Bob's CNC Quantum Mini

About the Machine

The Quantum Mini is BobsCNC’s smallest kit, with a 407 x 407 x 98 mm working area, NEMA 17 steppers on GT2 belts on X and Y and an acme-rod Z-axis, and ships with a Makita RT0701C variable-speed router. It runs GRBL 1.1 firmware on an Arduino Uno.

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.

If this machine's spindle cannot reach the listed speed, run the spindle at its maximum and control the cut with feed rate. For 65mm trim routers, the DeWalt DW611 dial maps to: 1 = 16,000; 2 = 18,200; 3 = 20,400; 4 = 22,600; 5 = 24,800; 6 = 27,000 RPM.

The Quantum Mini ships with a Makita RT0701C router, but BobsCNC’s page for this kit does not state a maximum RPM, so check the router’s own speed dial or plate before picking a spindle speed off the chart. This is BobsCNC’s smallest, lightest kit, on NEMA 17 steppers with an acme-rod Z-axis, not a heavy industrial machine, so depth per pass is limited by rigidity more than spindle power. 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. The Quantum Mini’s belt-and-acme-rod build falls well short of that bar, and the fix is simple: take 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. With the bit maker’s 0.025mm per tooth (0.0010 in): 16,000 x 0.025 x 2 = 800 mm/min (31 in/min) feed. For depth per pass, start shallow and check Community Cut Settings in Easel for what works on the Bob’s CNC Quantum Mini. 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.