The injection molding process does not require mold flow analysis. But maybe it should be, especially considering that it helps predict production problems before production starts.

Mold flow analysis software can simulate the injection molding cycle, using specific plastics and part designs. It evaluates the manufacturability of the design before manufacturing the mold. In this way, designers can identify design flaws that may cause costly redesigns and time delays.

We will explore the basics of moldflow software, determine how it helps optimize the injection molding process, and view the sample data generated by the analysis.

First, let us briefly review the three key components that are critical to the injection molding process: design, mold, and materials.

Injection production Injection molding is the most widely used method for mass production of plastic parts. Economical and efficient, it can produce simple to complex parts with little waste. For detailed information about the relevant knowledge and process, please visit our blog on injection molding.


The injection molding process requires a mold or tool to produce plastic parts. The mold design engineer designs a customized injection mold, and then a professional mold maker sets up mold production.

Even if the mold is designed and manufactured according to the precise specifications of the part, during the injection molding process, if the part itself is not optimized for injection molding, or the gate location is not placed in the best position for material flow, problems will still occur. For example, plastic may not completely fill the cavity of the mold, resulting in voids or part defects. Mold flow analysis helps determine how a given plastic will perform in the mold.

Plastic injection molding

Not all plastics flow, heat or cool the same. In fact, when designing plastic injection molding, there are more than 85K polymers to choose from. The large number of polymer choices makes material selection a challenge.

Mold flow analysis enables designers to evaluate various variables of the material, such as material shrinkage, cooling performance, ability to fill cavities, and potential aesthetic defects.

Moldflow analysis: optimizing the injection molding process

Reduce risk before production starts

Mold flow analysis helps to reduce risk and create a successful mold from the beginning. It helps designers:

Correct potential cosmetic and structural issues

Determine the appropriate wall thickness

Solve possible problems in the mold

Determine the best gate location

Adjust sufficient corner radius

Create uniform and clean edges

Determine the best material for the desired result

Create a successful model from the beginning

Moldflow analysis diagnostic report

Analyze and generate color-coded reports to illustrate how the plastic behaves in the mold. The report includes fiber direction, average temperature, braided thread, air trap, filling confidence, sink and warp, and filling time results.

We will check two elements of the report: the filling time result and the filling confidence.

Results of filling time

The filling time result report shows the position of the flow front when the cavity is filled. The molding flow balance indicates that the plastic part has a good filling time.

How to read the results

The designer evaluates the image flow path, completing and reaching the edge at the same time. The evenly distributed contour lines indicate the speed of plastic flow. Widely spaced contour lines indicate rapid flow; narrow outlines indicate that the part is slowly filling.

Something to look for

The fill time results report provides the following information:

Short shot: The flowing plastic does not completely fill the mold cavity, resulting in a short shot with incomplete parts

Hesitation: Hesitation occurs when the flow of plastic stops or slows down, resulting in asymmetric and unpredictable flow patterns

Overload: The result of one process being completed before other processes. Overpacking may cause high weight, warpage, and uneven density distribution

Welding line: also known as braided wire, this is when the forming defect occurs, the two flows meet before, and there is no ability to “weld”.

Air trap: Air bubbles generated when plastic flow fronts coincide. Air collectors can cause structural and visual defects

Racetrack effect: occurs when fluid quickly passes through a thicker cavity area before the thinner cavity is filled

The results help determine the probability of molding quality parts One way to use the results to determine whether you can mold the quality part is to consider how many colors are displayed. The results may indicate the need for: Change the design to better balance the runner Choose different injection positions to ensure that the part is completely filled Re-evaluate the choice of materials Change processing conditions

Moldflow analysis: optimize the design before manufacturing the mold

Accurate molds are the key to producing high-quality, repeatable plastic parts. Mold flow analysis software can help molds optimize the process before making molds.

First-rate Mold Solution Company is a trusted partner for injection molding solutions. Contact our team to discuss design challenges and upcoming projects.