Hi!
My school received a Denford Micromill Pro (manufactured June 2025) last autumn as part of our smart automation program.
Unfortunately the support bracket for spindle and motor broke during its trip across the pond. We got a new bracket and everything works except for the spindle. On spindle enable from the jog menu with the speed set at ~1000 rpm we can hear a relay click, but nothing happens.
We were sent a new motor and spindle control board, but these parts didn't resolve the situation.
We found the wiring diagram Steve kindly provided here and started running tests to see if any wires were damaged.
Everything checked out, so we tested the relay operation and contacts on the main board. All traces look good and the relays checked out just fine with 24VDC to the coils and continuity tests on the NO/NC contacts.
Although the schematic looks a bit different from what we are seeing, we were able to trace the path of AC power from the line connection, through the spindle fuse, through the spindle enable relay NO contacts, through the e-stop relays' NO contacts, and to the L1 terminal on the spindle control board. (We also confirmed the neutral path.)
We have an expected DC voltage drop between P1 and P2 based on the speed setting, but get 0 VAC between L1 and L2 on the spindle control board when the spindle should be enabled. It is notable that when testing VAC on the wires connected to the spindle enable relay COM and NO contacts we get 124 VAC even when these contacts should be closed. (We are assuming that this relay clicked based on several listening tests, but we don't have a stethoscope. I was able to visually confirm the two e-stop relays were working thanks to the clear shells.)
I am hoping someone can give us more advice here, as I would love to get this mill running for the students. It would also be great if there are updated schematics that match the boards we have.
Thank you for any assistance.
CNC Guru
Can you supply the serial number of the machine please.
Wow, thank you so much Martin!
After following the schematic we discovered we had never tested the guard latch electronics related to the spindle. (The guard open close state was reported correctly by the software.) We removed the Bernstein interlock and tested using the wires only and the spindle works!
The schematic is a little confusing in the section for this part. The wire colors appear to change between the connection to the board and the contacts on the interlock for the guard status and spindle enable.
The green terminal blocks on the interlock were connected as so, we would like to confirm if this is correct:
E2: White
21: Red
22: Yellow
E1: Violet
31: Black
32: Brown
After following the schematic we discovered we had never tested the guard latch electronics related to the spindle. (The guard open close state was reported correctly by the software.) We removed the Bernstein interlock and tested using the wires only and the spindle works!
The schematic is a little confusing in the section for this part. The wire colors appear to change between the connection to the board and the contacts on the interlock for the guard status and spindle enable.
The green terminal blocks on the interlock were connected as so, we would like to confirm if this is correct:
E2: White
21: Red
22: Yellow
E1: Violet
31: Black
32: Brown