Custom plastic PP ABS parts moulding

In addition, our company has established cooperative relationships with plastic raw material suppliers, printing manufacturers, etc. to ensure the supply of raw materials and printing quality. Through our rich experience and perfect supply chain, our company can provide customers with high-quality customized custom plastic parts moulding products to meet their specific needs. At the same time, we have 10 years of professional foreign trade service experience, understand the foreign trade process, and better serve our customers. For custom plastic parts moulding products, we can make corresponding plastic parts, which is mainly done through injection molds.

Below is a practical, comprehensive guide to key considerations for custom plastic manufacturing—compiled directly from factory floor experience. Free of jargon and fluff, it covers the critical points you will inevitably encounter during mold development, prototyping, and mass production. Read through it sequentially, and you’ll be well-equipped to avoid common pitfalls.

**Core Issues to Address in Custom Plastic Parts**

**I. Material Selection (The Deciding Factor for Product Success or Failure)**

**Function Dictates Material:** Do not base your choice solely on cost.

*   **Aesthetic/Exterior Parts:** ABS, PC/ABS, PC

*   **High-Temperature / Structural Parts:** PA6, PA66+GF (Glass Fiber), PBT

*   **Low-Cost General-Purpose Parts:** PP

*   **Soft-Touch / Overmolded Parts:** TPE, TPR

**Incorrect Material Selection Leads To:** Brittleness/cracking, deformation, poor heat resistance, assembly failures, or failure to pass product testing.

**Does the Material Require Modification?**

*   Additives such as glass fiber, talc powder, flame retardants, UV stabilizers, low-temperature modifiers, food-grade compounds, or anti-static agents.

*   **Warning:** If these requirements are not specified in advance, changing the material later is essentially equivalent to remaking the mold from scratch.

**Water Absorption & Drying Requirements**

*   **Must be dried:** PA, PC, ABS.

*   **No drying required:** PP, PE.

*   **Failure to dry leads to:** Bubbles, silver streaks, and reduced material strength.

**II. Structural Design (Where 90% of Pitfalls Occur)**

**Wall Thickness Must Be Uniform**

*   **Abrupt changes in thickness lead to:** Sink marks, bubbles, warping, and deformation.

*   **Rib Thickness:** Generally, the thickness of reinforcing ribs should not exceed 0.6 to 0.7 times the thickness of the main wall.

**Always Include Draft Angles (Taper)**

*   **Minimum:** 0.5° to 1°. Deeper cavities and textured surfaces require larger angles.

*   **No Draft Angle =** Drag marks/scratches, stress whitening (ejector marks), parts sticking in the mold, or scrapped parts.

**Avoid Sharp Corners and Acute Angles**

*   **Sharp corners create stress concentration points:** The part becomes prone to cracking upon impact (e.g., if dropped).

*   **Internal Corners:** Should have a minimum radius (R) of 0.3 to 1 mm; for aesthetic/exterior parts, R ≥ 1 mm is recommended.

**Ensure Proper Placement of Holes, Bosses, and Snap-Fits**

*   **Screw Bosses:** If too tall, they require reinforcing ribs.

*   **Snap-Fits:** If the undercut is too deep, ejection becomes difficult.

*   **Holes:** If placed too close to the edge, the material is prone to cracking.

*   **Warning:** If the structural design is flawed, even the most expensive mold will fail to produce a quality part.

**Minimize Undercuts, Sliders, and Lifters**

*   **The more complex these features are:** The more expensive the mold becomes, the longer the production cycle takes, and the lower the yield rate tends to be.

*   **Simplify whenever possible:** Otherwise, your tooling costs could easily double. III. Mold-Related Issues (Determining Quality and Cost)

Mold Lifespan and Steel Selection

Prototyping / Small-Batch Production: Aluminum molds, simple molds

Large-Scale Mass Production: 718H, P20, S136 steel

Poor mold steel quality leads to: excessive burrs on products, dimensional instability, and a short mold lifespan.

Number of Cavities (Cavity Count)

The higher the cavity count, the lower the unit price per part; however, the mold manufacturing cost increases.

For small orders, do not blindly opt for multi-cavity molds, as this results in wasted expenditure.

Gate Location and Size

Improper gate design can lead to:

Exposed fibers (fiber float), weld lines, sink marks, flow marks, and short shots (incomplete filling).

For cosmetic parts, the gate location must be concealed.

Cooling Channel Design (Is it Optimized?)

Poor cooling channels → Uneven cooling → Severe warping and deformation.

This is a critical factor for cosmetic parts and components with strict dimensional requirements.

Venting (Is it Sufficient?)

Poor venting → Burn marks, short shots, trapped air, and weak weld lines.

Venting is mandatory for deep ribs, dead-end areas, and material flow convergence points.

IV. Injection Molding Process Issues (Affecting Appearance and Strength)

Matching of Temperature, Pressure, and Speed

Temperature too high: Material degradation, discoloration, embrittlement

Temperature too low: Short shots, cold flow lines, prominent weld lines

Holding Pressure Time vs. Cooling Time

Insufficient holding pressure: Sink marks, undersized dimensions

Insufficient cooling: Ejection deformation, parts remaining soft

Special Considerations for Glass Fiber-Reinforced Materials

PA+GF (Nylon) and PP+GF are prone to: Exposed fibers, warping, and accelerated mold wear.

If the processing parameters are incorrect, the cosmetic quality may be completely ruined.

V. Dimensional and Shrinkage Issues (The Most Common Pitfall)

All plastics exhibit shrinkage

ABS: 0.4% – 0.7%

PP: 1.5% – 2.5%

PA+GF: 0.3% – 0.8%

If mold dimensions do not account for shrinkage → Finished parts will be undersized and fail to fit during assembly.

Assembly Tolerances Must Be Reserved

Typical clearance gaps for housing assemblies range from 0.1 mm to 0.3 mm.

Failure to reserve this clearance results in: Fits that are too tight (preventing assembly) or fits that are too loose (creating excessive gaps). VI. Appearance and Surface Finish Issues

Visible surfaces must be free of sink marks, flow lines, burrs, and ejector pin marks.

These are structural or processing defects that are extremely difficult to repair after production.

Specify Surface Finishes in Advance

Painting, silk screening, laser engraving, electroplating, texturing, matte finish, high-gloss finish.

Different processes impose different requirements on the mold; failure to specify these in advance will result in rework.

Color Difference Control

Color variations may occur between different production batches or different machines.

For mass production, retain reference samples and lock in the specific color masterbatch used.

VII. Mass Production Stability Issues

First Article Inspection (FA) is mandatory.

Dimensions, appearance, assembly fit, and structural strength must all be verified.

Yield Rate Estimation

For products with complex structures or high aesthetic requirements, the yield rate may be as low as 70%–80%.

The anticipated defect rate must be factored into the quotation.

Batch-to-Batch Consistency

Poor mold precision leads to dimensional inconsistencies between batches, potentially rendering parts unassemblable.

VIII. Cost and Lead Time Issues

Do not compare unit prices in isolation; consider the total cost.

Mold costs + Injection molding fees + Post-processing + Shipping + Losses due to defects.

Low-price offers often conceal hidden traps involving additional costs later in the process.

Prototyping ≠ Mass Production

A prototype may look good, but mass production stability is not guaranteed; the mold structure is the critical factor.

Lead Time Schedule

Mold fabrication: Typically 12–25 days.

Prototyping/Sampling: 3–7 days.

Mass production: 5–15 days.

Rush orders require prior communication and arrangement.

IX. Testing and Compliance Issues (Especially for Product Launch)

Strength Testing (Drop tests, compression tests)

High/Low-Temperature Cycling

Flame Retardancy Ratings (Mandatory for electrical products)

VOC / Odor Testing (For automotive and indoor products)

RoHS / REACH Compliance (Mandatory for export products)

Failure to conduct necessary testing may prevent the product from being shipped.

We are a custom plastic parts moulding manufacturer, providing high-quality custom plastic parts moulding manufacturing. As long as you want to customize/develop custom plastic parts moulding products, you can find us. We have professional injection mold design and mature manufacturing technology, providing you with one-stop service, from product design-mold making-product production-product packaging-product transportation, we can help you in every link. As long as you come to us, we will provide you with the ultimate service and satisfy you in terms of product quality, production time, information dialogue, etc.

Plastic Injection Mould making

Plastic molding specifications

Mold design:

Transaction process:

Mold testing:

Product packaging

Factory

We are Custom Plastic Mold factory. Our factory is plastic injection mold maker. we has 17 years of experience in professional custom plastic mold and 10 years of foreign trade experience. We are custom Plastic Mold supplier. We can provide custom Plastic Mold service. Our factory can make the Injection molded plastic parts, and the quality of the products will satisfy you.

We have more than 50 high-end machines and hundreds of engineers and designers. We can provide one-stop service, from product design - mold making - product production - product packaging - transportation. We have a complete production chain. We can meet all your requirements.

Services we provide:

Professional custom mold service, Plastic mold design and manufacturing .plastic product production, product design, mold design, blow mold customization, rotational mold customization, die-casting mold customization. 3D printing services, CNC manufacturing services, product packaging, customized packaging, shipping services.

We always adhere to the principles of quality first and time first. While providing customers with the highest quality products, try to maximize the production efficiency and shorten production time. We are proud to tell every customer that our company has not lost any customer since its establishment.If there is a problem with the product, we will seek a solution actively and take responsibility to the end.

FAQ

Q1: Are you trading company or manufacturer ?

A: We are manufacturers.

Q2. When can I get the quotation?

A: We usually quote within 2 days after we get your inquiry.

If you are very urgent, please call us or tell us in your email so that we can quote for you first.

Q3. How long is the lead-time for mold?

A: It all depends on the products' size and complexity. Normally, the lead time is 25 days.

Q4. I have no 3D drawing, how should I start the new project?

A: You can supply us a molding sample, we will help you finish the 3D drawing design.

Q5. Before shipment, how to make sure the products quality?

A: If you don't come to our factory and also don't have the third party for inspection, we will be as your inspection worker.

We will supply you a video for production process detail include process report, products size structure and surface detail, packing detail and so on.

Q6. What is your payment terms?

A: Mold Payment: 40% deposit by T/T in advance, 30% second mold payment before sending out the first trial samples, 30% mold balance after you agree the final samples.

B:Production Payment: 50% deposit in advance, 50% before sending out the final goods.

Q7: How do you make our business long-term and good relationship?

A:1. We keep good quality and competitive price to ensure our customers benefit for best quality products.

2. We respect every customer as our friend and we sincerely do business and make friends with them, no matter where they come from.