In a latch-needle knitting machine, the needle butt travels through a cam track. Rising or clearing flanks lift the guided needle, a high region provides clearing/feed opportunity, and a descending stitch flank lowers the needle to draw the new loop.
Knitting Machine Cam Mechanism Interactive Calculator
Explore the local constant-velocity relation on one straight cam flank. The full animated track supplies context, but its corners and dwell lengths are illustrative.
Equation Used
- Rigid guided needle butt remains in contact with a straight flank.
- Cam translation speed is constant over the evaluated flank.
- The shown entry, dwell and exit regions are illustrative rather than dimensioned machine geometry.
- No transition radius, acceleration, jerk, compliance, force, lubrication, wear or fatigue-life model.
The squared speed index is normalized arithmetic, not fatigue or life. Real transition radii determine acceleration and impact.
Needle butt and cam track
The needle is constrained to vertical travel while relative horizontal cam motion carries its butt through the track. On a straight clearing flank the vertical speed is constant; the high region holds the needle near clearing height; the stitch flank lowers it.
Local kinematic check
The straight-flank relation is useful for checking one constant-slope segment. It is not a complete cam design or machine-speed limit.
Slope converts horizontal speed to vertical speed
For a straight profile y=x tan(θ), the vertical speed magnitude is vneedle=vcam tan(θ). The sign depends on whether the needle rises or falls. Multiply meters per second by 39.37007874 to display inches per second.
The squared-speed index is 100[vneedle/(1.2 tan47°)]². Its reference is the calculator’s default setting, approximately 1.287 m/s. It is a numerical comparison only, with no interpretation as fatigue, wear or a permitted operating limit.
Read the diagram and numbers separately
At vcam=1.2 m/s and θ=47°, the straight-flank speed magnitude is about 1.287 m/s, or 50.66 in/s; the squared-speed index is 100%. Halving the entered speed halves the calculated needle speed and reduces the index to 25%.
The drawn needle traverses the stationary track over a fixed seven-second display cycle. Its horizontal travel represents relative motion through a cam box. The speed input changes the numbers, not playback speed; the angle changes the drawn slope.
What is outside the straight-flank equation
The equation assumes maintained contact with a rigid straight profile. It gives neither the acceleration at a corner nor the effects of compliance, clearance, lubrication or impact. Real cam transitions require a continuous motion profile rather than instantaneous changes in slope.
The diagram is schematic: it omits a complete needle guide and uses vertically offset lines for the track rather than a profile offset for the finite needle butt. At steep angles the hook can extend beyond the displayed frame. No force or service-life prediction is supplied.
Frequently asked questions
Is speed constant around the entire track?
No. The straight-flank relation applies locally. A dwell has zero vertical speed, and transitions require their own motion law.
What does the squared-speed index mean?
It compares the square of the calculated speed with the default-reference speed squared. It is not a fatigue or safety percentage.
Does the entered speed control the animation?
No. Playback is a fixed seven-second cycle; the input changes the numerical calculation.
Does the diagram account for the finite needle butt?
No. The track lines are a schematic illustration and do not define a contact-correct cam profile.
Further reading
Groz-Beckert, Flat knitting describes needle and loop-formation features. The local velocity equation above follows by differentiating a straight line’s rise with respect to its horizontal coordinate.
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