Mold Design > Mold Design

mold designInjection mold design is a systematic process to define mold structure, size, material, and other specification based on customer’s requirements like mold cost, manufacturing volume, quality, and lead-time. A high level of plastic injection mould design requires the mould designer to have rich experience and knowledge on mold structure design, plastic injection molding process, and full product design and assembly.



At Inno molding, plastic injection mold design is performed more than just a injection molded parts. Our sophisticated mold designers consider everything clearly from parts to finished products, including product structure, appearance, function, assembly, cost, and manufacturing efficiency, which ensures the molded products will completely align with customer’s specifications.



Prior to a mold design, our dedicated designers will work closely with customers to analyze product DFM, and work out best solution for parts draft, thickness of wall, radius, corners, ribs, inserts, finish, and color. Once those parts information are finalized, we will start our formal mold design.

Customer’s Requirement Determines Mold Design

When we are about to design a plastic injection mold, the first thing we need to do is understanding customer’s requirements. Otherwise we can never design a reasonable mould tooling for production. Here below are the three core information that we must notify them before initiation of mold design.

1. Manufacturing Volume

  • If customer requires a total manufacturing quantity of 500~10,000 pcs, we might suggest to use economical mold steel, simply mold structure, and one cavity mould;
  • If a manufacturing volume ranges 30,000~200,000 pcs, we would consider using high quality mold steel(like S138, P20, NAK80, etc), and design the mold parts and structure as durable, inexpensive, easy-manufactured.
  • However, for some high volume of order(50,000~150,000 pcs), we will use high quality mold steel with tempered treatment(HRC48~HRC54 Degree), meanwhile, a high volume mold would be designed as hot runner as it obtains better injection molded parts and save cost on injection gate material.

2. Quality Requirements of Molded Products

A product quality requirement will significantly affect mold structure like injection gate type, parting line, ejection structure, and venting. For instances:

  • Some simple products have no requirements on dimension and appearance( like plastic pallet, rubbish bin, chair, etc), we will design the molds as cheap as possible while not sacrificing product quality
  • For some normal engineering products(like electronic parts, home appliance parts, industrial parts, etc), the mold design will be accurate, durable, and inexpensive.
  • However, for some precision parts(like automotive, medical, and airplane parts, we will design the mold with high precision, perfect appearance, and longer life-time

3. Mold Making Lead-time

  • For short lead-time molds: Because of engineering stage, some of customers requires prototype molds with short lead-time(10~15 days), we will design the molds without mold cores, which means the parts shape will be directly manufactured on mold base. However this prototype mold is only suitable for some simple parts without sliders or lifters structure. On the other hand, the mold steel is not available for heat treatment(tempering).
  • For normal export molds or injection production molds, it will takes about 25~45 days to have the first mold trail sample after mold making almost finished. In this case, we can design the molds as durable, precision, and cost-effective as needed.
  • For long lead-time molds(45 days above): Some large molds(like automotive mold, home appliance molds, airplane molds) requires the molds to be functioned as high precision and longer life-time, we will have to design the molds with top level steel and heat treatment.

Part DFM Before Mold Design

Whatever how perfect a product design might be, but there is always a necessary to perform DFM analysis.

Prior to a plastic injection mold design, our experienced engineers will work closely with clients to perform a part DFM, because some of clients might not be expertise at plastic injection parts design, and their original design drawing would have obvious problem or imperfection for injection molding. During the part DFM process, we will make a checklist to check out each design drawing from clients, and provide improving solution for every problem. Here below are the main considerations for part DFM.

1. Parts Function and Fitting

product fittingThe first thing of our DFM process is to check out the parts function, which will help clients to verify if the parts can function correctly. Our engineers will use 3D design software(Pro/e, Solidworks, UG) to simulate parts working condition. Meanwhile, we will check out if parts fitting and tolerance are reasonable.

If any design mistakes or imperfection found, we will provide design optimization report to clients. So that they can improve their design to have better final products.

2. Thickness of Wall

thickness of wallThickness of wall is one of the most important factor that affects the quality of injection molded products. Since an improper thickness of wall will result in parts shrinkage while injection molding process, on other hand, if a thick wall will increase parts weight that definitely increase part cost

During the DFM process, we will check out customer’s design drawing carefully. If any incorrect part thickness found, we will highlight them in the DFM report. So that our customer can notify and refine their product design.

3. Draft Angle

draft angleDraft angle is used to make part release easily and smoothly when plastic injection molding, 0.5°~3.0° draft angle is needed for most of plastic parts, relatively to say, the deeper products requires to have more draft angle. For example, a 300mm-depth of rubbish bin requires about 2.0° draft, but a 800mm-depth of bin might need at least 4.0°~6.0° draft.

If a plastic part design without a draft, the molded parts will stick on injection mold and never be able to release.

While a DFM process, we will help to check out if customer’s design are well-added for draft angle. If not, we will report the problem so as to improve it before mold design.

Meanwhile, if needed, we can also directly help to add appropriate draft angle on parts.

4. Ribs

part RibIn order to enhance plastic parts strength, it is necessary to add some ribs onto bosses, windows, platform, etc. However an improper thickness of ribs would result in shrinkage issue. A correct thickness of ribs will be 50%~75% of basic part thickness. For example, a part with 1.5mm of thickness of wall, the ribs should be designed as 0.75~1.13mm.

Our dedicating engineer will check 3D drawing carefully, and try to improve their design as proper as possible.


5. Parts Material

plastic resin materialAs we know, parts material will directly determine part function, cost, and quality. Because of different requirement, there will be many different choice for part material. A proper material choosing will help clients to save cost while not sacrificing part quality. If not, it might result money loosing and put project on risk. Our engineers have rich experience on plastic resin properties and application. We will suggest customers to use the best suitable plastic material while DFM.


Having a Question on Plastic Parts Design?

Our professional mold design and manufacturing team are ready to help you out. Please just contact us if you have any question or project request on plastic injection mold.
Contact Us Now!

Six Typical Factors of Plastic Injection Mold Design

Plastic injection mold design is one of the most important job for plastic injection molding products. A good mold design requires mold designer to have rich knowledge and experience on plastic resin properties, injection molding process, and mold structure.

In order to let our clients or readers understand how we perform a mold design, we would like to share our main design process as below:

1. Mold Layout

mold layoutMold layout design is an overall planning work, which requires the mold designer to comprehensively realize mold cavity, gating type, parting line, ejection location, aesthetics surface, and potential molding defects. After those factors are resolved, our mold designer would create a mold specification sheet and 2D drawing for customer review.

At Inno molding, our experienced mold designers strive to work out best-optimized mold layout to save cost-saving and improve production efficiency and quality.


2. Parting Line

parting lineParting line is one of the most common terminology of mold tool structure. It exists on molded parts surface, which ranging about 0.01~0.15mm in size.

A parting line can also be explained as the board line of mold core and cavity when mold tool closes and opens.

When injection mold design, it’s very important to design and choose a proper parting line, we should consider comprehensively for draft angle, mold open direction, parts assembly, appearance, and critical dimension control, In theory, we need to balance all of those factors and minimize the parting line as possible. Or you can say”no parting line” is the best “parting line” design.


3. Gating System

injection gateA gating system refers to the whole channel through which the molten material flows to the mold cavity via injection machine. In the injection mold design process, designing a reasonable injection gate is one of the most important job, which defines where and which type of gate it should be. Because it not only just affects product appearance, production efficiency, but also it will directly affect manufacturing cost, as injection gate is a part of production scrap aspect.

Basically there are two main types of gating systems, which are manually trimmed gates and automatically trimmed gates. Generally speaking, manually trimmed gates include direct(or sprue) gate, side gate, tab gate; and automatically gates include banana gate, point gate, submarine gate, However manufacturing volume and parts requirements determines which type of gating system we should use.


4. Slider & Lifter

sliderAs we know, a simple plastic part can be divided into mold core and cavity, where a parting line locates. However for some complex part structure, like screws, clippers, cutouts, pillars that exist on different direction while mold opening, it must be obtained via slider or lifter.

Mold slider and lifter can also be understood as a mechanism of a mold tool, which consists of forming surface, pull and push block(or cylinder), guide pin, and wedge. When mold opens and closes, the pull and push block work with wedge forth-and-back to obtain the desired part structure. This is how slider and lifter works basically.

When our mold design process, our experienced mold designer will design the most proper slider and lifter for those molds that requires them.


5. Cooling system

coolingThe cooling system of a plastic injection mold is designed to improve injection molding quality, production efficiency, and mold life-time, as well as reducing production scrap. Needless to say, it’s quite important to both mold making and injection molding process.

When we design a cooling system of injection mold, we will follow our principle as below:

  • Try to make cooling system near the biggest thickness of products.
  • Keep the cooling channel an appropriate distance from the parting line and products
  • Try to increase the number of the cooling channel instead of enlarging the diameter of a single cooling channel.
  • Try to keep the whole mold core or cavity cools evenly rather than partially cooling.


6. Ejection System

ejection pinsDuring the injection molding process, after mold cavity is fully injected with molten resin material, then the mold tool opens, and injection molded is pushed to depart from mold tool. This is how a ejection motion works.

An ejection system consists of ejection pin or block, basement of ejection system, a proper ejection system will need to fully consider product appearance, draft angle, and product length, because those factors will directly determines ejection type, size, and location.

Generally speaking, we minimize number of ejection points and ejection marks as long as the product can be smoothly depart from mold tool.


Having a Question on Plastic Injection Mould Design?

Our professional mold design and manufacturing team are ready to help you out. Please just contact us if you have any question or project request on plastic injection mold.
Contact Us Now!

Our Mold Design Checklist

After our mold design finished, we perform a systematic check for each details, which avoid any mistakes or imperfection to happen. Here below is the main checklist:

  • Mold-design-ChecklistAre we using the latest part drawing for mold design?
  • Does customer have any mould standards?(Hasco, DME, DIN…)
  • Does the mold design fit injection machine tonnage?
  • Is the mold steel choosing reasonably?
  • Are we using the correct shrinkage rate?
  • Is the mold layout reasonable?
  • Are mould cavities reasonable?
  • Is the gating system reasonable?
  • Are parting lines reasonable?
  • Are the ejection pins/plate reasonable?
  • Are the slides, lifter, movable core reasonable?
  • Is the ejection stroke enough?
  • Is the slider / lifter travelling enough?
  • Is the cooling system is enough?

Ready to Start Your Injection Molding Project?

We are different from other injection molding manufacturers, we guarantee you will receive the best quality products, as we have rich experience in mold making, plastic injection molding, and product development. So we will partner with you better!
Get A Quote Within 24 Hours!