Novamill Stepper motors dead?

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RaspberryJam
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Joined: Sat 07 Aug , 2021 10:34 am

Novamill Stepper motors dead?

Post by RaspberryJam » Sat 07 Aug , 2021 15:58 pm

Hi all - I've recently took a punt and purchased a Novamill from a model maker who said he had never gotten the machine working and it's likely that the machine has not moved in 15 -20 years. It's an ATC version from 2000 with Denstep control box, lots of original floppies and FANUC desktop tutor keyboard but doesn't have a licence of VR milling. I've installed DOS 6.22 onto an old PC and managed to communicate with the machine using FANUCMD.exe. Red LED in the control panel shows an '8' and I can turn coolant on/off, move Z axis, start spindle, etc.

The machine still has the perspex cover intact and looks clean and dry but has been used to cut modelboard which coated the slideways. I cleaned down the machine sideways which look rust free and re-lubed with correct spec slideway oil but I think I was too hasty to get the machine moving. When I tried to home the machine, the Z axis homed first - moved to the top and moved back down a few mm. FANUCMD updates with Z+115. The Y axis initially made a drive noise as though it was trying to move the axis but I hit reset when I realised it wasn't moving. It now makes a very high pitched noise as though the motor has torqued out (or a belt has come loose?). The X axis doesn't make any noise whatsoever when I try to move it. Wondering if it's sitting on an X- limit switch? Is there one?

Spindle moves, then slows, then moves, then slows. Guessing there's a drive belt which has become stretched and so is grabbing (driving spindle) then becoming slack (slowing down) then grabbing again. Are there replacement belts available?

Is there anything I should check/move manually before I start taking things apart?

Don't want to go the conversion route as the machine looks in great original condition and everything seems to be communicating as it should.

I am a CNC machinist by day so I was hoping I could program using CAM software and load the programs into FANUCMD. Would this work?

Thanks in advance for any help!

RJ

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Re: Novamill Stepper motors dead?

Post by TDIPower » Wed 11 Aug , 2021 8:53 am

If i remember correctly the steppers are direct on the lead screws on the novamill. With the machine powered down check you can freely turn the lead screws and try putting x y in the mid travel point.
When you tell it to home it should home Z up to the limit switch them back off to clear it. This is to clear the work area. Then it should do x and y in the same way. I think the nova should move the bed to the front left of the machine as home so if it doesnt and heads the other way slowly in x or y that would indicate it thinks it is on the limit switch and is trying to back off to clear it for the zero point. (Thus a limit switch failure).
If the steppers are screeching or juddering and the bed isnt moving then that could be gibs are to tight or it is slipping on the linkage to the lead screw.

Hope that helps

Pete

Martin
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Re: Novamill Stepper motors dead?

Post by Martin » Wed 11 Aug , 2021 12:45 pm

All 3 axis are belt driven & there are no overtravel switches.

If you look round the back of the machine you can remove the cover plate gaining access to the Y axis motor, belt & pulley.

Mihail
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Re: Novamill Stepper motors dead?

Post by Mihail » Sat 14 Aug , 2021 18:56 pm

Please let us/me know how you get it fixed.

Following with great interest.

When you do get a better look inside, could you please check if the Z axis ballnut is a Hiwin on your machine?

RaspberryJam
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Re: Novamill Stepper motors dead?

Post by RaspberryJam » Thu 02 Sep , 2021 13:09 pm

Finally got time to work on the machine so I've done the following:

Opened back cover and manually moved the Y axis which was sticking. With it freed up I cleaned and lubed the slideways and it now moves back and forward nicely. However, the axis doesn't always move in the direction I ask via the Desktop Tutor keyboard. Sometimes pressing Y+ moves the machine Y- and vice versa. Any ideas why?

Using the "TRVRS." button should home the machine in Z, then Y, then X, but all that happens is that:

Z axis is already homed so it does a little jump up Z+ then back down again.
Y moves either Y+ or Y- (depending on how it feels at that particular moment) and moves the table to the axis limit until the motor overloads and I hit reset. Tried both ways hoping a switch would home the axis but no joy.
X motor doesn't move at all when I try to jog it. Can I measure anything at the motor wiring to see if it's getting power or not? My first time measuring a stepper motor but I'm fairly handy.

Z axis is currently homed and can't jog it down to see if it's a Hiwin or not. Can't see any markings on the lower ballscrew bearing.

All help greatly greatly appreciated!

RJ

RaspberryJam
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Re: Novamill Stepper motors dead?

Post by RaspberryJam » Thu 02 Sep , 2021 13:13 pm

Also, is there a source for belts? All the ones I've looked at so far on the machine are past their useful life and permanently deformed. Do Denford sell a belt kit with XYZ and spindle belts? I know I can source them myself but curious if there's spares kits available before I go hunting through catalogues online.

Thanks!
RJ

Martin
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Re: Novamill Stepper motors dead?

Post by Martin » Thu 02 Sep , 2021 20:43 pm

It sounds like the Y axis is missing a phase to the motor.

Check the resistance on the motor wires going in to the rack in the electrical box. it may be just a pin pushed back in the harting plug socket on the side of the machine. You should be able to do a visual inspection if you unplug the electrical box. The Y axis motor wires should be in pins 4, 5,6,7.

We don`t sell belt kits but we probably bought them from Spen Bearings if that helps.

RaspberryJam
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Re: Novamill Stepper motors dead?

Post by RaspberryJam » Sat 04 Sep , 2021 19:24 pm

So I did a few tests on the machine today:

- Checked the wiring between the orange connector blocks to the Denstep control board and the Harting plug and all looks ok so don't think it's a cable issue.
- Did a check to see if the steppers are all 'working' by putting an LED across the motor coils at the orange denstep connector end (as per this video https://youtu.be/1U9pf7S_ov4) and got the LED to light across two coils per motor. Hoping that means that the steppers are all working?
- Checked the connections between the Y axis stepper and the control board and they all look correct (colours all correct to the electrical diagrams and everything seated correctly). Hoping that if a phase was missing it wouldn't have lit the LED when I spun the motor?
- Removed the X axis motor so it's completely free and so I can manually spin the pulley or see if it's moving.

Noticed a couple of things:
1. The analogue controls for feedrate override and spindle override don't change the % values on the home page. I would have expected them to move up and down as I rotate the pots?
2. Y axis homes when I manually press the Y+ datum switch with the axis around halfway. I think what's happening is that the machine moves to the Y+ switch then instead of moving back off the limit, it tries to keep moving Y+. Need to sort out the Y+ / Y- direction problem and then see if there's an issue with the position of the Y datum switch.
3. Tried using the QWERTY keyboard control rather than the Desktop Tutor in case it was something to do with that. Didn't resolve any issues.

Can't get X axis to move even though the wiring looks correct and the stepper will light an LED.

Is it likely that the Denstep board is damaged? Are there any things on there which might explain the Y axis +/- confusion and X not moving at all? Are there any common failure points/components I can check?

Thanks for all your help TDIPower, Martin and Mihail! All help greatly appreciated.

RJ

RaspberryJam
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Re: Novamill Stepper motors dead?

Post by RaspberryJam » Tue 07 Sep , 2021 10:48 am

Pulled the X axis stepper motor off and connected it up to one of the other axis motor terminal blocks. The X axis stepper runs perfectly when connected to the Y and Z axis outputs so it must be an issue with the X axis (AXIS 0) drive electronics. Can anyone help with diagnosing the issue?

Checked the X axis home switch and it looks to be operating correctly. Could it be something as simple as a faulty capacitor?

Thanks,
RJ

RaspberryJam
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Re: Novamill Stepper motors dead?

Post by RaspberryJam » Tue 07 Sep , 2021 11:31 am

Checked the output directly from the Denstep for each drive and am getting the following:

Z Axis (AXIS 2) = 5V across each coil and physically working correctly
Y Axis (AXIS 1) = 5V for only ONE coil (other motor coilreads 0V continually?) Guessing that explains the random direction choices?
X Axis (AXIS 0) = 0V on both coils

Really gutted. Don't want to go the route of a conversion as the machine is in absolutely mint condition - apart from the fact that it doesn't work. Where's the facepalm emoji when you need it... :(

All help really appreciated!!!

RJ

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Re: Novamill Stepper motors dead?

Post by DavidB » Thu 09 Sep , 2021 21:17 pm

You may find that one or more of the main power drive ICs have been damaged. If you search for L298 you'll get a number of likely useful posts on this BBS.

RaspberryJam
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Re: Novamill Stepper motors dead?

Post by RaspberryJam » Fri 19 Nov , 2021 0:26 am

So I've had a good read up on the L297 and L298s and I'm thinking they're the most likely culprit. I know I can go down the IC swap route, but before I break out the soldering iron, can I swap my Baldor F391 Issue 2 board for an F391 issue 1 from a Micromill?

Thanks!

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Steve
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Re: Novamill Stepper motors dead?

Post by Steve » Tue 23 Nov , 2021 18:49 pm

Denford can supply a replacement Base board with the stepper drives. They have stock.

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