What is Machinability and How to Improve Machinability of Materials?

Are you constantly battling with delayed shipments, failed quality inspections, and the inevitable financial blow these issues bring? You’re not alone. Improving the machinability of the materials you use can drastically optimize your operations.

Machinability refers to the ease with which a material can be cut, shaped, or finished using machining processes. Improving machinability means optimizing these processes to enhance production efficiency, reduce costs, and maintain high quality.

Intrigued? Stick around. I’m about to unfold the secrets of machinability that could save you time, money, and a lot of unnecessary stress.

What is Machinability?

Put, machinability is the quality of a material that makes it easy or difficult to machine. We’re talking about how a material behaves when it meets a cutting tool—does it yield gracefully, or does it put up a fight like a bull seeing red?

Machinability isn’t just a textbook term; it’s a tangible metric. It tells you how efficiently a material can be removed using cutting tools, what tool wear you can anticipate, and what surface finish you can expect, among other things.

Have you ever heard of the Machinability Index? No? Well, for materials like metals, this index is often calculated, and it can be a great point of reference. For instance, B1112 steel has a machinability rating of 100% and serves as the comparison baseline. If aluminum has a rating of 150%, it means aluminum is 1.5 times easier to machine than B1112 steel. Simple math, significant implications. Read in here.

Why is Machinability Important?

If you’re in the game of CNC machining like I am, you’d know that time is of the essence. A delay of a few hours could cost you big bucks, not to mention the strain it puts on your relationship with clients. But why should you care about machinability?

Firstly, machinability directly impacts production speed. The easier a material is to machine, the faster you can churn out parts. A high Machinability Index is basically your fast pass in a queue of sluggish manufacturing processes.

Second, let’s talk about tool life. Ever get annoyed changing out your cutting tools way too often? Poor machinability wears out your tools quicker than a sprinter in a 100-meter dash. The higher the machinability, the less frequent the tool changes, and the more cash stays in your pocket. 

Quality, my friends, is not to be compromised. Good machinability ensures a smoother surface finish. You know how some clients can be—a single imperfection, and they scrutinize the entire batch. High machinability can spare you those awkward quality talks.

Fourthly, the Material Costs. Believe it or not, good machinability can help you get more bang for your buck on materials. How? Higher machinability usually means less waste, as you can achieve more accurate cuts and make more efficient use of your material stock.

Next is Labor Efficiency. Time is money, but so is the workforce. Materials that are easier to machine require less manual intervention, allowing your skilled labor force to focus on other critical tasks. Plus, this reduces the likelihood of human error, which can be a costly affair in itself. 

Remember the Machine Longevity. This one’s a bit of a long game, but worth mentioning. Easier-to-machine materials cause less wear and tear on your machines, extending their lifespan. This means fewer breakdowns, less downtime, and a more seamless operation overall.

Quality Consistency. Good machinability isn’t just about making one part well; it’s about making every part to the same high standard. When the material is consistent in its 

machinability, you can predict the outcome better, which is golden for quality control. 

It reduced Testing and Rework. With improved machinability, you’ll likely face fewer quality issues, meaning fewer resources spent on inspections and rework. This can significantly speed up the time-to-market for your products.

Improve Client Satisfaction: Let’s remember happy clients are returning clients. Delivering parts with consistently high quality on time makes you the go-to supplier. And that reputation is priceless.

What Factors Affect Machinability?

Now, what sorcery is behind this mysterious attribute we call machinability? 

Material Hardness: The more complex the material, the more challenging it is to cut. This one’s a no-brainer. More complex materials not only slow down the cutting process but also accelerate tool wear. Keep your eye on hardness levels like a hawk on its prey. You can get the exact data from this link.

Thermal Properties: Some materials dissipate heat better than others. Materials that can’t handle heat well tend to soften and gum up the cutting tool. This is one hot topic you can’t afford to overlook. 

Chemical Composition: Believe it or not, even the material’s chemistry plays a role. Elements like sulfur can improve machinability, while others, like carbon, can make your machining life miserable. A little chemistry knowledge goes a long way here.

Grain Structure: The internal grain structure of a material, whether it’s okay or coarse, influences how it reacts to being cut. Coarse grains usually lead to quicker tool wear but can offer easier machining. It’s a balancing act.

Workpiece Complexity: The more complex your workpiece, the more difficult it is to machine. Complex geometries require more intricate tool paths and often slower cutting speeds, impacting overall machinability. 

Cutting Tool Material: The choice of cutting tool material, be it carbide, cobalt, or high-speed steel, significantly influences machinability. Your cutting tool should be as fine-tuned to your material as a violin is to a virtuoso. 

Lubrication: Yes, the humble cutting fluid. The correct lubrication can dramatically improve machinability by reducing friction and heat, not to mention extending your tool’s lifespan. 

Machine Tool Rigidity: A rigid machine tool can absorb more cutting forces, allowing for higher cutting speeds and improving machinability. It’s like having a sturdy ship in a storm; you’ll weather it much better. 

How to Measure Machinability?

Machinability Index: As mentioned earlier, certain materials have a machinability rating as a baseline. Usually, B1112 steel sits at a machinability rating of 100%, and other materials are compared against it. An index over 100% signifies better machinability; below 100% means more challenging machining conditions. 

Tool Life Criterion: The longevity of a cutting tool during the machining of a specific material is another direct measure. You can assess this through Taylor’s Tool Life Equation, which relates tool life to cutting speed.

Surface Finish: You can gauge the machinability of a material by the quality of the surface finish after machining. Good machinability generally results in smoother finishes. This is often quantified through the surface roughness parameter, Ra. 

Cutting Forces and Power Consumption: Measuring the forces exerted on the cutting tool and the power consumption during machining can provide invaluable insights into machinability. Lower forces and energy consumption typically indicate better machinability. 

Material Removal Rate (MRR): This is the volume of material removed per unit of time, usually expressed in cubic inches per minute or cubic millimeters per minute. A higher MRR usually indicates better machinability.

Empirical Tests: These are specialized tests to measure machinability under controlled conditions. The data collected often includes tool wear rates, cutting temperatures, and chip formation. 

Operator Feedback: Remember to consider the value of skilled operators. Their insights into a material’s behavior during machining can be qualitative but immensely valuable.

How to Improve Machinability?

Material Selection

First thing first: pick your material wisely. If you’re designing a part and have flexibility in material choice, opt for materials known for good machinability. Sometimes, switching from high-carbon steel to re-sulfurized steel can save you time and headaches.

Hardening Techniques

Before hammering and tongs on that workpiece, consider pre-hardening or case-hardening techniques. They can dramatically improve machinability by creating a softcore but hard exterior, making it easier to achieve precise cuts without affecting tool life. 

Heat Treatments

Ah, heat—the secret sauce in the metallurgy kitchen. Heat treatments like annealing can alter material properties and improve machinability. Annealing softens the material, making it easier to cut while reducing internal stresses. 

Cutting Tool Selection

Please don’t skimp on your cutting tools; that’s like buying a sports car and putting budget tires on it. Invest in high-quality cutting tools made of materials that can withstand the rigors of the machining process. Carbide is often a good choice for rigid materials. 

Cooling and Lubrication

Trust me; a little lube goes a long way. Proper cooling and lubrication reduce friction, prolong tool life, and improve the quality of the cut. Opt for high-performance cutting fluids that are suited to your specific material. 

Machine Calibration

Keep your machines in tip-top shape. A well-calibrated device minimizes vibrations and maintains alignment, which can improve machinability. A poorly maintained machine can undo all your other efforts.

What Types of Materials Have Good Machinability?

Aluminum Alloys

When it comes to easy-peasy machining, aluminum is often your go-to guy. It’s soft lightweight, and the chips break easily. For many CNC shops, aluminum is the bread and butter of machinable materials. 

Brass and Bronze

Think of brass and bronze as the friendly neighbors of machinable materials. The machine runs smoothly and doesn’t put up much of a fight, making it popular for intricate components. 

Low Carbon Steels

Among the steels, the low-carbon variants offer better machinability. They’re less wear-and-tear on your cutting tools and often don’t require any unique treatments before machining. 

Plastics like Delrin and PTFE

You heard me right—plastics. Materials like Delrin and PTFE offer excellent machinability. They’re great for parts that need a good finish and tight tolerances, minus the metallic heft. 

Magnesium Alloys

If you’re into lightweight materials but need something more robust than aluminum, magnesium alloys are an excellent choice. The machines are used in applications requiring low density. 

Lead Alloys

They’re less commonly used due to health concerns, but when it comes to machinability, lead alloys are a piece of cake to work with. 

Conclusion

Now, what’s the next step? It is time to put this knowledge into action. Evaluate your materials, optimize your processes, and don’t hesitate to reach out for expert advice. At Worthy Hardware, we specialize in CNC machining parts and offer on-demand solutions that meet your quality and pricing requirements. So, let’s connect and make your machining projects not just doable but worthy of praise.

Ready to level up your machining game? Contact Us today.