Pallet
What is the main purpose of a pallet in CNC?
To let the machine exchange a fully set-up workholding platform quickly and repeatably, minimizing downtime between parts or operations.
Is a pallet the same as a fixture?
No. A fixture holds and locates the part; the pallet carries the fixture and serves as the repeatable interface to the machine or pallet changer.
Why are pallets common on HMCs?
Horizontal machining centers often use pallet changers because they are well suited to staged loading and continuous spindle utilization.
In CNC machining, a pallet is a rigid workholding platform that locates and secures a part, vise, fixture, or tombstone so the machine can repeatably bring that setup into the cutting zone; in pallet-changer systems, one pallet can be machining while another is being loaded offline. It preserves location accuracy across exchanges through precision locating features and clean seating surfaces.
On a horizontal or multi-pallet CNC cell, the pallet is preloaded outside the spindle with the fixture and workpiece already indicated or hard-located, then transferred into the machine so cycle time is not wasted on part loading. Pallets may be plain, drilled, or T-slotted, and locating features like dowel pins, keys, or precision fixture interfaces are used so the part returns to the same X-Y-Z datum each cycle. In high-mix production, pallet systems reduce setups, support lights-out running, and keep the spindle cutting while the next job is prepared. A pallet is not just a tray; in production machining it is part of the datum strategy. The pallet must preserve repeatability between exchanges, because any shift in pallet seating, clamp force, or chip contamination directly becomes part-location error at the cutting tool. This is why pallet systems are often paired with precision receivers, zero-point locating, or dedicated fixture plates rather than loose fixturing. The entire system relies on consistent geometry and cleanliness to achieve high accuracy over many exchanges.
Chip-on-seat error: Chips, coolant sludge, or burrs under the pallet interface prevent full seating, which creates angular or height error and shows up as features cut out of location, bad hole position, or inconsistent Z depths across pallets.
Poor datum control: If the pallet is designed without a single, stable origin or without consistent locating pins/keys, every reload can shift the part zero, causing mismatched features between operations and forcing re-indicating or re-probing.
Weak workholding on the pallet: If clamps, vise jaws, or fasteners are undersized for the cutting load, the part can walk, lift, or chatter during roughing, especially on large components or when using aggressive toolpaths; this defeats the productivity gain of the pallet system.