7 Common Mistakes When Sourcing Injection Molding from China

China is a popular sourcing destination for custom injection molding thanks to its mature supply chain, strong tooling capabilities, and competitive pricing.

However, sourcing injection molding from China does not automatically mean that your project will run smoothly.

Many buyers experience quality issues, unexpected costs, or delivery delays—not necessarily because the supplier is unreliable, but because some critical steps were overlooked before placing the order.

Here are 7 common mistakes we often see, along with practical ways to avoid them.

Mistake 1: Sending an Incomplete RFQ

If you only send a product image and say:

“I need this plastic part. Can you give me a quote?”

This type of vague inquiry can easily lead to weeks of back-and-forth communication.

A complete RFQ (Request for Quotation) should normally include:

3D CAD files (STEP or IGES) and 2D drawings

Material requirements

Order quantity

Surface finish and color requirements

Critical dimensions and tolerances

The product's final application or use

Complete information helps an experienced supplier understand your requirements faster and provide a detailed quotation and DFM feedback within 24 hours.

If key information is missing, you may need several rounds of emails to clarify the requirements, which wastes time for both sides.

Mistake 2: Choosing a Supplier Based Only on the Lowest Price

The lowest unit price often means the supplier is cutting costs in other areas, such as:

Using lower-cost mold steel

Using regrind or recycled material

Skipping complete quality inspections

Providing unclear shipping or trade terms

When comparing quotations, don't look only at the unit price. Instead, break down the total project cost.

Pay attention to the following:

Mold Steel

For example, P20 is generally less expensive than H13, but they offer different levels of wear resistance and mold life.

Plastic Material

Virgin resin and regrind/recycled material can differ significantly in performance, consistency, and appearance.

Mold Life

Check whether the supplier provides a clear mold life guarantee. If it is not stated in the quotation, ask for clarification.

Shipping Terms

The actual landed cost can vary significantly depending on whether the terms are EXW, FOB, or DDP.

Therefore, when comparing quotations, focus on the total project cost, not just the price per part.

Mistake 3: Skipping DFM Analysis

DFM (Design for Manufacturability) analysis helps identify potential manufacturing problems before mold making begins.

If you skip DFM, you may not discover issues until after the mold has already been manufactured, such as:

Uneven wall thickness

Insufficient draft angles

Poor gate location

Part geometry that makes ejection difficult

Potential defects such as sink marks or warpage

Making design changes during the DFM stage usually avoids costly mold rework.

However, if a design problem is discovered after the mold has already been manufactured, the modification cost can be 10–50 times higher than making the change during the DFM stage.

That's why DFM analysis before mold making is an important step in reducing project risk.

We start every injection molding project with a free DFM analysis. Before mold making begins, we identify potential design and manufacturing issues to help our customers save time and avoid unnecessary costs.

Mistake 4: Not Requesting T1 Samples

T1 samples are the first trial parts produced after a new mold is completed.

They are one of the last opportunities to identify and correct potential problems before mass production.

T1 samples can help identify:

Dimensional deviations

Surface defects

Assembly issues

Warpage or deformation

Injection molding problems

Some buyers skip T1 approval to save time and move directly into mass production.

In reality, this can lead to more rework and production delays later, ultimately costing more time.

We usually start mass production after the T1 samples are ready and we get the client’s written approval.

Mistake 5: Ignoring Material Compliance

If your product will be sold in a market with regulatory requirements, material compliance is not optional.

Different markets and industries may have different regulatory and certification requirements, such as:

European Union: RoHS, REACH

United States: UL requirements may apply to electronic and electrical products; food-contact or medical products may be subject to relevant FDA requirements

Automotive: Requirements may include IATF 16949 and PPAP

If your project has specific compliance requirements, make sure they are clearly stated in the purchase order (PO) in advance.

Our materials are traceable, and we can provide COA, RoHS, and REACH documentation for each batch according to project requirements for the material.

Mistake 6: Not Having a Quality Inspection Plan

Finding quality problems after the products arrive overseas is often too late.

International returns are expensive and time-consuming, and they can also affect your production schedule and customer deliveries.

That's why quality requirements should be clearly defined before production begins, including:

Critical dimensions and tolerances

Appearance inspection standards

Functional and assembly requirements

For volume production, you can also ask the supplier to conduct:

DUPRO (During Production Inspection)

An inspection performed during production, typically when around 20–30% of the order has been completed. This helps identify batch-level problems as early as possible.

PSI (Pre-Shipment Inspection)

A final quality inspection performed before shipment. The supplier can provide product photos and an inspection report for approval.

We inspect all critical dimensions and provide a complete inspection report and product photos before each batch is shipped.

Mistake 7: Not Assigning a Dedicated Project Contact

An injection molding project usually involves several teams on the supplier's side, including:

Sales

Engineering

Production

Quality Control

Project Management

If you have to communicate with different people for different issues, information can easily get lost. This can lead to misunderstandings, missed design changes, or delays in communication.

That's why we recommend asking your supplier to assign a dedicated Project Manager at the beginning of the project.It is also helpful to establish a regular project update process, such as:

Weekly project updates

Written confirmation of design changes

Immediate communication of any schedule changes

Regular production photos and videos

This makes project communication clearer and more efficient.

We assign a dedicated project manager to every customer and provide regular project updates through photos and videos.

 Sourcing

Quick Checklist When Sourcing Injection Molding From China

Common Mistake	How to Avoid It
1. Incomplete RFQ information	Provide 3D files, product specifications, and order quantity
2. Choosing only the lowest quote	Compare the total project cost, not just the unit price
3. Skipping DFM analysis	Get a DFM report before mold making
4. Skipping T1 trials	Review and approve T1 samples before mass production
5. Missing material compliance documents	Request COA, RoHS, REACH, UL, or other required documents
6. No quality inspection plan	Request DUPRO and PSI reports
7. Too many communication contacts	Assign one dedicated project contact

Start Your Next Injection Molding Project

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Simply send us your 3D files, and we'll provide a free DFM analysis and detailed quotation within 24 hours.