Why Does The Tool Bit Break Easily In Micro Milling?

By:cyberryo

Micro milling is one of the three common micro cutting techniques used in micro machining.

In micro milling, the tool bit with diameter as small as 0.1mm is held in a high speed spindle rotating at 20,000 to 150,000 rpm, and used to mill steel, brass and aluminum with depth of cut at about 30 microns and feed rates of 120mm/m to 240mm/m to provide surface quality finishes as good as 0.2 microns.

While micro milling has been successfully applied in manufacturing bio-medical components, embossing dies and micro encoders, the breakage of the tool bit has been identified by many users as a teething problem.

Why does the tool bit break so easily in micro milling as compared to conventional milling?

There are 3 main reasons:

Firstly, when metal is removed by machining, there is a substantial increase in the specific energy required as the chip thickness decreases. This means that in the case of micro machining, as the chip gets thinner with smaller depths of cut, the micro tool bit will be subject to greater resistance when compared to conventional machining. It is as if the workpiece material becomes harder during micro machining. This resistance force is strong enough to exceed the bending strength limit of the tool bit even before the tool experiences any significant wear, and leads to the breakage of the tool bit. One way to prevent this is to make the chip thickness smaller than the edge radius of the tool bit.

Secondly, a sharp increase in cutting forces and stress from chip clogging during the micro milling process would cause the tool bit to break. In most micro milling operations using miniature micro tool bit with two cutting edges, each cutting edge removes the chips from the machining area only within half a rotation. However, if chip clogging occurs, the cutting forces and stresses will increase beyond the bending strength limit of the tool bit within a few tool rotations, and the tool bit will break. Some users prefer high speed steel tool bits as these are very much more flexible and tolerate clogging better than carbide tool bits.

Third, the tool bit tends to lose its cutting edge due to built-up edge and cannot machine efficiently. As the workpiece starts to push on the tip of the tool bit, the tool bit will deflect slightly. The increase in tool deflection and the stress generated by the milling with every rotation will eventually cause the breakage of the tool bit. This process is also called extensive stress-related breakage.

In view of the above phenomena occurring in micro milling, most micro milling machines are sold with sensors to measure the forces acting on the tool bit, and advanced CAM software to predict the chip load throughout the micro machining process. In this way, precision manufacturers seeking a niche in micro milling could try to keep their machines running smoothly with minimal machine downtime.

Digg del.icio.us Blink Stumble Spurl Reddit Netscape Furl

Article keywords: micro milling, micro machining, tool, micro, tool bit, milling, machining, precision, precision machining, suwa, engineering, manufacturing, japan, miniature

Article Source: http://www.articles2k.com

Author Ken Yap is a director of Suwa Precision Engineering in Singapore and represents precision swiss machining, deep draw and high speed metal stamping, pcb and miniature precision ball manufacturers from Suwa, also called "The Oriental Switzerland" in Japan due to its Swiss resemblance for rich watch-making industry, its mountainous terrain and its precision component making industry.

Top Education Articles
1). Passing Cisco's CCNA And CCNP Exams: Ping And Extended Ping By : Chris Bryant, CCIE #12933 Passing Cisco's CCNA And CCNP Exams: Ping And Extended Ping
2). Goku & Friends: The Invasion of Dragon Ball Z By : Dave Carter Dragon Ball Z is an anime show that has gone from cult following to smash sensation in the United States. What started out as a cult following among high school and college students has spread to enjoy a more mainstream popularity among these younger groups, while continuing to expand through other demographics. A Japanese creation, this show in many ways opened the door for others to follow.
3). Intonation In English: Nouns And Adjectives Are Stressed Differently Than Verbs By : Frank Gerace Listen and Learn: Nouns and Adjectives one way; Verbs another Chinese has "tones" but all languages have their own special intonation. The "music" of a language is its intonation and it is perhaps the most important element of a correct accent. A "ggod" accent is not only a question of good pronunciation. Many people think that pronunciation is what makes up an accent.
4). V3 Screen Printing By : Mike Pedretti Everywhere around logos, designs and art shows up and comes out of the woodwork using a modernized version of an older technology. Screen printing is a helpful way to expose a company name and/or logo to the public. Screen printing originally started out using silk as a medium but has since moved on to using stretched porous, finely woven nylon or polyester fabrics, with carefully stenciled designs, and delightful creations take form and come to life.
5). The Challenges of teaching math today By : Robert D. During my years of teaching I’ve been wondering what to do to improve math education. My own teaching philosophy is simple, but throughout the years it has proven to be effective. While the groups I have taught have been diverse, there are certain consistencies in their responses, particularly, students appreciate a clear and sound explanation of a difficult concept, and experience the greatest growth when they have the chance to express themselves by asking any questions they might have and feel comfortable in class.
6). How To Teach Art And Drama In Schools By : Simon Oliver Let’s face it, arts and drama are considered extra-curricular activities when we think of what we expect to learn in school. In fact, arts and drama usually fall in line with extra-curricular activities, which are deemed by most as not as important as learning science, English or math. The indifference to arts and drama may have been brought about by the super high technology lifestyles that we lead.
7). Importance of Reading By : Tyler Benson What is the best way to spend free time? There can be so many different answers to this question. That depends on the preferences of a person. If you are lively and active, you may spend time outdoors or doing sports, if you are sociable, you may enjoy holding a party and communicating with various interesting celebrities. Some of us get so tired of the noise than wait till a nice evening to tackle in and read a nice book to relax or to learn something new or to get to the new world of wonders and travel in it, forgetting about the reality.
8). Online degrees - specially suited to adults looking to improve their employment prospects By : Ventura No longer is a university degree only available by physically attending university lectures, seminars and tutorials. Now you can work for your degree 100% online, never setting foot into the hallowed halls of learning unless you choose to. There are universities that offer Bachelors and Masters degrees online. You can even get a Doctorate 100% online.
9). Panj-aab: My brethren please listen to us. By : Dinesh singh Where water (aab) is means name, language, land, arts and culture. There water makes merry go, that land is called Punjab. The land of five sisters 1. Beas (ancient name Vipasha) 2. Chenab(ancient name Askini,) 3. Jhelam (ancient name Vitasta) 4. Ravi (ancient name Irawati,) 5. satluj (ancient name Shatadru) All these five sisters take birth in high and hygiene Himalayas, and then play in open fields of Punjab, making this land of warriors full of joys.
10). These complicated graduate studies. By : Chris Wells For every student, whether he is an undergraduate or graduate it is imperative, almost indispensable to turn to the help of other persons, to use their knowledge, skills and experience. Certainly, if you are working on your dissertation, it might be advisable to do the same. This dissertation help program should comprise several elements. The first element is the organizing of your dissertation.

New Education Articles
1). Great Tips on Getting Your Kids to Read By : Lisa James Getting your kids to read is often a daunting task, put the odds in your favor by following these tips.
2). Building Up Your Vocabulary In A Foreign Language By : Michael Gabrikow Find out how to build up your vocabulary in a foreign language from this article. Several techniques that will help you boost your vocabulary are covered as well as some interesting tips and tricks on this subject being given out in the text below.
3). How To Memorize Words By : Michael Gabrikow The following article will try to present some of these methods that could help you learn how to memorize words faster when learning a foreign language.
4). Increase the Value of Your Learning Easily By : Jean Morgan To aid in the lifelong process of learning, you will want to know and understand the differences between adult learning styles.
5). Getting Into Graduate School By : Lisa Parmley The GRE General Test is the most widely accepted college admission exam for graduate school. This test strives to measure the knowledge that test takers have gained over long periods of time (like through their undergraduate programs).
6). The Challenges of teaching math today By : Robert D. During my years of teaching I’ve been wondering what to do to improve math education. My own teaching philosophy is simple, but throughout the years it has proven to be effective. While the groups I have taught have been diverse, there are certain consistencies in their responses, particularly, students appreciate a clear and sound explanation of a difficult concept, and experience the greatest growth when they have the chance to express themselves by asking any questions they might have and feel comfortable in class.
7). The History of Crossword Puzzles By : Fran Black The first book of crosswords was published in 1924. It became a best-seller and crosswords replaced mahjongg as the most popular American game. Crossword puzzle design and solving is an excellent way to sharpen focus. Regardless of whether design and or solve numerous crossword puzzles, you will learn one more way to enhance memory and creative expression.
8). Dragons Through History By : Fran Black The Dragon has played an important part in myths and religions since pre-historic times. The history of dragons goes back at least six thousand years, and there are dragon tales and legends from every continent except Antarctica. In almost every culture, and all throughout history, there are stories of these mythical and magical creatures called dragons.
9). Forcible Rape Defense; False Accusations in Relationship and Date Rape Cases By : William F. Nimmo Forcible rape and attempted forcible rape between people who know each other, either casually or well, make up a sizeable percentage of the false accusations in the criminal justice system. The cry of rape or abuse is a familiar cry when a relationship goes sour or when a woman has second thoughts after a night of sex or near intimacy. While there are certainly legitimate claims of rape and attempted rape in the world, from the defendant’s perspective there are good reasons to view each claim with skepticism.
10). Criminal Defense Lawyers: Reducing Murder to Manslaughter By : William F. Nimmo Reducing murder to manslaughter is a task that presents itself in many murder cases. Depending on your state or jurisdiction you may be able to reduce murder to manslaughter by eliminating the element of “malice.” Classically, this is where the defendant acts by being provoked into a sudden quarrel or into a state of mind known as the “heat of passion.