Milling of high-hardness materials usually uses CBN solid tools, CBN cutter heads or ceramic tools to process hardened workpieces, which is often called hard cutting. The new process of hard cutting can cut hardened steel, gray cast iron, ductile cast iron, powder metallurgy and special materials. Of course, some materials such as bronze are not suitable for hard cutting. Hard cutting technology can also be used for turning, surface machining, tapping, milling, grooving, master machining, turning cones, etc. Processing of steel materials with hardness exceeding 56HRC, or strength exceeding Rm> 2000N / mm2, we generally call it hard cutting.

The success of hard milling usually involves many factors. Today, let ’s follow the editors to understand what are the factors, so that everyone can have a clear idea of machining when encountering hard cutting workpieces.

Hard Cnc Milling Shop
Hard Cnc Milling Shop

“Hard-milled steel-63 Rockwell hardness, 6000 rpm, 100 inches / minute, 0.012 per pass (ramp)”

The first important factor to consider in hard milling is the structure of your machine. So in order to achieve the ideal hard milling effect, we first need a very robust machine with a high degree of vibration reduction.

Hard milling cnc machine
Hard milling cnc machine

Hard Cnc Machining machines require stiffness provided by a granite working machine or polymer concrete and cast steel structures
Generally speaking, machines made of polymer concrete have the cushioning capabilities of many machines made of cast iron. At the same time, it is important to have a CNC controller that can handle the dynamic requirements of constant and fast acceleration and deceleration!

Hard milling cnc machine process
Hard milling cnc machine process

The solid granite machining table makes it a rigid hard milling machine.

The next thing to talk about is the clamping of the spindle and the tool. These are two very different things, but their use is closely related.

First you need a rigid rotor! If your spindle is beating, the most concentric and best tool holder in the world will only help you. That said, combining a high-speed spindle with the best tool can produce unexpected results.

HSK series tool holders are one of the most popular tool holders in hard milling because of its interface with the spindle for increased rigidity and concentricity.

HSK CNC MACHINING SHAFT
HSK CNC MACHINING SHAFT

Hard milling spindles and toolholders should be selected based on rigidity and low runout. In processing, we found HSK’s tool holding system to be very effective!

Of course, we must not forget the tool itself. We have also done some investigations and found that there are many mold makers tailoring specific tools for hard milling. But we have not been too convinced of these parameters. Most of these mold makers have experts who can help select materials and specific processing tools, and we can take advantage of these services to save us time and increase efficiency. At the same time, cutting tools selected for hard milling applications must be coated to withstand the high heat and extreme friction associated with these materials.

And, these tools are probably not cheap! So, if you make a purchase request to your boss, and when the price of your end mill is higher, then you can offer him so many advantages to justify the purchase. Also, if you need to buy two, you can ask to buy four. In this way, when he asked to buy only two, he also felt that he saved the company a lot of money.

HSK Hard milling tools
HSK Hard milling tools

“Hard milling tools such as this 8mm 4 blade end mill have edge radii of 0.5mm and coating thickness of 0.5mm, which can show excellent cutting performance and durability.”

Back to the topic. CAD / CAM software is the last problem (not really, the problem will never be missing). Programming software is one of the most important considerations for hard milling, and it controls the load on the tool. You want the cutting tool to be loaded without impact, which means that trochoidal milling is performed sequentially, or as it is commonly said, dynamic. The principle behind dynamic milling in relation to hard milling is that your tools can easily and permanently join materials. No sharp jumps, smooth power. Most major CAD / CAM software packages now have some form of dynamic milling.

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