Magnetic Chip Conveyor for Machine Tools: How It Works

• 1
  Key takeaways
• 2
  What the magnetic circuit actually does
• 3
  Which chips the magnets will and will not catch
• 4
  Coolant flow, tank layout and carryover
• 5
  Sizing the unit to the machine and the job
• 6
  Setup, running checks and common failure modes
• 7
  Setting up a magnetic conveyor on a running machine
• 8
  Magnetic conveyor vs. other chip removal options

A magnetic chip conveyor for machine tools runs a closed loop of permanent magnets through the coolant tank. The magnets sit inside a stainless or polymer carrier chain, separated from the wet side by a thin plate. As the chain moves, ferrous chips are pulled against that plate and carried up an incline, out of the liquid, and dropped into a bin.

The key point is that the magnet does not touch the chips directly. The carrier plate is the wear surface. Chips slide along it, which is why the plate thickness and surface finish matter more than magnet strength alone. A rough plate holds chips longer and lets them ride back down. A polished plate releases them at the scraper edge.

Magnet grade is usually neodymium (NdFeB) in the N35 to N42 range for machine tool duty. Higher grades give more pull per unit volume, but they also lose more strength at temperature. Above roughly 80 °C, standard NdFeB grades start to demagnetize permanently. That limit matters when the conveyor sits close to a spindle or a high-pressure coolant return.

The chain speed is typically 1 to 3 m/min. Faster is not better. Run too fast and the chip layer never builds up, so fine swarf slips past. Run too slow and chips pile up at the inlet, which can block the return flow and raise the tank level.

• 1
  Separation happens on the plateMagnet strength, plate thickness and plate finish all set the capture efficiency.
• 2
  Chain speed sets the chip layer1–3 m/min is the usual working band for mixed chip sizes.
• 3
  Temperature is a hard limitStandard NdFeB loses strength permanently above about 80 °C.

The conveyor only works on ferromagnetic material. That means carbon steel, alloy steel, most tool steels, and ferritic stainless grades such as 430 and 17-4PH. Austenitic stainless grades like 303, 304 and 316 are weakly magnetic at best, and cold working changes how much they respond. A 304 chip that has been heavily deformed may stick a little; the same grade in a soft state will not.

Aluminium, brass, copper, titanium, Inconel and magnesium are non-ferrous or only marginally magnetic. They will not be captured. If your shop cuts mostly aluminium, this device does almost nothing for you, and a scraper conveyor or a settling tank is the better answer. Mixed shops need to know the ratio before they buy.

Chip shape also changes the result. Fine powdery swarf from grinding or from a finishing pass has low mass and high surface area, so it holds onto coolant and tends to float. Long stringers from a roughing pass have more mass and stick firmly, but they can bridge across the inlet and stall the chain. Neither extreme is ideal without some adjustment.

A practical field check: take a magnet from the toolbox and hold it in the chip bin for ten seconds. If less than roughly half the chips stick, the material mix is wrong for this design and you should look at a different separation principle.

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  Strong captureCarbon steel, alloy steel, 430 stainless, 17-4PH.
• 2
  Weak or no capture303, 304, 316 stainless in the annealed condition.
• 3
  No captureAluminium, brass, copper, titanium, Inconel, magnesium.

The conveyor sits in the return path between the machine bed and the coolant tank. Flow direction matters: chips should move toward the magnet plate, not away from it. If the return pipe dumps coolant directly onto the chain, the jet can wash chips off the plate before they are lifted. Inlet baffles and a stilling zone fix this.

Coolant viscosity sets how fast the liquid drains from the chip pile. Water-miscible coolant at 5–10% concentration drains in seconds, so the chip bin stays dry. Neat cutting oil is thicker and clings to chips; the pile may still be wet when it lands in the bin, which means more oil loss and more disposal cost. A short drain section on the incline helps.

Carryover is the amount of coolant that leaves the tank with the chips. On a well-set-up unit it is small, but it is never zero. If you run neat oil and the bin fills with wet chips, check the incline angle first. A shallower angle gives more drain time. A steeper angle moves chips faster but carries more liquid.

Tank volume should be sized so the conveyor is not the only settling stage. A two-chamber tank, with the conveyor in the first chamber and a weir to the second, keeps the pump intake cleaner. The pump then sees fewer fines, which extends impeller life.

Start with the chip generation rate. A light finishing operation on a small mill may produce a few kilograms per shift. A heavy roughing cell on a large horizontal machining center can produce hundreds of kilograms. The conveyor width and chain speed must match that rate, or chips will back up at the inlet.

Next, look at the chip size distribution. If most chips are under about 3 mm, use a fine-pitch magnet arrangement and a slower chain. If you run long stringers, increase the clearance at the inlet and add a breaker bar so the stringers are folded before they reach the plate. Mixing fine and coarse without adjustment usually means one of them is handled badly.

Then check the mounting envelope. The conveyor needs a straight incline above the coolant level, plus room for the discharge chute and bin. On compact machines this is often the limiting factor. Measure the actual space before you commit to a model, not after.

Finally, consider maintenance access. The chain, the scraper edge and the plate all wear. A unit that needs the tank drained to change a scraper is a poor choice for a high-utilization cell. Look for a design where the drive end can be opened without breaking the coolant circuit.

For shops that also machine non-ferrous parts, a magnetic unit can be paired with a secondary stage. A settling chamber or a fine screen after the magnet catches what the magnets miss. That combination covers mixed-material production without doubling the footprint.

After installation, run the conveyor empty for ten minutes and watch the chain tracking. The chain should sit centered on the sprockets with no rubbing on the side plates. A chain that climbs the sprocket teeth under load will wear the teeth fast and eventually jump. Adjust the tensioner before you add chips.

Once chips are flowing, check the discharge three times in the first shift. The chip pile should be mostly dry and should fall cleanly from the scraper. If chips cling to the plate and ride back down, the plate surface is too rough or the scraper edge is worn. If the pile is soaking wet, the incline is too steep or the drain section is too short.

The most common failure is not a magnet problem. It is a blockage at the inlet caused by long stringers or by a build-up of fine sludge. A breaker bar and a slightly larger inlet opening solve most of these. The second most common issue is a worn scraper edge, which lets a thin layer of chips pass back into the tank.

Check the plate for scoring every few months. A scored plate holds chips and reduces capture. On units with a replaceable plate, swapping it is a short job. On units where the plate is welded into the frame, the whole assembly has to come out, which is a much larger downtime event.

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  Chain tracking firstCentered chain, correct tension, no side rubbing.
• 2
  Dry chip pileWet chips mean the incline or drain section needs adjustment.
• 3
  Inlet is the weak pointStringers and sludge block the flow before magnets ever fail.