So you want to buy blenders/feeders for your molding machines! Maybe, you’re just getting started in the field. Perhaps, you wish to enhance the quality of output while reducing the material cost. No matter the reason, getting familiar with the various types of blenders is advisable to make an optimal choice. Typically, you’ll find volumetric blender/feeder and gravimetric blender systems. Both the feeders deliver results. However, some molding businesses favor a volumetric feeder, whereas others endorse a gravimetric feeder. Let’s get familiar with both types of feeders and find out what suits you the best.Volumetric feeder systemsThe concept of feeding or blending volumetrically starts by filling the auger completely. The volume displaced by the auger, the rotational speed, and the auger’s pitch is known beforehand. So, an auger with a 1-inch pitch rotating at 100 revolutions per minute (RPM) will move the material (in volume) forward 100 inches in one minute.As far as everything is okay and constant, the volume of the material dosed will remain the same throughout the operation provided the auger is full all the time. Keeping the auger’s pitch constant, you can change the volume of the material dosed in the machine by altering the rotational speed. Varying the speed offers linear control over the material (in volume) being dosed.This method of feeding presents consistent, repeat metering with better linear control for materials that are termed as good powders. Good powders have consistency in bulk density with manageable characteristics. The problem in this method of feeding arises when the powder lacks consistency in bulk density.Volumetric feeding/blending lags in capacity requirements if the bulk density of the material varies. Such materials will struggle to meet the feeding requirements. Consequently, the quality of the output will be affected. However, volumetric systems make a great fit for small scale industries where accuracy isn’t a matter of preference. Also, they’re far more affordable systems.Gravimetric feeder systemsGravimetric feeding (gain in weight or loss in weight) presents a way to dose by metering or weight continuously. It provides methods for tracking and recording materials used. Additionally, it could offer the means for running recipes for feeding/dosing systems. Since the system is mostly automatic and features a control mechanism, there are hardly any chances of errors.A gravimetric blending/feeding system costs almost double the price of the volumetric blending system because it includes a control module, scale, and an HMI (microprocessor-based). Despite the high cost, a gravimetric model is essential for certain applications for accuracy, record keeping, and overall control.In gravimetric feeding, each cycle of material dispensing is verified by weighing the material dose. The control system is meant to self-correct any mistake in dispensing on subsequent doses, on the basis of weighted results. The self-correcting operation measures the results of metering and adjusts itself for very high accuracy. Consequently, the quality of the output is greatly enhanced.Although volumetric feeding is also a good way to dose materials, gravimetric feeding is an improved version over volumetric dispensing. Accuracy and self-adjustment of weighted doses are the highlights of gravimetric systems which make them hugely popular in fields where a higher degree of accuracy is desired.While both volumetric and gravimetric dispensing systems are meant for dosing materials into the machines, they differ in many respects. In volumetric systems, the user has to know the rate of dispensing of materials into the system. In the case of gravimetric feeding, the user doesn’t need to know this thing.Volumetric blenders offer a good accuracy when the material in question has a consistent bulk density. Gravimetric blenders, on the other hand, render a very high accuracy even if the bulk density of the material varies.In volumetric blending, the user needs to adjust the weight of the material. In gravimetric blending, the system automatically adjusts the weight. Volumetric blenders come at a lower price compared to gravimetric systems. Gravimetric blending delivers a high quality of output compared to volumetric systems.Bottom lineChoosing the right kind of blender or feeder is imperative for any molding business. Although you can use a gravimetric feeder or volumetric feeder in most cases, each of the two feeders is unique in some respects. So, check out the working and benefits of these feeders in view of your particular situation. With handy information by your side, choosing an ideal feeder becomes a lot easier without doing much legwork.
A wide variety of plastic products are manufactured either by the injection molding or extrusion molding process using specialized machines. The plastic raw material which is used as the input to the machines has to be mixed with a large number of other additives so that the finished plastic product has the desired physical and chemical properties. Most manufacturers have decided the right combination of the various ingredients which are being used after extensive research. Yet during manufacturing, the accuracy of the mixture which is being used and quality of the finished product depends to a large extent on the type of plastic blender which is being used.There are different types of blenders available for plastic material before it can be used for manufacturing products. Volumetric blenders will mix the various materials based on the volume of each material. These blenders are using a mixture of sensors and timers, to calculate the quantity of each material being mixed. On the other hand gravimetric blenders are measuring the weight of each ingredient in the mixture. The volumetric blenders are usually cheaper than the gravimetric blenders, since they have a simpler design, yet increasingly manufacturers prefer gravimetric blenders due to their advantages which are discussed below.The gravimetric blenders can be further divided into batch blenders and continuous blenders. In the batch blender, depending on the amount of plastic raw material required, all the other ingredients are added to the mixture in the desired weight. Load cells are used to ensure that each of the ingredients is of the weight desired. After the plastic material and the ingredients have been added to the batch blender, the material is blended so that the various ingredients are uniformly mixed. However using this method, there is no guarantee that the mixture will be completely uniform; some parts of the mixture may have a higher or lower concentration of the additives. For ensuring greater accuracy of the mixture, some manufacturers are using continuous blenders. There are a number of hoppers which contain the various raw materials required for manufacturing the plastic product in the plastic blender. Each of the hoppers has a load cell for monitoring the loss in the weight of the hopper as the material is being fed into the blender. The different ingredients in the plastic fall into the blender, where they are mixed together, before being transferred to the next part of the manufacturing process. This method ensures that the mixture created is uniform, since the desired proportions of the raw materials are present and being mixed. Typically for making plastic products, plastic raw material and more expensive additives are used. While it is easier to uniformly blend materials which are similar in particle size and shape, if the ingredients are different like flakes and powder, the mixture may not be homogeneous. Since this will affect the quality of the finished product, most manufacturers are adding more of the additives to compensate for the lack of uniformity. These additives are more expensive than the plastic raw material and this adds to the cost of the finished product, since the raw materials used are more expensive.For higher volumes it is observed that continuous gravimetric plastic blenders are the most accurate, ensuring that the mixture has the desired ingredients in the ratio required. When the volume of the plastic material used is less at approximately 5 kg per hour, studies indicate that the accuracy of both the batch type and continuous gravimetric blenders is similar. Both the gravimetric blender types are significantly more accurate compared to the volumetric blenders, so the additional amount of additive which is required to compensate for the lack of accuracy is less.Typically due to the blending accuracy for each shot for a gravimetric plastic blender, the manufacturer will have to add 1% more additive. In comparison the amount of additive to be added for a volumetric mixer may be 3% more. Hence using a highly accurate gravimetric blender can help the manufacturer save a lot of money in expensive additive costs in the long term. Research has indicated that a well-designed gravimetric blender will pay back the higher price compared to other blenders in less than one year. So businesses who wish to reduce their manufacturing expenses should consider purchasing a high quality gravimetric blender.
Whether it’s a wet winter or humid summer, damp indoor air could be an issue. It’s uncomfortable and encourages dust mites and mold growth. Plus, condensation could stain and/or ruin the paintwork. The situation could be worse in case you need to dry plastic products in a commercial setup. So, how do you avert any such potential problem? Your best bet should be a dehumidifying dryer. It’s an easy, practical solution to get rid of excess moisture from air indoors. However, choosing the best device is the key. Here’s a useful guide that should help you pick an ideal dehumidifier.Tips to buy the best dehumidifying dryerWhen it boils down to buying an ideal dehumidifier, many buyers don’t do any homework. They just drive to their nearest store or surf the net with suitable keywords. As soon as the first model comes across, they pick it. However, most of the shoppers repent later on for making a hasty decision. Picking an ideal machine warrants a little bit of time and diligence on your end. However, your time will pay off substantially in terms of a top-class dehumidifying dryer matching your needs and budget. Define your needsAs stated earlier, a little bit of labor on your part is important before shopping. Ideally, you may want to jot down your expectations with the device. For instance, figure out whether your place features humid and damp weather conditions for a major part of the year or not. If this is the case, you may need a high-quality machine that can soak up adequate water from air and dry your products efficiently. On the other hand, a common dehumidifying dryer will make a good choice for places with moderate dampness.HumidistatA humidistat allows you to set target humidity for your room. Depending on the make and model, this could be an accurate number setting or it may offer some basic settings such as high, medium, and low. If you want to have the exact amount of humidity, then a dehumidifying dryer with accurate number settings could be your better bet. Such a device will let you ensure an ideal amount of humidity, necessary for drying particular products.Remember, a 40 to 60 percent humidity range is perfect for human comfort. However, you may go for as low as 30 to 20 percent for a dry feeling. If you live in a region that has moderate dampness, then a model with basic settings such as low, medium, or high might be a good choice.Low-temperature effectivenessExcess moisture can occur at low and high temperatures. Most manufacturers give moisture removal rates for conditions that make their devices look best - usually 30 percent and 80 percent relative humidity. However, the performance of their devices is often lower, weaker at colder temperatures. If you wish to deal with colder condensation, seek figures at 10 degrees centigrade and 15 degrees centigrade. A dehumidifying dryer that performs better at these conditions will make a good choice for your place, especially for drying plastic and other products.PortabilityDehumidifiers could be heavy depending on their shape, size, and end-use. For example, if you need a dehumidifier for your home, you may want it to move from one room to another. Moving heavy devices can take a heavy toll on any person.Handles, castors, and wheels are useful for the movement of the unit. This is even more correct in the case of a commercial setup where you need bigger units for drying commercial items. So note this important parameter when checking suitable models.Continuous drain capacityDrain capacity means the ability of the dehumidifying dryer to drain water continuously. Many folks don’t pay attention to this feature. If you need a small machine for your home that has moderate humidity, then the constant draining feature may not be that important.However, extreme temperatures necessitate the need for continuous water draining. The draining feature is also useful for commercial establishments. So, figure out the end-usage and weather conditions of your place, and then check the draining capability of the model.Brand nameAs with any other product, the maker of the device is an extremely important factor that shouldn’t be overlooked. The choice of the right brand can make a big difference between a good dehumidifying dryer and a bad model. So, list out reliable brands engaged in providing dehumidifiers.Make a checklist of brands through offline and online sources. As far as offline sources are concerned, your contacts and acquaintances could come in handy. You may also want to explore online platforms, including social sites and forums to compose your checklist.DurabilityNot all dehumidifiers are created equal. Some models are fragile and break out quickly. On the flip side, certain models stand to the testing of time and last longer. As a prudent buyer, you may want to buy a durable unit. To do that, check the construction of the unit and find out what materials are used in engineering the product.Warranty No matter how carefully you use the dehumidifying dryer, it may sustain damages and repairs. While it’s okay to expend some money on repairs, you may want to cover yourself against major damages, especially during the initial months of your purchase. This is where the warranty of the product comes in handy. A reputed brand will offer a decent warranty on the model. If a particular brand doesn’t offer any warranty, you’re better off checking other brands.PriceObviously, you wish to buy a good-quality dehumidifying dryer without denting your wallet. You may do so by comparing the price of various brands. Examine the rates, warranty, durability, portability, and quality of each model minutely. Finally, commit to the brand that provides top-class models at reasonable rates.Bottom lineChoosing a good-quality dehumidifying dryer can be a difficult job, thanks to numerous models out there. However, you can get through this pressing chore by sticking to the above advice. If you follow the above tips and depend on a reputed brand, there’s no reason why you won’t get an ideal dehumidifier matching your particular requirements.
Brief Introduction of Gravimetric Dosing Systems In plastic production industries, many processors use two or more materials like virgin material, master batch, additive, filler or something else for a single product, and all the above materials need to be mixed based on certain ratios prior to processing in the molding machines like injection, extrusion, bottle blowing or film blowing machines.Some processors prefer to mix them manually, but it takes much time and labor cost, moreover, people make mistakes, if they mix one of the ingredients by incorrect ratio, then the whole batch in the mixing tank will be ruined, thus factory loss money if the materials are expensive. And if the worker didn't notice the mistake and convey the ruined mixture to the molding machines, they will get defect products and that's another loss. Luckily, now more and more manufacturers are paying increasing attention to this issue, and they are looking for a suitable dosing device for their production.There are many different dosing devices for the plastic production industry, for example, the gravimetric blender also called as gain-in-weight blender, volumetric blender, also called as a masterbatch feeder/doser, loss-in-weight blender, etc. We mainly focus on the gravimetric blender and volumetric blender. And I'd like to explain what they are, how they work, and how to select a suitable blender for your production.What Is a Gravimetric BlenderGravimetric blender also called as gravimetric dosing system or gravimetric batch blender, is an industrial device used in plastic production industry to dose or weigh two or more components and then mix them together prior to processing in the molding machines. It's a high-end technology for the discontinuous blending of materials at the highest level of accuracy. After years of exploring deeply in the industry and upgrading system many times, now Hengju's gravimetric blender can dose up to 8 materials at accuracy ±0.5%. That means, for example, if your recipe is comprised of virgin 80%, masterbatch 18%, filler 2%, and if we set the batch weight as 1000g, then it means that the amount of any ingredient could be off by 5g. That's very close to Europe- made blenders and with much lower cost. Gravimetric Blender’s Advantages:
Obviously, the gravimetric blender boasts of many advantages like the following:*With the highest level of accuracy, for some factories or for some high-end products, the dosing accuracy matters a lot to the quality of the final products.*Fully automatic operation, with one touch on the touch panel, you can sit back and watch the blender working, all you need to do is to check and refill the material silos.*Easy setting for recipes, touch the recipe button on the panel and input the ratios of each material, then name it as Recipe A or whatever you like and save it at last.*Saving labor cost, once having a gravimetric blender, factory owner only need one worker to refill materials and operate the blender for every shift. And you can calculate the ROI (Return on Investment) based on this.It's expensive compared with the normal type of mixer, but you'll find it much worth it once you have one.*Increasing productivity, with a throughput of up to 2000kg per hour, the blender can increase your productivity on a large scale. How Does a Gravimetric Feeder Work?
A gravimetric blender has two or more hoppers arranged above a weigh-pan which is controlled by a very sensitive load cell. And the hoppers will open and close under control of the slide-gate valve. Once the blender is turned on and the recipe is selected, it will dose and mix materials automatically.For instance, if you select recipe A which is comprised of natural resin 90%, regrind 8%, color 2%, and you preset the batch weight as 1000g, then the PLC inside the blender will control the open/close of the hopper valves in order. First natural resin hopper open and resin flows down into the weigh-pan until it reaches 900g, then the valve closes. Secondly, the regrind hopper valve opens and regrind flows down into the weigh-pan until it reaches the amount of 80g, then the valve closes, and the same as the color. Once the batch has been weighed out, the contents of the weigh-pan are dispensed into a mixing chamber where they are blended. The resulting mixture exits the base of the mixing chamber into the processing machine. A look at Hengju’s HGB Series Gravimetric Blender
Over the past years, Hengju’s engineers put numerous time and effort into the upgrading and improvement of our blenders. We got many patents on blender hardware and software, and also we are honored with New High-Tech Enterprise by government. Right from the beginning of our establishment, we’ve always been adhering to the value of “customer-oriented, quality first”, beside the upgrading system software, we also use the best parts we can find around the world, for instance, the most important part-load cell, we buy from Mettler Toledo, which is the best for now. The air cylinder, we buy from Festo, Germany, and PLC & touch screen are from SIMENS, all the best parts guarantee the best performance of the machine.Our blenders can dose up to 8 materials with capacity ranging from 50kg/hr to 2000kg/hr.With dosing accuracy 0.5 %, our blender ranks top 3 among all suppliers from China.Gravimetric Blender Gravimetric Blender for Food Packaging Production 3Herewith a specific datasheet: Now more and more customers are introducing gravimetric blender to their production for LED, auto parts, non-woven bag, film, bottles & containers, all injection parts, cables, and wire, etc. And the areas are expanding. Hereafter are some application cases for your reference:1) 4-components gravimetric dosing system for drinking bottle production:Material: HDPE, regrind, masterbatch.Customer's blowing machine has two layers, and one layer uses mixture material of HDPE, regrind, and master batch, the other uses HDPE virgin. 2) 5-components gravimetric dosing system for 3-layer extruder:The customer has many sets of 3-layer extruders, and they make PP/PS sheet which will be made into disposable food containers. They use five materials, PP, PS, filler, etc., each layer uses the same recipe comprised of 5 materials, but they have up to 20 different recipes. To do the dosing and mixing job manually is a huge job for their workers, now they just need one worker to monitor the five silos and refill the materials. 3) 6-components gravimetric blender on single-layer film blowing machine Customer uses LDPE, LLDPE, additive, filler, and other 2 materials for his film production, and before having this gravimetric blender, he mixed the 6 materials manually which was quite common around his area but slow and less accurate, but right now he loves the blender very much and considers to purchase more for his new plant.To make good gravimetric blender and offer gravimetric blending system to customers, it’s not just about technique, it’s more about the experience and also engineers. For example, when we make blenders or select models, we’ll do that based on material bulk density around 0.65kg/L, that’s the normal B.D. for most resins. But if the resin bulk density is much less than 0.65kg/L, say 0.35kg/L, then the model we selected should be twice bigger as it should be. Moreover, if the bulk density of the materials differs too much, then it’s better to place the blender right above the feeding inlet of the molding machine to avoid the delamination problem which could increase the rejects.Gravimetric Dosing Unit VS Volumetric Dosing UnitA volumetric dosing unit is a dosing device for one main material and one side ingredient, either color master batch or additive. It's also known as synchronous dosing stations, as it can meter all ingredients simultaneously. The mass flow corresponds to the recipe at all times, and the dosing station's control system ensures that the right amount of each ingredient is metered, on the basis of calibrated values and in the ratios required by the recipe. The material is fed directly into the feed throat of the processing machine, if the side ingredient is in a very small ration, then no need to mix the components prior to the processing machine, otherwise, it's necessary to mix the components. Industrial Mixer Volumetric DosersMaster-Batch FeederWith injection molding, the mass flow is constant during the cycle time of the molding machine or to be precise, during the plasticizing time of the IMM, the doser's control system calculates the speed and cycle of the dosing modules on the basis of shot-weight, additive ratios, and calibrated values. The injection molding machine gives a signal to start the dosing cycle. When you select a suitable model, the following aspects should be considered:1) Cycle time or plasticizing time of the injection molding machine2) The ratio of color master batch or additive3) Shot weight of the injection molding machineBut for extruder or blowing machine, you only need to care about two aspects:1) Output capacity required per hour2) The ratio of color master batch or additiveHerewith a specification sheet of our HSD series volumetric doser: Here comes a question, which dosing unit is suitable for you? We may get some ideas after we compare these two dosing devices from the following aspects:1) CostGravimetric blender is much more expensive than volumetric dosers, nearly twice the price.2) OperationGravimetric blender is with an easy setting for recipes and easy cleaning. If you use many recipes or change color quite often, it's better to use a gravimetric blender. But if you use only one or two recipes and you don’t change color quite often, then the volumetric doser is a good choice for you.3) Space occupyingGravimetric blender is quite big while the volumetric blender is quite small, for some factories with narrow space, the volumetric blender seems to be the only option for the dosing job.4) Dosing accuracyGravimetric blender is with highest dosing accuracy of 0.5%, while the volumetric blender’s dosing accuracy can only reach up to 1%.For products which require high accuracy, the gravimetric blender is the best choice. Otherwise, the volumetric blender is acceptable.5) Secret recipes protectionSome factories have secret recipes that the factory owners don't want to disclose to anybody; then it's best to have gravimetric blender into which the factory owners can input the recipes by themselves and name them as recipe 1, recipe 2, ...without showing the details of your formulas. 6) Dosing output capacityThe gravimetric blender can dose up to 2000kg per hour, while the maximum dosing capacity for volumetric doser is only 50kg per hour.7) Lead timeThe lead time of master batch feeder is pretty quick, normally 2-3 weeks, some models are even quicker because we keep stock for some hot-selling models.While the gravimetric blender takes much longer time to make, usually 20-35 working days, as most of them are customized and the testing also needs 2-3 days to make sure the dosing accuracy can meet customer’s demand.How to Select a Suitable Model of Gravimetric BlenderSUBTITLEBefore you choose a gravimetric blender, please take all the following elements into your consideration:1) What dosing accuracy do you need?2) How much dosing capacity is required?3) How many materials need to be dosed and the ratio of each component?4) How many kinds of recipes do you use in your production? 5) Where would you like to place the blender, either on your molding machine or on the ground?Operation of Gravimetric BlenderIt’s very important to read through the manual book before you start the blender. And hereafter is some basic instructions for operation.The gravimetric blender is controlled by PLC, and all settings can be edit through the touch screen. 7.1 Power onPlease check the following items before you switch on the blender:* The machine is wired correctly.*the compressed air is properly connected, no air leakage.*All material hoppers are filled with correct materials.And the following requirements must be followed:1) Do not operate the touch screen with sharp objects instead of hands and any violent bump is also prevented.2) The touch screen may generate much static electricity in dry air. So before you touch it, use earthing metal to release the static electricity.3) Use economic alcohol or benzine to scrub the touch screen. Other solvents may cause the touch screen to fade.4) don't open it without permission or take out any circuit board for that may cause damage to the blender.For more operation instructions, please download the blender manual on our websitehttps://www.plasticmach.com.Maintenance Instructions
1.1 Safety1.1.1 qualifications of personnelThe maintenance and repair work should only be carried out by qualified and authorized technicians.If by insufficiently qualified personnel, the danger of injury or incalculable risks may happen.1.2 Before starting workBefore starting maintenance, the following instructions must be followed.1.2.1 power of the blender/disconnect from the compressed air supplyDanger of injury: mixing paddle inside the mixing chamber may bring body part injury.1.3 InspectionChecking emergency stop function and testing safety interlock switch.For more maintenance tips, please download the blender manual on our website.
Hengju is a professional manufacturer which is dedicated to research and manufacture auxiliary equipment for plastic processing industry. Meanwhile it’s a leading supplier of automation solutions for plastic moulding machines.