Hello! This is the editor from Hongxiangda.
When customizing silicone products, one of the biggest concerns for many clients is: the finished product doesn't match the drawing dimensions.
The drawing clearly shows the measurements, so why does the product come out larger or smaller?
Today, let's talk about the common reasons why silicone product dimensions can be inaccurate and how to avoid this problem.
Inaccurate Dimensions – Usually Traceable to Five Areas
From drawing to finished product, a silicone part goes through many steps. Dimensional issues can occur at any of these stages.
1. Mold Problems
The mold is the first checkpoint that determines product dimensions.
Insufficient mold machining accuracy
If the mold itself is not machined accurately, the resulting product will naturally be inaccurate. For example, the mold cavity dimensions may deviate from the drawing, or wear may occur during mold manufacturing.
Unreasonable mold design
Silicone shrinks after molding. Different hardness levels and different product shapes have different shrinkage rates. If the mold design does not account for this shrinkage, the product will differ from the drawing dimensions after cooling.
Mold aging or damage
After many production cycles, molds can wear out or become deformed. Loose alignment pins or worn parting lines can cause unstable product dimensions.
How we handle it:
All molds are precision‑machined and undergo full dimensional inspection after completion.
During mold design, we accurately calculate shrinkage based on silicone properties and product shape.
Each mold has a usage log; we perform regular checks and maintenance, and replace molds when they reach the end of their service life.
2. Raw Material Issues
The raw silicone itself can also affect dimensions.
Different batches have different shrinkage rates
Silicone from different manufacturers or different batches may have slightly different shrinkage rates. If the raw material batch is changed during production without adjusting the process, the product dimensions may shift.
Uneven mixing of the compound
If additives are not evenly kneaded during mixing, the flowability of the compound becomes inconsistent. When different areas of the part shrink differently during molding, local dimensional deviations occur.
How we handle it:
Every incoming batch of raw material is inspected and recorded; key parameters like shrinkage must pass our standards.
When switching to a different batch, we first run a small trial to confirm dimensional stability before mass production.
The mixing process is strictly controlled to ensure a homogeneous compound.
3. Molding Process Problems
Various parameters during the molding process directly affect final dimensions.
Incorrect vulcanization temperature
If the temperature is too high, the compound flows too much and the part can become “oversized.” If too low, the compound does not fill the cavity completely, resulting in short shots or undersized parts.
Unstable molding pressure
Too much pressure flattens the product (smaller dimensions); too little pressure makes the part less compact (larger dimensions).
Incorrect vulcanization time
If the time is too long, the compound overcures and may shrink excessively. If too short, the cure is incomplete and the part can continue to deform after demolding.
Poor venting operation
Venting helps the compound flow better and release trapped air. Improper venting frequency or venting distance affects how well the cavity fills, leading to dimensional inaccuracies.
How we handle it:
Each product has standard molding parameters (temperature, pressure, time, venting settings).
We monitor machine parameters in real time during production and adjust promptly if deviations occur.
Operators follow work instructions strictly and do not change parameters based on guesswork or habit.
4. Post‑Processing Problems
Sometimes dimensional deviations happen after the part is removed from the mold.
Improper demolding method
Forcing the part out or using the wrong demolding angle can stretch or distort it. This is especially common for long, thin, or thin‑walled parts.
Improper cooling method
When a silicone part comes out of the mold, it is still hot. If parts are piled up randomly or cooled too quickly, they will shrink and warp during cooling.
Effect of post‑curing
Some products require post‑curing (baking). If the temperature or time of post‑curing is not well controlled, additional shrinkage can occur.
How we handle it:
We design proper demolding structures and use auxiliary tools when necessary.
After demolding, parts are arranged properly and allowed to cool naturally without stacking or pressure.
Post‑curing is carried out according to strict standards, with temperature and time precisely controlled.
5. Measurement Problems
Sometimes the part is actually correct, but the measurement method is flawed.
Inaccurate measuring tools
If calipers, optical projectors, or other measuring tools are not calibrated regularly, the data they produce will be inaccurate.
Incorrect measurement position
The drawing specifies a dimension between two specific points. If you measure the wrong points, you are not measuring the dimension that the drawing requires.
Different part state
A hot part just out of the mold has different dimensions than the same part after cooling. Measuring at the wrong time gives the wrong result.
How we handle it:
All measuring tools are regularly sent out for calibration.
Our measurement personnel are trained to follow the drawing and use the correct measurement positions.
Dimensional inspection is performed after the product has cooled to room temperature.
How Does Hongxiangda Ensure Accurate Dimensions?
Dimension control is not a single‑step task; it is a systematic effort that runs through the entire production process.
Design stage
When we receive a customer's drawing, we first evaluate whether the product structure and dimensional requirements are reasonable. For areas prone to deformation, we proactively suggest improvements.
Mold stage
After a mold is completed, we run trial shots. The mold is only released for mass production after the trial sample passes a full dimensional inspection.
Production stage
Before each production batch, we perform a first‑article inspection. Mass production proceeds only if the first article meets the dimensional requirements. During production, quality inspectors take samples at regular intervals to check dimensions. If a deviation is found, production is stopped and adjustments are made immediately.
Before shipment
Before finished products are shipped, we perform a final dimensional inspection according to the sampling plan to ensure that the delivered products comply with the drawing dimensions.
What If Dimensions Are Off? Our Handling Process
If a dimensional deviation does occur, we follow a complete process:
Confirm the issue: Re‑check the drawing and measurement method to verify whether a real deviation exists.
Identify the cause: Check step by step – mold, raw material, process, operation – to find the root cause.
Adjust and improve: Once the cause is found, adjust the relevant process parameters or equipment.
Re‑validate: After adjustments, run a new trial or trial batch to verify that dimensions are now correct.
Record and archive: Document the problem and the solution so that the same issue does not recur.
A Final Word
Whether dimensions are accurate is one of the fundamental criteria for judging whether a silicone factory is reliable.
At Hongxiangda, we do not treat “accurate dimensions” as a bonus. We treat it as a basic requirement that must be met. From molds to raw materials, from molding to inspection, every step has corresponding control measures.
If you are looking for a silicone products factory that delivers stable dimensions and peace of mind, please contact Hongxiangda. With 15 years of experience, we help you make your products more precise.