If you’re new to the world of 射出成形 in the production industry, the term ‘sprue bushing’ may confuse you. Simply put, it’s a component used in 射出成形機 that plays a vital role in production.
But there’s more to exploring how sprue bushing works and what should be considered to ensure the best production returns while using sprue bushing. Are you curious about these details? Then let’s go ahead and learn all about sprue bushing, shall we?
What is a Sprue Bushing?
Sprue Bushings are an internal sprue component. They’re made of hardened steel and aid in accepting an extrusion nozzle. Sprue bushings offer the necessary opening for the molten plastic to be transferred into its respective mold cavity. These components contribute to a more rigid sprue and shorter cooling periods. Sprues must be sturdy because pickers and other industrial robots pick up molded pieces when ready for removal.
Sprue bushings are shaped and sized similarly to bolts. Because they are intended to aid in the attachment of the sprue, they are secured with two bolts to ensure that the sprue does not separate during periods of high injection pressure. Sprue bushings are made of hot working steel SKD61 and have heat and wear resistance qualities.
Sprue bushings are often constructed of hardened steel or a copper-based alloy. In some circumstances, they may be lined with carbide to help with wear and corrosion resistance and faster heat transmission rates. Carbide-lined sprue bushings can be extremely useful when working with abrasive resins.
Their primary role is to prevent plastic material leakage during the injection mold process. To accomplish this, we must size the sprue bushings properly to work with the feed throat. Typically, the feed throat is built as a chamfer R. The mold sprue’s spherical radius, or SR, must be one to two millimeters bigger than the injection nozzle’s spherical radius.
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どのように機能するのか？
When the process of injection molding first begins, the plastic material that will be used is pumped into the sprue bushing. From there, it moves through the runners, which are channels that transport the molten plastic to various spots within the mold. Once it reaches the end of those channels, the mold is complete. The runners ultimately lead to the gates, which are small apertures that route the plastic material into the mold cavities where the final product is made. The gates are located at the end of the runner system.
The sprue bushing is essential, as it helps ensure that the mold cavities are filled effectively and uniformly. It helps manage the flow rate and pressure of the molten plastic, preventing difficulties like air pockets and partial filling by ensuring that the proper pressure is maintained. In addition, sprue bushings have the potential to be developed with other characteristics, such as temperature control, that are intended to assist in the upkeep of ideal processing conditions.
During the mold opening process, the sprue and runner system and the sprue bushing are normally separated from the final product and removed before the mold is opened. This occurs after the plastic material has cooled and set inside the mold. Because of this, the product can be extracted from the mold in a pristine state.
In conclusion, a sprue bushing is a component used in injection molding and serves as a conduit for the liquid plastic to enter the mold cavity. This component is also known as a sprue bushing. It is an important part of the injection molding process and helps guarantee that the mold is properly filled with the material.
The Types of Sprue Bushing:
There are two common types of sprue bushing used in injection molding. These types include:
● Cold Sprue Bushing:
A cold sprue bushing is not heated and produces a sprue that must be removed during a secondary operation. This bushing type is inserted into a mold and aids in forming a channel between the molding machine nozzle and the mold chamber. The spherical radius and the O-shaped hole opening are the two most essential nozzle dimensions of the cold sprue bushing.
● Hot Sprue Bushing:
Like a cold sprue bushing, a hot sprue bushing is placed into the mold. However, these sprue bushings offer a hot path between the mold chamber and the mold nozzle. Furthermore, a heating element housed within the bushing assists in keeping the melted resin or plastic hot as it travels through it.
Design and Operation:
Sprue bushings normally have a spherical radius of .50″ or.75″ flat-type bushings with a flat surface rather than a nozzle radius are also available. Buyers must also specify several other dimensions, including:
● The Length of the Shank:
Start measuring the shank length from the sprue bushing head’s underside to the bushing’s end. Like the overall length measurement, this dimension does not include the nozzle.
● The Diameter of the Tip Hold:
The diameter of the entrance hole on the nozzle seat is described by the tip hold diameter, also known as the “O” diameter. This measurement is also known as the ‘gate diameter’ or potentially the melt passage diameter.’ This measurement, by whatever name it is known, is effectively the hold that connects the nozzle tip to where the material enters the sprue bushing.
● The Total Length:
When measuring the overall length of the sprue bushing, measure it from the beginning to the end, excluding the nozzle measurement.
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Common Issues That Occur in Sprue Bushing:
Knowing what could go wrong with sprue bushings and the kinds of problems they could create is a crucial component of comprehending the function of these components.
It is essential to know how to identify and fix sprue bushing issues on the production floor to avoid processing problems and improve cycle times, two key goals for any production process. Because of this, it is important to know how to detect and resolve sprue bushing issues.
Surface Finish Issues:
Be on the lookout for rust, scratches, pitting, and other machine markings when inspecting your sprue bushing. If any of these irregularities are present in the bore of the sprue bushing, the sprue may become obstructed in the bushing. Although pitting brought on by corrosive or abrasive materials could be to blame, most of these situations are brought on by either human mistakes or improper machine maintenance.
When someone tries to remove a sprue lodged within a bushing, this common situation leads to internal scratches and rolled edges.
The conventional approach, which consists of using a brass rod to force the sprue out from the nozzle seat side, can potentially present a problem because it is difficult to manipulate the rod in that position.
In this instance, the issue can be remedied by heating a brass screw with propane or a MAP gas torch and then putting it into the sprue through the mold’s parting line. This should bring about the desired result.
A pair of brass pliers can pry out the sprue once it has cooled down to the appropriate temperature. Because sprues can be quite pricey, it is recommended that you avoid using instruments made of hardened steel, such as screws, screwdrivers, various kinds of pliers, and gate cutters.
Shrinking Issues:
成型されたスプルーは、わずかに収縮させることによって、ブッシングのテーパー・ロックの一部を減らす必要がある。スプルーがどのような材料で製造され、どの程度しっかりと詰め込まれているかは、スプルーの収縮具合に直接影響します。
浅い成形材料を使用しない場合 縮み そのため、適切な収縮量を達成することは、 問題になりません。フィラーを密に含んだ非晶質材料と液晶ポリマー（LCP）は、このカテゴリーに入る2種類の材料です。
一方、収縮が問題になるのは、成形によってスプルーに材料が詰め込まれすぎて、適切な収縮ができなくなった場合である。ゲートが凍結した後、充填圧力がかなりの時間残っている場合、これは頻繁に発生するものである。
さらに、スプルー回収を急いでいる間にスプルーオリフィスがまだ液体である場合、または着色剤を組み込むために高い背圧が使用される場合、スプルーはオーバーパックになる可能性があります。これに対して、スプルーが回収されている場合は、スプルーがオーバーパックになる可能性があります。
徐々に収縮する可能性のあるもう一つの状況は、サイクル期間がかなり早いにもかかわらず、金型のブッシュが十分に冷却されない場合である。
ノズルシートの問題
各工程の開始時には、スプルーブッシングノズルの目視検査が不可欠である。この検査では、作業者は、エッジの圧延、欠け、亀裂、バリ、へこみ、プラスチック、残留物の蓄積など、故障の可能性が高い兆候を探す必要があります。
各製造工程の後、品質保証のためにノズルシートも検査する必要がある。そうすれば、金型がまだ使えるうちに部品を修理しなければならないかどうかを判断しやすくなる。
ノズルシートの修理について、最も頻繁に利用される方法は、リフェイスツールと超硬カッターの2つである。超硬カッターを初めて使用する前に、刃先の半径を確認する必要がある。
カッターは常に適切な公差で作られているわけではありませんが、スプルーブッシングのノズルシート半径の寸法が正確であることを確認することは、問題を回避するために不可欠です。スプルーブッシングの座面を加工する場合、ロータリー放電加工機を使用すると、溶融プラスチックの流出やキャリッジのブローバックのリスクを低減できます。
スティップル仕上げを採用するのも、将来的なダメージを素早く発見し、補修するための良い方法だ。
結論
スプルーブッシュは、射出ホースから金型キャビティへの溶融材料の流れを円滑にすることで、製造に欠かせないものです。スプルーブッシュは、大きな機械の一部品に過ぎませんが、注意深い監視と適切な整備が必要です。
したがって、製造工程を成功させるためには、その適切な性能に寄与する数多くの部品や側面を十分に認識することが極めて重要である。
について、さらに質問がある。 スプルーブッシュ?私たちの専門家にお気軽にお尋ねください。 プロトツール・ドットコム.
