CRON Craft Medium

About the Machine

The CRON Craft Medium is the mid-size CRON Craft Station, with a 400 x 630 x 50mm working area. It runs the same 12,000 RPM air-cooled spindle as the rest of the line at up to 3000mm/min (118 in/min) feed rate, weighs 14.2kg, and connects over USB with GRBL control. CRON does not publish a spindle wattage, stepper motor spec, or drive system for this machine.

Cut Settings on this Machine

Every cut starts with one formula: Feed Rate = Spindle Speed (RPM) x Chip Load x Number of Cutting Edges (flutes). Chip load is the thickness of material each cutting edge removes in one revolution of the bit. This number comes from the manufacturer of the bit, which publishes a chip-load chart for each bit diameter and material. Look up your exact bit and material, start from the middle of the published range, and you have the third number in the formula. The chart below shows the recommended spindle speed for each material and bit type.

CRON Craft's spindle tops out at 12,000 RPM, in range for most of the chart. CRON does not publish a wattage for it or any detail on the drive system, so treat this as a lighter machine until you know otherwise: run conservative feed rates and watch how the cut sounds. Depth per pass is where a machine's build sets the limit: a truly rigid machine with a powerful spindle can cut as deep as the bit is wide in a single pass, but that takes real spindle torque, a drive train and clamps that hold firm, a gantry that will not flex, and enough mass to soak up vibration. Without published specs on any of that for this machine, start with shallow passes. Push too deep and the bit deflects and chatters, leaving scalloped edges, or it rubs instead of cutting and burns the material. The fastest way to dial in a cut is to see what has already worked for other people.

Worked example for feed rate: 1/8in (3.175mm) two-flute solid carbide end mill in hard wood. The chart says 16,000 RPM, but this spindle tops out at 12,000 RPM, so run 12,000. With the bit maker's 0.025mm per tooth (0.0010 in): 12,000 x 0.025 x 2 = 600 mm/min (24 in/min) feed. Note that CRON states a maximum machine feed rate of 3000mm/min (118 in/min), well below that number, so cap your feed there regardless of what the chip-load math suggests. For depth per pass, start shallow and check Community Cut Settings in Easel for what works on this machine. If the cut sounds strained, reduce the depth, not the feed. Slowing the feed below the chip load makes the bit rub instead of cut.

Community Cut Settings shows the spindle speed, feed rate, and depth per pass other makers actually run for your machine, material, and bit.