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Mold Wiki

Soft Tool vs Hard Tool

What is soft tool and hard tool?Soft tool is the tool made of pre-harden steel, it is an economic solution for a small volume production. It has advantages of low cost and fast turn around, but pre-harden steel is a lower grades steel that process lower hardness and wear resistance, so the soft tool can only stand molding cycles no more than 500k shots, it's also difficult to maintain tight tolerances. Hard tool is a high quality tooling for mass production, it's made of the best quality steel, like H13,420 etc. Hard tool requires more procedure and longer time to manufacture. Difference between soft tool and hard tool Soft tool The tool's inserts are made of P20 or 718, (pre-harden steel). Inserts can be drill, mill and grind using normal process of machining. The tool life is guarantee up to 500 K shot. The lead-time of manufacture is shorter than hard tool. For prototyping, medium or low volume production. Hard Tool The tool's inserts are made using H13 or Stavax (harden to 46 -54 HRC). Inserts can be drill & mill, but after hardening special process will be required. The tool life is up to 1 million shots. The lead-time of manufacture is longer than soft tool due to the heat treatment process and extra machining job. For high precision parts and high volume injection molding. Why you need a soft tool before a hard tool? Usually price of hard tool could be many times of soft tool, it is could be a huge risk if you invest a big amount on tooling without a marketing test, plus, hard tool require much more time to get the parts, sometimes, there are just not possible for you to wait 2-3 month to get the samples. Soft tool is different, it can be flexible on both manufacturing time and price as long as you specify your requirement in details to tool makers

Mold flow Analysis

What is mold flow? Mold flow analysis is widely employed in mold making industry, utilizing data simulation software, the injection molding process can be simulated and presented on the computer, you can improve part design or mold design base on the out put results. Moldflow, Moldex3D are very popular mold flow analysis software used by many mold makers. Advantages of mold flow analysis Mold flow analysis will advise if the cavity is fulfilled, it can also provide other useful information such as the required injection pressure and clamping pressure. You can get benefit by knowing whether the filling problem exists or not. Many filling problems, such as short shot, bubbles and imbalances, can be predicted by a careful analysis of the filling curve. Mold flow analysis allows you to change the position of the gate, injection speed, and other processing conditions, so you would know if these problems can be improved or corrected. Mold flow analysis can predict the deformation of parts. Predictions can be used to compare the deformation by changing gate location, wall thickness. You can check and correct the problem by mold prototype. The best way to detect mold problems is to do "short shot" with the mold prototype. Mold flow analysis can suggest what changes will be effective. The cooling analysis analysis can evaluate the cooling efficiency and increase accuracy. It is very difficult to modify the cooling after the mold making is finished, so it is very important to make it right at the beginning. Mold flow analysis can predict the location of weld lines. Weld line usually is not allowed on some critical area, and weld line on the part also weaken the strength of the part. Injection mold designers can alter the position of weld line by changing the gate locating.Evaluate and optimize your part design The advantages of using the moldflow analysis to avoid potential defect like deformation, shrinkage, welding line etc, part designers can change the wall thickness or enhance the ribs to improve their part design base on the analysis result.Do mold flow analysis before mold making Simulation of injection molding helps to determine the best mold design solution before cutting steel, cooling layout, temperature distribution, gate location, venting area are all important issues to determine the success of a mold project, a blind design sometimes lead to modification on mold many times, which means longer lead-time and much more cost of mold making.

Injection Molding Basics (Advantages and Disadvantages)

Injection molding is one of the most important processing methods to produce plastic parts. Plastic injection molding techniques have been used and developed for a long time. Look around you, the case of your laptop, the case of intelligent cell phone, water filters, food containers, wash machines and quite a few components in your car... yes, we are living in a world that are full with plastic parts, most of the common plastic parts are made by injection molding. This article will show you the basics of plastic injection molding advantages and disadvantages.Injection Molding Basic Process Feeding raw material from the hopper into the barrel, the plunger start to push, the plastic raw materials are pushed into a heating zone and then through the bypass shuttle, the molten plastic through the nozzle into the injection mold cavity, then water or oil run through the designed cooling system to cool down the injection mold to get a plastic article. Plastic Injection Molding Advantages 1) High efficiency Plastic injection molding is high efficiency production method, it takes very short time to supply custom plastic parts to the market, the injection molded parts come out of the mold by every few seconds, usually the injection molding operation runs all night and day once the mold is set up. 2) Cost effective Automatic production of injection molding is possible, which means the operation is cost effective to manufacture custom plastic parts, in a full automatic injection molding factory, you only see a few workers there to ensure the machine runs smoothly. 3) Multiple materials molded at the same time The benefit of co-injection molding is you can produce plastic part with more than one plastic material at the same time. 4) Wide range of plastic material can be used Thanks to the development of chemical industry, more and more types of plastic materials can be used, and the performance and characteristics are more diverse, some of the materials with high strength can take place of steel in application, such as POM, some of the materials are soft, like PP, TPE. All of them can be benefited by injection molding to produce custom plastic parts. 5) Low scrap losses Utilizing hot runner, plastic injection molding production can maintain very low scrap losses. Basically, in a stable production situation, the scrap loss is zero. 6) In Mold Decoration In Mold Decoration technology allows the decoration to be molded together with the plastic parts, it means you don't need to do secondary process after molding. 7) High tolerances are repeatable Usually precision injection mold are built with steel cutting tolerance 0.005 mm, injection molded parts tolerance can reach 0.01 mm. This tight precision can be repeatable during injection molding cycles by cycles. Although injection molding has a bunch of advantages, there are also some basic disadvantages need to be taken into consideration when you planning to molding plastics. Plastic Injection Molding Disadvantages 1) High initial tooling cost Plastic injection molding can't work without a tooling, actually quality of the plastic parts rely heavily on the quality of tooling, tool making is a technical and labor intense job, a high quality tool could cost you a lot. 2) Expensive equipment investment The injection molding equipment is very expensive, it could take a molder 2-3 years to cover the investment. When you ask an injection molding factory to produce your custom plastic parts, you need to know about the basics of their machines, different brand of machine cost differently and the performance of the machines are different accordingly, also machine with different capacity (usually by ton) cost differently as well, machine cost is one of the main cost of the injection molding. 3) Plastic parts must be designed with injection molding consideration All the plastic parts designed to do injection molding must follow the basic rules of injection molding. Under cuts are allowed but part designers are required to minimize it as much as possible because it increase the complexity of injection molding and it's cost, some other considerations like sharp edges, uneven wall thickness etc should be avoid as much as possible; most of the plastic parts are asked to make a draft angle for better de-molding. So usually a qualified part designer would know some basic knowledge of mold making and injection molding, so they know how to avoid injection molding problems during plastic part design. When manufacturing custom hard cases for our clients, injection molding ensures that we provide a durable product at a reasonable cost to the client. This is especially important since we have so many large-scale orders that need to be done within a relatively short timeframe. While I'll agree that it was an expensive initial investment, the injection molding machinery has since paid for itself several times over.

Injection Mold Setup

After a new injection mold is construction is finished, the mold maker need to set up the injection mold to do test or molding plastics. Setting an injection mold is more than loading and fixing the mold to injection machine, there are many other important things to do after you clamp the injection molds. This article will give you a comprehensive explain of how to setup an injection mold, and the critical checklist you should pay attention to. Mold height Setting mold height is a critical step in the setup of the new job. With this step the machine clamping force system is set to the particular mold dimension. Every brand of injection molding machine requires his own method to set the mold height, which can be found in the machine manual. During the process of mold set up the mold height is set two times. First, the initial setting, this is done during the clamping of the mold when the injection molding machine is closed to make the clamping of the mold on the fixed machine plate possible. Second, the final setting, after the mold heater/ cooling is connected and the injection mold reached the required process temperature, during the heat up or cooling of the injection mold, the mold dimension will change due to the increase or decrease of the temperature. Remarks If you set the mold height make sure the central ejector is pulled completely back. Before closing the mold select the Set-up mode, now the injection molding machine plates close the limited closing speed and clamping pressure. During closing of the injection mold make sure that that all the connection on the mold, injection mold heater and safety connections have enough slack and not wear during opening and closing of the plastic injection mold. Mold heater/ cooling These connections are required to bring the injection mold to the required process temperature by adding or removing energy from the mold. To achieve the process temperature a medium, water or oil is directed in circuits through the mold, one in and one out connection is called a set. If special connection schematics are required for a particular process it can be found on the molding data sheet. If no special connection schematics are required connect as much sets as possible this will increase the temperature control performance. After connecting and switching on the mold heater/ cooling the working of the heater or cooling can checked by feeling with your hand if there is an increase or decrease of temperature on all the connections that are connected to the injection mold. Hot runner connection If the injection mold is designed with a hot runner system, there will not be a runner ejected from the injection mold during the ejection of the plastic part. The runner will remain in a melted condition in the mold to be injected in the cavity during the next cycle. To keep the plastic at the right process temperature an electric heating system is build into the injection mold and is controlled by an internal or external controlling system. Before connecting the hot runner system, make sure the connections are not damaged and free on contamination. Let the system warm up long enough before you start up the process, a cold part of plastic in the hot runner can damage or break the hot runner system. Do not let the system warm up too long, this will result in degradation of the polymer. Ejector Safety Sensor If the design of the part/ mold requires ejector pins at location where they can be damaged during mold closure if they are not in the right position, for example an injection mold mounted with slides. The mold will be fitted with an ejector safety sensor. Connect and check the ejector safety sensor during injection mold setup before you close the mold for the mold height setting. Check the working of the sensor by placing a small piece of paper between the mold plate and ejector plate, if the sensor is working correctly the injection mold will not close. Core pull connection If the part geometry not allows the plastic part to be ejected freely from the mold one of the possibilities is to equip the mold with retractable cores. The movement of these cores is established with the aid of pneumatic or hydraulic cylinders. The risk of mold damage by wrong operation or failing of the injection mold is high; To reduce the risk core pull molds must be equipped with position sensors, to use the core pull option the injection molding machine must be equipped with a core pull program. The parameter setting of the core pull program (positions, pressures and speed) can be found on the molding data sheet. Always connect and check the working of the core pull sensors, program and settings before you close the injection mold.

Benefits of mold flow analysis

A good mold flow analysis has lots of benefits, although it is time consuming, the cost is much lower than the cost of trials during nights and days on a production injection molding machine. The difficulty is not to produce colored pictures but to explain to the customers the different results, some customers have enough knowledge to understand some others no. In 90% of cases, I work before the injection mold is cut, so I am ready to take the responsibility of cycle time, warpage, sink marks and so others issues. I am specialized in gas assisted injection molding and I assist Chinese companies to produce plastic parts for the German automotive industry which generally use overflow. With short shot process, we can obtain a production costs reduction of 20% by simulation and 30% in practice. Moldflow is very important tool for verifying mold design and product design, I can say it is 99.9% helpful, mold flow analysis has lots of advantages and will save a lot of money. Mold flow analysis can provide you following benefits: Moldflow Filling Analysis Optimize gating Optimize runner system Predict fill pattern Predict injection pressure Determine clamp tonnage Predict temperatures Visualize shear rate Visualize shear stress Determine fiber orientation Predict volumetric shrinkage Predict sink Determine venting Avoid air traps Locate weld (knit) lines Develop optimum ram-speed profile Moldflow Cooling Analysis Find hot spots Calculate time to freeze Visualize uneven cooling across core and cavity Determine uneven cooling between core and cavity Define required coolant flow rates Measure pressure drop in cooling system Determine (and reduce) cycle time Optimize the cooling layout Moldflow Packing Analysis Calculate proper packing pressure Define optimum packing profile Moldflow Warpage Analysis Predict warpage Find cause of warpage Determine warpage due to orientation Predict warpage due to differential cooling Understand warpage due to differential shrinkage Moldflow Gas-Assist Analysis Determine optimized gas channel layout Predict gas penetration See gas permeation Predict skin/core ratio Establish required gas pressure Define optimized gas pressure profile Refine spillover design Moldflow Co-Injection Analysis Compute skin/core ratio Calculate skin/core distribution Establish switch over points for skin/core (A-B) Establish switch over points skin/core/skin (A-B-A) We see benefits of using mold flow analysis technology in companies that correctly understand the power of the different simulation tools, and when and by whom these tools can be used. During the product design, many decisions are made that affect cost and quality, and unfortunately many decisions are made in a knowledge vacuum by a product designer. Once he/she is done many of the costs are locked in. Moldflow introduced Autodesk Simulation DFM, to help a designer develop a viable plastic part (this is as much as you can expect from a designer). Feedback on manufacturability is provided in real time. It uses minimal input from the designer, and can help avoid basic and obvious mistakes before they become expensive. After the designer is done, someone has to figure out how to make the plastic part. This requires expertise and a different set of tools like Moldflow Adviser or Insight. This requires a different user, more precise input and results accuracy. These tools should ideally be used throughout the product development, rather than at one single stage in the process. A designer does not have the background of plastics expert, and analyst should not have to chase down basic design errors.

Custom Plastic Enclosures

Plastic enclosures are plastic cases or housings manufactured by injection molding process. Usually a popular consumer product with great enclosure design catch people's eye immediately without promoting how good the function are, a very success example is Apple product, success industrial design contribute a lot to the success of Apple in worldwide.How to make a custom plastic enclosure? First you need to make a design for your custom plastic enclosure, a complete and professional design will includes plastic parts size, structure, selection of proper plastic materials, assembly method, finish. Then you need a plastic mold maker to make a custom injection mold for it, mold price and lead-time will be determined by the quantity demanded, complexity of structure, size finish of the plastic part. If your plastic parts are in high volume demand, then a high quality and long durable mold is a must, get a warranty for how many plastic parts the mold can produce before you sign a mold manufacturing contract with your injection mold supplier. After the custom mold produced, you need to run the mold on an injection molding machine, finally, you get your custom plastic enclosure done. Plastic enclosure materials Selection of plastic enclosure material should follow basic foundation: functionality and economic. Enclosure for different product has different function requirement, for example, enclosure for chargers need ABS with anti static for safety consideration, enclosure of tool box need material with good intensity for the purpose of protection, some engineering material are very expensive so it is not common to used by consumer products but in special accession like military and aerospace applications.Secondary process for plastic enclosure Plastic enclosure parts come out of the injection mold are just primary product, secondary process make them into a real attractive eye catcher, these process include oil painting, nickel or chrome painting, silk printing. Aco Mold can provide one stop services from mold making, injection molding and secondary process, using a single supplier for your project like Aco Mold would minimize the scrap rates and shorten the lead-time.Application of plastic enclosure Plastic enclosure is widely used in many applications, including consumer electronics, home appliances, packaging products, cosmetic products, mechanical products, etc.

Injection Mold Guiding System

Guiding system of injection mold works as guides to ensure precise mechanic movements. Generally the standard mold base all have guiding design, like guide pins between cavity side and core side, mold designers can just choose the proper mold base. Typical mold guiding system include, guiding between A/B plates, guiding for stripper plates, guiding for runner plates, guiding for ejector pins. All this guiding system can be customized when you order the mold base.But when the parts have particular structure and require high precision, this customized guiding system might not be enough, the guiding pins could not perform as well as before after a long time running, so injection mold designers should consider special guiding design besides these customized guiding design on the mold base.    Precision guiding components have been standardized, such as tapered dowel pins, side lock, etc. some precision guided positioning device must be designed according to the specific structure of the injection mold.

Compression Molding and Extrusion

CompressionThe process of compression molding may be simply described by reference like two-piece mold provides a cavity in the shape of the desired molded article. The mold is heated, and an appropriate amount of molding material is loaded into the lower half of the mold. The two parts of the mold are brought together under pressure. The compound, softened by heat, is thereby welded into a continuous mass having the shape of the cavity. The mass then must be hardened, so that it can be removed without distortion when the mold is opened. If the plastic is a thermosetting one, the hardening is affected by further heating, under pressure, in the mold. If it is a thermoplastic, the hardening is affected by chilling, under pressure, in the mold. Compression molding is used principally for thermosetting plastics, and much less commonly for thermoplastics (for which injection is the preferred method of molding). ExtrusionExtrusion of thermoplastic materials can be accomplished through various means, depending upon the product being manufactured. Typically, extrusion with polymeric materials (plastics) involves a continuous operation as opposed to making a product with an intermittent process as done in injection molding. The various products made by extrusion include pipe, tubing, coating of wire, plastic bottles (blow molding), plastic films and sheets, various plastic bags (blown film), coatings for paper and foil, fibers, filaments, yams, tapes, plastic plates and cups (thermoformed sheet), and a wide array of profiles. Extrusion is accomplished by melting the material and forcing the melt through a forming die. The polymer material is fed to the extruder through a feed opening and can be introduced to the extruder in pellet (or cube) form or alternately as a powder, a granulate, or, in some processes, a melt. Extruders used in rubber extrusion and with some adhesives must accept a strip as the feed form .The extruders that are fed a melt are used for pumping to pressurize and to force the material through the die system or to aid in such parameters as cooling the melt from a melting extruder. The typical extruder is required to take a solid feed material and to melt, homogenize and pump the melt through the die system with acceptable output uniformity. The output consistency is measured by the uniformity of the dimensions of the finished product. The extruded melt is continuously shaped and cooled by downstream equipment placed after the extruder. This sizing/cooling equipment can be comprised of cooling rolls, water tanks, and vacuum sizing fixtures, air cooling tables, pulling devices, cutting equipment, coiling or winding equipment, and so on.

Scientific Molding

Scientific Molding to me is a bit different than having a whole lot of data studies. To me, and to many of my peers, scientific molding is an disciplined elimination of multiple variables, which yields an range of conditions/settings/protocol/things that you must do. This will yields the highest volume of acceptable parts with the least amount of cost. I.E., when you do this, and you do that - the press operates thus and you get money. Going thru the methology checklist eliminates the variables in a disciplined fashion resulting in an updated group of setting, updated methods of handling material change outs, setting up a mold, scheduling jobs, etc. and reduction of scrap. Happy customers, happy plant operators, more money. Here is the other key, you have to have the discipline to relook at the methods you are using and look beyond just machine set-up. (I.E. what was in the machine before certain jobs are run, - which dryer did the material dry in, what was the dryer cycle, etc.) Of course when the part production drops below a certain level or the scrap rates rise too much you should repeat the process. And, one has to weigh the cost of doing this in a thorough study versus writing down anecdotal notes and "what we used before." I was molding for 20 years before I became a Master Molder. I was also lucky enough to have John come to our plant a couple of times and go through studies and universal truths. It is surely true that even though I thought I was good, I had no clue...I was truly inspired by scientific molding. Well, after the honeymoon, reality set in. Loose shutoffs, gates, vents, locks, wall sections, etc. That's a lot of money. We are not spending money on this at this time. Nothing beats a good tool. Scientific molding has dramatically increased the chance of making a safe, repeatable process, but it is not a magic wand. With a total IQ-OP-PQ approach, this is a good tool for the process part of the qualification, but it still depends on individual to understand what knob to turn.

Electric vs. Hydraulic injection molding machine

You can get a larger shot size out of a hydraulic injection molding machine. There are times when you are pushing the injection capacity of the injection unit that hydraulic machines are a better choice than all-electric injection molding machines. However, if the job is within the range of the injection unit and specified properly, the electric machines outperform hydraulic for repeatability and energy consumption. The main consideration when considering an all-electric injection molding machine is energy efficiency. Electricity savings of 20%-40% are typical when compared to hydraulic machines. Also, an all-electric machine can offer unmatched repeatability due to the servo drives that are used for injection forward and clamp rather than hydraulic pumps/valves. One way that the electric injection molding machine saves energy is that they only use the energy that is needed for the job that is being run. A typical hydraulic injection molding machine wastes energy by centrally recycling the hydraulic oil through the pump even when the process does not require it. This can be overcome by adding a modular valve and control to the hydraulic package, but this brings the price up and you add other maintenance items. If you are molding with very high pressures and very low velocities, you may need to bump up (oversize) the servo unit on the electric injection molding machine. This is due to the limitation of servo drive performance at very low speeds relative to capacity. This is a specification issue, not a technology problem, but it does add cost to the injection molding machine. This is a major reason why the assessment of high costs of the larger tonnage electric machines. Big servos are not cheep! Another benefit of electric over hydraulic is that, with no hydraulic pumps, valves, tanks, etc. the unit has far less parts to maintain and can be serviced very easily. Oh, and the injection molding machines are very quiet when running. Don't get me wrong, when shot sizes are very large (700 oz. for example) hydraulic units become a better choice because the servo motors begin to get very expensive and ROI starts to get longer. This is why large tonnage machines are often offered as Hybrid machines using both electric and hydraulic technology. With a hybrid injection molding machine, you are able to get the larger capacity while saving some energy and up front costs. This is why most injection molding companies do not offer the higher tonnage machines. However, machines in the range of 100T - 800T are usually right in the wheelhouse for all electrics. They require a larger investment up front, but the energy consumption savings and reduced maintenance costs offset this quickly.

Injection Molding Clamp Pressure

Two types of injection-compression used for thin walled high aspect ratio parts. The first uses a moving side core or secondary cylinder that leaves the cavity spaced and upon injection clamps forward to compress the part stress free. This usually requires a specific capability of the press. The second method sometimes referred to as coining closes the mold under reduced clamp pressure and the cavity is filled. Injection profile can be set that as the cavity is filled to peak pressure and the clamp pressure is overcome, the injection has a near zero fill speed and then picked up to 10~20% speed for the crossover to hold. This method usually needs a very repeatable injection and clamping system and dial indicators are used to monitor the clamp breathing stroke. As the material goes in to hold and begins the shrink process, the clamp will follow the melt movement typically not completely closing. I have used this process for over 25 years to yield 0.55 mm thick by 120 mm diameter center gated parts. The flatness, thickness uniformity and stress are significantly reduced, but part to part overall weight can vary depending on your repeatability and press control. In this design it is also typical to have roughly a 7 degree draft angle on the parting/vent line to avoid flashing during the injection-compression stroke depending on the material and criteria for edge definition. keep in mind other critical control parameters are melt viscosity, plastification, pellet size uniformity as the cushion is typically much lower than with standard straight injection to avoid shot to shot variance.