designing parametric worms

Designing parametricworms with Catia V5

Published at http://gtrebaol.free.fr/doc/catia/worm.htmlWritten by Gildas Trébaol on June 26, 2005.Zipped part: worm.zip (306 KB).VRML97 model: worm.wrl (304 KB).

The worm is a part of a worm / worm wheel reduction gear

This tutorial shows how to make a basic worm that you can freely re-use in your assemblies.

1 Sources, credits and links

The worm can be coupled with a worm gear or with an helical gear.The principle for designing a worm consists in drawing a thread helix that cuts a cylinder.The worm dimension is taken from the part catalog Engrenages H.P.C, June 1999 edition.The worm above corresponds to the part ref. W1,5-1 page 358.

2 Table of worm parameters and formulas

# Parameter Type orunit

Formula Description Name in French

Designing parametric worms with Catia V5 http://gtrebaol.free.fr/doc/catia/worm.html

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1 aangulardegree

20degPressure angle: technologicconstant(10deg ≤ a ≤ 20deg)

Angle de pression.

2 m millimeter — Modulus. Module.

3 N real —Number of turns of the thread(3 ≤ N ≤ 15).

Nombre de tours du filet de la vis.

4 D millimeter — Diameter of the pitch cylinder. Diamètre du cylindre primitif.

5 L millimeter p * (N + 1) Length of the thread. Longueur du filetage.

6 ψ (psi)angulardegree

atan( m / D)

Angle of the worm helix. Mustmatchthe angle of the worm wheelhelix.

Angle d'hélice de la vis. Doit êtreégal àl'angle d'hélice de la rouecorrespondante.

7 dZ millimeter -L/2Translation offset of the wormsurface on the Z axis.

Décalage de la surface de la vissuivant l'axe Z.

8 p millimeter m * πPitch of the teethon a straight generative rack.

Pas de la denture sur unecrémaillère génératrice rectiligne.

9 e millimeter p / 2Tooth thickness,measured on the pitch circle.

Epaisseur d'une dentmesurée sur le cercle primitif.

10 ha millimeter mAddendum = height of a toothabove the pitch circle.

Saillie d'une dent.

11 hf millimeter m * 1.25Dedendum = depth of a toothbelow the pitch circle.

Creux d'une dent.

12 rr millimeter m * 0.38

Radius of the root concavecorner.(m * 0.38) is a normativeformula.

Congé de raccordement à la racined'une dent. (m * 0.38) vient de lanorme.

1 Make the pitch helix


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2 Add straight segments at each end of the thread


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3 Draw the thread profile


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4 Make the helical thread


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5 Make the thread extremities


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6 Insert a cylinder tangent to the outside circle


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7 Intersect both surfaces


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8 Fill the worm surface and add a hub


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ψ angle of t

End of File


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designing parametric worms

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