A waved-wheel cam to upright bar is a rotating disc with a wavy (undulating) face that drives a vertical bar up and down as it spins. Unlike a single-lobe disc cam that produces one rise-and-fall per revolution, a waved-wheel cam produces multiple lifts per revolution — one per wave. The wave count sets the stroke frequency, the wave amplitude sets the stroke length, and the result is a smooth, near-sinusoidal reciprocating motion useful for shakers, screen feeders, and small stamping ejectors running 60 to 600 cycles per minute.
Waved-wheel Cam to Upright Bar Interactive Calculator
Vary RPM and wave count for two cam cases and see the resulting stroke rates and animated follower motion.
Equation Used
The upright bar completes one reciprocating stroke for every wave on the rotating cam face. Multiplying shaft speed in RPM by wave count gives strokes per minute; dividing by 60 converts the result to hertz.
- Each cam wave produces one full follower stroke per revolution.
- Follower remains in contact with the cam face with no float or slip.
- Cam profile is sinusoidal or modified-sine for smooth reciprocation.
How the Waved-wheel Cam to Upright Bar Actually Works
The cam is a flat or shallow-dished wheel with a sinusoidal contour machined or cast onto its face. As the wheel rotates on its shaft, the upright bar — sitting vertically against the cam face with its end shaped as a flat foot, roller, or rounded tip — rides up and down each wave. Wave count matters: a 4-wave cam at 60 RPM gives you 240 strokes per minute, a 6-wave cam at 60 RPM gives you 360. So you tune output frequency by either changing wheel speed or changing wave count, and most designers pick wave count first because cutting more waves is cheaper than running a faster gearbox.
The profile must be a true sinusoidal cam motion or a modified-sine for the bar to track without slap. If you cut the waves as plain triangles or scallops, the follower sees infinite acceleration at every wave peak and the bar hammers the cam face — you'll hear it as a sharp tick at every cycle and you'll see brinell marks on the cam within 100 hours of running. The wave-to-wave pitch tolerance should hold within ±0.05 mm on a 100 mm-diameter cam, otherwise the bar develops a long-period wobble that beats audibly against any return spring.
The upright bar needs a positive return — either gravity (heavy bar, vertical orientation), a compression spring, or a conjugate cam on the opposite side. Without it, the bar lifts off the cam during the descending portion of each wave and the timing collapses. Common failure modes are: spring rate too low so the follower floats above 200 RPM, flat-foot follower wear on one edge from a cam shaft that's not perpendicular to the bar axis, and galling on the cam face when lubrication drops below 5 cSt at running temperature.
Key Components
- Waved cam wheel: The driving disc with a sinusoidal contour cut into its top face. Typical diameters run 50 to 250 mm with wave amplitudes of 2 to 15 mm. The contour is usually ground after heat treatment to 58-62 HRC for durability — a soft cam will wear flat in under 200 hours of continuous service.
- Upright bar (follower): A vertical rod or shaft that rides on the cam face and transmits the reciprocating motion upward to the working tool. The bar must be guided by at least two bushings spaced apart by 3× the bar diameter — closer spacing lets the bar cock and bind under side load.
- Follower tip: The contact end of the bar — flat-foot, mushroom, roller, or knife-edge depending on the wave geometry. Roller tips of 8-12 mm diameter handle the highest speeds with the least cam wear, but a flat-foot is cheaper and tolerates dirty environments better.
- Return element: A compression spring, the bar's own weight, or a conjugate cam that keeps the follower in contact during the descending half of each wave. Spring rate is typically sized so the seating force at top of stroke is at least 3× the inertial force of the bar at peak acceleration.
- Cam shaft and bearings: Carries the cam wheel and absorbs the axial reaction force pushed back by the upright bar. Angular contact or tapered roller bearings are standard because the load on this shaft is almost entirely axial — a deep-groove ball bearing will fail in months under continuous axial loading.
- Bar guide bushings: Hold the upright bar perpendicular to the cam face within 0.1° of true vertical. Bronze SAE 660 or PTFE-lined sleeves are typical. Misalignment beyond 0.5° concentrates wear on one side of the follower tip and causes premature scoring.
Who Uses the Waved-wheel Cam to Upright Bar
The waved-wheel cam to upright bar is the mechanism of choice when you need many strokes per shaft revolution from a single cheap rotating part. It shows up in vibratory feeders, screen-deck shakers, small printing platens, valve-train test rigs, and any place where a designer wants to multiply input RPM into a higher stroke frequency without a step-up gearbox. It survives in dirty, dusty, oily environments because the geometry is simple and the contact area is large. It struggles when the application demands precise dwell or asymmetric rise-and-fall — for that you want a profiled disc cam, not a wave cam.
- Bulk material handling: Eriez HVF-series vibratory feeders use a wave-cam-driven upright bar to shake the tray at 600-3600 cycles per minute for metering powders and granules into packaging lines.
- Aggregate screening: Sweco round separators run a waved face cam off the main shaft to drive vertical agitator bars in fine-mesh sifting decks for sand, grain, and pharmaceutical powders.
- Textile machinery: Karl Mayer warp-knitting machines historically used a waved-wheel cam stack to drive the guide bars vertically against the needle bed at 1200 strokes per minute.
- Letterpress printing: Heidelberg Windmill platen presses use a wave-profile cam to lift the inking-roller carrier bar in synchrony with the platen cycle at 30-50 impressions per minute.
- Music and automata: Reuge and Sankyo cylinder music boxes use a waved-disc cam variant to lift the comb-tooth lifter bars in cuckoo-clock strike trains, producing 4 to 12 lifts per shaft revolution.
- Laboratory test equipment: Retsch AS 200 sieve shakers run a waved-wheel cam against a vertical pushrod to deliver 50-300 vertical taps per minute for particle-size analysis.
The Formula Behind the Waved-wheel Cam to Upright Bar
What you need to compute first is follower stroke frequency and peak velocity, because both scale directly with cam speed and wave count. At the low end of a typical operating range — say 30 RPM with a 4-wave cam — you get 120 strokes per minute, which feels like a deliberate, visible thump suitable for coarse separation or agitation. At the nominal mid-range of 60-120 RPM you hit the sweet spot where the follower tracks cleanly and the motion looks smooth to the eye. Push past the high end where peak follower acceleration exceeds what the return spring can hold against, and the bar floats — you lose contact, the timing breaks down, and the cam starts hammering. The formula below gives you the peak velocity of the upright bar so you can size the spring, the bar mass, and the cam profile against real inertial limits.
Variables
| Symbol | Meaning | Unit (SI) | Unit (Imperial) |
|---|---|---|---|
| vpeak | Peak velocity of the upright bar | m/s | in/s |
| A | Wave amplitude (half of peak-to-peak stroke) | m | in |
| nw | Number of waves around the cam face | — | — |
| N | Cam shaft rotational speed | RPM | RPM |
| fs | Stroke frequency = nw × N / 60 | Hz | strokes/s |
Worked Example: Waved-wheel Cam to Upright Bar in a benchtop herb-grinding sieve shaker
You are sizing the waved-wheel cam that drives the vertical agitator bar on a benchtop herb-grinding sieve shaker — think of a small-batch unit similar to the Retsch AS 200 used by craft tea blenders for sorting dried chamomile through a 40-mesh screen. The cam wheel is 80 mm diameter with 6 waves around its face, the wave amplitude is 4 mm (so peak-to-peak stroke is 8 mm), and the cam shaft is driven by a 24 V DC gearmotor with a working speed range of 30-180 RPM and a nominal of 90 RPM.
Given
- A = 0.004 m
- nw = 6 —
- Nnominal = 90 RPM
- Nlow = 30 RPM
- Nhigh = 180 RPM
Solution
Step 1 — at nominal 90 RPM, compute stroke frequency first to confirm the shaker hits its target tap rate:
That puts the shaker right in the middle of the 300-600 strokes/min band that Retsch specifies for fine-mesh sieving — particles get enough vertical kick to clear the screen but not so much that they bounce off and miss the next aperture.
Step 2 — compute peak follower velocity at nominal 90 RPM:
Step 3 — at the low end of the operating range, 30 RPM, the cam crawls and the bar barely lifts:
At 0.038 m/s and 180 strokes/min the chamomile sits on the screen and barely moves — you'd see slow agitation but the fine particles never get enough vertical kick to pass the mesh. This is a useful setting for clearing a clogged screen by hand without shutting the motor off, but useless for production sifting.
Step 4 — at the high end, 180 RPM:
In theory you double the throughput. In practice, peak follower acceleration scales with the square of speed — so it's 4× the nominal value — and unless the return spring is sized for at least 3× that inertial load, the upright bar lifts off the cam face during the descending half of each wave above roughly 150 RPM. You'll hear it as a metallic clatter and you'll see the screen-tap rhythm go irregular.
Result
Nominal peak bar velocity is 0. 113 m/s with a stroke frequency of 9 Hz (540 strokes/min) at the design point of 90 RPM. That feels like a brisk, even buzz through the sieve frame — fine particles clear the mesh cleanly and the bar tracks the cam without audible slap. Across the operating range the velocity scales linearly from 0.038 m/s at 30 RPM up to 0.226 m/s at 180 RPM, but the usable sweet spot sits between 60 and 130 RPM because below 60 the screen barely sifts and above 130 the follower starts skipping. If your measured velocity comes in 20% below predicted, check three things in order: (1) bar guide bushing alignment — more than 0.5° off vertical robs stroke through side-binding, (2) cam-face wear flats showing as shiny patches that have flattened the wave peaks by 0.5 mm or more, and (3) return spring fatigue — a spring that has lost 15% of its rated rate lets the follower lift mid-stroke and the bar never reaches peak amplitude.
When to Use a Waved-wheel Cam to Upright Bar and When Not To
The waved-wheel cam to upright bar competes with two main alternatives: an eccentric-driven scotch yoke for higher precision sinusoidal motion, and a solenoid or voice-coil actuator for electronically tunable strokes. Each has a clear application window — pick by stroke frequency, accuracy, cost, and how much dirt the mechanism has to swallow.
| Property | Waved-wheel cam to upright bar | Eccentric scotch yoke | Solenoid / voice-coil actuator |
|---|---|---|---|
| Typical stroke frequency | 120-3600 strokes/min | 30-1200 strokes/min | 1-500 strokes/min |
| Stroke length precision | ±0.05 mm (cam-cut limit) | ±0.01 mm | ±0.1 mm (open-loop) |
| Strokes per shaft revolution | 2-12 (set by wave count) | 1 | N/A — electrically driven |
| Cost (mechanism only, small-batch) | $60-200 | $120-400 | $80-600 |
| Service life under continuous duty | 8,000-15,000 hours | 20,000+ hours | 5,000-10,000 hours (coil heating) |
| Tolerance to dust and contamination | High — open contact tolerates dirt | Medium — yoke slot traps debris | Low — coil gap clogs |
| Best application fit | Vibratory feeders, sieve shakers, music boxes | Pump drives, single-stroke presses | Programmable taps, lab dispensers |
Frequently Asked Questions About Waved-wheel Cam to Upright Bar
The most common culprit is the follower never actually reaching the wave peak. If the return spring is too weak or the bar mass is too high, the follower lifts off the cam face partway up the wave and the bar coasts ballistically — peak velocity is then set by inertial coast, not by cam contour. Push a screwdriver against the bar at running speed and feel for spring force at top of stroke; if it's mushy, the spring is undersized.
The second cause is cam-face wear. The wave peaks flatten first, dropping effective amplitude A by 10-20% before the cam looks visibly worn. Measure peak-to-peak stroke at the bar tip with a dial indicator — if it's down even 0.3 mm from new, you've lost meaningful velocity.
Pick wave count first. More waves give you more strokes per revolution at the same shaft speed, which means lower bearing wear, lower gearmotor cost, and lower noise. The ceiling on wave count is geometric: each wave needs at least 8-10× the follower-tip contact length around the cam circumference to avoid the follower bridging two waves at once. On an 80 mm cam with a 10 mm roller, you can comfortably fit 8 waves; squeeze in 12 and the roller skims the peaks instead of dropping into the valleys.
Once you've maxed out practical wave count, then increase RPM — but watch the inertial limit because peak follower acceleration scales with the square of speed.
Use a roller above 200 RPM cam speed or when wave amplitude exceeds 5 mm. The reason: sliding contact between a flat foot and a steep wave flank creates contact pressures that exceed the cam's hardness limit at higher speeds, and you'll see galling marks on the cam within days. A roller converts that sliding contact to rolling contact and drops the surface stress by roughly an order of magnitude.
Stick with a flat foot when the environment is dirty (flour mills, foundries) — a roller bearing packs with debris and seizes, while a flat foot just keeps sliding. Also stick with flat foot when wave amplitude is under 2 mm and speeds are below 100 RPM, because the cost saving is real and there's no wear penalty at that duty.
The cam shaft can be perfectly perpendicular and you'll still get side-load wear if the wave profile has any asymmetry — meaning the rising flank and the falling flank aren't mirror images. An asymmetric profile pushes the follower tangentially during one half of the wave, and that tangential force translates into a side load on the upright bar. Check the cam by running a dial indicator radially against the wave flanks; rising and falling flank slopes should match within 2°.
The other cause is the bar guide bushings being too close together. If the centre-to-centre spacing is less than 3× the bar diameter, the bar can cock under any side load and wear one side of the lower bushing into a slot.
Yes — and it's a common trick in old textile and music-box mechanisms. Stack two cams with different wave counts (say 4 and 6) and a single follower riding both, and you get a beat pattern: the bar follows whichever cam is currently higher. The result is a non-repeating-looking stroke pattern that repeats only every 12 shaft revolutions (the LCM of 4 and 6).
The catch: the follower has to be wide enough to span both cam faces, and the cam stack has to be ground so the two faces sit within 0.02 mm of the same axial plane at the contact point. Any axial mismatch and the follower rocks instead of riding cleanly.
Expect 65-80 dB at 1 m for a small benchtop unit running 300-600 strokes per minute with steel-on-steel contact. The dominant noise source is not the cam contact itself — it's the upright bar's return impact at the bottom of each stroke when gravity or spring slams it back against the cam. Wrap the bar guide in a polyurethane sleeve or fit a small elastomer bump-stop and you'll knock 10-15 dB off the total.
If you're hearing a metallic tick at every wave peak rather than a smooth buzz, the cam profile is non-tangential at the peak — meaning the wave was cut as a sharp peak rather than a rounded sinusoidal crest — and the follower is hammering. That's a profile fix, not a damping fix.
References & Further Reading
- Wikipedia contributors. Cam. Wikipedia
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