Do you go with the “Flow”?
It should depend on the inputs you use and the experience assessing the results.
Mold flow analysis has been around for a very long time and has evolved to where a number of different software products have been developed. Prior to software packages, the original “mold flow analysis” was a mold designer using experience and accumulated knowledge to plan the mold design based on the geometry of the part and the material being used. Whichever “hardware” or software your mold designer uses, you need to know that it is an involved process.
By definition, a mold flow analysis is an injection molding process simulation that, at a minimum, includes the filling of the part cavity with a specific plastic material. Information that can be gained from such analyses includes projected processing settings like cycle time, injection pressure, and cooling time. It can also provide finished part criteria insight on possible sink marks, and weld line locations. You can also get clued in on in-mold dynamics like cooling problem areas, gas pockets and runner balancing/fill rates. All that is required for a basic analysis is a solid model and material spec.
As the software versions have evolved, people’s opinions on their effectiveness to predict molding vary from cannot live without it, to it’s alright, to poor and waiting for improvements. Perhaps this stems from the very nature of doing a simulation. First and foremost, as with all software, poor input results in poor output. An adequate simulation relies on accurate material properties information being entered, along with an accurate understanding of the dynamics occurring in the proposed mold from a flow and sheer perspective. Bottom line, the more detail and accurate parameters going into the simulation, the more value the output of the simulation.
If mold flow analysis is available, a good question to ask your molder is “does the mold designer use it as a guide to the mold design or a verification of the mold design.” A good mold designer with a myriad of designs and materials under his belt can go a long way to verifying the validity of the simulation output based on the mold design he has initiated rather than waited to design.
The end goal is for your time to market being optimized by your molder. Last thing you want is the tail wagging the dog and you lose time with a poor or marginal mold design that sees major revisions.
Other articles you might enjoy:
Material selection – past experience, spin the wheel, throw a dart or ask the expert?
Taking up residence – is the resin overstaying its welcome?
Resin selection – The past vs the future?
Your chosen plastic/composite, is it up to the task?
Fighting black specks can be a screwy endeavor