A compression latch pulls a panel toward its frame after the cam engages behind it. This closes any initial axial gap and then compresses the gasket. The calculator separates those two portions of travel and shows them in a connected cutaway.
How actuator stroke affects Compression Latch Mechanism
With compression latch mechanism, the motion profile matters. A linear actuator gives direct extension and retraction, but the output linkage may still create non-linear speed, changing mechanical advantage, and end-of-travel loads.
For cam-driven motion, look for dwell, rapid lift, and shock loading. A linear actuator may simplify positioning, but it will not naturally reproduce a cam profile unless the control system is designed for it.
The mechanism may also change speed as the linkage angle changes. A constant actuator extension speed does not always create constant output speed, so timing should be checked at the actual output point.
- Map actuator stroke to the actual output travel before choosing a model.
- Check for binding, changing leverage, and peak load near the ends of travel.
- Decide whether timed motion is acceptable or position feedback is required.
For a FIRGELLI design review, calculate the load case with the FIRGELLI actuator force calculator and plan the switching or controller arrangement with the linear actuator wiring diagram generator. If an actuator or cylinder is already installed, the linear actuator replacement finder helps keep the comparison tied to real dimensions.
Compression Latch Interactive Calculator
Explore the compression phase of a panel-mounted latch. The cam is already behind the frame; further handle rotation draws the door toward the gasket. Enter the available pull-up stroke, selected compression-phase angle, target compression and axial gap before gasket contact.
Equation Used
- The cam has already rotated behind the frame; this angle covers only axial compression.
- Rigid frame and door, with no bending or fastener compliance.
- Axial clearance is measured in the direction of closing, not lateral alignment error.
- The selected target compression is supplied by the user; check gasket manufacturer data.
- The diagram shows the inferred gasket through the selected stroke; housing and cam dimensions are schematic.
Illustrative cosine pull law, not the measured travel curve of a particular latch. The target percentage is a user choice, not a seal-rating or material limit.
From cam engagement to gasket compression
The housing mounts through the door panel. The shaft carries an offset cam that catches behind the frame. Once engaged, axial movement between shaft and housing draws the door against the gasket while the cam bears on the back of the frame.
The manufacturer reference below shows a two-stage example: an initial quarter-turn aligns the cam behind the frame, and the next quarter-turn produces compression. The animation on this page begins after engagement and shows only that compression phase. It is a generic explanation, not a dimensional copy of that product.
The cutaway keeps the frame fixed, the housing attached to the panel and the cam against the frame. Gasket thickness and the closing gap respond to the calculator inputs. The front view shows the selected compression-phase handle angle.
Use the calculator to understand pull-up travel
Compression latches are used on access panels and enclosures where the door must be drawn against a gasket. This tool helps separate available travel, clearance take-up and gasket compression.
It does not select a latch or certify the enclosure. Actual cam travel, grip range, retention, operating force and gasket behaviour must come from the selected hardware and assembly design.
Travel, clearance and inferred gasket thickness
The illustrative pull law is x = S(1 − cos θ), with θ from 0 to 90 degrees during the compression phase. S is the full pull-up stroke and x is travel at the selected angle. Actual products can use a different motion law.
Let g be the axial gap before gasket contact. Gasket shortening is δ = max(0, x − g). For a chosen target C percent, the inferred free thickness is t = δ/(C/100), and the compressed thickness is t − δ. If travel does not exceed the gap, a positive thickness cannot be determined for the requested compression.
Remaining gap is max(0, g − x). Check the selected latch dimensions and allowable misalignment before choosing an installation tolerance.
Two millimetres of pull with a half-millimetre gap
At S = 2 mm and θ = 90 degrees, the illustrative travel is 2 mm. Taking up a 0.5 mm axial gap leaves 1.5 mm of gasket shortening.
For a user-selected target of 30%, free thickness is 1.5/0.30 = 5 mm. Compressed thickness is 3.5 mm. No gap remains. These values describe geometry, not proof of an ingress rating or expected gasket life.
If the selected angle provides only 0.4 mm travel while the initial gap is 0.5 mm, 0.1 mm clearance remains and no compression occurs. The calculator keeps the drawing visible but does not invent a gasket size.
What the result does and does not establish
Travel must be sufficient to close the initial gap before it can compress a gasket. A thicker inferred gasket is not automatically a better seal, and greater compression is not automatically acceptable.
Use the gasket supplier’s compression and force data and the latch manufacturer’s actual travel, grip and load information. Panel stiffness, seal continuity and installation details also matter. This simplified model provides no universal IP or NEMA rating, operating torque, service-life figure or safe alignment tolerance.
Compression latch questions
Does this angle include rotating the cam into engagement?
No. The animation starts with the cam already behind the frame and shows the subsequent compression phase.
Does every latch follow the cosine travel curve?
No. The curve is an illustrative assumption. Use the actual product travel curve when sizing a particular latch.
What does the take-up gap mean?
It is axial clearance that the closing movement must remove before the panel touches the uncompressed gasket. It is not sideways misalignment.
Why can gasket thickness be unavailable?
The chosen travel may be no greater than the gap, so there is no positive compression from which to infer a gasket thickness.
Does 30% compression guarantee a seal?
No. The target is a user input. Seal performance depends on the gasket, enclosure and installation and requires appropriate verification.
Mechanism reference
Southco E3 VISE ACTION compression latch catalogue, pages 90–91 shows the panel-mounted housing, shaft, offset cam and fixed frame, and distinguishes engagement rotation from axial compression. Its product specifications do not apply to the generic calculator on this page; the stated cosine law is a modelling assumption.
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