Common Injection Molding Defects & Solutions

Looks into some of the most common injection molding defects and possible solutions. It dives deeper into possible processing solutions to solve the problems and potential ways to prevent the defect from occurring in the first place. This is one reason to outsource your injection molding to an experienced partner to assist should problems arise. Discover these techniques by watching the video.

Transcript

00:00:00 today let's look at some of the most common injection molding defects and the solutions that we use here at Crescent Industries to consistently produce a high quality Parts perhaps the most common injection molding defect is Flash which is simply when a thin layer of plastic flows outside of the mold cavity usually Along The Parting line where the two mold halves are pressed together

00:00:21 flash can also appear along the ejector pins and really anywhere that you have metal on metal contact when this thin layer of plastic cools it remains attached to the part and creates not only an undesirable aesthetic but can alter the function of that part depending on its end use Flash can be trimmed after the fact but this increases labor and can even cause mold

00:00:43 damage over long periods of time which ultimately means a higher cost so the best way to eliminate the flash is by adjusting the injection molding process first we check the amount of pressure being used to press the two halves of the mold together which is typically measured in a tonnage if not enough force is being applied to each half of the mold then the melted plastic can

00:01:05 more easily find its way outside of the mold cavity increasing this clamping Force may be the easiest way to eliminate flash but sometimes the material is too fluid meaning that the melts or mold temperature can be lowered to improve the material flow and then of course flash can simply be caused by a low quality or worn down tool that no longer fits well together Along The

00:01:27 Parting line Crescent remedies this by having our in-house mold maintenance department just a few feet from our general production floor allowing us to regularly clean and maintain our molds before this sort of thing becomes a problem these are certainly not the only causes of flash but something the most common for sure the next injection molding defect is called a short shot

00:01:48 and this simply refers to an incomplete part where the melted plastic is not fully filling the mold cavity as you can see here short shots can range from entire sections of the part not being filled to two very subtle defects that need to be carefully looked for in smaller parts short shots are often the result of a material with a high viscosity meaning it does not flow

00:02:10 easily especially into hard to reach areas in this case you may want to consider increasing the Melt temperature or mold temperature to allow the material to flow more easily or try an entirely different resin with a lower viscosity short shots may also be caused by inadequate venting in the mold which can trap air pockets a frozen flow channel that may need to be cleaned or

00:02:33 simply not packing enough resin into the mold cavity during the injection process as you can tell much of this has to do with the injection molding process which involves many complex variables so here at Crescent we utilize a proven process called decoupled molding and we have a number of certified Master molders who are able to optimize the process not just to produce a good part but to do it

00:02:56 as efficiently as possible over long production runs alright those first two defects are perhaps the most common and easy to spot but these next few are much more subtle which is why having an experienced Mulder in your corner is so important sink marks are a localized indentation or depression that appears on the surface of an injection molded part after cooling usually you'll find a

00:03:18 sink Mark along thicker portions of the part where cooling rates can vary significantly again depending on the parts and application this may not be a huge deal and really is purely aesthetic but for many of the components that we make here at Crescent a sink Mark like this needs to be corrected since we do make many medical and defense related components once again there are many

00:03:41 potential causes and solutions but the most common are lowering the mold temperature since an overheated mold can increase the uneven cooling you can also increase the hold pressure increase the hold time and if the process alterations don't make a difference then it may be necessary to adjust the part design and reduce the thickness of certain sections in order to promote more even Cooling

00:04:03 and lower the likelihood of a sink Mark as you can imagine altering a mold once it is already in an injection molding machine and producing Parts is incredibly expensive which is why our full service tool shop offers design for manufacturing support from the start of the process allowing us to help you design an optimized injection mold from these starts that will ultimately be

00:04:25 able to produce a high quality consistent part having a tool Builder build your mold and a separate molder run that mold is completely removing any Synergy between these two worlds and can lead to a lot of headaches that can be easily avoided by more carefully selecting your injection molding partner the last defect we'll look at today is burn marks and surface contamination a

00:04:47 burn mark specifically is the result of overheated material which is especially noticeable on white or clear components similar to the previous defects we've looked at burn marks can be addressed by altering the injection molding process and adjusting variables like injection speed lowering the mold temperature improving mold venting and properly cleaning and maintaining the mold to

00:05:10 ensure that material does not become trapped and burn the broader defect of part contamination can be caused by a number of variables but for medical Parts specifically we utilize our ISO 7 and ISO 8 clean room facilities and preventative maintenance to drastically reduce the potential for part contamination before they become a problem these are just some of the many

00:05:33 injection molding defects that you may encounter during the manufacturing process but you may also encounter warping flow lines splay voids bubbles weld lines jetting discoloration delamination cracking and the list goes on as you can tell having an experienced molder in your corner from the first conceptual design of the mold all the way through to full production is

00:05:55 incredibly important so to learn more about Crescent Industries and the Manufacturing Services that we we offer feel free to reach out to us using the contact information down below thank you so much for your time and we look forward to helping bring your idea to life [Music]