Compact CNC Power Supply: What the Tormach 1100MX Really Needs

• 1
  How a compact CNC power supply is loaded on the 1100MX
• 2
  What 60 A single phase actually means in the shop
• 3
  Symptoms that point to a weak power supply
• 4
  How much margin a compact CNC power supply needs
• 5
  When the 1100MX power envelope is the right fit
• 6
  Compact CNC power supply vs three-phase VMC service

A compact CNC power supply is sized by the worst 200 ms of a cut, not by the idle current. The Tormach 1100MX has an 8 HP spindle and an industrial controller running PathPilot, so most of the nameplate amperage is reserved for spindle acceleration and rigid tapping. Axis drives draw far less, and the control cabinet draws almost nothing once the machine is in cycle.

That split matters when you compare the machine to a full-size VMC. A 60 A single-phase feed is enough because the spindle does not start and stop on every tool change the way a high-production machine does. On a compact CNC power supply, the load meter is a better guide than the circuit breaker rating.

Rigid tapping is the hardest single event. The spindle reverses under load, and the inrush current can spike well above the steady cutting draw. If the circuit is shared with a welder, the voltage sag shows up as a spindle fault before the breaker ever trips.

Spindle acceleration is the second hard event. Going from 0 to 10,000 rpm takes more current than holding speed while cutting aluminum. The machine ramps the spindle during rapid moves, so the power supply rarely sees both peaks at the same instant.

Feed rates above 400 IPM in aluminum rarely push the spindle past 60% load. The limit is usually the tool, not the circuit. A 12 mm carbide end mill in 6061 at 3,000 rpm will run comfortably on a 60 A feed.

In stainless and titanium, the same machine spends more time in the cut at lower rpm. The spindle holds torque instead of speed, and the average current rises even though the peak is lower. This is the case where a compact CNC power supply margin of 20% matters most.

The control cabinet itself draws under 500 W. Servo drives add a few hundred watts during hard acceleration. Everything else on the nameplate is headroom for the spindle, which is exactly what a compact supply needs to deliver.

A 60 A single-phase circuit at 240 V delivers 14.4 kW of apparent power. The Tormach 1100MX does not use all of it continuously. The breaker is sized for the start of the spindle, and the wire is sized for the breaker. That is the whole logic of a compact CNC power supply for this class of machine.

The practical limit is voltage drop, not breaker rating. A 30 m run of undersized cable will sag more than the machine tolerates. Keep the run under 15 m if you can, and use 6 AWG copper for the 60 A feed. Aluminum feeders need one size up.

A dedicated circuit is the first rule. Sharing the feed with a compressor, welder or another mill invites nuisance faults. The spindle drive does not tolerate a 10% dip during acceleration, and it will fault before the breaker opens.

Grounding matters as much as the hot legs. The 1100MX expects a low-impedance earth path. A separate ground rod tied to the panel ground is fine, but a loose conduit ground is not. Bond the machine frame to the panel with a dedicated conductor.

In Europe and Asia, the machine is often fed from a 400 V three-phase supply through a step-down transformer. That adds a second source of voltage sag. Size the transformer at 15 kVA or more, and keep the cable from the transformer to the machine short.

Single-phase 60 A is unusual in an industrial shop, which is why the 1100MX gets called compact. A full VMC in the same work envelope wants 30–40 kVA of three-phase power and a much larger service. The trade is spindle torque and cycle time, not part quality.

Spindle faults during acceleration are the clearest sign. If the drive faults on ramp-up but runs fine at speed, the supply is sagging under inrush. Measure the voltage at the machine terminals while the spindle ramps, not at the panel.

Random drive faults in the middle of a cut often come from a shared circuit. A compressor kicking on next door pulls the line down for 300 ms, which is long enough to trip the spindle drive. Log the voltage for a week if the faults are intermittent.

Alarm codes that reference overcurrent or undervoltage are the machine telling you the supply is not holding. In PathPilot, the fault log timestamps each event, so you can match it against other equipment on the same panel.

If the breaker trips, the circuit is undersized for the spindle start. Do not solve this by installing a larger breaker on the same wire. Check the wire gauge first, then decide whether the feed needs to be upgraded.

A machine that runs fine for months and then starts faulting is usually a loose connection, not a supply problem. Torque the lugs at the panel and at the machine once a year. A high-resistance joint heats up and sags under load.

In a shared building, harmonics from other drives can also raise the neutral current. This is rare on a single machine, but it matters if you run several mills on the same distribution board. The fix is a dedicated feed, not a filter.

A 20% margin over the machine nameplate covers normal voltage sag and temperature rise. For the 1100MX on 240 V single phase, that means a feed that can carry 72 A without excessive drop, even though the breaker is 60 A. The margin lives in the wire, not the breaker.

Do not add margin by upsizing the breaker. The breaker protects the wire. Upsizing it without upsizing the conductor creates a fire risk and does not fix the fault. If the machine needs more current, run a larger circuit from the panel.

Transformer-fed installations need more margin. A step-down transformer adds 3–5% impedance, and that shows up as sag at the machine. Use a 15 kVA transformer for a single 1100MX, and 25 kVA if two machines share the feed.

Voltage tolerance is the real spec. The machine expects 240 V ±10%. On a 208 V supply, the spindle loses about 13% of its available power, which shows up as longer cycle times and more load on the tool. Check the actual voltage, not the nominal.

Temperature matters in a small shop. A 30 °C panel room can push the breaker closer to its trip curve. If the panel is in an unventilated corner, leave more headroom and check the breaker temperature during a heavy cut.

For prototyping and short runs, a compact CNC power supply is the reason the machine fits in a small shop. The trade is that heavy roughing in hard metals is slower. For parts that need full 5-axis motion, we move the job to a machine with more spindle power.

Prismatic parts, plates, brackets and fixtures are the sweet spot. These jobs use moderate spindle load for long periods, and the compact supply handles them without strain. Cycle time is predictable because the load is steady.

Prototype work is a natural fit. The machine is easy to set up, and the small footprint means it can sit next to a design office. For one-off parts, the spindle rarely runs at its limit, so the power supply is never the constraint.

Light 5-axis work is possible with a trunnion, but simultaneous motion in hard metals pushes the spindle harder. The 1100MX can do it, but the compact CNC power supply leaves less headroom for aggressive cuts. Plan lighter depths and higher feed rates.

Jobs that need 4,000 mm of travel or a Ø400 mm rotary table go to our larger machines. We run 16 simultaneous 5-axis centers and 16 mill-turn centers, with travel up to 4,000 × 400 × 150 mm. Those machines use three-phase power and hold ±0.005 mm on hard metals.

The decision rule is simple. If the part fits the 1100MX envelope and the spindle load stays under 80%, the compact supply is not a limit. If the part needs heavy roughing in titanium or Inconel, move it to a machine with more spindle power and a larger service.

We quote both paths the same way. Send the drawing and we return DFM feedback within 12 hours, with the machine recommendation and the tolerance we can hold. No minimum order quantity, from one prototype to 10,000+ parts.