One of the most common applications is to add a soft. Polycarbonate injection moulding stephens injection moulding. Two injection molding processes dominate the manufacture of overmolded products. Injection too slow during the injection portion of the molding cycle, the material does not fill the mold in the recommended injection time. The last production of degradable plastics materials in the cylinder, screw, valve adapter maybe curing inside the aggregate hot runner pipe. Troubleshooting molding injection molds plastics troubleshooting. Due to the wide range of options and plastic injection moulding materials available, this information is for use as a guide only and is supplied in good faith. Downloadable pdf for troubleshooting injection molding.
Yes, this is the reason why many industries are opting for this technique given that it allows you to design this material suitably. When injection molding issues rear their head, the methods and accuracy of your troubleshooting are often directly related to the speed and effectiveness with which youre able to. Injection pressure inside mold usually 1,000 psi to 5,000 psi lower than hold and pack pressure between 10,000psi and 20,000 psi 2. Polycarbonate is not considered a good bearing material, but when formulated with an internal lubricant such as ptfe, it has been successfully used in bearing applications. Polycarbonate injection molding refers to the efficient process that you can use to produce polycarbonate parts in almost any shape. Insert molding the most widely used process is insert molding, where a premolded insert is placed into a mold and the tpe is shot directly over it figure 1. This information is intended to be used only as a guideline for designers and processors of modified thermoplastics for injection molding. Increase stock temperature by increasing back pressure andor barrel temperature. Philosophy of troubleshooting injection molding problems. Bob hatch is manager of technical service and customer support for. As a result, molded parts with solid external skin and porous inner core are obtained.
Nov 27, 2018 when injection molding issues rear their head, the methods and accuracy of your troubleshooting are often directly related to the speed and effectiveness with which youre able to remedy a problem or problems remember that symptoms of an issue will often have more than one underlying cause. Stack plastics is an industryleading provider of pc injection molding services for your part and component manufacturing needs. Thermoforming lexan sheet, a polycarbonate material, is a manufacturing process where a plastic sheet is heated to its softening temperature, formed to a specific shape in or. Kim 20 pressure control hold pressure packing compensate shrinkage rule of thumb. Plastic injection molding with polycarbonate lexan. Here are 11 common injection molding defects to watch out for when inspecting. If it did, this obviously would mean the molding tech would have to back off the injection unit and pound the sprue out with a brass rod. Molding troubleshooting guide bond readout bond readout is a surface distortion similar to a hump or sink that occurs over a bond line probable cause material process mismatch of compliance between. Instead a large force must be used to inject the polymer into the hollow mould cavity. Apr 29, 2015 thermoplastic injection molding has several sub categories, such as rapid injection molding, which is best utilized in fine tuning prototypes prior to a product being given the goahead for. Plastic injection moulding is the biggest part of the business in the world.
If 5 minutes, use smaller shot machine or reduce cycle time. A wide variety of polycarbonate injection molding options are available to you, such as injection, mould. A wide variety of products are manufactured using injection molding, which vary greatly in their size. Molding troubleshooting guide bond readout bond readout is a surface distortion similar to a hump or sink that occurs over a bond line probable cause material process mismatch of compliance between outer panel, inner panel and adhesive incompatible thermal expansion coefficients between the sm and the adhesive. Top10 injection molding defects and how to fix them tony rogers on june 12, 2015. Troubleshooting guide for injection molding troubleshooting is the art and science of remedying defects after the process has demonstrated the ability to produce acceptable production parts.
Thermoforming lexan sheet, a polycarbonate material, is a manufacturing process where a plastic sheet is heated to its softening temperature, formed to a specific shape in or over a mold by using vacuum, and trimmed to create a usable product. The simple fact is that vacuum forming has some very big advantages over injection molding and also over other plastic forming processes. Applied at the end of the initial injection stroke, and is. Lexan is a brand name of polycarbonate of which we injection mould. The conditions for moulding will of course depend on the design of the article, the ratio of. Part 1 scientific troubleshooting solutions for common.
Injection moulding troubleshooting guide please note the injection moulding troubleshooting guide covers some of the common problems encountered with this process, but is by no means complete. That is especially important when parts should be suited for superheated steam sterilization. The bisphenol a component of the molecule contributes to the high glass transition temperature 150 c 302 f. For injection molding, this means there are several items on the mold and press that should be checked before troubleshooting any molding. Injection moulding troubleshooting guide pdf grid author. The injection molding machine consists of the injection unit and the clamping unit, and their features are described below. Today, thermoforming can offer many benefits over other. Infuse obcs can be blended at the press with materials such as hdpe, pp, caco 3 concentrates, and oil concentrates. Injection molding troubleshooting guide brittleness contamination bubbles cont.
Pc materials pc polycarbonate typical applications. Investigate steps in the process to find the cause of warp and revise. Cause solution under packing increase pressures and. Hangup of molten material in injection barrel or runner system. For molders, the advantage of insert molding is that. Parts exhibiting mould flashes are characterized by filmlike plastic edges attached to the molded parts. Different terms are used throughout the industry to identify defects in plastic materials, fabricating.
Liquid silicone rubber injection molding guide healthcare injection molding of silicone parts has enabled producers to achieve higher levels of automation and productivity than ever before. Improper runners or gates mold temperature too low material excessive moisture operator inconsistent cycle machine excessive injection speed or pressure excessive back pressure screw speed too high improper compression ratio of screw. There are a number of different forming techniques, some of which only require heating to allow the sheet to conform to. Machine injection temperature too high injection pressure too low injection forward time too low insufficient material feed improper injection temperature profile excessive injection speed insufficient. This processing guide will cover the technical fundamentals, optimization and troubleshooting of mucell. Polycarbonate pc, first introduced in 1958, is an amorphous engineering thermoplastic with exceptionally high impact. Plastic flow into the part channels or snake flows. A polymer is classified using different criteria and is considered to be either. Polycarbonate injection molding injection molded polycarbonate. Injection molded plastic begins its journey through the part tooling via an entry section called a gate. Machine injection temperature too high injection pressure too low injection forward time too low insufficient material feed improper injection temperature profile excessive injection speed insufficient back pressure mold improper venting section thickness too great injection molding troubleshooting guide brittleness contamination bubbles cont. Injection molding troubleshooting guide tritan mold it. However, when observing a molding machine in operation, the smell of degraded plastic may be an overwhelming indicator of a problem. Black spots, brown streaks blisters air entrapment.
The advantages of plastic injection molding for manufacturing parts imethods include fast production speed, high efficiency, automation of operation, shapes and sizes flexbility. Injection molding defects and solutions moulding defects. Void at base of sprue use alloy sprue bushing with ample water flow. But as with any quality problems, knowing how molding defects arise is half the battle. Thats what this injection molding reference guide is all about. Injection molding training put together by experts.
Design considerations for overmolding and insert molding overmolding is an injection molding process that allows an additional layer of resin to be added to an existing molded part to provide a combination. Troubleshooting tips for plastic injection molding revpart. One of the main causes for warping in injectionmolded plastic and similar. Plastic injection molding with polycarbonate lexan plastic. In the injection moulding largely used polymer processing method due to the more production and low cost of the product. Here are some steps you can take to prevent this defect. This polycarbonate part presented cosmetic problems for the molder, inside each gate, down the side of the part, and at the endoffill weld lines.
The temperature during polycarbonate injection moulding should be as high as possible, because that helps to obtain ready parts with very low inherent stress level. Troubleshooting solution guide injection molding machine 1. Solving molding air trap problems definition air traps occur when converging flow fronts surround and trap a bubble of air. Materials, design, process optimization, troubleshooting and more from the experts at routsis training. To excel, you need a good grasp of a wide range of concepts and data. Injection molded plastic begins its journey through the part tooling via an.
Not all troubleshooting approaches are created the read more troubleshooting tips for. Design considerations for overmolding and insert molding overmolding is an injection molding process that allows an additional layer of resin to be added to an existing molded part to provide a combination of characteristics that no single material can provide. A large number of the defects mentioned above can be prevented in the design process by incorporating proper tooling design into the iterative process. Call 9783429000 for details or email email protected. The polycarbonate injection molding process produces plastic parts and components that display high degrees of strength, impact resistance, and clarity. Ten injection molding defects and how to fix them flow lines, sink marks, voids. Solve plastic injection moulding problems with this onepage troubleshooting grid. Injection molding troubleshooting guide rtp company. Polycarbonate injection moulding stephens injection. The flashes often appear near commissures, sealing. Adopt optimal molding conditions like injection speed, injection pressure, mold temperature, and proper gas venting. Regions within the molded part without plastic are referred to as internal voids or bubbles.
Because injection mold design and processing is complex, a set. If problems are found they should be corrected and the parts reevaluated before proceeding. The material can be modified by the addition of glass fiber. In light of these facts and because injection molding does not have many of these restrictions, why would anyone persist in doing vacuum forming. Lexan polycarbonate sheet products are easily thermoformed and a wide variety of applications can be produced using the process. Reduce injection speed, especially at the beginning of the shot. Injection molding is the most commonly used manufacturing process for the fabrication of plastic parts. Melt temperature too high measure and reduce melt temperature. Troubleshooting download download a printfriendly troubleshooting guide in pdf format. In order to create injection moulding products for our customers, we extremly take injection moulding machine parts details and injection moulding step by step to heart before manufactruing parts and during the injection molding process. Possible cause corrective action melt temperature too low increase melt temperature. Stack plastics is an industryleading provider of pc.
Calculate melt residence time by formula in molding guides. Obc products for injection molding obc grades designed for injection molding applications are available in a range of densities with melt indices of 5 and 15 g10 min. Check injection throttle position and if possible, increase its setting. Natural polymers are those found in nature, such as rubber, cotton, and silk. The broad portfolio of makrolon polycarbonate resins from covestro includes general purpose, lighting, medical and food contact, flameretardant, impactmodified and glassfiber reinforced grades, which can be used for injection molding, extrusion and blow molding. Chapter 2 injection moulding process injection moulding is the most widely used polymeric fabrication process. Design considerations for overmolding and insert molding.
Injection molding silicone polycarbonate amorphous thermoplastic. This brochure is intended to provide general guidelines for equipment, procedures and molding machine conditions that will help the customer obtain the best possible performance from the the lubrizol lifesciences of tpu molding grades. It may be necessary to move the mold to a machine with less injection capacity. Molding troubleshooting guide dieseling dieseling is a burnt spot on the laminate, often accompanied by nonfills probable cause material process air entrapped in the tool which burns tooling corrective action material process increase material flow distance slow press closure vary mold temperature differential. General purpose grades of polycarbonate used in plastic injection molding typically exhibit heat deflection temperatures of 270f at. At wayken, we have encountered many similar plastic injection molding problems and solutions in some cases of prototype injection molding. This article continues our series of troubleshooting reports from one of the leading onthespot problem solvers in the molding industry. This brochure is intended to provide general guidelines for equipment, procedures and molding machine conditions that will help the customer obtain the best. Feb 18, 2009 join andy routsis, founder and president of a. Sample pages injection molding advanced troubleshooting guide.
Bob hatch is manager of technical service and customer support for prime alliance, the des moinesbased resin distributor. Injection molding reference guide materials, design, process optimization, troubleshooting and other practical information from the experts at routsis training plastics is a sophisticated and diverse. This article continues our series of troubleshooting reports from one of the leading onthespot problem solvers in. Most defects respond to one of a variety of process andor material changes. Lexan polycarbonate sheet technical processing guide. Injection molding training guides troubleshooting injection molds. Tips to possible solution on some common plastc injection moulding problems.
All generalpurpose polycarbonates are based on bisphenol a. The basic steps involve the heating, shaping and cooling of a thermoplastic sheet product. Most importantly, it will help you design solutions to these problems. For injection molding, this means there are several items on the mold and press that should be checked before troubleshooting any molding problem. Injection molding reference guide materials, design, process optimization, troubleshooting and other practical information from the experts at routsis training plastics is a sophisticated and diverse discipline. Ppd407b injection molding troubleshooting guide eastman. The conditions for moulding will of course depend on the design of the article, the ratio of the longest glow path to section thickness, and the machine on which it is moulded. Routsis associates, as he presents a scientific troubleshooting framework for five of the most common injection molding defects. Read the best guides for troubleshooting molding put together by plastics troubleshooting experts. The trapped air can cause incomplete filling and packing, and will often cause a surface blemish in the final part. Before his present assignment, bob managed a molding operation for 25 years.