Novamill RPM not changing

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50Hz
Posts: 2
Joined: Tue 25 Jan , 2022 12:35 pm
Hardware/Software: Denford Novamill
Quick Cam 2D
VR Milling V5
Quick Cam Pro
Fusion 360

Novamill RPM not changing

Post by 50Hz » Sun 20 Mar , 2022 12:39 pm

Hello

Bought a Novamill & spindle speed is stuck on a single RPM (around 4500).

RPM adjust pot on unit controls software on PC so I know that side of things is working.

0-10v to motor control is at constant voltage around 4.6v if I remember correctly regardless of RPM selection.

Looking at the Baldor board (F391 issue 1)
There's a pot trimmer on the 0-10v circuit, I'm assuming this calibrates RPM. Rotating this pot has no effect on 0-10v motor signal.
Interestingly, there is a 4.1 Ohm resistance across the pot which seems a little odd. This resistance can be metered across Vcc & Gnd pins of the opto-coupler & also across 0v & 5v output pins of 12v DC - DC converter.

My next plan is to scope the output of D71054L (U11) ic which provides the signal to the opto-coupler to determine if the issue is located on the isolated o/p section, or on the digital side.

In the meantime - does anyone have any advice on this issue? Could it be that this particular mill was programmed to run at a fixed RPM for some reason?

Thanks

50Hz
Posts: 2
Joined: Tue 25 Jan , 2022 12:35 pm
Hardware/Software: Denford Novamill
Quick Cam 2D
VR Milling V5
Quick Cam Pro
Fusion 360

Re: Novamill RPM not changing

Post by 50Hz » Thu 07 Apr , 2022 22:27 pm

Update on this issue

Ended up replacing 12v DC-DC converter, SMD capacitor & op-amp on control PCB isolated output which got the 0-10v control signal working again but the motor would still not spin correctly. Further investigation revealed the Sprint motor control board minimum speed setting was at fault & not providing the common connection required for the 0-10v control signal. I suspect the pot maybe faulty but I overcome the problem by connecting negative wire of 0-10v signal to sprint board common pin.
Replaced some capacitors & soldered dry joints along the way. Everything is up & running again

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