Tolérance de position du moule pour un alignement répétable

There is no single mold positioning pin tolerance that works for every mold. Repeatable alignment depends on a complete tolerance chain: the pin diameter, the mating hole or bushing diameter, the fit between them, the position and orientation of both features, and the dimensional changes that occur during operation.

A pin can be ground to a very tight diameter tolerance and still fail to locate the mold correctly if its hole is misplaced, its axis is tilted, or two locating pins create an overconstrained pattern. For broader guidance on guide systems, Usure, and fit selection, voir Broches et bagues de moulage (déduit). This guide focuses specifically on defining, calculating, documenting, and inspecting positioning-pin tolerances.

What Does a Mold Positioning Pin Tolerance Actually Control?

The word “tolerance” may refer to several different requirements. These controls are related, but they are not interchangeable.

Control	Ce que cela définit	Ce qu’elle ne définit pas
Tolérance à la taille des broches	Le plus grand et le plus petit diamètre acceptable de goupille	La position de l’axe de la broche
Tolérance de trou ou de bague	Le plus grand et le plus petit forage d’accouplement acceptable	Si le canon est correctement situé
Ajustement par goupille à trou	L’écart ou l’interférence possible entre les deux caractéristiques	Erreur totale d’alignement du moule
Tolérance géométrique	La position et l’orientation autorisées de l’axe de la goupille ou du trou	L’espace réel entre les pièces
Répétabilité du système	À quel point le moule revient régulièrement à la même position	Savoir si cette position répétée est la position nominale correcte

Le Système ISO 286-1 de limites et d’ajustements defines size tolerances and fit relationships for holes and shafts. It does not control where a hole is located or whether its axis is perpendicular to the mold plate. Those requirements need geometric controls, such as those defined by ISO 1101.

Size Tolerance, Ajustement, and Alignment Are Different Requirements

Suppose a positioning pin and its mating hole are both within their specified diameter limits. That confirms only that their sizes are acceptable.

It does not confirm that:

• the pin and hole centers coincide;
• their axes are parallel;
• two locating holes have the correct spacing;
• the mold returns to its intended position;
• the assembly will still engage after heating or wear.

The actual fit comes from the combination of both size ranges. The smallest permitted hole paired with the largest permitted pin creates the tightest possible assembly. The largest hole paired with the smallest pin creates the loosest possible assembly.

Both extremes must be checked.

Poste, Orientation, and Repeatability Complete the Specification

A bore may have the correct diameter but still be offset from its basic location. A pin may be positioned correctly at the plate surface but tilted enough to bind over a long engagement length.

A complete positioning specification may therefore need:

• a functional datum reference frame;
• basic dimensions locating the pin or hole;
• positional tolerance;
• perpendicularity or another orientation control;
• pattern control for multiple locating features.

Repeatability and accuracy should also be distinguished. Repeatability describes how consistently the mold returns to the same position. Accuracy describes how close that position is to the intended nominal location.

A locating system can be repeatable but consistently offset if the feature pattern was manufactured in the wrong position.

Les goupilles de positionnement ne doivent pas automatiquement être considérées comme équivalentes à Goupilles guides de moule. Guide pins primarily control movement as mold halves open and close. A dedicated positioning pin may establish a more precise final location after the mold halves approach engagement.

Définir l’exigence fonctionnelle avant de sélectionner l’ajustement

A tolerance should start with the required function, not with a familiar fit designation.

Before assigning limits, Définissez:

1. The maximum permitted translational alignment error.
2. The maximum permitted angular error.
3. The nominal pin diameter and engagement length.
4. Whether the pin is permanent, removable, or replaceable.
5. How often the mold will be assembled or disassembled.
6. Which side retains the pin.
7. Which side provides the locating engagement.
8. The operating temperature range.
9. The expected wear, Lubrification, and contamination conditions.
10. The manufacturing and inspection methods available.
11. Whether binding or excess clearance creates the greater functional risk.

A positioning system used for a removable insert may prioritize easy engagement and interchangeability. A permanently installed locator may require stronger retention on its mounting side. A heated mold may need enough room for differential thermal expansion between the pin, bushing, and mold plate.

Application labels alone do not determine the correct fit. An “automotive mold” or “medical mold” still needs a defined alignment requirement, material combination, temperature range, and inspection plan.

Séparer l’interface fixe de l’interface de localisation

The two ends of a positioning pin usually perform different jobs.

Interface	Fonction principale	Possible Fit Direction
Côté de montage	Conservez la goupille dans la plaque de support et prévoyez son axe	Controlled transition or interference, depending on design
Côté de localisation	Entrer dans le trou d’accouplement ou la bague et limiter le mouvement relatif	Controlled clearance or transition, depending on function

Using the same fit on both sides can create avoidable problems. A locating-side interference fit may prevent normal assembly. Excessive mounting-side clearance may allow the pin to shift or loosen.

The final selection must also consider plate thickness, surrounding material, removal method, replacement needs, and the risk of distortion during installation.

Choisissez l’ajustement et calculez la mise au sol réelle

Dégagement, Transition, and interference fits describe the relationship between the complete pin and hole tolerance zones.

Dégagement, Transition, and Interference Serve Different Functions

Type d’ajustement	Résultat dimensionnel	Utilisation fonctionnelle typique	Risque principal
Ajustement de dégagement	Le plus petit trou reste plus grand que la plus grande goupille	Engagement de positionnement coulissant ou amovible	Mouvement excessif si le dégagement est trop grand
Ajustement de transition	Some valid combinations have clearance; others have interference	Localisation proche ou rétention modérée	Force d’assemblage variable
Ajustement par interférence	La plus petite goupille reste plus grande que le plus grand trou	Conservation permanente ou semi-permanente	Distorsion, Retrait difficile, ou des dommages à l’installation

These categories describe outcomes, not universal recommendations. A clearance fit may be suitable on the locating side while an interference or transition fit is used on the mounting side.

The hole-basis system is common because standard hole-making tools can establish a defined hole tolerance while the shaft or pin tolerance is selected to create the required fit. Toujours, a designation such as H7/g6 or H7/m6 is incomplete without the nominal diameter and governing standard. The numerical deviations change across diameter ranges.

Utilisez les dimensions limites pour vérifier les deux extrêmes d’assemblage

Calculate the limits before approving the fit.

Garde minimale

Minimum clearance = Smallest permitted hole − Largest permitted pin

Garde maximale

Maximum clearance = Largest permitted hole − Smallest permitted pin

A negative result represents interference.

Consider a hypothetical example:

Caractéristiques	Diamètre minimal	Diamètre maximal
Localisation du trou	10.010 mm	10.018 mm
Goupille de positionnement	9,998 mm	10.004 mm

The tightest possible assembly is:

10.010 − 10.004 = 0.006 mm minimum diametral clearance

The loosest possible assembly is:

10.018 − 9.998 = 0.020 mm maximum diametral clearance

These values are examples only. They are not recommended SunshinePro specifications or universal mold tolerances.

Diametral clearance also should not be treated as the complete alignment error. In an ideal single-pin interface, the pin center may move radially by up to approximately half the diametral clearance before contact. The actual mold position also depends on the second locator, feature positions, axis angles, engagement lengths, Déformation, et conditions de fonctionnement.

Control the Locating Pattern, Not Only the Pin Diameter

A precision fit cannot compensate for an incorrectly located pattern.

The pin and mating feature must be controlled from datums that represent how the mold is assembled and functions. These may include a seating face, a side reference, or another stable mold-base feature.

Use Functional Datums, Poste, and Axis Control

A practical drawing should identify:

• the surfaces establishing the functional datum reference frame;
• the basic locations of the pin and mating hole;
• the permitted positional variation;
• any required perpendicularity or axis-orientation control;
• the relationship between multiple locating features.

ISO 5458 provides complementary rules for pattern specifications under the ISO GPS system. Drawings using ASME conventions should follow ASME Y14.5.

The drawing should clearly use one governing convention. Mixing ISO and ASME symbols or assumptions without clarification can create conflicting interpretations between the designer, manufacturer, and inspector.

Éviter la surcontrainte avec une paire de tombés ronds et relevés

Two fully round pins entering two close-fitting round holes can overconstrain the assembly.

For both pins to engage, the distance between the pins must agree closely with the distance between the mating holes. Even when every individual diameter is acceptable, accumulated spacing and position variation can cause binding.

A common locating arrangement uses:

• one round pin as the primary locator;
• one diamond, relieved, or flattened pin as the secondary locator.

The round pin controls movement in two planar directions. The relieved pin controls the required secondary direction while allowing some variation along the relieved axis.

The secondary pin must be oriented correctly. Rotating its relieved direction by 90 degrees changes which movement it permits and which movement it controls.

Locator spacing also affects angular definition. Greater spacing can reduce angular movement for a given amount of linear clearance, but no universal spacing rule applies. Taille de la plaque, Chargements, Espace disponible, hole-position capability, and engagement geometry still need evaluation.

Construire une pile de tolérance dans le pire des cas pour un alignement reproductible

The fit calculation covers only one part of the positioning system. A complete tolerance budget should include every variation capable of moving, tilting, or preventing engagement between the mold halves.

Typical contributors include:

Contributeur	Effet possible
Pin diameter	Changement de dégagement ou d’interférence
Trou ou alésage de bague	Changement de dégagement ou d’interférence
Position de montage de la goupille	Déplace l’axe de localisation
Position du trou d’accouplement	Déplace l’axe de réception
Orientation des axes	Crée un décalage angulaire ou un contact avec les arêtes
Ajustement du diamètre extérieur de la bague	Permet ou restreint le mouvement des bagues
Relation d’ennui envers l’extérieur	Décale l’alésage fonctionnel de la bague
Espacement par motif de goupilles	Affecte l’engagement simultané
Température de la plaque de moule	Modification des dimensions des composants
Usure	Augmente la dégagement efficace
Débris	Réduit le dégagement au sol ou empêche une place complète
Incertitude de mesure	Réduit la confiance dans la décision d’acceptation

A practical worst-case process is:

1. Define the maximum permitted alignment variation.
2. Identify each dimensional and geometric contributor.
3. Calculate the tightest and loosest component fits.
4. Add the possible positional and orientation effects.
5. Check whether every permissible combination can assemble.
6. Reserve allowance for operating temperature, Usure, and contamination.
7. Confirm that the inspection system can verify the specified limits.

Worst-case analysis is appropriate when assembly must be guaranteed at every permitted limit. Statistical tolerance analysis may be useful in established, capable production processes, but it should not replace functional verification without a justified process model.

Différence entre la fabrication et la variation opérationnelle

Manufacturing variation includes:

• component diameter;
• hole diameter;
• feature position;
• Perpendiculité;
• pattern spacing;
• bushing installation position.

Operating variation includes:

• Expansion thermique;
• Usure;
• Débris;
• état de lubrification;
• plate movement or deformation.

A fit that works during inspection at room temperature may become too tight after heating. A fit that begins with acceptable clearance may lose repeatability as the pin or bushing wears.

Lubrication can reduce friction and seizure risk, but it cannot correct an invalid tolerance stack. Material and hardness affect how well the components retain their dimensions over time, but those decisions should remain separate from the basic fit calculation.

Utilisez une pile hypothétique pour tester la conception

Assume a design permits 0.030 mm of total lateral variation at a functional location.

A simplified hypothetical budget might allocate:

Contributeur	Effet autorisé
Mouvement radial de la goupille à la bague	0.008 mm
Variation de la position des quilles	0.006 mm
Variation de la position des bagues	0.006 mm
Orientation et effet d’engagement	0.004 mm
Tolérance de température et d’usure	0.004 mm
Marge de conception restante	0.002 mm

If the calculated worst-case total exceeds 0.030 mm, the design must change. Possible actions include:

• reducing maximum clearance;
• improving positional control;
• increasing locator spacing;
• using a replaceable bushing;
• revising the relieved-pin geometry;
• reducing operating variation;
• redefining the functional requirement.

The example demonstrates the budgeting method only. Real values must come from the mold’s geometry, Conditions de fonctionnement, and manufacturing capability.

Spécifiez clairement l’exigence sur le dessin ou la demande d’offres

A supplier cannot reliably manufacture or inspect an ambiguous precision requirement.

The drawing or request for quotation should identify:

• nominal pin, hole, and bushing dimensions;
• limit dimensions or an unambiguous fit designation;
• the governing tolerance standard;
• separate mounting-side and locating-side requirements;
• Données fonctionnelles;
• basic feature locations;
• position and orientation tolerances;
• primary and secondary locator roles;
• the orientation of any relieved or flattened pin;
• material and hardness where functionally necessary;
• Condition de traitement thermique;
• surface finish on locating diameters;
• operating temperature assumptions;
• whether components must be interchangeable;
• whether selective assembly is permitted;
• required inspection characteristics;
• required inspection records;
• whether pins and bushings are supplied as matched components.

The supplier should also know which characteristics are function-critical. A tight pin diameter may be less valuable than a slightly wider size tolerance combined with better positional control.

Évitez les notes de précision ambiguë

Specifications that need clarification include:

• “high-precision pin” without dimensional limits;
• “±0.005 mm” without naming the controlled feature;
• an ISO fit class without a nominal diameter;
• pin diameter tolerance without a mating-hole tolerance;
• diameter controls without feature-position controls;
• room-temperature dimensions without relevant operating conditions;
• a tolerance with no defined inspection method;
• “100% inspection” without identifying the inspected characteristics.

A numerical tolerance has meaning only when the feature, datum, Standard, conditions, and measurement method are clear.

Verify the Pin, Hole, Pattern, and Assembly

Inspection should follow the structure of the specification.

Exigence contrôlée	Directive de vérification appropriée
Pin diameter	Mesurer à des emplacements et orientations définis
Diamètre du trou ou de la bague	Vérifiez les limites du forage avec une méthode calibrée appropriée
Position de la goupille ou du trou	Mesure relative au référentiel de référence de référence indiqué
Orientation des axes	Vérifier la perpendicularité ou la relation angulaire
Espacement des motifs	Mesurer la relation entre les caractéristiques de localisation
Engagement complet	Utilisez un contrôleur contrôlé de l’ensemble ou un manomètre fonctionnel lorsque cela est approprié
Répétabilité	Tester l’assemblage répété dans des conditions définies

No single measurement verifies every requirement.

A micrometer may confirm a pin diameter but cannot establish the pin’s position in the mold plate. A bore measurement may confirm hole size but not perpendicularity. A functional gauge may show that the current assembly engages, but it may not identify which individual feature is approaching its tolerance limit.

The inspection plan should also consider:

• instrument resolution;
• État de calibration;
• Fixation;
• measurement temperature;
• accessibility of the feature;
• measurement uncertainty.

If the measurement uncertainty is too large relative to the tolerance, the conformity decision becomes unreliable. Component conformity also does not automatically prove long-term repeatability under heat, Usure, and repeated mold cycles.

Décidez si une tolérance standard ou personnalisée est nécessaire

A standard pin or bushing is suitable when its published dimensions, Classe de tolérance, Géométrie, Matériel, and mounting configuration satisfy the calculated tolerance stack.

Customization may be justified when the design requires:

• a non-standard diameter or locating length;
• separate mounting and locating diameters;
• une épaule ou une rebord spéciale;
• a defined relieved-pin orientation;
• a specific material or hardness;
• a controlled surface finish;
• unusual retention or removal features;
• a tolerance not available in a standard series.

The decision should start with the functional requirement rather than an assumption that custom parts are automatically more precise. A custom pin still depends on the mating hole, bushing, Système de dates, et méthode d’inspection.

SunshinePro states that it supplies mold components and supports non-standard accessories based on drawings or samples. Son Localisation de la bague guide de goupille page lists straight, bridé, and custom structures, along with standard or customized sizes. Buyers comparing catalog and drawing-based options can also review the broader guidance on Moulage des pièces standard.

Avant de commander, confirm which feature the supplier’s stated tolerance applies to, how it will be inspected, and whether the component must be interchangeable with other pins or bushings.

For a drawing-based review, provide the pin and mating-feature limits, datum scheme, Ajustement obligatoire, Conditions de fonctionnement, material or hardness requirements, and inspection expectations through the Page de contact SunshinePro.