Hydraulic drive pumps for in-situ line boring and surface facing have historically been heavy for operators to handle and lacked control and power at low cutting speeds.
AVS Engineering, in Bellevue WA, has recently released a brand-new innovation in this area – a servo controlled hydraulic pump.
The new pump is the result of extensive design, development and testing in WA by industrial automation engineer, Morne Grundling, and was initiated by AVS Engineering’s need for more consistency and control in their own jobs on mine sites across the state. The final product developed is now available for sale through AVS Engineering, to other onsite machining companies and the word is spreading fast.
Conventional ‘Wisdom’
Conventional hydraulic pump controllers for these applications regulate cutting speed by restricting the flow of fluid to the pump. Choking the flow through a small valve and bypassing most of the hydraulic oil creates an enormous amount of heat and that requires a system of heat exchangers and a large reservoir of fluid (often 2.5-times the volume actually needed) to be taken to site in order to have enough volume and tank surface area to cool that fluid during the machining process.
If, for example, a pump is being driven by a motor constantly supplying 7.5kW and the actual cutting job only requires 2kW for an optimal cut, then 5kW of energy is being converted into heat in the oil and must be dissipated.
Typically, operators allow the entire system to warm up or heat soak to between 65°C and 85°C before starting the job.
A second problem caused by reducing the flow of fluid to the pump is that the amount of power it can produce at lower rotating speeds is significantly reduced. This is not ideal if more power is needed to cut through harder material – particularly if slow feed rates are required.
These two detrimental effects of conventional pumps and motors are compounded because as the oil heats up, and therefore thins, the loss of density reduces the amount of power the pump can generate in the first place.
Operators are then forced to increase the pressure in the system to compensate. In many cases this means running back and forth from the pump to the cutter, trying to achieve the best balance possible.
A perfect cut requires consistent flow and pressure, so ‘the way it has always been done’ just doesn’t deliver the goods.
Smarter Approach
AVS knew what it needed for a smarter way to achieve highly consistent line boring and surface machining results. Morne Grundling is a very experienced industrial automation engineer with enormous experience in high precision robotics and the ability to create an innovative and far more efficient solution.
He started with a clean sheet of paper and adopted the very latest servo motors as the basis of the new system. When properly controlled with suitable software and power source, these servo motors are able to deliver 100% torque at only 1rpm for unmatched cutting control. By controlling the speed of the pump and not restricting its oil flow, the new system only makes the flow required to maintain a given rpm – no matter the torque or load. This is revolutionary.
What’s more, a completely in-house designed software system constantly updates the servo motor to maintain a constant rpm, and therefore cutting rate, while automatically compensating for minute changes in torque requirements (as a function of cutting tip load) and changes in oil temperature.
This extraordinary control is made possible by a sensor on the servo that reads two million pulses per revolution in 16-bit resolution. Operators soon discover that they can very quickly find the sweet spot for any cutting job and rely on this highly responsive system to maintain that exact cutting speed for the duration of the job.
Thus, the intelligent control system instantly compensates for variances in the hardness of the material being machined. If the cutting tip suddenly encounters a harder material, the controller instantly responds by applying more load to maintain the exact cutting speed and give an even cut. Conversely, if the material becomes softer, the controller with reduce the load to provide the same degree of consistent machining.
Perfect for Big Bore Diameters
By providing a degree of control that allows operators to dial in cutting speeds as low as 1rpm with constant monitoring of load and delivery of torque – all while standing at the job and fine tuning the process with the remote hand controller – the new system is ideal for large diameter bores. The larger the bore diameter, the longer the radius from the centre of the rotating head to the actual cutting tip.
With conventional line borers, it can be very difficult (or impossible) to reduce the speed of the head enough to stop a cutting tip located a metre or more away from over-speeding or causing sub-optimal cutting finishes.
This pump and servo combination gives the operator an unprecedented level of control for a perfect cut, even in the largest of bores.
Multitude of Advantages in the Field
The new servo pump system is drawing attention right across the mining sector because it puts to rest so many of the inefficiencies of the past. In a nutshell, the improvements include:
- Only 30l of oil is required in a much more compact tank, which results in 1/3 less payload
- The system will never exceed 45°C
- Only the exact amount of power required to do the job is input, which results in reduced loads on generators and less fuel consumption
- The power for the system is stored in a DC bus, which allows a ‘soft start’
- Less components to transport – pump, servo, tank, unique software and controller and the cutting head
- System alarms out in the event of an overload – no damage and improved operator safety
- No more than 24V exposure and CAT 6 safety system in the rugged, fully earthed, ISO-approved, hand controller
- The latest pump version incorporates a new billet manifold for even greater durability and reduced use of flexible hoses
- Internal safety pressure relief valve
The in-built software system also logs data while the tool is in operation to allow analysis and to help operators make continual improvements in the quality and efficiency of their work.
It is interesting to note that every servo and pump unit is individually tuned and calibrated before having its serial number applied. This allows AVS to supply exactly the right service parts during its life to maintain that high level of calibration.
In-house and Onsite Machining
Apart from designing, building and now selling revolutionary electronically controlled hydraulic pumps, AVS Engineering has full in-house and onsite machining capabilities with all the equipment needed for minesite maintenance, refurbishment and repairs.
Its latest acquisition is a simply massive mill that enables it to handle any earthmoving requirements including the very largest of graders, excavators and tip trucks.
Line boring has been the mainstay for many years and the company’s capabilities in this area are second to none. AVS can deliver accuracy within 0.002 inches over a span of 12m to ensure even the widest spaced pin bores run perfectly true, centre to centre.
Its equipment allows them to handle bores from a tiny 35mm to a massive 1200mm in diameter, which caters for everything from the smallest PTO link to the largest excavator arm.
AVS regularly takes on the large jobs or the tricky jobs that require out of the box thinking and the fabrication of custom tools.
One recent example was the repair of the rails on a 50t crane fork. Bearing failure had caused significant damage to the inner and outer runners on the lift, so AVS built an automated surface grinding rig to run up and down the inside of the rails to machine them back to a flat surface after reclamation welding had been completed.
AVS’s founders, father and son team Vaughan and Adrian South, have decades of experience working on mine sites across the country and all that expertise is passed on to each and every client. This is what enables them to solve difficult engineering problems and come up with innovative solutions.
A major part of their business is in line boring and surface machining and that has led them to design and build the new DC controlled pump, which is now available for other machinists to purchase. Australian know-how and expertise applied to Australian industry – a smarter thinking success story.
SOURCE
AVS Engineering
P 0429 991 927
W www.avsengineering.com.au
E [email protected]
