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Frequently Asked Questions
About Mould Parting Locks

Find direct answers to the technical and buying questions mould designers, tool rooms, maintenance teams and procurement professionals ask about Mould Parting Locks. This guide covers frictional plate holding, lock selection, bolt adjustment, mounting bores, temperature, dry installation, failures, custom manufacture, price, MOQ and delivery.

Function & Product Selection

A mould parting lock creates controlled friction between selected mould plates so one plate can be pulled or retained until a desired opening condition is reached. The official page describes it as acting like a puller. We select the lock from the required plate sequence, opening travel, holding force, mould orientation, temperature and available mounting space.
A parting lock normally uses friction or controlled interference to hold or pull a plate for a limited portion of mould opening. A mould latch uses a defined latch-and-release mechanism to create a staged plate sequence. The two can solve related sequencing problems, but their release behaviour, load capacity, adjustment and mounting are different.
A runner lock pin grips or retains the runner or sprue system so it separates from the moulded part or moves with the intended plate. A mould parting lock acts between mould plates to control their relative opening. One manages runner retention, while the other manages plate movement. Both may appear in a three-plate mould but perform different duties.
The parting lock provides enough gripping force that when the moving platen opens, the lock pulls the designated mould plate with it. This can separate the runner, break the gate or open a cavity before the lock’s friction is overcome and the plate stops moving. The actual pulling action depends on the lock adjustment and required travel.
They are commonly used in three-plate moulds, stack moulds, floating-cavity tools and any mould where a specific plate must travel a short distance before the main parting line opens. Standard two-plate moulds without floating plates normally do not require parting locks.
No. Parting locks are rated or selected by their holding force and diameter. A small lock cannot safely pull a large, heavy mould plate, overcome high guide-pin friction or resist strong vacuum forces. The mould mass, required opening distance and operating resistance must be verified before confirming the lock size and quantity.
Yes. The official pages list the Parting Lock RPL series and the Parting Lock DPL series, along with a general page. These series may have different friction materials, internal mechanisms, holding capacities, installation requirements or adjustment methods. We request the exact drawing and required force so we do not substitute an incompatible series.
Provide the required plate opening sequence, estimated plate mass, friction or runner-release resistance, operating temperature, available plate thickness, diameter preference and required quantity per mould. The supplier can then compare this data against the holding force and dimensional constraints of the RPL, DPL or other available series.
They function differently. A latch holds positively and releases at a specific distance determined by a cam. A parting lock relies on friction that can be overcome by plate stops or increased resistance. Replacing a latch with parting locks changes the opening behaviour and safety limits, so the mould sequence must be re-evaluated.

Friction, Holding Force & Plate Travel

The parting lock normally uses an internal mechanism—such as a tapered bolt, spring or wedge—to expand a friction sleeve against the sides of a mounting hole, or it uses interference fit between its components. The exact method of generating friction depends on the DPL or RPL series design.
Most friction-based parting locks allow force adjustment by tightening or loosening the internal taper bolt, which changes how much the friction sleeve expands. If the lock cannot be adjusted, it may be the wrong series, incorrectly installed or damaged. Follow the supplier’s adjustment instructions to prevent over-expansion.
The lock must overcome plate weight (if moving vertically), guide-pin friction, vacuum created between plates, runner sticking, the force required to break the gate or separate the sprue, and opening acceleration. Underestimating these forces can cause the plate to separate prematurely or fail to open.
The parting lock pulls the plate until the plate hits a positive mechanical stop (such as a pull-rod collar, stripper bolt or stop block). When the plate hits the stop, the pulling force exceeds the lock's friction limit, causing the lock to slip and allowing the remainder of the mould to open.
If locks are installed asymmetrically or adjusted to different friction levels, they pull the plate unevenly. This racks the plate on the guide pins, causing severe binding, guide-pin wear, uneven parting-line separation and potential damage to the mould components. The force should be balanced across at least two or four positions.
Yes. High-speed opening increases the dynamic load on the locks and can alter the effective friction. Fast opening can also cause the plate to bounce when it hits the stop, while slow opening relies more consistently on steady static friction. The adjustment should be verified at the actual production machine speed.
Yes. High temperatures can change the clearance of the mounting hole, alter the friction characteristics of the plastic sleeve or soften internal components. A lock adjusted while cold may slip or jam when the mould is hot. Select a lock rated for the operating temperature and verify the friction setting during production.
Over-tightening increases the expansion beyond design limits, which can crush the friction sleeve, jam the taper bolt, damage the mould plate hole or prevent the lock from slipping when the plate hits the stop. This can tear pull-rods or damage the press. Adjust tension incrementally.
Under-tightening reduces the holding friction. The plate will separate prematurely or fail to follow the intended opening sequence. This means the runner may not drop, or the part may drag against the cavity, causing component damage and machine stoppage.

Material, Bolt & Component Design

The internal bolt, taper plug or core is typically made from alloy steel or high-tensile steel to resist stretching and provide secure adjustment. The outer friction sleeve is often made from engineered plastic (like nylon or proprietary high-temperature resin) to provide consistent friction against the mould plate without scoring it.
Yes. The plastic material determines the coefficient of friction, wear rate, temperature resistance and chemical compatibility. Standard nylon sleeves may soften or degrade at high temperatures, while specialised resins can survive hotter moulds. The correct material must be specified for the actual process temperature.
The internal taper bolt (or expanding cone) forces the slotted plastic sleeve outward as the bolt is tightened. This outward expansion creates the radial friction against the wall of the mould plate hole. The taper angle and bolt thread pitch allow fine adjustment of the holding force.
RPL and DPL likely indicate different standard designs, dimensional proportions, friction materials, load capacities or installation configurations. Without detailed catalogue diagrams, they cannot be assumed to be identical. We request the required dimensions and holding force to confirm the correct series for your mould.
This depends on the specific lock design and the supplier’s spare parts policy. Some friction sleeves are supplied as replaceable spares, while other locks are sold as sealed or complete assemblies. If the internal taper is also worn, replacing the entire unit is usually safer and more reliable.
Yes. Oil, grease, rust preventatives or leaking coolant can change the friction characteristics of the plastic sleeve, causing it to slip unexpectedly. Certain chemicals or aggressive mould cleaners may also degrade the plastic over time. The mounting hole and sleeve should be kept clean and dry unless the manufacturer specifies otherwise.
They can be, provided the plastic friction material does not generate unacceptable dust or outgassing during operation, and the lock mechanism does not require liquid lubrication. Confirm the cleanroom requirements and evaluate the lock design before final selection.
If the thread strips due to over-tightening or wear, the lock can no longer maintain or adjust tension. The friction sleeve will contract, and the lock will fail to hold the plate. A stripped bolt cannot be repaired and the complete parting lock must be replaced.

Installation, Adjustment & Replacement

The mounting hole must be machined precisely to the diameter, depth, tolerance and surface finish specified for the selected lock series. An oversized hole will prevent the sleeve from creating enough friction, while an undersized hole will cause installation jamming or premature sleeve damage.
Yes. The finish must be smooth enough to prevent rapid abrasive wear on the plastic sleeve but not so polished that it cannot provide adequate friction. Follow the surface roughness (Ra) guidelines provided by the lock manufacturer for the mating steel bore.
The central bolt or the solid end of the lock is usually threaded directly into a tapped hole in one mould plate. The plastic friction sleeve portion then projects into a smooth bore in the adjacent plate. Ensure the threaded hole is deep enough to accept the bolt fully.
Start with low friction tension. Tighten the adjustment bolts equally on all installed locks by small increments (e.g. quarter-turns) and test the mould opening sequence slowly. Continue adjusting evenly until the plate is pulled reliably, then stop. Do not apply maximum tension immediately.
No. Do not grease or oil the outside of the friction sleeve or the inside of the mounting bore unless explicitly instructed by the manufacturer. Lubrication will drastically reduce the friction coefficient, preventing the lock from generating the required holding force.
The lock must slide exactly parallel to the mould opening direction. If the mounting hole is angled or misaligned, the lock will bind severely, causing immediate sleeve wear, high unlocking force, damaged mounting threads or failure to pull the plate correctly.
Check the tension during regular preventive maintenance, after a long storage period, or if the mould sequence begins to falter. The plastic sleeve wears gradually over many cycles, so occasional minor retightening may be necessary to restore the original holding force.
Always test the opening sequence at low pressure and low speed. Ensure pull rods, stripper bolts or mechanical stops are correctly installed to catch the floating plate. If the locks fail or the stops break, an unconstrained plate can drop and cause severe injury or tool damage.
Loosen the central taper adjustment bolt fully to release the expansion pressure on the plastic sleeve. Carefully unscrew the main body from its tapped hole. If the plastic sleeve is seized in the bore, it may need to be extracted or drilled out carefully without scoring the steel hole.

Failure, Troubleshooting & Maintenance

The parting lock tension may be too low, the sleeve may be worn, oil may have contaminated the bore, or the plate may be jammed on the guide pins. Alternatively, the force required to break the gate or separate the runner may be higher than anticipated. Check these factors before replacing the lock.
Slipping occurs if the friction sleeve is under-tightened, excessively worn, contaminated with mould grease or exposed to temperatures that soften the plastic. It can also slip if the opposing forces (vacuum, sticking, guide friction) exceed the lock’s maximum rated capacity.
The lock may be over-tightened, creating more friction than the machine opening force or the pull rods can handle. The plastic sleeve might also be jammed or melted into the bore, or the mounting hole may be misaligned, causing mechanical binding rather than controlled friction.
Rapid wear is usually caused by a rough bore surface finish, severe angular misalignment, over-tightening the adjustment bolt, operating beyond the temperature limit, or high-speed cycling. Replacing the lock without improving the bore finish or alignment will result in repeated failure.
Twisting or racking happens when the parting locks are adjusted to different friction levels or are located asymmetrically. The side with higher friction pulls harder, twisting the plate on the guide pins. Ensure all locks are identical, positioned symmetrically, and adjusted equally.
Bolt failure indicates extreme overload. This can happen if the lock binds due to misalignment, if the plate crashes during closing, if the required pull force far exceeds the lock's rating, or if the bolt was severely over-torqued during adjustment. Evaluate the alignment and load capacity.
Noise is caused by dry friction between the plastic sleeve and the steel bore. While some noise is normal, loud squeaking or shuddering (stick-slip) suggests the sleeve is glazed, the bore is too smooth, the tension is too high, or the lock is misaligned.
Inspect parting locks whenever the mould is serviced or if the opening sequence becomes inconsistent. Check the sleeve for excessive wear, burning or glazing. Test the adjustment bolt for free movement. Clean the mounting bore with a dry cloth and remove any oil or grease.

Quality, Price & Ordering

Provide the original part number or series (e.g. RPL or DPL), outer sleeve diameter, overall length, thread size for mounting, required holding force, operating temperature and quantity. A photograph or drawing of the existing lock helps ensure the correct replacement is quoted.
Send the mould assembly drawing showing the plate sequence, required opening distance, estimated plate mass, runner details, guide pin layout, operating temperature, available space, and preferred diameter. This allows the supplier to confirm whether the chosen series has adequate holding capacity.
Pricing depends on the specific series (RPL vs DPL), diameter, load capacity, high-temperature material upgrades, order quantity and delivery location. We provide an accurate quotation once the exact model, size and application requirements have been verified.
The minimum order quantity may vary by series, size and stock status. Some standard sizes may be available in small quantities for repair work, while others may require a batch order. Please request confirmation of the MOQ along with the price and lead time.
They are typically packed in individual boxes or sealed blister packs to protect the plastic sleeve from being crushed, scratched or contaminated with oil during transit. Bulk orders are placed in sturdy outer cartons with appropriate labelling for safe delivery.
Common diameters and series are usually held in stock for prompt dispatch. However, specific high-temperature variants or unusual sizes may require a short lead time. Request current stock availability before scheduling urgent mould maintenance.
Yes. Vardhman Dies & Mould Tools supplies precision parting locks from Maharashtra directly to toolrooms and mould makers across India. We also process international export orders, providing correct protective packaging and necessary commercial documentation.
Use the website enquiry form, email or contact number. Provide the required series (RPL/DPL), diameter, load requirement, operating temperature, quantity and delivery address. Review the quotation, technical specification and lead time before authorising the purchase.

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