Bobcat® Improves Productivity 300% with Engis Single-Pass Bore Finishing System
For more than 50 years, Bobcat skid-steer loaders have represented durability and reliable performance for construction, landscaping, and agricultural applications in the USA. The key to a dependable loader is to have properly balanced horsepower and hydraulics so operators can work efficiently in rugged conditions. With an eye to continuous product performance and reliability improvement, Bobcat recently invested in an Engis bore finishing system which has not only improved the quality of a key hydraulic component, but increased manufacturing throughput 300%.
Tightening the Process
Previously, Bobcat finished the control valves on its skid-steer hydraulic pump bodies by using a multi-pass honing system that required operator manipulation with each part. The honing machine would make a pass to finish three dia. 15.877 mm (0.6251″) bores on the G2 steel casting. Then, an operator would move the part 180 degrees on the die so the machine could make a second pass through the valves on an off-set bore.
“We had to take extra measures to make sure the valves wouldn’t leak, which is essential for our customers,” said Dean Cota, Bobcat Sr. Manufacturing Engineer. “We had to run the honing system through multiple times because each spindle had only one stone on it. Each head would go through the bore three times to perform the roughing, semi-finish, and finish steps. Then we would manually reposition the part and run it through again.”
The finishing process was slow and required extra operator care to guarantee tight bore tolerances. While researching other honing options that would improve productivity, Cota discovered Engis’ single-pass bore finishing, which provides a multi-spindle head that hones with three/four tools in close proximity to each other. This unique arrangement allows the roughing, semi-finish, and finishing operations to be performed simultaneously on all of the valve bores in a part.
Engis custom designed theto Bobcat’s specifications. The machine has six stations for which the part is transferred through by a rotary index table.
The Engis system achieves tolerances to 0.5μm (0.000020″) ensuring bores are consistently straight and cylindrical, which are critical for the spool and valve bore to fit properly in the hydraulic system. When hydraulic valves perform optimally, they can withstand a higher pressure, which improves overall performance of the skid-steer loaders.
Theis achieved through a series of progressively finer, high-precision electroplated diamond tools. The diamond size grit on the tools are to 100/120, 200/230 and 325/400. The free-floating nature of the tooling results in superior bore consistency and a faster cycle time.
The old multi-pass honing system took 253 seconds per part, which included two boring passes, re-setup of the machine and flipping parts. The new single-pass boring system takes 89 seconds, improving throughput by nearly 300%.
By automating the bore finishing system and reducing operator contact with the parts, Bobcat has reduced the chance for mistakes.
“When someone handles a part, it introduces an opportunity for errors to happen,” said Cota. Now, with the new Engis boring system, where we don’t have to flip the part, the operator doesn’t have to touch anything, so the potential source for errors has been eliminated.”
Operator transition to the new single-pass bore finishing system was simple due to built-in CNC programming. “When the machine hit our production floor, the programs were all ready to use,” said Cota. “Now the operator just pulls up the right program for each part. It’s been running pretty much flawlessly since we first got it more than a year ago.” The machine’s vision system identifies that the right parts are loaded before the program runs, which further prevents errors.
The advanced gauging system 100% inspects and measures the bores for geometric precision so that every part coming off the line is exactly to spec, which provides further peace of mind for the operators. Because the single-pass process spreads the workload over a series of high-precision electroplated diamond tools, Bobcat requires very few tooling changes, which saves on consumable costs.
“The tooling costs are so low on the new bore finishing machine that we have a hard time measuring our tooling cost savings,” noted Cota. “We ran the machine for six months, six days a week for 20 hours a day before we had to change the tooling. At an average run of 165 parts per day, we produced nearly 24,000 parts before we needed to change out the tooling.”
In addition, the new Engis bore finishing system has decreased cycle times to the point that the plant can take on additional honing production without requiring any additional capital investments.
Thanks to additive manufacturing, MAPAL now offers hydraulic chucks in miniature format with HSK E25 connection, for example for the direct clamping of tools with a diameter of 3 mm. These meet all the demands on chucks for the miniature sector with respect to radial run-out accuracy, balancing value, cooling lubricant supply and handling.
In order to guarantee perfect radial run-out accuracy, innovative clamping chamber systems are integrated into the new chucks that fit tightly against the shank of the tool. They are fitted with dirt grooves as protection against micro-soiling. The demanded balancing value is ensured thanks to the internal balancing geometries and supporting structures that also aid the optimisation of weight and strength. The miniature chucks allow homogeneous acceleration and deceleration of the whole tool system of chuck and tool for less loading of the spindle.
The innovative manufacturing method has also enabled the chucks for the miniature sector to be equipped with decentralised coolant outlets. These outlets are designed using parameters such as coolant pressure, setting dimension and spindle speed so that they deliver the cooling lubricant precisely to the cutting edge. In the best case, a metered total-loss lubrication system is achieved that eliminates the need for subsequent cleaning of the parts.
The new miniature chucks from MAPAL allow quick and simple clamping of the tool. Neither training courses nor high setup costs or expensive peripherals are required for implementation of the chucks.
The new small hydraulic chucks also offer new possibilities for the clamping of workpieces. For example, for the clamping of artificial hip joint balls. Specially formed clamping chambers inside the chuck and a special outside geometry ensure that the balls are very precisely and at the same time gently clamped. Particularly in medical technology, topics such as reproducible precision are taking on enormous importance – and this is ensured during machining thanks to the new chucks.
Please contact us for more information.
Thin-walled parts are used in a wide variety of applications. These components are often manufactured close to the net shape, but nevertheless require a great many machining operations. The particular challenge for these machining processes is that due to their design, these parts are very unstable and susceptible to vibration. That creates special demands upon the design of the process and the tools.
These parts are preferably machined in a single clamping system. In order to meet this demand and to make as many of the surfaces to be machined as accessible to the tools as possible, certain allowances have to be made in the clamping system. As a consequence, the workpiece is not optimally supported and tends to vibrate. Thin webs, voids and interruptions to be machined and widely fluctuating stock removals from the cast blank also call for special tool solutions. For large parts with many machining steps, this would require a huge number of tools. The merging of these steps using combination tools in order to reduce the non-productive times and the number of tool slots is an ideal solution.
Thanks to its vast understanding of the processes for the machining of unstable structural parts, MAPAL is able to offer cost-effective and reliable processes. Three aspects are of particular importance here. Firstly the adjustment of the cutting rate is a factor for reducing or avoiding rising vibration. Both vibration of the tool – which would result in short tool lives and poor machining results – and vibration of the workpiece have to be prevented. The latter would result in a recoiling of the part against the cutting edge and could cause damage to the tool. The second important adjustment in the tool design is the evaluation of the tool body. Vibrations can be reduced here by an appropriate design and choice of material. Furthermore, an intelligent arrangement of the cutting edges in form and position helps to keep the cutting forces low. And finally the machining process itself offers possibilities for reliable machining of parts susceptible to vibration. Reorganization and the choice of alternative sub-processes create a change in the distribution of forces that can increase the process reliability. For example, the use of a circular milling operation instead of a solid drilling operation can help to stabilize the process.
Please contact us for more information on machining of Structural Components.
– This article is an excerpt from Mapal Innovations – Process Solutions
The Flex-Hone® Process (Super finishing) produces a controlled surface condition unobtainable by any other method. It involves finish, geometry and metallurgical structure. A high percentage plateau free of cut, torn and folded metal (with radiused ports).
A resilient, flexible, cylinder honing tool with a soft cutting action. The abrasive (points) globules each have independent suspension that assures the Flex-Hone® to be self-centering, self aligning to the bore, and self-compensating for wear.
Specifically, it is a low-temperature abrading process that exposes the undisturbed base metal structure to produce a long wearing surface. It is a method of developing a surface on a metal part which is optically smooth and metallurgically free of any fragmented, amorphous or smeared metal from previous operations. It is accomplished at a low pressure where the “stones” float.
The particular type of Flex-Hone® crosshatch is extremely efficient in providing a multiplicity of oil grooves or valleys for oil retention as opposed to the often undirectional or uneven valleys common to the conventional type rigid hone. A crosshatch that usually remains as the cylinder wall has been wear-reduced by the FlexHone®.
The Flex-Hone® Tool is available in a variety of abrasive types and grit selections to provide the optimum surface finish on any base material. The Flex-Hone®, also known as the cylinder ball hone, is commonly used to reduce Ra, Rk and Rpk values while maintaining Rvk and Vo volume for oil retention. Using the Flex- Hone® Tool for surface finishing allows the sizing tools to do their jobs quickly and accurately without fighting surface finish. The Flex-Hone® is also used in adhesive bonding applications where a rougher surface is desired for bonding integrity.
The deburring of cross drilled holes is an expensive, time consuming operation. The Flex-Hone® Tool can be used to remove burrs from cross drilled holes leaving a clean, radiused intersection. Because of its unique construction, the Flex-Hone® can be used online in machine tool applications or offline as a secondary operation.
The cylinder honing tool is self-centering and self-aligning to the bore so elaborate, rigid set-ups are not required. It is advisable to use the tool in the main bore into which the cross holes break. Best results are obtained by rotating and stroking the flex hone a few strokes in a clockwise direction, removing the tool from the part, reversing the spindle and then rotating and stroking the tool in a counter clockwise direction for a few more strokes. This forward and reverse rotation creates a more symmetrical deburring pattern.
Brush Research pioneered the concept of a plateau finish and is a strong proponent of the benefits of a cross hatch, plateaued finish. The concept involves using flex hones to remove the peaks produced by prior machining operations to create a substantially flat or plateau finish. A plateau finish created by the elimination of peaks allows rings and seals to seat without damaging their edges. The cross hatch pattern will aid in lubrication control and retention, reduce seepage in hydraulic and pneumatic applications and promote longer seal life.
Horn and W&F Werkzeugtechnik have come together to offer customers a complete solution covering everything from the spindle to the tool cutting edge. The focus is on equipping Swiss-type lathes with a quick-change system. “By entering into this cooperation, we are filling the gap that exists in our offering between the cutting edge and the machine. It will allow us to respond rapidly to customer enquiries and optimise their machining processes”, says Managing Director Lothar Horn, Paul Horn GmbH. Under the deal, HORN will be responsible for selling W&F tool solutions from Großbettlingen all across the world via its subsidiaries and sales partners in more than 70 countries.
The cooperation also brings many advantages in the OEM area by making it possible to offer customers “everything from a single source”. Thanks to the experience of both partners, new solutions and optimisation approaches can be developed in next to no time. To begin with, the cooperation will focus on quick tool change systems for Swiss-type lathes and internally cooled whirling units. A special Horn catalogue for Swiss-type turning is due to be launched in the autumn of 2018.
The first jointly developed technology to have come out of the cooperation is JET-Whirling. The internally cooled whirling tool is a real USP of the whirling method. Having the coolant supplied directly to the cutting edge during whirling results in higher surface quality, improves the flushing action for removing chips and extends the life of the tool inserts. The tool system – comprising the W&F whirling unit and Horn whirling head – was officially unveiled at AMB 2018 in Stuttgart.
Please contact us for more information on solutions from Horn + W&F!