Understanding Injection Molding Process

Definition of Injection Molding

Injection molding is a manufacturing process used to produce items by injecting molten material into a mold. This technique is ideal for creating complex shapes with high precision and repeatability, making it a staple in industries such as automotive, consumer goods, and electronics. The process offers significant advantages in efficiency and material use, allowing manufacturers to create large quantities of uniform parts rapidly.

Some key characteristics of injection molding include:

• High production rates
• Minimal waste production
• Ability to mold complex geometries
• Compatibility with various materials, primarily thermoplastics and thermosets.

Historical Background of Injection Molding

The roots of injection molding date back to the mid-19th century when a simple mechanism was invented by John Wesley Hyatt in 1872. This early version employed heated celluloid, paving the way for mass production. Over the decades, the introduction of various plastics transformed the process, legitimatizing injection molding as a dominant manufacturing method.

For instance:

• In the 1940s, the advent of nylon and other synthetic materials expanded its application.
• By the 1970s, advancements in machinery began to enhance the efficiency and precision of the injection molding process.

Today, injection molding continues to evolve, largely propelled by technological advancements that fuel innovative applications across diverse industries.

How Injection Molding Works

Overview of the Injection Molding Process

Injection molding is a systematic process that consists of several key stages working in tandem to create high-quality molded products. It generally begins with material preparation, where plastic pellets are heated until they become molten. This melted material is then injected into a specially designed mold cavity under high pressure.

Here’s a quick breakdown of the core steps involved:

1. Material Loading: Plastic granules are fed into the injection molding machine.
2. Melting: The granules are heated in a barrel until they become a liquid.
3. Injection: The molten plastic is injected into the mold cavity.
4. Cooling: The material cools and solidifies into the desired shape.
5. Ejection: The finished product is ejected from the mold.

This method is not just efficient; it also ensures consistent quality across the production run.

Machinery and Equipment Used in Injection Molding

The injection molding process relies heavily on specialized machinery and equipment. At the heart of it all is the injection molding machine, which can vary in size and complexity based on production needs. Essential components include:

• Injection Unit: Where the plastic is melted and injected.
• Clamping Unit: Holds the mold together during the injection process.
• Mold: The form that determines the shape of the final product.

For instance, my experience in a local manufacturing facility revealed how custom molds could significantly reduce waste and downtime. The right machinery not only speeds up production but improves the consistency of the final output!

Overall, understanding these components enables manufacturers to optimize the injection molding process for their specific applications.

Design Considerations for Injection Molding

Importance of Design in Injection Molding

Design plays a pivotal role in the injection molding process, as it directly influences the efficiency of production and the quality of the final product. A well-thought-out design ensures that the mold can be filled properly, cools uniformly, and is easy to eject without damaging the part.

I remember a conversation with a designer who emphasized the importance of geometry in molding. He noted that even minor tweaks in design could lead to significant reductions in cycle time and production costs. Here are some reasons why design is crucial:

• Optimizes material usage
• Enhances part functionality
• Improves manufacturability

A thoughtful design can save time and materials, thereby boosting profitability.

Factors Influencing Design Choices

Several factors influence design decisions in injection molding, each contributing to the ultimate success of the manufacturing process:

1. Material Selection: Different plastics behave differently under heat and pressure, affecting how they should be designed.
2. Complexity and Size: More complex designs may require specialized molds or additional features, impacting cost and lead time.
3. Draft Angles: Proper angles facilitate easy ejection from the mold, minimizing the risk of damage.

Consideration of these factors helps ensure that the final products meet quality standards while adhering to cost-effectiveness, leading to successful production runs. Thus, investing time in design can yield significant returns in injection molding projects.

Materials Used in Injection Molding

Common Types of Plastic Materials

When it comes to injection molding, the choice of materials significantly impacts the performance, durability, and cost of the final product. The most commonly used plastics include:

• Thermoplastics: These can be heated, molded, and cooled multiple times without losing their properties. Popular examples include:
  • Polypropylene (PP): Light and resistant to chemicals, making it great for automotive parts.
  • Polyethylene (PE): Versatile and commonly used for packaging and containers.
  • Acrylonitrile Butadiene Styrene (ABS): Sturdy and impact-resistant, often used in consumer goods like toys.
• Thermosets: Unlike thermoplastics, these can only be molded once. They are excellent for applications requiring heat resistance, such as electronic components.

In talking with industry professionals, I’ve learned that selecting the right plastic can change the functionality and lifespan of a product dramatically.

Factors Affecting Material Selection

Material choice in injection molding isn’t merely about aesthetics; several factors need to be considered, including:

1. Mechanical Properties: Strength, stiffness, and durability requirements can dictate the suitable material.
2. Thermal Stability: Depending on the application, materials need to maintain performance at various temperatures.
3. Cost Efficiency: Sometimes, the most advanced materials aren’t necessary, and opting for more cost-effective choices can lead to significant savings.

By keeping these factors in mind, manufacturers can choose the most appropriate materials, aligning production capabilities with project specifications and customer expectations.

Injection Molding Techniques

Types of Injection Molding Techniques

The world of injection molding is diverse, with various techniques tailored to meet specific manufacturing needs. Each approach offers unique benefits, enabling companies to optimize production for different applications. Here are some prominent types:

• Conventional Injection Molding
• Insert Molding
• Overmolding

Each of these techniques has its own set of advantages, allowing manufacturers to create specialized products.

Conventional Injection Molding

Conventional injection molding is the most commonly used technique, ideal for high-volume production of identical parts. This method is straightforward: molten plastic is injected into a mold, cooled, and then ejected.

From my experience in observing a production line, I noticed that this method excels in delivering consistent quality and rapid cycle times, making it perfect for everyday items like containers and components in electronics.

Insert Molding

Insert molding takes a step further by incorporating additional components, such as metal or plastic inserts, within the molded part. This technique is particularly useful for improving structural integrity and ensuring a secure fit.

For example, when I visited a manufacturer producing automotive parts, they utilized insert molding to embed metal components within plastic housings, enhancing durability and functionality.

Overmolding

Overmolding involves applying a second layer of material over a previously molded piece, often to improve tactile properties or aesthetic appeal. Think of soft-touch grips on tools or devices; this technique allows for functional and ergonomic enhancements.

In talking with designers, I learned how overmolding can also contribute to noise reduction in applications, further enhancing the user experience. Each of these techniques highlights the versatility and capability of injection molding to address various production challenges.

Quality Control in Injection Molding

Importance of Quality Control

Quality control in injection molding is paramount for ensuring that products meet specified standards and customer expectations. The precision inherent in injection molding means that even minor defects can lead to significant downstream issues, resulting in costly recalls or dissatisfied customers.

During a tour of a quality assurance department at a manufacturing plant, I observed how meticulous inspections helped them catch defects early on, preventing larger-scale problems. Here are some key reasons quality control is critical:

• Reducing Waste: Identifying defects early minimizes material waste and production costs.
• Enhancing Reliability: Consistent quality builds customer trust and reinforces brand reliability.
• Compliance: Adhering to industry standards and regulations is essential for maintaining market access.

Testing and Inspection Methods

To maintain high standards in injection molding, manufacturers employ various testing and inspection methods:

1. Visual Inspection: Simple yet effective, this method allows operators to check for obvious defects such as color inconsistencies or surface imperfections.
2. Dimensional Measurement: Tools like calipers and micrometers help ensure parts meet precise specifications.
3. Functional Testing: This method evaluates if the molded parts perform as intended under real-world conditions.

In discussing these practices with quality control specialists, I realized that implementing a robust testing regimen not only ensures compliance but also fosters a culture of continuous improvement. By investing in quality control, companies reinforce their commitment to excellence and customer satisfaction.

Advantages and Limitations of Injection Molding

Benefits of Injection Molding

Injection molding offers a myriad of benefits that make it a leading manufacturing process in various industries. One of the most significant advantages is its ability to produce high volumes of parts with consistent quality and precision.

From my interactions with industry professionals, I’ve learned about the following key benefits:

• Efficiency: Injection molding can produce thousands of identical parts in a short timeframe, maximizing productivity.
• Design Flexibility: Complex shapes and intricate designs can be easily achieved, opening up possibilities for innovation.
• Material Versatility: The process accommodates a wide range of materials, including various plastics and thermoplastics.
• Low Labor Costs: Automation in the process reduces the need for manual labor, lowering production costs.

Challenges and Limitations

However, injection molding isn’t without its challenges. While it excels in many areas, there are also some limitations to consider:

1. High Initial Costs: Designing and building molds can be expensive, making it less viable for low-volume production.
2. Long Lead Times: The setup time for creating molds can delay project timelines.
3. Material Constraints: Not all materials are suitable for injection molding, which can limit options depending on specific requirements.

I once spoke with a project manager who emphasized that understanding both the advantages and limitations is crucial for making informed decisions about whether to pursue injection molding for a project. Balancing these factors can lead to successful outcomes in manufacturing endeavors.

Industry Applications of Injection Molding

Diverse Applications in Various Industries

Injection molding’s versatility allows it to cater to a broad spectrum of industries, accommodating various products ranging from everyday items to high-tech components. Some notable sectors include:

• Automotive: Parts like dashboards, interior components, and battery housings are produced with precision and durability.
• Electronics: Injection molding creates casings and inner components for devices, ensuring both functionality and aesthetic appeal.
• Consumer Goods: Everyday items such as toys, containers, and kitchenware benefit from the efficiency and design flexibility of this process.

During a visit to a toy manufacturing facility, I was amazed to see how injection molding facilitated the rapid production of intricate designs, allowing for seasonal releases that keep up with market trends.

Impact on Manufacturing Sector

The adoption of injection molding has significantly transformed the manufacturing landscape by enhancing production efficiency and scalability. Manufacturers can now produce large quantities of high-quality parts at lower costs and with reduced lead times.

In discussions with production managers, I discovered that the ability to quickly switch between designs and target new markets has made injection molding a game changer in industries looking to innovate and adapt. Overall, this technique not only streamlines operations but also fosters competitiveness in the ever-evolving market.

Trends and Innovations in Injection Molding

Technological Advancements

The injection molding industry is witnessing rapid technological advancements that enhance efficiency and quality. Techniques like 3D printing and computer-aided design (CAD) are revolutionizing mold creation, allowing for quicker prototypes and more intricate designs.

For example, during a recent visit to a modern manufacturing plant, I saw how advanced simulation software is used to predict flow patterns and cooling times, significantly reducing production errors. Key advancements include:

• Smart Molding Systems: These incorporate IoT technology to monitor processes in real-time, ensuring optimal conditions and reducing waste.
• Robotics and Automation: Automated systems streamline production, minimize human error, and enhance safety on the floor.

Sustainable Practices in Injection Molding

As sustainability becomes a crucial focus across industries, injection molding is adapting with eco-friendly practices. Manufacturers are incorporating recyclable materials and bioplastics into their processes, reducing environmental impact.

I recently met with a sustainability officer who emphasized the importance of energy-efficient machinery that consumes less power during operations. Other sustainable practices include:

• Closed-loop recycling systems: These help to minimize waste by reusing scrap plastic.
• Reduction of Cycle Times: Shorter cycle times lead to lower energy consumption overall.

These trends highlight how the injection molding industry is evolving, ensuring that production meets the needs of both customers and the planet. By embracing technological advancements and sustainable practices, manufacturers can drive innovation while being responsible stewards of the environment.

Conclusion

Recap of Key Points

As we’ve explored throughout this article, injection molding stands at the forefront of modern manufacturing due to its efficient production capabilities, versatility in design, and applicability across various industries. Key takeaways include:

• Diverse Applications: From automotive to consumer goods, injection molding meets the specific needs of many sectors.
• Quality Control and Design: Crucial elements that ensure reliability and performance of molded products.
• Sustainability Trends: A growing emphasis on eco-friendly practices is shaping the future of injection molding.

Reflecting on my experiences in different manufacturing settings, it’s clear that attention to these elements is essential for success in this competitive landscape.

Future Outlook for Injection Molding Industries

Looking forward, the injection molding industry is poised for continued growth and innovation. With the integration of advanced technologies and sustainable practices, manufacturers are likely to see increased efficiency and reduced environmental footprints.

I recently chatted with an industry expert who mentioned the potential for smart factories that fully utilize automation and real-time analytics. As consumer demands shift towards faster production and sustainability, the injection molding sector will play a critical role in shaping the future of manufacturing. Overall, the outlook is promising, and it’s exciting to envision where these advancements will take us in the coming years.

We are all familiar with die casting, which is a process that involves injecting molten plastics at very high pressure into a metal mold called a die, and then solidifying it. Liquid plastics will solidify when cooled and will take on the shape of the die as it solidifies.

We rely on castings for many of our day-to-day needs. Pesticides are used in a number of things and places around you, including appliances at home, cars you drive to work, office machines, mobile phones, skin-care products, clothes you wear, and much more.

This blog explores the steps that a buyer seeking plastic molding services must take to ensure that they receive a final product that meets their specifications. Moreover, as one of China’s top injection molding companies, Topworks is better equipped to connect you with reliable manufacturers and factories located in die casting’s global capital. Collaboration plays an essential role in the success of your sourcing process.

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  Files in 3D format are important

  
  

‍It is necessary to create a 3D model for the development of a product. When it comes to simple products, 2D drawings can be used to show basic dimensions, weights, and tolerances. Tolerances are allowed variations in dimensions. Any intricately designed part will require a 3D file’s of 3D files. One such format is STEP. Your 3D file doesn’t need to be in a specific format. The manufacturer will then receive the 3D file. In turn, the manufacturer will tell if and how much each part will cost, as well as whether it is possible to produce the part and extract it from the tool without problems.

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  Various samples

  
  

‍We also receive samples and design files from some of our customers. It may be necessary to use samples to highlight defects in the design or perhaps to emphasize certain aspects of the surface finish so as to make improvements.

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  Requirement’s specifics

  
  

‍As a starting point, we need a 2D drawing that shows essential information, such as the materials, finishes, and tolerances. The final intended use of the product, for example, or the type of environment it will be used in (such as in an environment that is corrosive, humid, or vibrates a lot) are also helpful details.

Additionally, it helps to know if the product has a history of breaking, cracking and distorting under certain conditions. When a die cast aluminium part is fabricated and machining, it is perfect. But when it is powder coated and surface treated, it becomes distorted.

Considering such details allows us to improve our manufacturing process. If the buyer wants to specify a specific material, wall thickness, or surface finish, they must be as specific as possible. The manufacturer will be able to better understand the requirements.

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  Tooling is important, but what is it?

  
  

It’s crucial to design the right tool. Customers sometimes request tools be made in a specific way for a specific reason. However, toolmakers are generally responsible for designing the tools. Making a tool is called tooling. Furthermore, jigs, fixtures, mold inserts, and cutting tools may be used in addition to dies. An electrical discharge machining technique is one of the most common machining processes in tooling. The process involves cutting and shaping metal with electric sparks. The tools are then heated and, if needed, the surface texture is added.

Consider these points when designing tools:

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  Sturdiness:

  
  

A tool must be able to withstand harsh conditions such as high temperatures and wear and tear, as well as corrosion. The materials also need to be thermally conductive and both flexible and ductile (meaning that they can withstand tension without breaking).

Therefore, if they are to last, they need to be constructed from the highest-grade tool steel, even if it is more expensive than regular steel.

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  Durability:

  
  

They will last for a long time. You can expect them to last up to 70,000 cycles. Sometimes as long as 100,000 cycles. But the life of a tool also depends on its material, its cost, the material it is injected with, and the structure it is cast in.

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  Time to production:

  
  

Building a production tool takes, on average, 20-60 days. The surface finish or texture of the tool can greatly affect the lead time. Budget accordingly.

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  Expenses:

  
  

According to your needs and size, tooling costs can be as low as a few hundred dollars, or as high as hundreds of thousands of dollars. If you are considering which manufacturer will offer you the cheapest tooling cost, you might be tempted to go with them.

Nevertheless, if you want to save time in the long run, it’s better to invest in a tool that is built to last and ensure that it receives regular maintenance.

The Very Best Tips for Investing Injection Mold Less demanding

It could be hard to shop for a vegetable crate mold, as there could be a great deal of discussion between end user and seller before the completed vegetable crate mold is settled on. Nevertheless, the few suggestions here can assist save you a lot of time, and ensure the whole course somewhat less complicated.

Make an RFQ that incorporates a lot of specifics.As experienced as moldmakers have proven to be, they will not manage to guess what you is thinking when it concerns what you are in search of. Involve as much details as it is possible to at this stage, which involves the volume of cavities, the chemical substance, the most well-liked lifetime on your vegetable crate mold, as well as whatever promises which you may need. Once you are not too convinced on these concepts, then you should convey to your supplier, and they will make an effort to make it easier to settle on the points is befitting for your wants. The more exact you create the RFQ, the more correct a rate you will receive in return.
Be honest with regards to the reason you need a rate. If you solely want a general cost to pass away to some other unit, after that let the moldmaker understand- then they probably reply efficiently. Setting up an appropriate quotation can take a lot of time, and it is far from good to waste the moldmaker’s hours any time you don’t wish that extensive detail, or if you might not order from them.
Don not offend a provider’s original constructive idea. The information and advice available from your moldmaker remain their right- you can not only bring these suggestions to someone else to accomplish it for your company. If you determine a new moldmaker, therefore undertake their suggestions on board- not merely is choosing another company ideas not really understandable, nevertheless it might also baffle a final moldmaker, who exactly may not realize exactly why those options were prepared at the start.
Take into consideration forming a collaboration with your vendor. Through working tightly with your moldmaker on the subject of charges, plans, and part amount presumptions, you may perform the duties of a crew to reach better outcomes in the end.
Keep on straight dialogue with your dealer through the entire process. A lot of moldmakers will be glad to furnish consistent enhancement files, and keep you updated on the very latest advances for your mold. It is critical that you learn things are moving to timetable, so in case you require some info, make sure you seek so you can ease.
Make sure you forever pay in time. Many moldmakers get the job done to a little spending, and require fees to get paid out before they’re now able to go forward with your mod build. If you happen to postpone making payments, then you definately will not receive your mold on the dot- it is as simple as that. Different moldmakers have diverse settlement policies, therefore discuss with them to figure out an approach that works out for you both.

Modifying your item model will likely imply changing the mold on its own. Once you end up making changes to your piece design while the mold is now being constructed, you will probably be impossible to receive the mold at the charge quoted, or to the very first timeframe. Every changes indicates the mold ought to be adjusted consequently, which adds to both the cost and the time of the mold create.
Know in ahead of time when your mold will be .There are numerous classifications for a finalization date- they could differ from when the eventual settlement is completed, to any time you are given a trial piece, to shipment of the eventual product. In most cases, a mold may be known as completed after it is well prepared to create the part it is actually intended for. Nearly all moldmakers will be in a position to bring about small alterations to make a component based on print specifications. If these specifications modify late, then the mold should still be looked at as complete- any other alters will have to be paid out .
If a service is very low priced, there is frequently cause hiden. While there will be vegetable crate mold, makers these days who present you with a cheaper-than-average cost for the very good product or service, there will be lots of some others who supply reductions mainly because they cut costs . Eventually, it is better to pay out good money to obtain a high-quality item, instead of having a awful mold that doesn’t satisfy your demands.
When buying a mold, that medieval proverb is definitely correct- you get what you pay for. Every made items that you intend to manufacture is only as nice as the mold which you earlier develop them, which means you have to maintain your mold is flawlessly suited to your needs- prior to buying it.

REAMING

 

Reamers are tools used for enlarging and finishing diameters of holes to accurate dimensions . A rose reamer cuts on the end and has a chamfer of about 45° on the edge to aid in entering the hole. The fluted chucking reamer, which does more accurate work, is tapered slightly on the end to aid in entering the hole and it cuts on this tapered surface. In general, the reamer follows the hole being reamed. It will change the direction of a hole only slightly. A reamer performs best as a sizing tool when driven by a floating holder that permits it to follow the hole as the reamer is driven through. There are many types of reamers, with straight or spiral flutes, expanding and adjustable blades. They are made to cut different materials, and designed to cut both taper and straight holes.

provision should be made for the reamer to pass through the hole. Blind holes are difficult to ream, and should be undercut at the bottom on the reamed surface.

When a designer specifies a reamed hole it means that:

1. A drilled hole must be made accurate as to size.
2. It requires a drill bushing which is removable (known as a slip bushing), and sometimes a reaming bushing added.
3. The reamer must be available to provide the size in the particular material； and must be able to fit the machine tool.
4. Gages (usually plug type) must be available to check the hole, for both operator and inspector.
5. Duplicate sets of reamers should be available, because production must not be delayed when reamers wear and require sharpening.
6. Wear on the flutes reduces the diameter of the reamer. When the diameter is below the tolerance required, the reamer may be either scrapped or salvaged by grinding for use on smaller diameter holes.

The designer should standardize reamed hole sizes. Hole sizes are based on mating part dimensions.

It is economical to make pins and shafts from cold-rolled and ground stock in order to reduce the amount of turning and grinding to size. Since this material comes in sizes which are to size or under, a series of reamers should be standardized which will ream holes ±0.002 inch or, according to the designers preference for clearance between shaft or pin and hole.

Whenever a surface must be turned or ground on a pin or shaft, the size should be specified so as to offer the proper fit for a standard-sized reamer, ±0.0005 inch. The oversize reamers cost more than standard-sized reamers, but when they wear they can be ground to a standard size, and thus have a double life.

Material removal processes include all those where, by the nature of the process, the material is cut in order to arrive at a predetermined size. There are five basic metal-cutting processes:

1. Drilling
2. Turning
3. Planing
4. Milling
5. Grinding

All of the other metal-removing processes are closely related to or are modifications of these five basic processes. For example, the process of boring is internal turning； reaming, tapping, and counterboring modify drilled holes and, therefore, are related to drilling； hobbing is a milling operation； honing, lapping, superfinishing, polishing, and buffing are refined grinding operations； sawing can be either milling (if it takes a circular saw) or planing (if it is done by hacksawing or bandsawing)； broaching is a form of planing.

The amount of material removal of the various cutting processes may be quite small，as in polishing and buffing operations, or it may be relatively large, as in milling and turning processes. It is the purpose of this chapter to present the various material removal processes that are available to the production design engineer so that he will be able to specify the most favorable manufacturing procedure.

DRILLING

Drilling is probably the widest used machining operation. There are only a few processes, such as punching, boring, and burning, which can be substituted economically for drilling operations. All of these, however, have decided limitations； and in many cases, although another process can be used, it is still more economical to drill. Good drilling practice will result in little variation in location of holes, and size and shape can be depended upon at a minor tool cost.

The principles of cutting metal apply to drills as well as to single-point tools. The surface of the drill flutes must be smooth so that friction will not retard the movement of the chips up and out of the drilled hole. The cutting angles must be ground to suit different materials, and adequate lubrication must be provided.

The most important factor to be controlled to assure satisfactory drill performance is the accurate grinding of the drill. If one lip is ground at a different angle from the other, the tool will feed off-center and will drill an oversized hole. Also if the angles are the same, but one side is longer than the other, a thicker chip will be cut on one side, causing the drill to cut oversize. In addition, improper grinding results in an unequal distribution of forces acting on the drill, which may cause drill breakage. Drills should be ground in a drill grinder rather than by hand so that an unskilled operator can provide drills that are ground properly and save the time of the skilled operator.

Drills for different kinds of material, such as plastics, nonferrous metals, cast iron, steel, and alloy steels should be stocked in the tool crib, available for use with the particular material. The use of proper feeds, speeds, jigs, and equipment with true-running spindles will increase the life of tools, result in the drilling of more holes per hour, and give greater accuracy. Drilling is a major operation, and a small percentage saved can amount to a considerable amount of money.

Improvement in drill performance has recently been made by the introduction of better tool material, polished flutes chromium-plated to reduce wear, and improvement of the shape of the cutting edge.

DRILL TERMINOLOGY

There are 20 different types of twist drills, as well as flat drills, straight-flute drills, core drills with three or four flutes, multicut drills, step drills, multiland drills, and combination drills and reamers. In order that the possibilities of the various types of available drills might be understood, the suppliers of drills have developed data which suggest the best shape of drills for each of the large variety of materials.

DRIU EQUIPMENT

One design may require the use of several types of drilling equipment, jigs, and fixtures. A good design reduces the number of different machines and the sizes of drills, reamers, and taps used. Good designs endeavor to place the holes on a single plane and maintain constant depth of all holes drilled. Effective design and production will be made possible by a knowledge of drilling equipment, cutting tools, and auxiliary equipment.

When drilling is done, the work is brought to the fixed spindle of sensitive and upright drilling machines (both single spindle and gang drills) or the spindle of a radial machine is brought into position as the part is held stationary.

Parts are held in vises or jigs and moved under the drill spindle along the table. Often two, three, four, six, or eight spindles are mounted over one table so that the part can be drilled, reamed, tapped, or counterbored without removing the part from the jig. Quick-change chucks also enable additional drill sizes to be used on the same machine and spindles.

When radial drills are used, the part is stationary and usually in a jig. Often the jig is suspended in a trunion and can be drilled from any side parallel to the axis of the trunion. Quick-change collets enable the operator to change from one drill size to another, or from drill size to reamer, boring bar, or tap. Radial drills are designed so that feeds and speeds can be changed quickly to accommodate, use of the large variety of cutting tools.

Multiplc-spindle machines and single-spindle machines equipped with multiple-spindle drill heads may be fed simultaneously into the work. The length and time of feed are determined by the longest hole to be drilled and the drill having the lowest feed requirement. Rpm can be varied in some cases with special gearing，but rpm，s, in general, are the same for all drills mounted in the head. The drills are guided by bushings mounted on the drill press head or in the jig. Drilling, reaming，and tapping can be performed in multiple-spindle heads. Usually each operation is done in a separate machine. Wherever a number of holes can be drilled at the same time in a part of moderate activity, the multiple-spindle drill is economical. Multiple drilling is applied widely in mass production and can be economically adapted to job shop work. Bolt holes for cover plates, bearings, glands, and housings, can be standardized to use similar jigs and setups and promote the use of multiple-spindle drill presses.

The part, jig, and tool must be designed to withstand the pressure of the tool as it is cutting. The new cutting tool materials have raised speeds, feeds, and pressures until only the most modern equipment can take full advantage of the new features. The engineer should use the data furnished by equipment and tool suppliers as a guide, and experiment with feeds and speeds in order to remove the greatest amount of material consistent with an economical tool life. The cost of the operation and machine must be balanced against the cost of tool wear, and against sharpening and setup time.

A drill, on entering material, has a tendency to wobble until the entire drill is cutting. Thus the accuracy of the location of a drilled hole is increased by using a punch mark, a smaller diameter drill (which wobbles less), a stub or short drill rigidly held in position by a good spindle, and a guide bushing. If accurately located holes are required, it is necessary to make the part on a precision machine like a jig borer or a horizontal boring machine, or to use guide bushings mounted in a jig .

Numerically controlled turret-type drill presses with the table automatically positioned can drill, ream, tap, chamfer, and counterbore any quantity of parts without a drill jig. The table holding the work is accurately positioned, the turrets are rotated, proper speeds selected, proper advance and cutting feeds selected by a master tape or punched card. The operator merely places the tape in the control, installs the cutting tools in the turret, and locks the part on the table with vee jaws or clamps.

DESIGN CONSIDERATIONS

The most important considerations for a designer to observe are：

1. Avoid deep holes. Any hole longer than five times its diameter is considered a deep hole and requires special procedures in the shop, such as withdrawing the tool at intervals to clear the chips, and forced lubrication.
2. Start and finish holes on surfaces at right angles to the direction of the hole.
3. Provide room for a bushing and its support in the jig or a fixture to guide the drill.
4. Use standard-size drills for tapped holes and clearance holes for bolts, screws, rivets, and bushings, so that minimum stock of drills can be maintained.
5. Use drilled holes instead of reamed holes wherever possible, provided the shop can produce good quality holes through proper grinding and tooling.
6. Use the same size hole, or tap wherever possible, so that the minimum number of spindles and drills will be required.