Tormach PCNC 770 - Wire Hairs; Poor Cable Connections; Sensors (Limit Switches); Unexplained Stop or Limit Switch Error While Running

Chapter 10
178
UM10350_PCNC770_Manual_0916A
Troubleshooting
10.3.2 Wire Hairs
Somemes with stranded wire we nd that a stray strand, or wire hair, from the stripped end of the
wire may be scking out and touching another wire or the mill frame; this can cause short circuits.
10.3.3 Poor Cable Connections
There are a number of cables on a PCNC mill. Some are at cables connecng the control board to
the axis drives (or other devices), and some cables connect to the controller. An improperly seated
cable can allow some funcons to work and cause others not to. We have found that the ribbon
cables’ plug connecons can become loose during the shipping process.
10.3.4 Sensors (Limit Switches)
Sensors are one of the most common sources of problems on any mill. On the PCNC, the X- and Y-axes
have one limit switch which actuates at the end of travel in each direcon of both axes. The Z-axis
on earlier mills has two limit switches: one for each upward and downward movement. Newer mills
have one limit switch for upward movement. For more informaon, refer to Axis Troubleshoong.
10.3.5 Unexplained Stop or Limit Switch Error While Running
Electrical noise can oen cause strange and unrepeatable problems. Adding a ferrite noise suppressor
to the DB-25 cable going from the controller to the mill eliminates many of these problems. In
addion, adding a second DB-25 cable in series with the exisng cable reduces electrical noise
problems. We recommend using quality IEEE parallel cables.
If extension cables are used frequently there are exposed metal parts on the connectors. If these
metal parts contact other metal objects such as the mill frame, noise problems may occur. To x the
problem, tape o the exposed metal parts of the connectors to prevent contact.
10.4 Electrical Maintenance
10.4.1 Electrical Service
Certain service and troubleshoong operaons require access to the electrical cabinet while power
is on. Only qualied electrical technicians should perform such operaons.
Many electrical problems are self-apparent. Tracing electrical problems can be done with a
combinaon of the mill operang system, the LED indicators within the electrical cabinet, and the
mill acon.
The operang system has colored rectangular indicators, referred to as LEDs, on various screens to
indicate output or funconal status. The diagnoscs screen also has indicators for X, Y and Z home/
limit switches and accessory input status. These are useful to determine if the input is operaonal.
There are also various physical LED indicators within the electrical cabinet. Among these are: