How to Prepare Bore Holes for Air-Jet Valve Installation
Key Takeaway: Air-jet valve bores require H7 tolerance with Ra ≤ 1.6μm surface finish for O-ring sealing. Press-fit installation — never hammer the valve face directly. Air pressure: 4–7 bar (58–100 PSI).
Bore Preparation Steps
- Drill pilot hole — undersize by 0.5mm
- Ream to H7 tolerance — use a precision H7 reamer matched to the valve OD
- Surface finish — verify Ra ≤ 1.6μm on the sealing surface (top 15mm of bore). Polish if needed.
- Counterbore — machine a 2mm deep counterbore at the cavity face for the valve flange seat
- Air channel — drill a connecting channel from the bore bottom to the air fitting port
Installation Procedure
Per DME installation guidelines:
- Lubricate the O-rings with silicone grease before insertion
- Press the valve into the bore using an arbor press or soft-jaw vise — never strike the valve face with a hammer
- Verify the valve poppet moves freely after installation (push with a soft rod, it should spring back)
- Connect the air line and test at 4 bar — you should hear a sharp air burst when the poppet is depressed
Critical: Ensure the air line fully vents to atmosphere after the ejection cycle. If the valve remains pressurized during injection, molten plastic can enter the valve, causing permanent damage.