Genmitsu 24V Power Supply

When the voltage sags, the controller board browns out and resets. On the bench that looks like a disconnect in Candle the instant the spindle starts, or a job that stops dead on the first plunge. The new spindle gets blamed, but the brick is the cause.

Genmitsu's upgraded supply is built to ride through that burst. It is still a 24V 4A, 96 W brick in normal running, but its starting current reaches 8 to 10 A, enough to get a 20,000 rpm motor up to speed without pulling the rail down.

• Normal load: 24V at up to 4 A for steppers, board and spindle together.
• Start-up burst: 8 to 10 A for the moment the spindle spins up.
• Protection: cut-outs for over-voltage, excess current, overheating and short circuits.
• Marks: CE, FCC and UL certified.

This brick carries the model number GM95-240400-D, the same designation the aftermarket replacements copy. Genmitsu asks owners to check whether their existing supply is the old version before ordering, since the model name alone may not show which one sits under the bench.

Doubling the rpm changes how the machine cuts. At the same feed rate, each flute takes a thinner chip, and a thinner chip means less force on a light frame and a smoother edge. Or the feed can rise while the chip stays the same, which shortens jobs.

Acrylic shows the change most clearly. It needs a real chip, not rubbing, or the edge melts and re-welds behind the bit. A single-flute bit at high rpm with a brisk feed and shallow steps gives clear, glossy edges.

Faster is not always better, though:

1. Keep the feed up as rpm rises, or the bit rubs and heats.
2. Update GRBL setting 30 to the new maximum rpm so spindle commands scale correctly.
3. Check runout on the new collet; at 20,000 rpm a bent bit breaks quickly.

Heat is the other variable. More rpm with too little feed turns cutting into friction, and on acrylic or PVC foam that melts the kerf shut. Start from a conservative feed, listen for a steady cut rather than a squeal, and raise the feed in small steps until the chips come off as flakes rather than dust.

The steps, on a 3018-PRO or PROVer:

1. Power the machine off and unplug the old brick from the wall and the controller.
2. Check the old brick's label for 24V, and keep it as a spare if it still works.
3. Plug the new brick into the controller's barrel socket and then into the mains.
4. Connect to Candle or UGS and confirm the board responds before touching the spindle.
5. Start the spindle at its top speed with no bit load and watch for a disconnect.

If the spindle comes up to speed and the board stays connected, the swap has done its job. Run a short test pocket in pine or MDF to confirm it holds under cutting load.

Placement matters more than it seems. The brick is 12.7 by 5.6 by 2 cm and sheds heat through its case, so it wants air around it:

• Keep it off the spoilboard and out of the chip spray.
• Do not wrap it in the machine's cable bundle or bury it under stock.
• Leave enough cord slack that the gantry never tugs the plug.

Genmitsu sells the supply on its own and bundled with the GS-775M 20,000 rpm spindle. Buying the pair together removes the guesswork, since both were designed as one upgrade. The upgrades logbook covers the spindle swap itself.

For a machine that will stay stock, an aftermarket 24V 4A brick is a reasonable replacement. For a machine with a faster spindle, the published 8 to 10 A start-up figure is the reason to buy Genmitsu's own.

Where this supply is the wrong choice:

• 300 to 500W spindles. Those draw far more than 96 W and come with their own supply or controller box.
• Non-Genmitsu frames. It is built for Genmitsu machines; check the barrel plug and polarity before using it on another make.
• 12V machines. Some 3018-SE V2 kits run on 12V, and 24V would damage their boards.

There is also the question of what happens when a brick fails. A supply with over-voltage and short-circuit protection shuts itself down rather than passing a fault on to the controller board. Genmitsu lists all four protections on this unit, along with its certification marks.

Three conditions make it the right brick: the machine is a Genmitsu 3018-PRO, PROVer, PROVer Mach3 or 4040; the planned spindle is a 775-size motor; and the existing supply is the older version. If all three hold, this brick is the matching half of a spindle upgrade. The Genmitsu 3018 logbook covers the machines it powers.