Blog

Avoiding Common Cosmetic Defects in Molded Parts | Plastics Technology

A 360-degree look at resin conveying systems: types, operation, economics, design, installation, components and controls.

This Knowledge Center provides an overview of resin moisture and the drying process, including information on the best drying practices for your manufacturing facility. Plastic Mold Injection Company Near Me

Everything you need to know about plastics compounding technology—from feeding solutions to application profiles and expert advice.

Combat the skilled labor shortage using this comprehensive resource to train your own plastics processing experts.

Deep dive into the basics of blending versus dosing, controls, maintenance, process integration and more.

This Knowledge Center provides an overview of the considerations needed to understand the purchase, operation, and maintenance of a process cooling system.

Learn about sustainable scrap reprocessing—this resource offers a deep dive into everything from granulator types and options, to service tips, videos and technical articles.

While price initiatives for PE and PVC were underway, resin prices had rollover potential for first two months of 2024, perhaps with the exception of PET.

Flat-to-downward trajectory for at least this month.

A mixed bag, though prices likely to be down if not flat for all this month.

Trajectory is generally flat-to-down for all commodity resins.

Flat-to-down trajectory underway for fourth quarter for commodity resins.  

Generally, a bottoming-out appears to be the projected pricing trajectory.

Resin drying is a crucial, but often-misunderstood area. This collection includes details on why and what you need to dry, how to specify a dryer, and best practices.

Take a deep dive into all of the various aspects of part quoting to ensure you’ve got all the bases—as in costs—covered before preparing your customer’s quote for services.

In this collection of articles, two of the industry’s foremost authorities on screw design — Jim Frankand and Mark Spalding — offer their sage advice on screw design...what works, what doesn’t, and what to look for when things start going wrong.

In this collection, which is part one of a series representing some of John’s finest work, we present you with five articles that we think you will refer to time and again as you look to solve problems, cut cycle times and improve the quality of the parts you mold.

Gifted with extraordinary technical know how and an authoritative yet plain English writing style, in this collection of articles Fattori offers his insights on a variety of molding-related topics that are bound to make your days on the production floor go a little bit better.

In this three-part collection, veteran molder and moldmaker Jim Fattori brings to bear his 40+ years of on-the-job experience and provides molders his “from the trenches” perspective on on the why, where and how of venting injection molds. Take the trial-and-error out of the molding venting process.

Mike Sepe has authored more than 25 ANTEC papers and more than 250 articles illustrating the importance of this interdisciplanary approach. In this collection, we present some of his best work during the years he has been contributing for Plastics Technology Magazine.

In this collection of content, we provide expert advice on welding from some of the leading authorities in the field, with tips on such matters as controls, as well as insights on how to solve common problems in welding.

Mold maintenance is critical, and with this collection of content we’ve bundled some of the very best advice we’ve published on repairing, maintaining, evaluating and even hanging molds on injection molding machines.

Thousands of people visit our Supplier Guide every day to source equipment and materials. Get in front of them with a free company profile.

Medical-component specialist LightningCath has carved a niche meeting the needs of small to medium-sized entrepreneurs with complex catheter designs … quickly.

Plastics Technology is closing in on its 70th anniversary. Here are some of Editorial Director Jim Callari’s observations to commemorate the occasion.

As with everything else, there are pros and cons, but more of the former. They provide processors higher rates while decreasing the temperature of the extrudate while enabling downgauging.    

The drop in plastics activity appears to be driven by a return to accelerated contraction for three closely connected components — new orders, production and backlog.

Beginning the first of this year, 12 states are following EPA bans on potentially damaging cooling fluids. Chiller suppliers have adjusted equipment designs to accommodate the new regulations. Here’s what all this means to processors.  

Pairing external big picture training with internal job-specific instruction can help your process technicians meet quality expectations as well as production targets.

In less than a decade in injection molding, US Merchants has acquired hundreds of machines spread across facilities in California, Texas, Virginia and Arizona, with even more growth coming.

Demand for bioresins is growing in molded goods, particularly as a sustainability play to replace fossil-fuel based materials, but these materials are not a drop-in replacement for traditional materials. Molds and hot runners need to be optimized for these materials.

There are many things to consider, and paying attention to the details can help avoid machine downtime and higher maintenance costs — and keep the customer happy.

Flat-to-downward trajectory for at least this month.

Topping five other entries in voting by fellow molders, the Ultradent team talks about their Hot Shots sweep.

Serendipitous Learning Opportunities at PTXPO Underscore the Value of Being Present.

Introduced by Zeiger and Spark Industries at the PTXPO, the nozzle is designed for maximum heat transfer and uniformity with a continuous taper for self cleaning.

Ultradent's entry of its Umbrella cheek retractor took home the awards for Technical Sophistication and Achievement in Economics and Efficiency at PTXPO. 

technotrans says climate protection, energy efficiency and customization will be key discussion topics at PTXPO as it displays its protemp flow 6 ultrasonic eco and the teco cs 90t 9.1 TCUs.

Shibaura discusses the upcoming Plastics Technology Expo (PTXPO) March 28-30

Competition will invite participants to help reshape life cycle management in plastics.

Sign up to attend North America’s leading trade show for plastics.  

Offerings range from recycled, biobased, biodegradable  and monomaterial structures that enhance recyclability to additives that are more efficient, sustainable and safer to use.  

Ahead of the first NPE since 2018, PLASTICS announced that its triennial show will stay in Orlando and early May for ’27, ’30 and ’33.

New features of NPE2024 aim to “bring the whole plastics ecosystem together to innovate, collaborate and share findings.”  

Hundreds of tons of demonstration products will be created at NPE2024 next spring. Commercial Plastics Recycling strives to recycle all of it.

Mixed in among thought leaders from leading suppliers to injection molders and mold makers at the 2023 Molding and MoldMaking conferences will be molders and toolmakers themselves. 

After successfully introducing a combined conference for moldmakers and injection molders in 2022, Plastics Technology and MoldMaking Technology are once again joining forces for a tooling/molding two-for-one.

Multiple speakers at Molding 2023 will address the ways simulation can impact material substitution decisions, process profitability and simplification of mold design.

When, how, what and why to automate — leading robotics suppliers and forward-thinking moldmakers will share their insights on automating manufacturing at collocated event.

As self-imposed and government-issued sustainability mandates approach, injection molders reimagine their operations.

August 29-30 in Minneapolis all things injection molding and moldmaking will be happening at the Hyatt Regency — check out who’s speaking on what topics today.

Get your clicking finger in shape and sign up for all that we have in store for you in 2023.  

Molding 2023 to take place Aug. 29-30 in Minnesota; Extrusion 2023 slated for Oct. 10-12 in Indiana.

Key technologies — such as multicolor molding, film molding and PUR overmolding for both exterior and interior applications — are at the forefront of this transformation. Join this webinar to explore the vast potential of eMobility in molding large components — including those with fiber reinforcements — thereby driving the need for large injection molding cells with a clamping force of up to 11,000 tons. You will also gain insight into Engel's innovative two-stage process, a solution for future recycling processes. This webinar will provide an in-depth overview of challenging applications, production concepts and best practices, including:       BMW iX front panel production cell Smart rear panels concept based on IMD and 2C molding Sustainability concepts based on two-stage process Large tonnage equipment for battery moldings

In today's manufacturing environment, robust processes that meet strict industry and regulatory standards are essential. With the advent of servo-driven ultrasonic welding technology, enhancing product quality and maintaining consistency has become remarkably effortless. Discover the fundamentals of ultrasonic welding, delve into vital components within these systems, explore how servo-driven ultrasonic welding enhances weld quality via advanced control features and gain insights into optimizing your assemblies for welding in these high-performing machines. Join Dukane to unlock the potential of ultrasonic welding in modern manufacturing for plastic devices and components. Agenda: Fundamentals of ultrasonic welding Key components in an ultrasonic welding system Using servo-driven ultrasonic systems to control your welding process Designing your parts and components for servo-controlled ultrasonic welding

This webinar will help you make informed decisions to confirm the equipment access stairs in your facility are OSHA compliant and meet the highest standards of safety and ergonomics. Agenda:  Identifying opportunities to increase safety in the work place Utilizing space saving stairways Ensuring code compliance for equipment access

4.0, EUROMAP, OPC, OLE, QC, DSN, SQL, VNC, MES, ERP, FTP, CMS, SPI — are you confused by all buzzwords being tossed around in the plastics industry? Not convinced the data collection is necessary? Or are you unsure of how it could be implemented and improve your molding processes? Wittmann has been on the cutting edge of the data collection push for nearly 20 years. In this webinar, take a step back from the idea of the manufacturing facility of the future and discuss what you can do today to improve your process. Using readily-available technology, Wittmann can help reduce downtime, limit scrap and wasted material, and predict required maintenance. Let the experts at Wittmann help you understand: what data can be collected, what that data can be used for, what systems are used, and how to implement them. Agenda: Demystifying the terminology Tracking the material flow and lot information through the material handling system The data available from various auxiliary equipment, such as: dryers, blenders, mold temperature controls and robots Automating the process through changes in the data collected at the machines during production Adding visualization to increase productivity

Learn how targeted, modular, dosing and blending solutions — covering powders, granules, regrinds and liquids — provide plastics processors of all kinds with best-in-class accurate dosing while delivering significant raw material savings and ensuring highest quality.  Agenda:  Introduction to Movacolor Blending in plastics applications Movacolor feeding and dosing technology Hybrid blending to combine high material throughput and dosing accuracy

This presentation will explore the in-situ polyurethane (PU) overmolding of injection-molded and composite parts, allowing for direct out-of-mold class "A" surfaces. KraussMaffei will review the process and equipment required. It will also discuss tooling types currently available for PU systems for this process. KraussMaffei will compare the pros and cons of this technology over currently-available coating and painting systems. Agenda: Introduction and evolution of the ColorForm technology Overview of the ColorForm process Equipment required Tooling and PU systems Benefits of the system compared to typical spray-applied coatings Pros and cons of the technology

The global plastics industry has been navigating through what is arguably the most volatile period in decades. Unprecedented amounts of new production capacity are scheduled to start in North America, Europe, and China in the near term and compete for demand during a period of economic challenges. How will trade flows shift? Will this lead to regional cost disparities and rationalization? Energy transition and sustainability targets continue transforming the plastics market and increasing the competitive landscape. As the market evolves, what impact will new technology, policy, regulation, the growing role of chemicals versus fuel and other factors have on industry restructuring and business models? At GPS 2024, leading global experts will come together to discuss pivotal impacts and initiatives shaping the plastics industry. Join us and participants from across the globe to gain the latest insight and deep analysis as you connect with your peers and industry professionals. This year’s conference will explore the theme Disruptive Global Dynamics Reshaping Plastics and include a full day workshop focused on the Global Plastics Business and Plastics Transition to Circularity, 1.5 days of expert content and numerous networking functions.

Every three years, leaders from almost every major industry gather at NPE to advance their businesses through innovations in plastics. The largest plastics trade show in the Americas, NPE offers six technology zones, keynote speakers, workshops and opportunities to build partnerships. 

The 3D Printing Workshop @ NPE2024 – The Plastics Show, is an immersive, half-day workshop focused on the emerging possibilities for part production via 3D printing and additive manufacturing. Presented by Additive Manufacturing Media, Plastics Technology and MoldMaking Technology, the 3D Printing Workshop will build upon a successful model first introduced at IMTS 2014. Attendees will benefit from a program focused on practical applications of 3D technologies related to plastics processing. This event will conclude with a 3D Printing Industry Reception sponsored by Additive Manufacturing Media.

The Society Plastics Engineers (SPE) Extrusion Division and the SPE Eastern New England Section will co-host the Screw Design Conference-Topcon on June 19-20, 2024 @ UMass Lowell in Lowell, MA.  This highly technical program will focus upon screw design principles for single and twin screw extruders with wide ranging topics relating to screw designs for feeding, melting, mixing, venting and pumping plastics products and parts.   Areas of focus will include screw designs for melt temperature and gel management, gel minimization, bioplastics, recycled materials and foaming.   In addition to the technical sessions, a tour of the UMass Lowel Plastics Processing Laboratories will be integrated into Day 2 of the event.    This program is not just for screw designers, but to help anyone responsible for any type of extrusion operation to evaluate existing extrusion equipment; and also to prepare for future projects. Price to attend:  Less than $1000!  Registrations will be accepted in early 2024. Call for papers – To be considered to give a presentation, please submit a talk title and abstract on or before December 15 to:   Technical Chair: Eldridge M. Mount III, e-mail emmount@msn.com Corporate sponsorships - A limited # of corporate sponsorships (15) are available on a 1st come basis.  Included is a 6’ tabletop display (must fit on table), denotation in all promotional activities, and 1 no charge registration.  To become a sponsor contact: Charlie Martin, Leistritz Extrusion, e-mail cmartin@leistritz-extrusion.com, cell 973-650 3137 General information:   A reception on Day 1 and a tabletop display area will allow the attendees to meet and discuss state-of-the-art screw technologies with industry experts.  The SPE Extrusion Division will issue a “Screw Design Certificate” to all participants who have attended the program.  Students are encouraged to attend and will receive a discounted rate.   For additional information contact:  Program Chair:  Karen Xiao, Macro Engineering, KXiao@macroeng.com

Debuting in 2010, the Parts Cleaning Conference is the leading and most trusted manufacturing and industrial parts cleaning forum focused solely on delivering quality technical information in the specialized field of machined parts cleansing. Providing guidance and training to understand the recognized sets of standards for industrial cleaning, every year the Conference showcases industry experts who present educational sessions on the latest and most pressing topics affecting manufacturing facilities today.  Discover all that the 2022 Parts Cleaning Conference has to offer!

Presented by Additive Manufacturing Media, Plastics Technology and MoldMaking Technology, the 3D Printing Workshop at IMTS 2024 is a chance for job shops to learn the emerging possibilities for part production via 3D printing and additive manufacturing. First introduced at IMTS 2014, this workshop has helped hundreds of manufacturing professionals expand their additive capabilities.  

Identify familiar flaws and then work to eliminate them with these mold and part design tips, and process considerations.

Today’s consumers expect a certain level of finish in the products they purchase. Increasingly, style has become an important and deciding factor when comparing products. So, it’s important to understand how a part is manufactured to ensure that even basic design issues don’t become bigger problems for consumers or affect part functionality.

Injection molding comes with a specialized set of design guidelines, and design engineers who understand the best practices will increase their chances of catching these issues early and developing structurally sound and cosmetically appealing parts and products.

There are a number of common issues that we see in injection-molded parts at Protolabs. Here are some ideas on how to avoid them in the first place.

Draft can be as simple as adding a degree or two to a wall to avoid right angles. Photo Credit: Protolabs

Injection-molded part aesthetics start with draft. Sufficient draft is an important part of any mold design, even with quick-turn tooling. Vertical walls, meaning those part surfaces parallel to the direction of mold operation, should have a minimum draft angle of a 1/2 degree, though 2 degrees is even better. Heavily textured surfaces may require 5 degrees or more. Without proper draft, part ejection becomes difficult if not impossible, and unattractive drag or scrape lines may occur.

As its name implies, sink appears as a dimple or shallow depression on the surface of a molded part. It’s caused by thicker than normal cross sections, non-uniform part design or improper gate placement — the doorway through which hot plastic first enters the mold cavity. Polypropylene and acetal are very susceptible to sink, while fiber- and glass-filled materials are less prone to sink. We recommend assigning a recommended wall thickness to each material and advise that the minimum wall thickness be no less than 40 to 60% of a workpiece’s thickest section. Material flow within the mold should travel from thick to thin whenever possible, which might mean reorienting the mold cavity or placing the gate in an area originally reserved for a cosmetic surface.

Meeting the recommended wall thickness for a material will help avoid sink. Photo Credit: Protolabs

If you design a part with walls that are too thin for the target material, it’s likely to curl up like a potato chip. Warp, as this phenomenon is known, is easily avoided by following the same rules used with sink, namely staying within the general wall-thickness guidelines. Ironically, the glass-filled materials that work well with sink-prone parts are more susceptible to warp. That’s because, as the part cools, the glass fibers tend to line up in the same direction, creating internal stresses. You can improve your parts with internal support structures (such as gussets) to support thin walls or ribbing of large, flat surfaces.

The type of uniform wall thickness displayed here is vital in preventing part distortion or warp. Photo Credit: Protolabs

Trimming of parts is often necessary to avoid flash, depending on the material. Photo Credit: Protolabs

Look closely at a rubber O-ring and you’ll see a thin line of material at its outermost periphery. That’s a parting line, the seam where the two halves of the mold come together. If you’re working with free-flowing materials such as Santoprene or unfilled nylon, a small amount of flash can sometimes ooze into the seam and typically requires trimming once the part has cooled for improved aesthetics. On a donut shape such as this, there’s little choice about the parting line location, but many orthogonal parts have sharp corners, which make a clean, crisp junction that’s a perfect place for the mold to separate. Flash or no, you should expect a parting line on most molded products. Digital manufacturers like Protolabs are able to identify the parting line location during the quoting process and may suggest ways of modifying the part geometry to avoid one.

Adding and mixing colorants consistently can prevent swirling. Photo Credit: Protolabs

From honey beige to cornflower blue, manufacturers stock a variety of colorants. These are mixed with natural resin pellets just before the molding run and are usually quite close to the target color. Still, the final product color may vary due to the polymer being used; texture and polish of the tool; and swirling during the mixing process. If you want an identical color match on your parts, it would be best to purchase color-matched pre-compounded resin from an external vendor.

Worried about those fine lines that look like hairline cracks in your injection-molded part? Don’t be. Those are knit lines, formed when two opposing flows of material join together in the mold cavity. Commonly seen at the edge of a hole or other cored feature, as a rule, knit lines are purely cosmetic but may create a physical failure point if present in an area of the part that receives substantial stress, such as the head of a screw. In this case, designing a strengthening boss feature around the hole is a good precaution, or just skip the hole entirely and drill it afterward.

Knit lines have the potential to create structural issues for parts in the areas where they’re located. Photo Credit: Protolabs

If you select a PM-F0 noncosmetic finish on a tool, the finished part will likely show small, circular, end-mill marks and tool transition lines. If you need a surface finish that’s more cosmetically appealing, it’s generally a simple, if more expensive, matter to manually polish the tool. A PM-F1 finish removes most tool marks, while an SPI-A2 will be smoother than a fresh jar of peanut butter.

Texturing via bead blasting is another option that generally leaves a uniform matte finish (except in thicker areas) around knit lines and in darker materials. Bear in mind that deep slots and cavities are difficult to reach for polishing and texturing, and that fine finishes may affect turnaround time because of the additional effort needed for polishing. Suppliers sometimes offer multiple surface finish options to choose from (like pad printing and laser engraving) as well as finishing options (like mold texturing and part marking).

A secondary operation like bead blasting can ensure a uniform finish. Photo Credit: Protolabs

Gate vestige is that small ugly spot at one end of the part left by removal of the gate after molding, usually with a side cutter or razor knife. It’s an unavoidable fact of injection molding. For the most part, the only thing that can be done to avoid it is to orient the part in the mold such that cosmetic surfaces are unaffected. For example, when molding a Statue of Liberty replica, the gate should be placed on the soles of Lady Liberty’s feet. When submitting a design to an outsourced manufacturer like Protolabs, always be sure to speak to an applications engineer to ensure surfaces that require a vestige-free appearance can be accommodated. There may be options to change a gate style depending on the material and part geometry. It is much easier to do this during the review stages rather than after the mold design stages have begun.

There are several other problems that can crop up with injection molding, some of which can be tied back to wall thicknesses that exceed general recommendations:

A draft adjustment or a new finish option will help prevent drag marks. Photo Credit: Protolabs

Thankfully, most of these issues can be resolved through slight modifications to part design and/or selecting a different material. Difficult part geometries often require fine-tuning of the molding temperature, injection speed, hold times or all three. Material selection also plays a big part with cosmetics. Two examples of this are polypropylene and HDPE, which tend to sink more than polybutylene or acetal, but flow better into small part details. It is possible to test different materials using the same mold, but unfortunately shrink factors may prevent parts from having dimensions that match the CAD. In some cases, after testing multiple materials, a new mold may be required for further testing or production parts.

About the Author: Rob Young is the senior global product leader for injection molding at Protolabs. Young has nearly a decade of experience in digital manufacturing and specializes in on-demand production and supply chain optimization for Industry 4.0. He came to Protolabs after working with early stage startups at the Ina Mae Rude Entrepreneur Center and Center for Innovation Tech Incubator in Grand Forks, North Dakota. Young holds a B.B.A. in Entrepreneurship from the University of North Dakota. Contact: 877-479-3680; rob.young@protolabs.com; protolabs.com.

With cavity steel or alloy selection there are many variables that can dictate the best option.

First find out if they are the result of trapped gas or a vacuum void. Then follow these steps to get rid of them.

Cold pressed-in threaded inserts provide a sturdy and cost-effective alternative to heat staking or ultrasonically installed threaded inserts. Discover the advantages and see it in action here. (Sponsored Content)

Modifications to the common core pin can be a simple solution, but don’t expect all resins to behave the same. Gas assist is also worth a try.

Modifications to the common core pin can be a simple solution, but don’t expect all resins to behave the same. Gas assist is also worth a try.

Make sure the designers you work with understand that there are limits to what processing can do.

Splay adjustments can be a simple fix, or can require several hours of babysitting a press and head scratching. Learn to find the root cause.

Multi Shot Injection Molding Plastics Technology covers technical and business Information for Plastics Processors in Injection Molding, Extrusion, Blow Molding, Plastic Additives, Compounding, Plastic Materials, and Resin Pricing. Learn More