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Better Balanced Toolholders Lead to Best Machining Results

Jim Lorincz
By Jim Lorincz Contributing Editor, SME Media

K&G Manufacturing (Faribault, MN) has learned a thing or two about precision machining in the 80 years it has been in business. One lesson the company learned long ago is that balanced toolholders are a key to customer satisfaction and achieving the best possible machining results. Located just south of the Minneapolis-St. Paul area, K&G has installed a new Tool Dynamic TD Comfort Balancing Machine from Haimer USA (Villa Park, IL) to provide balanced toolholders for its new 20,000-rpm CNC machines.

K&G Manufacturing produces precision profilings like this skeg (center)
for marine application using toolholders balanced with Haimer’s Tool Dynamic TD Comfort Balancing Machine.

K&G does a lot of work for some challenging industries, including marine, military, and aerospace. To keep up with the demand for their services, K&G purchased several new high-speed CNC machines. Because parts for their previous balancer were no longer available and it was quite old, there was an obvious need for new balancing equipment to provide balanced toolholders.

Unbalance is caused by uneven weight distribution of the toolholding assembly. The consequences are vibration, run out, poor surface finish, and shorter tool life. High machining speed intensifies these negative effects. Reducing spindle speed can lead to smoother cutting, but it also decreases metal removal rates and productivity.

K&G Mfg. has found that only high-precision balancing of the complete tool assembly allows their high-speed machines to reach maximum capability. Combining this knowledge with Industry 4.0-style best practice protocols has helped the shop improve its operations.

To assure uniformity and the highest level of efficiency, all tools are prepared offline. Balanced toolholders are combined with the tool in a centralized toolcrib. The assemblies are preset and balanced offline while the machines continue to run production. Balancing, which is generally done with weighted balancing screws, is always the last step in the process before the assembly is sent to the machine. Necessary offset measurements defined by the presetting operation are uploaded directly to the machine control via the presetter’s built-in postprocessor, so operators don’t even have to key in the numbers manually and risk entry errors.

K&G Manufacturing does a lot of work in the marine, military, and aerospace segments, machining workpieces as diverse as sabots for small caliber ammunition to variable displacement ring pump housings (center) machined from blocks of forged aluminum for auxiliary aircraft fuel pumps.

“We looked at other balancing equipment, but the reps from Haimer seemed much more focused on our needs,” said Isaac Rupprecht, toolcrib coordinator for K&G Mfg. “We felt this level of detail would turn into superior service and support after the sale. And we were right.”

After installing a new Haimer Tool Dynamic TD Comfort Balancing Machine, it didn’t take long for the company to recognize that all balancing machines are not created equal in terms of accuracy and ease of use.
Test comparisons between the old and new balancers showed that, while the numbers were close, the repeatable accuracy of the Haimer Tool Dynamic TD Comfort was noticeably better. The machine has several features that are vast improvements. For example, the Haimer machine’s clamping is identical to that of a machine spindle (clamping and drawing on the retention knob), which eliminates variations seen previously with the old unit. Whether the toolholder is a CAT 40/50 or HSK63A, the Haimer machine provides positive clamping that ensures precise and repeatable measuring accuracy. Deviations caused by misalignment or poor seating of the holder in the balancing spindle are eliminated.

It was the elimination of such deviations that brought unsuspecting operators to notice a key change in setup practices. They no longer needed to make additional compensations at the machine for bore sizes and roundness. Tools were, for the first time, cutting to size from presetter to machine. This eliminated additional compensation allowances and reduced setup time.

K&G installed a Haimer Tool Dynamic TD Comfort Balancing Machine to provide balanced toolholders for its new high-speed CNC machines

The shop also found the Haimer software to be superior. While the previous balancer would indicate the grams of unbalance and its location, it did not provide any interface to help the user determine options for correcting the unbalance and specific guidance on where to make corrections. In golfing terms, it told them they were on the fairway, but didn’t tell them where the hole was or what club to use to get there.

It took a lot of trigonometry and many test spins to get it right on the old machine. The Tool Dynamic, on the other hand, offers several balance correction options, including rings, weighted balancing screws, and drilling or milling. Once an option is selected, the machine automatically calculates the correction needed and pinpoints the proper location for correction. Complete balance inspection and correction are achieved in less than three minutes, with the risk of human error reduced to zero.

How much difference did the Haimer balancers make? The proof is in the pudding. An operator who had not been informed of the change in equipment was working on the first job after the switch. Unbeknownst to him, the toolholder assembly had been balanced on the new Tool Dynamic. After the initial run, he was amazed by the resulting finish and went to the toolcrib to investigate. With a balancing system from Haimer, the improvement in finish quality was so obvious, the uninformed operator could tell at a glance that something had changed.

Surface finish on aluminum components is a huge concern for K&G. In fact, many of its aerospace customers utilize a provision on their prints called UVC (Unusual Visual Condition). Basically, this allows a part to be rejected for any subjective determination, including visual finishing flaws, casting discoloration, tooling marks, etc., even if all measurable part tolerances are within specification. K&G Mfg. has seen fewer UVC rejections since using the new Haimer balancing system.

“We promise our customers greater than 95% on time delivery and less than 200 DPM [defects per million] quality,” said Isaac. “Haimer balancing enhances our ability to achieve both of those goals by reducing setup times and helping our operators get excellent results on the first run. The performance of their equipment is only matched by the after-sales support we have received since purchasing the Haimer Tool Dynamic TD Comfort Balancing Machine.”

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