GMN USA has a highly qualified staff of spindle technicians and machinists, that uses original GMN parts, bearings and state-of-the-art equipment, to ensure that the best possible spindle service is provided to their customers. In addition to the GMN spindle line, they also provide service for most other make and model spindles.
What differentiates GMN USA's Spindle repair process?
Original GMN parts, precise measurement devices and tools, along with the expertise and experience of GMN's highly qualified staff guarantee that their spindle repair service meets our customer’s expectations of quality, reliability and performance.
GMN uses this same method when servicing spindles supplied by most other machine tool spindle manufacturers as well.
ORIGINAL GMN PARTS
GMN USA utilizes only the best components when refurbishing spindles. The use of GMN ABEC 7 and higher quality bearings assure the best possible accuracy and reliability for their spindle repairs. Motors, clamping systems, sensors and other critical parts supplied by vendors must meet strict GMN quality standards. All this attention to detail ensures that spindles are returned to our customers with “like new” performance and reliability.
GMN USA is equipped with a variety of grinding machines that cover all of their grinding requirements. All spindle component grinding operations are completed in their facility to ensure high quality and a quick turnaround time. The GMN USA assembly and test departments utilize state of the art spindle drives and vibration analysis equipment to confirm that each spindle meets very exacting demands.
The experienced team of engineers, machinists and spindle technicians at GMN USA is focused on providing the best possible service and technical advice to our customers.
Their spindle repair service includes an accurate evaluation of incoming spindles, replacement or refurbishment of damaged components, dynamic balancing, extensive testing and vibration analysis.
Below is a video showing GMN USA in Farmington, Connecticut going through their spindle repair process. It is the most comprensive repair process in the industry.
If you're thinking about getting a new spindle from high speed grinding to high power milling applications, GMN has the solution for all your machining needs.
In addition to a comprehensive range of standard spindle types, GMN also will design and develop special spindles to meet the specific requirements of our customers.
GMN is a market leader for spindle technology worldwide, especially in the field of innovative solutions for precision and high speed machining.
Give us a call with questions!
by, Bernard Martin
As carbide end mills gain higher and higher speeds and metal removal rates there has also been a trend by round tool manufacturers to tighten up the tolerances on both the cutting diameter and the shank diameter to improve concentricity. At the same time, shrink fit holders have become more and more popular because they hold a tighter concentricity as well. To achieve this both the shank and the bore now have similar surface finishes and this has led to a problem The tools pull out in the cut.
Shrink fit holders are the most accurate for TIR as the toolholder engages completely around round shank tools with a bore tolerance of -0.0001" to -0.0003". As high performance end mills have tightened shank tolerances to the same range of -0.0001" to -0.0003" they have used finer and finer grain grinding wheels which give the shanks a 'shiny' appearance.
Shiny means that the superfinished shank has a lower coefficient of friction. So, although the TIR is tighter, the shank is more "slippery". End mills traditionally had surface finish of about 8 μin on the tool shank. But that's changed. It's been recommended that tool shanks used in shrink fit holders should not have a finish finer than 16 μin. for optimum holding power, but tell that to the guy who just superfinished the end mill to a super cocncentric tolerance that you don't want it looking that good.
Everyone know that the last thing you want is for the end mill to slip in the middle of a heavy cut or on the finishing pass of a high tolerance part. These 'hi performance' end mills, often times have higher helix angles which are great for ejecting chips but also create a higher pull out force on that slippery shank. And reducing the helix angle is not the answer.
We already know that the gripping pressure is a function of the interference between the tool shank and the shrink fit toolholder bore. Most shrink fit holders have a already bore surface finish of between 12 μin. and 16 μin. So they are ground to a very high tolerance and have about the same surface finish as the toolholder shank.
End mill manufacturers and machinist have tried a variety of methods over the years to stop the tools from pulling out. This has ranged from grit blasting the shank to rubbing chalk on the shank, but most everyone in the industry has felt that the problem really needs to be addressed by the longer life toolholder rather than the replaceable cutting tool.
That's the problem that Techniks wanted to address. Techniks claims that their "proprietary non-slip TTG594 compound virtually fuses the tool shank with the shrink fit toolholder."
It’s not just a rougher bore finish that enhances the holding power. TTG-594 is a compound that has a much higher Brinell hardness than carbide so it can “bite” into the tool shank. But this does not affect the ability to perform tool changes.
Techniks arrived at their 4x the holding power comes from torsion testing vs. a standard shrink fit toolholder. They used a ¾” carbide gage pin in a standard holder and found the torque at which the tool will spin in the bore.
They then tested the ShrinkLOCKED holder using the same test.
According to Greg Webb, at Techniks,
"We actually could not find the point at which the tool would spin in the ShrinkLOCKED holder as we broke the carbide gage pins at 4x+ times the torque of the standard holder. The holding power is greater, we just have not found a way to measure this, so we kept our claims conservative at 4x."
The challenge was to achieve both hard and soft cost savings, as well as time spent on drilling flanges from one side, chamfering the backside and creating a controlled chamfer on the top surface which was a secondary process.
We designed an indexable drill with our rear cutting carbide deburring insert along with a fixed pocket chamfer insert to create the precision top chamfer that was required. The spade drill insert also had a special feature that allowed it to chamfer the top side of the bottom hole that was pre-drilled.
Four operations were completed in one pass.
The EZ Burr Burr-Free Drill drilled the hole, deburred and chamfered the back all in one step, thus eliminating the secondary step of chamfering the bottom surface on the top hole.
This saved time as well as money, plus the tool life of the Burr-Free Drill achieved a more consistent result and had a longer tool life than the previous method.
This article is about Blue Photon Technology and Workholding Systems LLC and how Post Processing; 3D printing presents challenges in workholding for finish machining.
Written by Mark Kirby AM Business Manager, Renishaw Canada
Metal 3D printing can enable rapid, low cost iterations of new medical devices, since no tooling costs are involved. All devices need testing to uncover problems and develop solutions—allowing the product shape to change “for free” is a powerful advantage with Additive Manufacturing (AM). Other benefits flowing from AM besides enabling more complex geometry are improved accuracy with no component tolerance stack up, and a simplified supply chain with reduced part count.
3D Printed Workholding
Plastic printed jaws are often a good first option, as they are cheap to manufacture—typically in just a few hours on a desktop printer, and can conform to complex geometries (although the design of the jaws can be more time consuming than a simple Boolean subtraction of the component from the plastic). When the design changes after product testing it is easy to print a new set of jaws.
The main disadvantage of plastic jaws is that they will often distort the component as they are tightened. Although the jaws hold the part rigidly for machining, when the component is released from the fixture any machined bores may no longer be perfectly round, and true positions of features will have moved slightly as the component relaxes back into its unloaded shape.
The tracker body was monolithically printed in titanium alloy Ti6-4, stress relieved and then cut from the build plate ready for finish machining of the kinematic mount and the four posts that hold the optical reflector globes.
A plastic set of jaws was designed to clamp the part while leaving the machining areas exposed. Although the plastic jaws clamp the part rigidly, they never clamp the part repeatably, so the exact position of the part must be found using a machine probe and best fitting software such as NC-PerfectPart, from Metrology Software Products Ltd. (MSP). Originally developed for machining of high value aerospace and Formula 1 composite structures, this software is perfectly suited to the challenge of precisely locating an organic-shaped AM part with no obvious datum features.
Points are selected on the component in the CAD environment and the deviations from nominal positions are measured by the probe on the CNC machine. The NC-PerfectPart software then creates a best fit alignment that is a 6-axis coordinate transformation—both translation and rotation. This coordinate shift is automatically recalled into the machine controller before CNC programs are executed.
Problems and Solutions
Unfortunately, the hip tracker component flexed imperceptibly when the plastic jaws were clamped, resulting in true position errors greater than 0.3mm on the machined posts. While the component had been optimized for handling loads during surgery, it had not been designed to resist machining forces.
In order to machine the part accurately it was essential not to bend it with mechanical clamping, but at the same time it was equally important to add rigidity.
The solution was to use Blue Photon’s UV activated adhesive and grippers. By gluing the part onto four gripper posts (that transmit UV light to cure the glue in approximately 90 seconds) the hip tracker was held firmly but still in the free state.
An aluminum block was machined to hold the four gripper posts in the correct positions for the tracker body. Initial machining was successful on the three posts directly bonded to the grippers, but one post was cantilevered above the gripper and vibrated during machining. A plastic support block was printed to hold this post and eliminated this problem. By cradling the part, the support block also allowed for more accurate positioning of the tracker prior to the glue being cured. The glue thickness is optimally around 1mm, and after machining the part and fixture can be separated by simply immersing the assembly in near boiling water for a few minutes, and then peeling apart.
The only disadvantage of using the glue grippers appeared to be the extra work to design and machine the gripper fixture. However, on a subsequent project for an industrial impeller Renishaw used plastic printing to produce the gripper fixture instead of machining. This proved that the manufacture of a robust, custom workholding solution can be reduced to an overnight desktop print.
Refining the Procedure:
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