New to me ZX45 milling machine

[Megar arc 5040dd]

What came that way? The table or the scale?

The table is straight the scale is curved. The reason it is currently shimmed out .020" at the one end is I was trying to get the ends to be the same reading before I payed closer attention to the dial indicator as it was crossing the middle and that is when I realized it had a bow. I will take the shims out and play some more.

I appreciate your concern. But 7 thou is nothing. You won't break it. Bottom line is that you can't fix that any other way without putting your read head onto a mechanism that moves it in and out to follow the scale. That's ridiculous. So you have to straighten out the scale.

The read head itself is spring loaded to stay against the class I assume this it to make up for any minor deviation in the extrusion. Also I don't know if the glass itself it bowed or just the extrusion or if its not bowed at all and it is just a variation in the width of the extrusion.

First step will be to remove the shims and see where I am at. I may also move my indicator to be in the center of the column. That way I can make sure things are the same from end to end as best I can. The way i have it now measures more to one side than the other. Not sure if this matters but I like symmetry.

 

[Susquatch]

What came that way? The table or the scale?
Just re-read the whole thread and I didn't see anything.

The scale. See post 71.

But reading his last post I'm no longer sure he knows.

 

[Megar arc 5040dd]

Well a bit of an up date and more of a head scratcher. I was playing around removing shims and taking measurements when I had the idea to flip the scale around end for end. In theory it should then read that it the middle is bowing out since before it was bowing in. Well it doesn't. It just reads that it is bowing in same when I put the straight edge on it. Also I noticed when playing with the shims that the straight edge didn't show a bow unless the scale is bolted top the machine. Something, though I don't yet know what, is making it bow when it is bolted to the table. I have checked the edge of the table with a straight edge and feeler gauges and it is flat. So as of now I am a little stumped.

 

[Susquatch]

In theory it should then read that it the middle is bowing out since before it was bowing in.

I don't agree with that. It should still bow in. Which it did.

Just put a Shim under the middle and be done with it.

 

[Susquatch]

Also I noticed when playing with the shims that the straight edge didn't show a bow unless the scale is bolted top the machine.

This is new info. What this tells me is that the end brackets are not parallel to the scale body.

FWIW, my magnetic scales have three screws on each end (in addition to the main mounting screw) which are meant to compensate for this as well as for twisting.

But....... I still say put a Shim under it and be done with it.

 

[Megar arc 5040dd]

I won't say how many hours I spent figuring this all out but it is now reading just under .001" over the span of 18".

This is new info. What this tells me is that the end brackets are not parallel to the scale body.

FWIW, my magnetic scales have three screws on each end (in addition to the main mounting screw) which are meant to compensate for this as well as for twisting.

But....... I still say put a Shim under it and be done with it.

You are right there was an issue with the end bracket. So long story short I shortened the scale to the exact length of the bed then had to drill and tap new holes for the end bracket. I did this by lightly clamping both the bracket and the scale body to a parallel on the side that would go against the table. And that worked great. Where the problem comes in is I then realized that the end caps on the cover/guard would then stick proud of the table. I decided to cut down the scale another 1/4" so the guard ends would be flush with the edge of the table. Otherwise it would bug me forever. I cut the opposite end this time because there was enough space that I didn't need to cut the glass scale just eh body. I then just drilled the existing holes a bit deeper and tapped a feww more threads and that was that. I didn't realize until tonight that the end bracket that I used the existing holes on wasn't perfectly flush. That was issue number 1.

Issue number 2 is that it turns out the back edge of the table is out of parallel with the X axis by .002" over the distance of 24". No idea why but it is. and it just happened to at the same end that the bracket was out.

At first I tried shimming the middle then I had low spots half way in between the ends and the center shim. Finally in the end I shimmed the one end .005" and that got me close. I then added another .0035" and that got me to where I am now at just under .001" of deviation over 18".

For the life of me none of this really makes any sense to me and I will freely admit that it was all trial and error and shear dumb luck. I can't understand why it curved like that initially. I would have thought if one end wasn't sitting right that it would just be at an angle. This was supposed to be the easy scale since it's the only one on a machined surface. The Z axis was way faster and easier and it was on a slightly tapered casting.

now I just have to make a mount for the read head and a new mount for the way cover. Then onto the Y axis.

 

[DavidR8]

I won't say how many hours I spent figuring this all out but it is now reading just under .001" over the span of 18".



You are right there was an issue with the end bracket. So long story short I shortened the scale to the exact length of the bed then had to drill and tap new holes for the end bracket. I did this by lightly clamping both the bracket and the scale body to a parallel on the side that would go against the table. And that worked great. Where the problem comes in is I then realized that the end caps on the cover/guard would then stick proud of the table. I decided to cut down the scale another 1/4" so the guard ends would be flush with the edge of the table. Otherwise it would bug me forever. I cut the opposite end this time because there was enough space that I didn't need to cut the glass scale just eh body. I then just drilled the existing holes a bit deeper and tapped a feww more threads and that was that. I didn't realize until tonight that the end bracket that I used the existing holes on wasn't perfectly flush. That was issue number 1.

Issue number 2 is that it turns out the back edge of the table is out of parallel with the X axis by .002" over the distance of 24". No idea why but it is. and it just happened to at the same end that the bracket was out.

At first I tried shimming the middle then I had low spots half way in between the ends and the center shim. Finally in the end I shimmed the one end .005" and that got me close. I then added another .0035" and that got me to where I am now at just under .001" of deviation over 18".

For the life of me none of this really makes any sense to me and I will freely admit that it was all trial and error and shear dumb luck. I can't understand why it curved like that initially. I would have thought if one end wasn't sitting right that it would just be at an angle. This was supposed to be the easy scale since it's the only one on a machined surface. The Z axis was way faster and easier and it was on a slightly tapered casting.

now I just have to make a mount for the read head and a new mount for the way cover. Then onto the Y axis.

Well it’s sorted now so well done.
Onwards and upwards!

 

[Susquatch]

For the life of me none of this really makes any sense to me and I will freely admit that it was all trial and error and shear dumb luck. I can't understand why it curved like that initially. I would have thought if one end wasn't sitting right that it would just be at an angle.

Good on you for getting it done. What I love most about machining is the learning. Hardly a day goes by when I don't learn something.

 

[Megar arc 5040dd]

So far there has been a lot of learning on this project and I love it. One thing I learned and will file away for the future is that cutting glass scales to length really isn't hard. Just takes patience and being careful. It's definitely not something to be scared of.