Parameters question on VMC15

Hobby Shop · Dec 12, 2022

Hey Guys. I bought a VMC15 a few months back and finally got it online last night. The guy I bought it from said it was running perfect, needed nothing and had the machine checked out and battery replaced by the “tech” before he sold it to me.

I tried to do a tool change and the Z axis won’t raise high enough. It’s 1-1/4” to low. I put an indicator on the spindle and measured Z.
From the indicator to the DRO.
.100” indicator = -.162” DRO

Full disclosure: I don’t know the first thing about anything CNC but flipping through the pages I found this. I think these numbers are for a VMC4020? I haven’t changed anything just looking at the moment.

Any and all help would be greatly appreciated.

Thanks
Andy

Wade C · Dec 12, 2022

Open the pendant door... should be a sticker on the back with all the original parameters. Verify those with what is in the parameters (SETP). Just by looking at your first pic, Id guess either the battery died again, or wasnt replaced, or was replaced but the parameters were not set.

Your issue with the Z is likely that the parameters are for metric screws and your machine has inch screws. But seeing 4020 and 10k spindle makes me feel like none of the parameters are right, and are likely just the default set.

RC Mech · Dec 12, 2022

4020 is the default. Parameters are incorrect for the machine. I’ve read that the machine power should be cycled after parameter changes, and also that it doesn’t matter. I command “2” then “Return for power off” to return slides to zero then cut power.

Start it up again and check the values in SETP.

Hobby Shop · Dec 13, 2022

Thanks again for all the help. I’m heading out to look at it now. I took a picture of the parameters inside the pendant but cannot post them because the resolution is too high with the new iPhone.

Andy

Hobby Shop · Dec 23, 2022

Just a follow up. I had the tech out. The battery was good so maybe the parameters weren’t installed after the battery change. He installed the parameters and so far so good and now the tool change is spot on. He showed me a few things and it didn’t hurt to bad. Only $175

The good, X & Y axis only have .0004”backlash. I did a quick sweep of the table in a 3” circle and the indicator didn’t move.

The bad, I have to dig into the Z axis. With an indicator in the spindle, I can move it .005” by pushing up and the backlash is showing .004”. Looks like it’s time to change the thrust washers.

Thanks again for the help.
Andy

ducesrwld · Dec 26, 2022

on the Z you are in for new bearings not washers. still relatively cheap fix on these machines. i've got a vmc15 the spindle drive is going out and my X axis servo just went out. you are getting off pretty easy didn't know a tech would even show up for under couple hundred bucks these days.

triumph406 · Dec 26, 2022

Hobby Shop said:
The bad, I have to dig into the Z axis. With an indicator in the spindle, I can move it .005” by pushing up and the backlash is showing .004”. Looks like it’s time to change the thrust washers.

Is that .005 spindle movement in relation to the Z-axis ram itself?

Or in relation to the table? If so then you may also be getting a contribution from Ram movement with that check.

Hobby Shop · Dec 26, 2022

triumph406 said:
Is that .005 spindle movement in relation to the Z-axis ram itself?

Or in relation to the table? If so then you may also be getting a contribution from Ram movement with that check.

Yes. It’s the Z axis, ceiling to floor movement. There is zero movement on the indicator when I do a slight pull front to back. I did a sweep of the table and it’s good there too. Hopefully I’ll get lucky and and it’s just the thrust bearings.

triumph406 · Dec 26, 2022

Hobby Shop said:
Yes. It’s the Z axis, ceiling to floor movement. There is zero movement on the indicator when I do a slight pull front to back. I did a sweep of the table and it’s good there too. Hopefully I’ll get lucky and and it’s just the thrust bearings.

Put an indicator base on the bottom of the ram, with the needle on the bottom of the leadscrew, any movement between the 2 will be backlash in the ball screw, subtract that from the .005 will be thrust bearing backlash.

triumph406 · Dec 26, 2022

Hobby Shop said:
Looks like it’s time to change the thrust washers.

Some people change the Belleville washers that provide tool retention force every year. As it's an unknown machine, might as well change those as well.

How to increase FADAL drawbar tension (using shims)

I changed the belleville washers a while ago, 1 washer was broken, and maybe 8-10 were split. That gave me a drawbar tension of 900# After changing the washers I measured a drawbar tension of 1200#. According to a FADAL source the locking drawbar tension should be 1650#-2000#. I haven't seen...

www.practicalmachinist.com

triumph406 · Dec 26, 2022

McMaster P/No for Fadal Belleviles is 96445K295

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