Fadal 4020HT z axis not stopping midway through tool change

We recently purchased this machine from an auction and everything had seemed fine I was getting ready to run a program and it won’t complete a tool change now. CS is aligned I went through M19 and made sure resolver was calibrated properly and it looks fine. I need to mention it was changing tools fine with a simple tc,1 command and now it is dropping the tool in the atc and when it goes up it keeps going until it smacks the bearing at the end faulting out the axis requiring auto estop and then it tells me to CS all over again. Here is a link to video I made showing what it’s doing. YouTube

The position doesn’t seem to be an issue it almost seems more so like a calibration problem but then it worked for a week while I was cleaning it up. In the auction it was mentioned that this issue existed. We only paid $300 for the machine so replacing a few prts isn’t a big deal. Auction happens first week of Covid and nobody showed up so we bought several machines. Anyways I did put a cam file in it and all 4 axis work fine as long as I don’t change tools. Hoping for insight. Thanks.

Have you put a tool in to see how the carousel lines up with the spindle?
Possibly the machine is set up for Cat tooling and you are trying to run
BT. 5+mm difference on the location of the the V flange.

The machine goes to Z plus 4" on a tool change. Can you jog to that point and
not have a problem?

Yes it aligns perfectly. When it rapids up it just keeps going. I know these machines don’t have limit switches that’s why I mentioned a calibration issue?

I checked to make sure dro reads zero z axis at cs but it says 2.7” when it’s all the way up. Does that mean resolver is defective? Being the tool alignment looks good I can only presume.

Bobw said:

Have you put a tool in to see how the carousel lines up with the spindle?
Possibly the machine is set up for Cat tooling and you are trying to run
BT. 5+mm difference on the location of the the V flange.

The machine goes to Z plus 4" on a tool change. Can you jog to that point and
not have a problem?

Click to expand...

Also forgot to mention that the resolver has 1.8v. I can try cat tooling but the mp12 probe that came with the machine is bt40.

Spindle bt40



You can see the offset typical of bt40 on the drive dogs. My cat 40 machines have even drive dogs.

I'm getting a little confused here as to what is actually going on.

2 things to do, and they may not help you immediately, but they will help
try to figure out what is wrong.

I'm swinging in the dark here, not a problem I've seen.

When you Cold Start, at the "Enter Next Command Line" type SETZ and enter.
That will make sure your machine Zzero is the same as the cold start position,
as it *Should* be. Then Type SETX and SETY also. There is a command SET?
that sets them all but I don't remember it. See what that does for you.

Then lets make sure you've got the right ball screws called out in the parameters.
If you have "Metric" in the parameters, but actually have "Inch" screws, you will
definitely overtravel.

Now lets jog up to Z plus 4"(it should stop, and not go beyond that), and look at the screen, is the following error HUGE!!
If it is, you are sitting on the springs at the end (are there springs at Z+?). That means we got a problem.

If the machine is setup for CAT tooling, and the CS is set for BT, you could possibly over travel
going up. If you want to run BT, you'll need to drop the carousel disc lower. Which sounds scary,
but apparently Fadal made this really easy, just unbolt it and flip it over. Then of course, adjust your
CS position(rotating the encoder, and/or CSing one ballscrew rev under the line).

Weather you are going to run Cat or BT, you'll always be able to use your BT probe by hand loading it.

Bobw said:

Then lets make sure you've got the right ball screws called out in the parameters.
If you have "Metric" in the parameters, but actually have "Inch" screws, you will
definitely overtravel.

Click to expand...

I was thinking this too, could be wrong screw settings. But I think its the opposite way around. Metric are coarser so if you have Inch in parameters, but actually have metric crews, it will overtravel.

If you move the machine an inch, does it move an inch?

Uguessedit said:

View attachment 285964

You can see the offset typical of bt40 on the drive dogs. My cat 40 machines have even drive dogs.

Click to expand...

Thats Interesting. I have a factory 1996 4020 cat 40 machine with org spindle. it has the same dogs as your picture.
I have a factory 2000 30x20 machine that is BT 40 same dogs as your picture.
We converted the 30x20 over to CAT40 last month. its very simple just reverse the tool change plate and put in new cat 40 clips then align and set your tool clearance height from the plate..
we been having a issue with it dropping tools and not always on the .050 deck height position Spindle to plate. took the thing apart to day and the tool changer spindle is bent.

Cat40 height is .050 BT40 height is .250 for proper tool engagement during tool change.

As far as your z going up and erroring out. bob mentioned some good things too look at. I have never seen fadal do that before. get that fixed before you start loading tools cause if your cold start is off you could bust up your plate(very expensive) or bend the tool change spindle(cheap)
dont always rely on the cs position MARKERS were it was before you got it. if its a cat machine make sure you spindle height above the tool change plate is .050 set your CS there.. in older machines you mover the resolver in the newer machines use the SV commmand. its in the manual as well as the manuals on fadalcnc.
then try a tool change. but only after verifying .050(for cat40) is there.

Yes I zero’d at CS setH, SETZ etc... so I went and jogged the machine so the drive dogs touched the pallet. This distance is approx -17-3/8”. The dro is reading -10.95” so there is a mismatch in actual travel to what I’m seeing on the dro. I was understanding that the resolver sent feedback for the actual travel indicated I don’t see any scales on this machine. I’m not all that familiar with these dc machines so I can only presume the functionality. Following the resolver test that Fadal instructed it suggests it is ok however if it was replaced recently perhaps something was done incorrectly or it was damaged. My only other thought is perhaps the resolver shaft wasn’t tightened enough and it’s mechanical slippage. I will check that next. I also need to finish reading your post. Thanks for helping I know it’s not easy online and getting proper description of issues. What suggests to me that there is no mechanical slippage is the fact I get the same readings back to back jogging the axis. I will get the part number off the resolver perhaps they installed the wrong one??

Hey, wanted to update. I figured it out. Someone changed the ballscrews to inch screws when these are 700ipm metrics. I changed the parameter and now everything works. Going to run another test program and see how she goes with a few tool changes. I appreciate the help sometimes just thinking it through and writing it down can be the difference in finding the issue.