# Cabinet air damper V1 - fixed seal-free PLA experiment Original CAD and copyright: Santeri Hukari. This is a fixed revision, not browser-parametric CAD or verified damping hardware. Materials: PLA, piano-wire spring and double-sided tape only. No O-rings or metal screws. ## Geometry All units mm. +X points from the door into the cabinet; Z=0 is the entire flat adhesive underside. Cylinder axis Y=0, Z=16. | Item | Default | |---|---| | Base | 80 x 44 x 3, R3 corners | | Shell | OD28, CAD bore20.40, X0..50 | | Piston | CAD OD19.70, length22, X0..22 at extension | | CAD radial sliding clearance | 0.35 per side; not a measured printed clearance | | Estimated printed diametral clearance | 0.29; unverified trial | | Rod and guide | 6 / 6.3 | | Button | OD12, X-29..-26, front R1 | | Working / maximum travel | 17 / 20 | | Working contact tip X | -12 | | Spring seat gaps, travel0 /17 /20 | 28 /11 /8 | | Spring reference | OD8, wire0.32, 6 turns, free32 | | Conservative solid-length allowance | 6; measure the real spring | | Reset inlet / PLA reed | OD1.5 / thickness0.24 | | Rear tape ring cut size | ID20.6 / OD25.9 | | Rear tape recess depth | 0.2; tape compression unverified | The original 37 mm chamber was lengthened to50 to accommodate the longer seal-free piston while preserving its original rod, stop positions and spring-seat spacing. A shallow cylindrical relief behind the housing lets the rear cap sit against its end without intersecting the base; at least 1.8 mm of base remains there, with its underside completely uninterrupted. ## Measured-Fit Trial 1 The first test pieces measured about 19.67 mm inside the housing and 20.00 mm outside the piston: approximately 0.33 mm interference. This revision uses a 20.40 mm CAD bore (+0.40 mm compensation) and 19.70 mm CAD piston (-0.22 mm compensation). If the same print errors repeat, the result would be about 20.07 / 19.78 mm: 0.29 mm diametral clearance, or 0.145 mm per side. These are estimates, not measured results. Measure roundness and taper too. The front cap STL is byte-identical to the previous release. Rod geometry is unchanged at 6.00 mm CAD diameter (reported print about 5.65 mm). Rear cap, pins, clips, reed and tape template also remain unchanged. Only the housing bore and piston sliding diameter have been adjusted. No whole part scaling is used. Existing caps and fasteners can be retained; use the revised housing and plunger together for this fit trial. This is an unprinted fit trial, not a verified damping revision. Additional air leakage may reduce damping. Dry-fit the parts without forcing them, then test leakage, reset and damping before installation. The original 0.04 mm radial design goal is not a claim about this trial's printed fit. ## What To Print This download contains separate, print-oriented STLs. Matching STEP files are available in the local CAD trial output, not in the website print set. `print_manifest.json` records quantities, validated bounds and volumes. | File | Quantity | |---|---:| | housing.stl | 1 | | plunger.stl | 1 | | front_cap.stl | 1 | | rear_cap.stl | 1 | | front_cap_pin.stl | 2 | | rear_cap_pin.stl | 2 | | cap_clip.stl | 4 | | reset_reed.stl | 1 | | reed_pin.stl | 1 | Front and rear pins presently have the same dimensions but remain separate files because cap thicknesses are independently editable. All parts are separate prints; do not print the assembly as one fused object. The GLB spring and tape, and STEP spring envelope, are reference items only. Use the matching housing.stl and plunger.stl from this revision. Previous near-nominal diameter alternatives are not part of this print set. The STL orientations are: - Housing axis vertical, original X0 on the bed; base stands on its front edge. Use a brim if needed and keep support material OUT of the bore. External ears/gussets may need support according to the slicer. - Plunger button down. The large piston shoulder needs external support; remove it carefully and finish the sliding lands. The rod must remain straight. These exports are not a support-free claim. - Front cap inner mating face down, guide up. Rear cap outer face down, spring boss up: printing its mating face down would suspend that face over the rear boss. Inspect/finish the rear valve seat and tape recess. - Pins head down; C-clips and reed flat on the bed. Use0.12 mm layers for the0.24 mm reed (two layers), without supports. The reed is small and experimental; print spares, avoid excessive first-layer squish. Around the housing bore, the original brief suggests0.12..0.16 mm layers and at least5 perimeters. Inspect slicer paths for the reed and clips before printing. PLA reed fatigue and printed retainer strength are unmeasured. ## Assembly And First Test 1. Fit the rod into the front guide cap before installing that cap. The integral button/piston will not pass through the small guide opening. 2. Insert piston from the open rear of the housing, with its rod emerging through the front. Slide the front cap onto its face; insert two pins from the front and fit their C-clips just behind the front ears. 3. With the rear still open, verify smooth motion over the entire stroke. Choose/finish a piston diameter before trying to seal the chamber. 4. Place the flat PLA reed against the inside of the rear cap, circular pad covering the reset inlet. Press the printed reed pin into the blind pilot atY0/Z23; its head clamps the anchor, not the round sealing pad. The reed must lift freely into the chamber and return to its seat. 5. Cut the rear tape annulus using `tape_cut_template.svg`. Keep tape and backing away from the bore and inlet. The nominal recess is0.2 deep; verify your actual tape compresses enough for the hard cap faces to seat and makes an airtight static joint. Adjust recess depth if needed. 6. Fit the wound piano-wire spring around the two centering bosses. Seat the rear cap, insert its two printed pins from the rear, and attach C-clips just ahead of the rear ears. Test the clips' retention gently. 7. A slow steady push must continue moving; a faster push should show more resistance, and the spring should reset the plunger. If it jams, stop and inspect the fit. If there is little damping, check cap/reed/wall leaks before making the piston larger. A nominal gap is not a result. 8. Only after bench testing, temporarily position against the real door. Existing hinges supply closing force; this weak spring only resets. Confirm door contact at17 mm travel, with3 mm travel remaining. This device must not serve as the door's end stop. Test tape shear/peel and door trajectory gently before permanent bonding. The spring is an editable geometric reference, not a proven spring recipe. Wire0.32 is a provisional starting dimension rather than the much stiffer 1 mm placeholder. Measure free length, outside/inside diameter and solid length. Its force must overcome piston friction without preventing the hinges from closing. Actual spring rate and hinge force are not simulated. ## CAD Verification `generated/fit_report.json` records41 sampled positions through0..20, all printed moving/fixed intersections, fixed-part pairs, and exact CAD checks at0/17/20. The reed pin's0.05 diametral interference is deliberate; other positive overlap is a failure. A conservative full reed-lift envelope is checked against the spring envelope. Piston travel stays inside the bore; spring/boss margins and uninterrupted tape area are checked. Every printable STL is watertight, positive-volume, and one connected body. Tessellation uses0.005 mm linear tolerance and0.05 angular tolerance to avoid a coarse mesh consuming the small fit clearance. These geometric checks do not measure actual leakage, reed flexure, fatigue, tape strength, closing time, hinge motion or manufactured tolerances. `longitudinal_sections.png/.svg` show extension, working closure and the mechanical limit; `reset_valve_section.png/.svg` cuts through the offset reset inlet. The gap is real scale, so it is barely visible in the overview.