How to choose a suitable chip conveyor with scrap cart

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  Key takeaways
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  Match the conveyor type to the chip you actually make
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  Size the conveyor on peak chip volume, not average
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  Set the incline angle and discharge height for the scrap cart
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  Check the coolant return path before you buy
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  Plan access, guarding and controls for maintenance
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  Step by step: selecting the unit on the shop floor
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  Conveyor type compared for common chip streams

Start with the chip, not the machine. A chip conveyor with scrap cart is only as good as its ability to move the shape of chip your cutters produce. Turn 1045 steel at 0.25 mm/rev and you get a continuous helical string. Face mill 6061 at 3,000 rpm and you get coarse flakes with a lot of fine dust. Those two streams behave nothing alike inside a conveyor.

Hinge-belt conveyors handle mixed ferrous chips and small parts well. The overlapping plates tolerate heat and impact, and they let fines fall through to the coolant return. Their weakness is aluminum. Soft, sticky swarf packs into the hinge gaps and slowly welds the belt into a solid slab. If your shop runs aluminum more than 40 percent of the time, look at a scraper instead.

Scraper conveyors use a chain of steel flights dragging along a wear plate. They push wet, stringy chips up an incline without jamming, and they handle cast iron fines that would blind a hinge belt. The trade-off is wear. The flights and the base plate erode, so budget for replacement parts on a two to three year cycle depending on duty.

Magnetic conveyors suit cast iron and carbon steel only. They are quiet and compact, and they return coolant very cleanly. If you machine stainless, titanium or aluminum on the same line, a magnetic unit will drop those chips straight into the tank. Do not buy one for a mixed-material shop.

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  Stringy steel or stainlessHinge-belt or scraper. Avoid magnetic.
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  Cast ironMagnetic or scraper. Hinge belts blind with fines.
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  Aluminum, soft and gummyScraper with wide flight spacing.
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  Mixed material, small batchHinge belt with a coarse pitch and good drainage.

Chip volume is measured by weight per hour and by bulk volume per hour. Both matter, and the binding constraint is usually volume because chips are about 15 to 25 percent solid and the rest is air and coolant. A conveyor rated at 100 kg/h of solid steel chips may only move 400 liters per hour of loose swarf.

Take your heaviest roughing operation and calculate the metal removal rate. A 50 mm face mill at 2 mm depth and 200 mm/min feed removes 20,000 mm³ per minute, which is about 1.2 liters of solid steel per hour. Loose chip volume runs four to six times that, so roughly 6 liters per hour. That number looks small until you add three machines feeding one central conveyor.

Add a safety factor of 1.5 on the calculated peak. Conveyors lose effective capacity as belts wear, as chips pack, and as coolant viscosity changes with temperature. A unit running at 90 percent of rated capacity from day one will start overflowing within a year.

Watch the fines fraction. Drilling and tapping produce chips under 3 mm that behave more like sludge than like chips. If fines are more than 20 percent of your stream by volume, specify a conveyor with a separate fines screen or a settling zone, otherwise the return tank fills with sludge and the coolant pump starves.

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  FormulaLoose volume ≈ solid volume × 4 to 6.
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  Safety factorSize for 1.5 × peak hourly volume.
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  Fines limitAbove 20 percent fines, add a screen.

The incline angle controls drainage and backflow. Below 20 degrees, coolant runs back down the belt and carries fines into the return tank. Above 45 degrees, chips slide back down the incline during a pause and pile at the base. For most water-soluble coolant applications, 25 to 35 degrees is the working band. Cast iron with a heavy fines load prefers the steeper end.

Discharge height is set by the scrap cart you intend to use. Measure the cart lip height when the cart is empty and when it is full. A standard 200 liter cart has a lip around 700 mm empty and sits lower under load if the casters compress. The conveyor discharge should clear the empty lip by at least 100 mm and the full-cart chip pile by at least 50 mm.

Cart capacity drives change-out frequency. A 200 liter cart holds roughly 100 to 130 kg of steel chips. If one machine produces 15 kg per hour of chips, that cart fills in seven to nine hours, which means one change per shift. If you cannot spare that labor, size up to a 400 liter cart or move to a central conveyor feeding a bin.

Keep the cart on rails or a captive guide. A free-rolling cart under a running conveyor gets nudged out of position, and chips spill onto the floor. This is the single most common complaint we hear after installation.

Most conveyor problems show up as coolant problems. The conveyor has to separate chips from coolant, return the coolant to the tank, and keep the fines out of the pump suction. If any of those three fails, the machine stops with a low-level alarm while the chips are being handled perfectly.

Return flow should be gravity-driven wherever possible. A pump on the return line adds a failure point and consumes power. Size the return channel so that the coolant velocity stays below 0.5 m/s, which lets fines settle in a trap rather than travelling to the tank. Put a removable screen or perforated basket at the tank inlet.

Coolant type matters. Straight oils drain slowly and leave a film that carries chips back down the incline. Synthetic and semi-synthetic fluids drain fast but foam when they drop into the tank. If you run high-pressure through-spindle coolant at 70 bar or more, add a separate fine filtration stage before the conveyor return line.

Check the tank volume against the return rate. A tank that holds 200 liters and receives 40 liters per minute of return flow will churn and aerate. Give the tank at least four minutes of residence time, so 160 liters minimum at that flow rate, plus the working volume.

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  Return velocityKeep below 0.5 m/s so fines settle.
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  Tank residenceAt least four minutes at peak return flow.
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  High-pressure coolantAdd fine filtration ahead of the return line.

A conveyor that cannot be serviced will be bypassed. Leave at least 600 mm of clear space at the drive end for belt or screw extraction, and make sure the service panel opens without removing a machine guard. On a lathe with a rear chip exit, this often means pushing the conveyor further out than the footprint drawing suggests.

Interlock the conveyor with the machine cycle. The conveyor should start before the first cut and keep running for 60 to 120 seconds after the spindle stops, so residual chips clear the incline. If the conveyor stops while the machine is cutting, chips pile in the chip pan and back up into the work zone. A simple current monitor on the drive motor gives you a jam alarm before the belt stalls.

Guard the discharge point. Chips leaving a scraper at 1.5 m/s will bounce. A short skirt or chute at the discharge keeps them in the cart and off the floor. If the cart is on casters, add a chute that reaches below the cart lip so wind and vibration do not scatter fines.

Wash-down matters more than most people expect. A conveyor with a coolant wash-down nozzle at the return end stays clean; one without it builds a crust of fines that hardens like concrete. Specify the nozzle at the order stage, since retrofitting one into a sealed return channel is awkward.