Automatic Chip Conveyors for Machine Tools: Types and How to Choose

A chip conveyor does three jobs at once: it carries chips away from the cutting zone, separates most of the coolant so it can return to the tank, and keeps the machine floor clear enough to run unattended. On a lathe turning 4140 at 200 m/min, that is a few hundred kilograms of chips per shift. On a small mill doing aluminum prototype work, it might be a bucket a day. The same conveyor type rarely suits both.

Chip form decides more than chip volume. Long stringy chips from ductile steel and aluminum wrap around augers and bridge across openings. Fine powdery chips from cast iron and graphite settle in low spots and pack into corners. Brass and aluminum make short, dense chips that flow easily but load a belt heavily by weight. A conveyor sized only on kilograms per hour will still jam if the chip shape is wrong for the mechanism.

Coolant volume matters too. High-pressure through-spindle coolant puts a large, fast stream into the conveyor, and the return path has to handle it without overflowing the tank or carrying fines into the pump. If your coolant is oil-based, or you run neat oil on a Swiss-type lathe, the conveyor also has to drain the chips well enough to keep oil loss acceptable.

Hinge belt conveyors use overlapping steel plates that form a continuous moving floor. The gaps between plates drain coolant while the belt carries chips up an incline. They handle mixed chip sizes, including long strings and nests, and they tolerate the heavy, hot chips that come off a lathe running hard. What they do not like is fine powder, which works into the hinge pins and stiffens the belt over time, and fine cast iron sludge, which can wash back down the incline.

Scraper conveyors run a chain with cross bars over a flat steel pan. Chips are dragged along the bottom rather than carried on top, so the design is compact and works well with short, broken chips from cast iron, brass and hardened steel. They are also used when headroom under the machine is limited. The trade-off is that long stringy chips can wrap around the chain sprockets, and the sliding action wears the pan faster than a hinge belt wears its plates.

Screw conveyors, also called augers, use a rotating helical flight inside a tube or trough. They are simple, cheap to run and easy to seal, which suits small lathes and grinders making short chips and swarf. Anything stringy will wrap the screw and stall the drive. Anyone who has pulled a bird's nest of aluminum off an auger knows this failure mode well.

Magnetic conveyors move ferrous chips with a moving magnetic field, usually under a stainless steel plate. No mechanical drag on the chips means very little wear and no jamming, which suits fine cast iron and steel swarf from grinding and finishing operations. Aluminum, brass and titanium chips will not move. Drum and disc separators do a related job: they pull ferrous fines out of the coolant stream rather than transport bulk chips. On mixed-material shops, these are usually paired with a hinge belt rather than replacing it.

• 1
  Hinge beltMixed sizes, long strings, heavy lathe chips. Watch fine powder in the hinge pins.
• 2
  ScraperShort broken chips, compact space. Risky with long stringy aluminum or mild steel.
• 3
  Screw / augerSmall lathes and grinders, short chips. Stalls on any stringy material.
• 4
  MagneticFerrous fines and swarf, near-zero wear. Will not move non-ferrous chips.

Start with the chip load per hour at the worst case, not the average. Take the heaviest roughing pass your machine will run, estimate the material removal rate, and convert it to chip mass. A 20 kW roughing cut in steel removes material far faster than a finishing pass, and the conveyor sees that peak every cycle. Sizing on the shift average is the most common way shops end up with an undersized belt.

Then look at the incline angle and the discharge height. Chips have to climb out of the machine and drop into a bin or cart. Steep inclines save floor space but let wet chips slide back, especially round or oily chips. If your bin sits high, plan for a longer incline rather than a steeper one. Confirm the discharge point clears the bin lip and that the bin can be swapped without stopping the machine for long.

Coolant return is the quiet failure. The conveyor has to pass the coolant flow rate your pump delivers, including peak flow during through-spindle operation, and drain it back to the tank without carrying fines that will wear the pump. Ask for the drain rate and the filtration level at the return. If the machine runs fine finishing with tight tolerances, fines returning to the tank will show up as surface scratches long before the pump fails.

Not every machine needs a conveyor. If you run one shift of light aluminum milling with short broken chips, a chip tray and a manual pull-out is cheaper and has nothing to jam. A conveyor earns its cost when the machine runs long cycles unattended, when chips pile up faster than an operator can clear them, or when coolant carryover on manual removal is a real loss.

Mixed-material shops create a specific problem. A hinge belt that works well for steel will carry aluminum chips into the same bin, and if those chips go to scrap, mixing them lowers the scrap value. Some shops run separate conveyors per material family, or a magnetic separator ahead of the bin to pull ferrous out of a mixed stream. Decide early whether chips are waste or revenue, because that decision changes the conveyor layout.

Maintenance access decides long-term cost more than purchase price. A conveyor buried under the machine with no clear panel to reach the drive, the tensioner or the discharge end will cost you hours every time it jams. Before you specify, walk the machine and confirm there is room to open the inspection cover, remove a jammed nest, and replace a worn belt section. That five-minute check is worth more than a small price difference between two suppliers.