Micromill losing alignment between layers diagnosis help

[gsport]

Hi,

Any advice on where to start (or rather look next) with this much appreciated.

I have recently aquired a used Micromill version with the conical slide end connectors to the stepper motors.

My first attempts at cutting are with MDF using a 6mm ball-end 2 flute cutter. I started with a cut of about 2mm depth and a feed of 280 but kept hitting issues with the X-axis drifiting about 4 or 5mm in a single layer (8 minutes).

I progressively reduced the feed until I was at 100mm/min and this seemed to work OK for the rest of that part but at 5 hours was way too slow.

My initial assumption was that the previous owner had been a bit keen tightening the Gibb strips or taking out backlash so I've slackened these all off. The previous owner also recommended lubing with Silicone lube whereas Sherline seem to suggest light oil, so I've drenched everything in WD40 to clean out and re-lube.

Doing a test using the "jog" function. I can take a big cut (3mm plus) at 500mm/min and it doesn't lose any alignment, so I thought I had it fixed. Started my next proper job and alignment issues are super bad and even the Z axis is losing alignment. I could understand Z axis being off if it was struggling to lift so getting too deep, but it's the opposite, ending up too high?!?

I tried cutting in air (well above the billet) and STILL had X axis getting out of whack by 5mm in 7 minutes or so.

So now I am wondering if something is happening between the computer and the miller, maybe some lines aren't getting sent or received? Or maybe stepper motors are just very tired?


Any advice on where to start diagnosing?

The PC it is linked to is very old (XP), but seems to work OK and is not connected to any networks or internet or doing anything else (though I may have left QuickCAMPRO running in the background).

George

[Martin]

What software & version are you using to control the Mill?

Also what connection do you have from the computer to the Mill?

[gsport]

What software & version are you using to control the Mill?

Also what connection do you have from the computer to the Mill?

Drawing with solidworks 2016
Processing with quickcampro

Sending to machine from vr milling v5 version 5.53.0.622

Rs232 cable from pc

Machine plate says software version v2.13


Rebooted the pc last night and when I started it it gave me an error that the machine version of something didn't match the driver (?) and prompted me to allow it to change it. (Which I did.. Sorry for vague description it was late and I was too hasty should have photographed it) still seems to be communicating ok but wonder if this is related.

George

[Martin]

If it has a NextStep top card fitted it would be worth running EasyUpgrader & checking the firmware is up to date.

[gsport]

If it has a NextStep top card fitted it would be worth running EasyUpgrader & checking the firmware is up to date.

Thanks. Had a quick search for how to check this but its not clear. Do I need to take the back off the machine (if so what am I looking for?)or is there a way to check through the PC? Took the back off and the numerical segment led display is red so that means not?
https://goo.gl/photos/QyZHf79wsWihnuRS9

Easy Upgrader doesn't seem to be installed currently.

George

[Martin]

It's a DenStep with a Denford Beta Eprom fitted so that should be fine.

Can you try cutting a 2D file.

It could be down to the gib strips being tight/slack or the backlash needing adjusting.

[gsport]

It's a DenStep with a Denford Beta Eprom fitted so that should be fine.

Can you try cutting a 2D file.

It could be down to the gib strips being tight/slack or the backlash needing adjusting.

I'll try a 2D file next but I really need the Z axis for most of the stuff I want to machine.

Already adjusted the Gibb strips and backlash nuts quite a bit and doesn't seem to make much difference.

Last cut was at only 200mm/min and in air and it still got well out of alignment on all axes within 10 minutes. The issue seems to be getting worse if anything.

Something is smelling a bit like it let the smoke out, but cant determine if it is the machine or the PC and nothing catastrophic seems to have happened inside either.

What is the best choice for lubricants for the slides and drive screws? Is it worth taking it all apart to properly de-grease and lube?

Would updating the board to a Nextstep and running newer firmware be a worthwhile step?

Is there any possibility the fnc file could be written as something impossible to cut? I have had issues in the past with my 3d printer where the .stl files created with Solidworks needed fixing before they would slice properly, but I am not seeing any error messages here.

Anything else?

George

[Martin]

It would make a big difference with a NextMove USB card fitted.

The lead screws require grease. We ship them with a tube of Isoflex NBU 15 grease & the sideways should be oiled.

[gsport]

It would make a big difference with a NextMove USB card fitted.

The lead screws require grease. We ship them with a tube of Isoflex NBU 15 grease & the sideways should be oiled.

Thanks, will try a full strip and re-lube, maybe there is a lot of old gunk in there.

Is the Nextmove USB card an easy conversion for the micromill? How would this be superior to the card I have now? I am assuming it is the NextmoveST card which seems to have a very long installation guide on the Denford site? What sort of cost would be involved? (Did try googling this but didn't find anything concrete)

George

[Martin]

The NextMove USB card would be more reliable as we can send info down quicker than down the RS232 line but as the Micromill only moves slowly you may not see that much of a difference.

[gsport]

So I've moved the machine round to get proper access to the back and found a few things.

1. The serial cable has a bit of a tear in the outer cover right by the connection to the machine. Could this be causing the problems I'm seeing? Or is it a case of either it works or it doesn't?
https://goo.gl/photos/9RbkeBF8VCRb78Ki6

2. The main heatsink by the fan was really really covered in dust. Could this have been a factor (though it seems a big bit of material to get hot that fast) I've given everything a thorough hoover and blown off with air now.
https://goo.gl/photos/86WPeCmuwmKUHAwJ9

3. There is a little white breaker that appears to be at 0 rather than 1. Is this correct? Or should that be "on"?
https://goo.gl/photos/a3aNWj6mZb5qRxre6

Thanks for any guidance

George

[Martin]

I think the cable would cause a software error but it may be worth changing it as it's not an expensive item. https://www.lindy.co.uk/cables-adapters ... emale-p528

The dust should not effect it.

The white relay will only move to 1 when you have power on, E-Stop released & turn the power key.

Have you managed to test it doing 2D work?

[Steve]

Hi. Just a quick note on here. The older machines with the Denstep controller cannot buffer moves so each line of the code is exicuted in turn. At the time the machine was built QuickCAM was not released and 3D manufacturing rarely considered. I suspect you are loosing steps as the machine is ramping to speed and stop during each move. The USB boards or controllers with a Green display (NS) have Ivac inter vector control allowing them to buffer moves and only slow down for axis reversal.
If you need the machine for 3D then you would be much better upgrading the control card.
You could try changing settings in the VR Milling to do with maximum exceleration etc but this would be trial and error.

[gsport]

I think the cable would cause a software error but it may be worth changing it as it's not an expensive item. https://www.lindy.co.uk/cables-adapters ... emale-p528

The dust should not effect it.

The white relay will only move to 1 when you have power on, E-Stop released & turn the power key.

Have you managed to test it doing 2D work?

Thanks. Got a new cable to try off a friend.
Not tried 2D yet as been overhauling everything and also I really need the 3D so it isn't that relevant whether that is OK unless it is a diagnostic test?

Hi. Just a quick note on here. The older machines with the Denstep controller cannot buffer moves so each line of the code is exicuted in turn. At the time the machine was built QuickCAM was not released and 3D manufacturing rarely considered. I suspect you are loosing steps as the machine is ramping to speed and stop during each move. The USB boards or controllers with a Green display (NS) have Ivac inter vector control allowing them to buffer moves and only slow down for axis reversal.
If you need the machine for 3D then you would be much better upgrading the control card.
You could try changing settings in the VR Milling to do with maximum exceleration etc but this would be trial and error.

That is very useful to know thanks. Do you know if it is possible to get the Nextstep board anywhere? Otherwise I suppose I should look at removing the board all together and using a break out board and something like Mach3?

George