4008400168 Glue Level Sensor 4-008-40-0168 Probe C-505 PEEK Edgebander Sensor

Need a drop-in glue level probe for a Homag glue pot instead of a new assembly? The 4008400168 glue level sensor, also written 4-008-40-0168 and listed in parts books as probe C-505, reads adhesive height in the QM glue pot on Homag R780, NKR782, KDF550 and KDF540 edge banding machines. The body is PEEK, rated to 260 °C (500 °F) and resistant to most chemicals used in adhesive applications. One number covers four models, and the swap is seven steps in the pot already on your machine.

Three things stop an edge banding line at the glue pot, and none is the pot itself: adhesive drops below the working level mid-shift and the machine waits for granulate, the pot is topped up past the mark so usable adhesive goes to the bin, and the probe softens in hot melt and reports a height that is not there. The 4008400168 sensor is the part that answers all three, because it is the part that reads the pot.

It is the level sensor for the QM glue pot on Homag edge banding machines, numbered 4008400168 or 4-008-40-0168 in dashed form and printed as probe C-505 in older lists. The same probe is listed for four models — R780, NKR782, KDF550 and KDF540 — so one spare line covers the Homag block, not four.

The body is PEEK, and the sheet states what that buys: heat resistance to 260 °C (500 °F) plus resistance to most chemicals used in adhesive applications. Inside that envelope it holds its shape against hot melt — the difference between a reading you trust and one you learn to ignore.

Fitting is seven steps: isolate the machine, open the pot compartment, remove the old probe, seat the new one in the same slot, reconnect the wiring to the terminals on the machine diagram, test the reading, latch the compartment. Price by quotation.

What decides whether this probe works in your pot:

• PEEK body — the material named on the 4008400168 sheet, selected for heat, adhesive contact and mechanical stress rather than for price alone.
• 260 °C / 500 °F — the ceiling stated on the specification, above what a standard hot melt pot reaches in normal running.
• Four models, one probe — R780, NKR782, KDF550 and KDF540 share it, so one spare covers every Homag pot on the floor.
• Two part numbers — 4008400168 and 4-008-40-0168 order the same item, and C-505 is the probe reference older lists still print.
• Level detection only — it reads adhesive height in the pot, the single signal the machine uses to call for granulate.
• Seven-step swap — the probe seats in the existing slot, so no bracket, no drilling and no new wiring run.
• Chemical resistance — PEEK is specified as resistant to most chemicals used in adhesive applications, which is exactly the environment inside a working pot.
• Serviceable in place — a soft cloth and a PEEK-safe mild solvent lift adhesive build-up without pulling the pot off the machine.
• Replaced on evidence — the maintenance note asks for periodic inspection for wear and damage, so a probe is swapped when it shows a defect, not on a calendar guess.

The usual choice is a probe you can fit this shift or a line that waits for a courier:

• No pot work. The probe goes into the existing slot in the QM glue pot, so the seven-step swap is the whole job — no bracket, no drilling, no new wiring.
• One number, four machines. R780, NKR782, KDF550 and KDF540 share this probe, so a single spare covers every Homag edge bander you run.
• No dry run. The machine calls for granulate on the level signal, and adhesive shortage at the pot is the documented downtime this part exists to prevent.
• Less granulate in the bin. An overfilled pot wastes adhesive and puts equipment at risk; the level signal stops the fill before the pot reaches that point.
• Material that matches the sheet. The specification says PEEK at 260 °C (500 °F); a substitute resin is a different part, not a cheaper version of this one.
• Clean reordering. 4008400168 and 4-008-40-0168 land on the same item, so purchasing and maintenance stop arguing over which line goes on the order, and the stock line stays one item instead of two.

Yes, if your machine is an R780, NKR782, KDF550 or KDF540. The probe is listed for the QM glue pot on those four models under 4008400168 / 4-008-40-0168. Check the number on the old probe or in the machine parts list first, because other models are not covered by this listing.

Yes. 4008400168 and 4-008-40-0168 are two formats of one number, and some parts lists also call the item probe C-505. Order either format and you get the same PEEK probe.

PEEK. The specification lists a PEEK body, an engineering plastic chosen for the conditions inside a glue pot: heat, adhesive contact and mechanical stress. That material is what makes the 260 °C rating on the sheet meaningful.

260 °C (500 °F), with resistance to most chemicals used in adhesive applications. That covers hot melt and the solvents met inside a heated pot, and it is the figure to quote if your process runs hotter than a standard pot.

Two failures: the pot runs short and the line stops for adhesive, or the pot overfills, wasting granulate and risking equipment. Both are the conditions this probe is fitted to prevent, which is why a spare on the shelf costs less than a stopped shift.

Seven steps, none of which needs a new bracket. Isolate the machine, open the pot compartment, remove the old probe, seat the new one in the same slot, reconnect the wiring to the terminals on the machine diagram, test the reading, then latch the compartment.

A soft cloth and a mild solvent that is safe for PEEK. Lift adhesive build-up before it hardens on the body, and skip abrasive pads — the aim is to restore the level reading, not to resurface the part.

Check the calibration, yes. Run the machine after the swap, confirm the reading against the pot, then re-check periodically and recalibrate to the machine maker's guideline if the reading drifts.