently with thread cemented screws...they wont budge.

anybody been in this deep?

[DocWheeler]

SCW,

I just replaced my rollers a month or so ago and do not think the washers are associated with them. The center part of the roller needs to go into the slight recesses in the back of the Z truck for position and stability, so there would be no other place for them.

What size and thickness are they?

[Tom75]

is the washer black ? on my michene when it had come back from lhr the first time it had a black washer on the bottom right screw of the z-truck . the bearing that you use a wrench on to addjust . i can not rember witch thread in the forum but it has been talked about . . i will see if i can find a pic and post it when i find it

[scw]

the washers are black
I haven't measured them but they look to be typical 1/4" washers.

Today I pulled the whole truck assembly again and triple checked everything.
I also lubed the flex.
Upon examination of the z truck belt I found several of the little ribs somewhat torn and folded over...I cleaned it up reinstalled and it runs a bit better but is still off on depth 1/16 too deep.
The shaky flex settled some during Y movement but is still present. I believe the pressed bearing inside the z truck is at fault and am awaiting a replacement part to confirm that the problem doesnt lie elsewhere.
Thanks for your help and thoughts guys...I hope the new truck delivers tomorrow...I'll keep ya posted on events.

[scw]

This problem has finally been solved thanks to input from everyone here and their shared experience. The LHR tech support is good, but the people here on the forum are the best.

The erratic cuts and shaky flex I experienced was, in the end, the Z Truck I received as "rebuilt"...LHR sent another replacement, problem solved. I suspect something was wrong with the spindle bearing.

1 last question- instructions say to apply thread cement to the screws on the adjustable roller bearings- do you all agree?
is thread cement the same thing as RED LOCKTITE?

I never found what the black washers went to.
Thanks again gang for all the help.

[DocWheeler]

scw,

About the washer - note the first picture of this thread (http://forum.carvewright.com/showthread.php?t=9624), is that it?

[liquidguitars]

Also, whenever the flex starts shaking on mine it means it's time to lube. Without fail, when I lube it, 15 to 30 seconds after starting it up again, the shaking goes away.

Yes, I think lube could be the major issue with the shaking shaft but also bad bearings on the spindle..

If your carvewright is extra loud it could be the QC not installed correctly, bad bearings and or the flex shaft lube..

LG

[scw]

scw,

About the washer - note the first picture of this thread (http://forum.carvewright.com/showthread.php?t=9624), is that it?

yes Doc, thats it..the washer on the screw to the lower adjustable bearing.
But my original didnt have any such washer on it...and in the pack of new roller bearings there were two such washers.

great detective work by the way!

[Hexe SA]

http://forum.carvewright.com/showthread.php?t=9091
check this thread it's on page 6. I got the washers too and didn't know what to do with them. They go on the right side on the outside of the Z-truck bearing screws. I first installed them on the inside and had a heck of a time getting those screws back off after the red lock tight, actually stripped them and had to buy new ones from a fastner place here in town.
Eva

[scw]

This should be cleared up once and for all with someone from LHR and added to an updated .pdf.

The washer mystery continues- following the recommendation of our knowledgeable users I have been pointed to photos concerning the placement of the washer(s) which come with new roller bearings when you replace the Z Truck.
apparently they are included (but never mentioned) to resolve a problem with pressure developing at the lower right corner of the Z Truck and causing a cracking issue.

Photos regarding this (both from senior members and both guys who are a wealth of "been there done that" info) show the washers....but one shows the washer on the top screw, one shows the washer on the bottom screw.

Two screws are included in the kit.
The question remains- exactly where do they go?

[ChrisAlb]

It's a mystery to me scw. I still have my original truck and it has no washers on the screws at all???

Also never had those bearing tensioner's come out either. Hmmmmm..... :confused:

[bjbethke]

This should be cleared up once and for all with someone from LHR and added to an updated .pdf.

The washer mystery continues- following the recommendation of our knowledgeable users I have been pointed to photos concerning the placement of the washer(s) which come with new roller bearings when you replace the Z Truck.
apparently they are included (but never mentioned) to resolve a problem with pressure developing at the lower right corner of the Z Truck and causing a cracking issue.

Photos regarding this (both from senior members and both guys who are a wealth of "been there done that" info) show the washers....but one shows the washer on the top screw, one shows the washer on the bottom screw.

Two screws are included in the kit.
The question remains- exactly where do they go?
The washer goes on the bottom like the two images you posted. It takes the stress off the casting of the lower right bearing.

[woodpecker12]

I bought my machine 2 wks ago and when cleaning it I found the 2 washers on my machine as the pictures will show. Not sure how I bought a brand new machine and it already has the washer in place (bottom right side). All I know is that the machine is working really good and a bunch of stuff already. Maybe don't look a gift horse in the mouth????

[jcorder]

I think that washer is there for reinforcement. I had my truck break in that exact spot and sent the machine back to LHR. When I got it back, they had replaced the truck and put a washer on in that location. Perhaps there is a lot of pressure in that area for some reason, but mine has worked like a champ since they returned it.


Jeff

[Digitalwoodshop]

The right picture in post 21 is my picture and the black washer is on the lower right Z bearing screw. It is a optical illusion and the screw that is in the bottom is actually the Y Bearing screw.

So the answer is the washer is for the lower right screw. It prevents the taper of the screw head from acting like a wedge and breaking the cast metal of the Z a common failure.

A cheap fix for a too thin casting.

AL

[scw]

Digitalwoodshop has it right...I see the optical illusion now. My mistake.
The washer goes on the bottom screw.

Thanks for help everyone.
Enojoy the holidays!