The team at Browne & Co are excited to invite you to join us at IMTS 2024, which will be held from September 9-14 at McCormick Place in Chicago. This premier event is a vital opportunity to explore the latest advancements in manufacturing technology, network with industry leaders, and discover innovative solutions that can enhance your operations. There will be participation of several of our key principals at the upcoming show.

Dümmel (Booth: 431481)
As part of Everede's booth, Dümmel will be showcasing their exceptional micro-cutting tools, which are ideal for small-part machining and fine-detail work. Dümmel's product range is designed to meet the highest standards of precision and reliability, ensuring optimal performance in intricate machining tasks.

Everede Tool Company (Booth: 431481)
Everede Tool Company will be showcasing their advanced cutting tools, including indexable tools, boring bars, and other precision cutting instruments. Everede is known for producing high-quality tools that provide superior performance and durability. Their products are designed to meet the rigorous demands of modern machining, offering solutions that increase efficiency and precision in manufacturing processes.

Haimer USA (Booth: 431510)
Haimer will be showcasing their industry-leading tool-holding systems, including shrink-fit technology and high-performance balancing machines. These products are known for their ability to improve machining accuracy, reduce vibration, and extend tool life, ultimately boosting overall efficiency in manufacturing environments. Additionally, Haimer's Power Clamp and Tool Dynamic series provide unmatched reliability in tool clamping and balancing, ensuring top-tier production quality.

Nine9 (Booth: 431481)
Also as part of Everede's booth, Nine9 will be exhibiting their innovative cutting tools that are designed to streamline complex machining processes. Highlighted products include the NC Helix Drill, which ramps at 20° angles, enabling the production of multiple features with a single tool, and the i-Center indexable center drill, which offers extreme repeatability and precision.

Precision Brand Products (Booth: 431781)
Precision Brand will display an extensive array of shim products, toolroom supplies, and maintenance tools at their IMTS booth. Their offerings include slotted shim kits, feeler gauge assortments, and stainless-steel shim stock, all of which are critical components in achieving exact measurements and ensuring the longevity of machinery.

IMTS 2024 is the ideal venue to explore these innovative products and speak directly with the experts who design and produce them. We strongly encourage you to add these booths to your IMTS show planner and take advantage of the opportunity to engage with the cutting-edge technologies that can propel your business forward.

For more information and to plan your visit, please visit IMTS 2024​

Let us know if you will be going and we can join you at one of our principals booths!!

Article is based upon information provided by Haimer
​written and edited by Bernard Martin

With rotating bodies, imbalance is an omnipresent phenomenon. A typical example are rotating tools on machine tools.

Because unbalance creates a centrifugal force, it increases linearly with the unbalance and squares with the number of rounds. The faster the rotor rotates, the more noticeable the unbalance. But how does unbalance arise, how can it be measured and how can it be eliminated by balancing?
​
On the following page we have put together the theoretical fundamentals of balancing, the basis for tool balancing.

As a side note to this discussion, there is sometimes confusion over use of the words "imbalance" and "unbalance". Imbalance is the noun meaning the state of being not balanced, while unbalance is the verb meaning to cause the loss of balance.

In rotating toolholder, addressing imbalance is crucial for efficiency and longevity. Imbalances arise from uneven mass distribution, design asymmetry, or manufacturing inaccuracies, leading to detrimental centrifugal forces during operation.

Balancing, achievable through mass adjustment or component alignment, mitigates these forces. This process involves precise measurement and correction to adhere to industry quality standards, though achieving absolute balance is challenging due to inherent mechanical and environmental factors.

Here's a quick overview:

• Unsymmetrical design of the rotor (e.g. gripping groove on tool holders as specified in DIN 69871 or clamping screw on Weldon tool holders).
• Unsymmetrical distribution of mass due to concentricity errors caused by manufacturing tolerances, e.g. concentricity of the tool outer diameter with respect to the taper.
• Alignment errors during assembly of a rotor consisting of several components, e.g. milling spindle and tool holder, tool holder and tool.
• Concentricity errors in the bearings of a rotor, e.g. the spindle bearing.

Static balance in rotary toolholders refers to the condition where the center of gravity is aligned with the axis of rotation, ensuring no lateral movement when the toolholder is stationary or rotating.

Dynamic balance, on the other hand, addresses both the static imbalance and the couple imbalance, ensuring that the toolholder remains stable and does not wobble during high-speed rotation, which involves balancing across two planes. Achieving dynamic balance is crucial for toolholders in high-speed applications to minimize vibration and wear.

Let's dig into some details:

​​STAT­IC UN­BAL­ANCE

Static unbalance in rotary toolholders manifests when their center of gravity doesn't align with the axis of rotation, leading to centrifugal forces that can cause significant issues when the rotor spins. This kind of imbalance can be detected even in non-moving rotary toolholders and is correctable by adjusting the mass distribution within a single plane. However, correcting static unbalance (a.k.a. Single Plane Balancing) might not address other types of imbalance, like couple unbalance, that can still affect the rotor's operation.
​

COUPLE UNBALANCE
Couple imbalance occurs when a toolholder's center of gravity is aligned with its rotation axis but still experiences a tilting moment during operation due to the distribution of mass. This condition, detectable only when the toolholder is in motion, results from opposing centrifugal forces that create no lateral movement but cause a rotational tilt.
​

DY­NAM­IC UN­BAL­ANCE
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Dynamic imbalance in a rotary toolholder refers to a scenario where both static imbalance and couple imbalance are present, causing the toolholder to experience tilting and wobbling during operation. This complex form of imbalance necessitates correction in two planes for the toolholder to rotate smoothly at varying speeds, thereby reducing vibration and wear on associated machinery.

In case you were wondering the ideas of dynamic balance was developed by R.S. Berkof, G.G. Lowen​ in the seminal work A New Method for Completely Force Balancing Simple Linkages. ​

BAL­AN­CING IN A SINGLE PLANE (STAT­IC BALANCING)

​Balancing in a single plane corrects the static imbalance by adjusting the toolholder's center of gravity to align with its axis of rotation, minimizing eccentricity. However, this method doesn't correct the couple imbalance associated with dynamic unbalance, which remains unaffected.

BAL­AN­CING IN TWO PLANES (DY­NAM­IC or DUAL PLANCE BALANCING)​

​Dynamic or dual plane balancing involves correcting both static and couple imbalances in a toolholder, achieving thorough compensation. The process allows for the selection of any two balancing planes, ideally positioned as far apart as possible, to ensure comprehensive balance throughout the toolholder's operation.

The first step in correcting imbalance is to determine where unbalanced mass is located in a single plan or 3 dimensional plane.  To do this, the tool holder is inserted into the balancing spindle and made to rotate.

The two primary factors to determine permissible unbalance, also called the balancing tolerance, are the mass of the rotating part (G) and the maximum operational speed (RPM). To put a more technically, the grade G values in toolholder balancing are determined based on the permissible residual unbalance for a given rotation speed and the weight of the rotary toolholder, as outlined in standards such as DIN ISO 1940-1 (previously VDI guideline 2060).

​These values guide the maximum allowable unbalance to ensure operational safety and efficiency, factoring in specific operational conditions.

Each grade G value (previously: Q) corresponds to a different level of balancing precision, tailored to the rotor's intended use and operating environment.

Keep in mind that the balancing quality grade is only valid for a specific rotation speed of the the toolholder. e.g. G2.5 at 25,000 RPM.  This permissible residual unbalance is calculated from the balancing quality grade, the rotation speed and the weight of the toolholder. Here's the actual formula: 

Uper = (G•M)/n • 9549

• Uper = Permissible residual unbalance of the rotor in gmm
• G = balancing quality grade
• M = weight of the rotor in kg
• n = rotation speed of the rotor in rpm
• 9549 = a constant that is produced

​

HERE IS AN EX­AMPLE

• A milling cutter is clamped in a collet chuck.
  
• The total weight is 0.8 kg.
• The milling cutter is to be used at a service speed of n = 15,000 rpm.
• The spindle manufacturer requires a balancing quality grade of G = 2.5.
• Permissible residual unbalance Uper = 1.3 gmm.
  

In the above example there is a permissible residual unbalance of 1.3 gmm. To illustrate
this value it is useful to convert the unbalance to eccentricity.

Uper = M • eper
eper = Uper/M =1.3 gmm/800g = 0.0016 mm = 1.6 μm
Therefore the centre of gravity of the tool holder can be offset by max. 1.6 μm from the axis of
rotation. During balancing the axis of rotation is assumed to be the axis of the taper or HSK.
However, in the milling machine the tool rotates about the axis of the spindle.

Even new spindles TIR of up to 5 μm (equivalent to eccentricity of e = 2.5 μm).

ANOTHER EXAMPLE

Balancing quality G = 1
Rotation speed n = 40.000 rpm
Tool weight M = 0.8 kg
Uper = 0.2 gmm
eper = 0.3 μm

This permissible eccentricity cannot be achieved in practice. Even good spindles have a repeatability of 1-2 μm when the tool is changed. Even small amounts of dirt, grime or swarf can worsen the result significantly.

The total unbalance in a milling spindle is influenced by a multitude of factors, including the inherent unbalance of the spindle, errors in concentricity within the spindle  (The symmetry axis is not the axis of rotation, openings for coolant, etc), and distortions in the spindle clamping system (Springs, drawbar, etc).

Additionally, the alignment and unbalance of the tool holder, along with errors in the pullstud installation torque, and event the tool itself, play significant roles. Consequently, achieving a residual unbalance of less than 1 gmm in practical settings is often considered unrealistic.
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Chardon, OH. - Browne & Company, a leader in the metalworking industry, is proud to announce the grand opening of its new Metalworking Technology Center in Northeast Ohio. This state-of-the-art facility is set to revolutionize the metalworking sector with its cutting-edge technology and tooling, provided by the renowned Haimer presetting and shrink fit tooling. 

​You can also find the latest high performance cutting tools displayed from Fullerton Tool, Regal Cutting Tools, Rocky Mountain Twist Drill, The Everede Family of tooling, Dapra, and others. 

The Technology Center is designed to meet the growing demands for higher precision, efficiency, and performance in metalworking. It is equipped with the latest advancements in Haimer technology and tooling, ensuring consistent set-up, unsurpassed machining accuracy, better tool life, and improved part finishes. The center represents a significant investment in innovation and demonstrates Browne & Company's commitment to advancing the metalworking industry.

"We are excited to unveil our new Technology Center, which symbolizes our dedication to providing the best in metalworking solutions," said Dave Browne, President of Browne & Company. "This facility not only showcases the latest in technology and tooling but also serves as a hub for innovation, collaboration, and education."

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Don't miss the opportunity to experience the latest in metalworking technology and innovation. Click the button below to schedule a demonstration with our team and discover how Browne & Company can elevate your metalworking projects.

About Browne & Company
Browne & Company has been at the forefront of the metalworking industry, offering innovative solutions and high-quality tooling to clients across various sectors. With a focus on precision, efficiency, and reliability, Browne & Company continues to lead the way in metalworking technology and services.

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