As many of us in the machine industry are aware, Plastic Injection Molding is just as relevant and important as any other machining process. There are many things to consider when considering purchasing plastic injection molding equipment, such as: Shot Size, Tie Bar Spacing, Ejector Stroke, Platen Size, and Tonnage.
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Shot Size
Shot size is best defined as the maximum amount of plastic that the injection molding machinery is capable of injecting into the molding cavity during one molding cycle. The amount is rated in ounces of &#;general purpose polystyrene&#; (GPPS) for U.S. machines, and cm3 for European and Asian machines.
When searching for a machine, it's always a best practice to look for a machine that is capable of producing 30-40% greater shot sizes than what your parts require.
Tonnage
In this case, I mean &#;clamp tonnage or clamping pressure.&#; This could be considered the same concept as when you're examining press brakes. With press brakes, tonnage capabilities are measured by how many tons of downforce the machine is capable of directing towards a workpiece. However, with plastic injection molding machines, tonnage is measured by how many tons with which the machine is capable of pressing together the platens, which hold the mold cavity and form the plastic that is injected into said cavity to produce the desired part.
Platen Size
The platen is the "table" or tool that holds the mold cavity. Spaced apart, the mold is inserted and clamped securely to the platens. Once the two platens come together and are held under the pressure of tonnage, the plastic is heated, injected under pressure, and then allowed to cool through a molding cooling cycle. Here, the plastic takes on its hardened, final shape while continuing to be kept in place with many tons of pressure to retain the desired shape.
Tie Bar Spacing
Tie Bar Spacing is defined as the space between the horizontal tie-bars on an injection molding machine. Basically, this measurement, along with the platen max spacing, determines the maximum size of molds that can be placed in the molding machine.
Ejector Stroke
Simply put, Ejector Stroke is the action of the machine pushing out (ejecting) the final workpiece from the platens using ejector pins. The ejector in the molding machine pushes against an ejector plate on the mold, Ejector "Pins" or rods are attached to this plate and perform a pushing operation on the molded part after the plastic has hardened and the mold has opened.
Once the action of molding the workpiece is completed, the mold opens and then the ejector pins slowly extend outwards, pushing (or ejecting) the finished part out of the mold cavity. Pin movement is timed with the mold opening&#;because pins that move too quickly could impact the plastic workpiece and damage the final product and pins that move too slowly may not fully eject the molded part.
At Southern Fabricating Machinery Sales, Inc. we have many Plastic Injection Molding Systems available and can assist you in selecting the right system for your part or application. Also, with equipment appraisers on staff we can help you evaluate and sell any excess plastics machinery you may have. Please call me directly at 813-444- X113 to discuss your machinery needs.
With competitive price and timely delivery, Yihua Mould sincerely hope to be your supplier and partner.
Injection molds are meant to make manufacturing easier and increase productivity. Of course, that&#;s only when the right one for each project is purchased. The wrong fit or design can result not only months of lost work and delayed production, but damage to the equipment itself. With this in mind, here are 6 tips you should consider when purchasing injection molds:
1. Timing Depends on the Project
For some projects, a general injection mold will do, and you will not need to plan too far ahead during the design process. But for more creative projects that depend on precision, you will need to start planning the mold design early on in product development. If it is a complete custom design or a rarely-seen one, you will need to allow for more time for both design and approval.
2. Collaboration is Key
The most successful and creative projects are when the part designer, mold fabricator and injection molder are able to communicate efficiently and collaborate. After all, you don&#;t want to go ahead and approve a mold design only to find out that it cannot be made to specifications or that it won&#;t actually function as the injection molder needs it to. Though taking the time to communicate every step of the process may feel like it&#;s taking extra time, it can save you a lot of time (and money) later on.
3. Anticipate Issues
Even the best planning can sometimes end up in errors, but you don&#;t need to let it take you completely off guard. Plan (set aside extra time and funds) for potential re-cuts, for example. You may need the mold to be adjusted a few times before the plastic portions are brought into the exact range they need to be in. You may even need to resize the design in general at some point.
4. Prepare Your Production Floor Team
Even the most efficient production / shop floor teams will appreciate advance notice for when any new injection molds are going to arrive. They will need time to install the mold where it needs to go and make sure it is connected properly. They will need to check a number of things like lift straps, hot runner and coolant controllers, heater plugs and cables, water manifold ports, fittings, hoses, bolts, and more. This cannot properly be done at the last minute.
5. Standardize Designs that Work for You
Many people wind up needing the same injection mold later on. You can maximize both cost savings and efficiency by making the design standardized. Additionally, standardizing different features like clamp slots and connection locations on different machinery can also save you both time and money (especially if you need to relocate the injection mold later on).
6. Cost Savings May Not Always Be Worth It
Even more basic injection molds require a high degree of craftsmanship and precision. While you may be able to trim costs on many projects by going with cheaper options, it is crucial to really evaluate whether or not you can afford small errors or misalignments on your current one. Even small savings can end up costing you big time down the road if it means having to scrap a ton of used up material or tools and having to spend more on labor costs.
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