Employing safety and flexibility when CNC machining a 45kg component.
Worker safety is always the first priority when working with new equipment or tools. However, manual loading of heavy housings or components onto a machine for further processing should be treated with equal caution, if not more so. It is one thing lifting 45 kilograms of weights above your head while lying on a bench in the gym, in fact it is a relatively easy task for most fit humans, but it is another trying to load the same amount of weight into the jaws on a CNC machine while you are at full stretch frontwards. It can be done but with difficulty and the chances of the operator over balancing and damaging the machine or component, or worse still injuring him or herself, are high.
This was the problem Vula Drilling (Pty) Ltd faced when moving to series production of their new down-the-hole drilling (DTH) bits. A down-the-hole drill is basically a powerful pneumatic hammer screwed on the bottom of a drill string. The fast hammer action breaks hard rock into small flakes and dust and is blown clear by the air exhaust from the DTH hammer. The DTH hammer is one of the fastest ways to drill hard rock. Now smaller portable drill cat drilling rigs with DTH hammers can drill as fast as much larger truck rigs with this newer technology.
The cell with a Doosan Puma SMX 3100S mill-turn, multi-axis, multi-tasking machine and a Fanuc R-2000iB robotic system
“Increasingly the owners in the mineral exploration and mining industries are looking at costs such as energy expenditure, and like many other industries in South Africa they have been exposed to cheap imports from countries such as China. We had taken a decision to manufacture our own range of rock drill bits for use on pneumatic rock drills, as well as threaded bits used in mechanised drilling, as a locally manufactured alternative to these cheap imports that were flooding the local market,” explained Otto Coetzer, Director of Vula Drilling.
“To meet these expectations of cost reductions and competition we had to have an in-depth look at our manufacturing setup. Our experience in manufacturing drill bits for the mining industry originated back in 1998 when we started to manufacture taper drill bit bodies for some of the major role players in the industry.”
“Even though we had many years of experience we knew we could improve on our processes. With an array of both large and small CNC turning and machining centers, we are well equipped to perform almost any CNC machining operation within our facility.”
Doosan Puma SMX 3100S mill-turn multi-tasking machine
“To achieve these objectives we introduced new CNC machining equipment, amongst others. In 2017 we purchased a Doosan Puma SMX 3100S mill-turn, multi-axis, multi-tasking machine, which integrates the capabilities of a vertical machining center and a horizontal turning center into one platform.”
The Fanuc R-2000iB robotic system moving a final machined component to a removable storage trolley
“Although not fully dedicated to the manufacture of our new product the DTH drill bits, which are manufactured in two versions – a 165mm and a 171mm diameter in QL60 and DHD 360 shanks – the majority of the machining time was taken up by the machining of the drill bit body.”
Not satisfied with loading/unloading – worker safety compromised
“Workholding solutions vary almost as much as applications. This gives shops the ability to choose workholding that’s targeted to their needs, prioritising different factors depending on the type of work they do. Job shops that handle high-mix, low-volume work will place a high value on flexibility in workholding. Production shops seek workholding that will increase throughput by working with automation systems. Shops that do five-axis machining need specialised workholding that provide access to five sides of a workpiece for machining. And those that handle delicate workpieces, or parts that require access to the full outer diameter for machining can benefit from ID workholding.”
“Despite these gains, manual loading of components that weigh many kilograms continued to be an obstacle to more substantial throughput improvements. Although operators used cranes to move bulky material to and from the machine and fixtures, the machine loading process remained both time consuming and physically taxing on the operator. We had to come up with a solution.”
Vula Drilling had to design their own removable storage trolleys for holding the rough machined components and a separate trolley for the final machined components, in the same location of the cell
“There is increased risk any time a worker comes into contact with pinch points which are present when loading raw materials or when unloading finished parts from a machine. Worker safety can be improved with CNC machine tending robots because they are designed specifically to tend to multiple machine tasks. In addition to safety improvements, uptime can be improved compared to manual loading and unloading times. Robotic machine tending can be utilised for bin picking, grinding, milling, turning, polishing, welding, deburring and parts cleaning.”
“Many are investing in machine shop automation to redeploy employees to tasks of higher value and using robotics to handle more mundane shop processes and even intricate detail work. Robotic machining is a manufacturing technology alternative to CNC machining to lower the overall costs, especially in large scale part manufacturing industries. Using robots for machining, implies many advantages. By using the flexibility robots have to offer, versatility can be provided. Nevertheless, there are several challenges to overcome to introduce a robotic solution that will suite your application.”
“However, CNC robotic equipment isn’t intuitive to the location of humans (yet) like cobots, and safety measures must be taken into account to protect against accidental injury. Protective cages, safety fencing and guards are reliable ways to increase operator and bystander safety without slowing down your machine’s production.”
The Fanuc R-2000iB robotic system removing the DTH drill bit from the sub spindle
“When we began this automation project we had no experience with machine-tending robots, but it was clear that an automated process was needed. Some components are heavy, cumbersome or awkward for handling by humans, leading to increased worker injury and costly component damage. CNC machine handling robots can be configured with various mounting options to handle heavy payloads and reduce risks to employee safety. They can also improve employee ergonomics.”
Robotic Innovations approach
“Through our research we discovered Robotic Innovations, who are very active in the industrial and manufacturing arena specialising in robotic system integration and designing turnkey automation systems for a number of manufacturing applications. As is the case in many of these new, industry specific challenges there is never an off-the-shelf solution.”
“Besides being very specific as to what we wanted from the solution, to compound our challenge our Doosan Puma SMX 3100S mill-turn was not setup for robotic association or tendering, which is almost standard with most manufacturers’ CNC machining equipment these days.”
“It was a challenge because although Robotic Innovations are robotic system integrators, they are not manufacturers or designers of CNC machine tools like our Doosan Puma SMX 3100S mill-turn.”
“It was a huge learning curve for all of us and we knew that the solution and software programming would be a first and unique to our situation but with adaptability and also be future relevant. For example we have set up the programme to accommodate the heaviest possible component but scaled it down to suite our component.”
Having fun while learning to incorporate a Fanuc R-2000iB robotic system into a machining operation
“When we embarked on this project we appointed our senior design engineer, Werner van Aardt, as project leader and he was assisted by Lyle Ireland, a recently graduated mechanical engineer.”
Senior design engineer and project leader Werner van Aardt with Otto Coetzer, Director of Vula Drilling
“I insisted that they make it a fun project while learning but not to be scared of incorporating their own intellectual property. The result is that they have incorporated some technology that would not normally be associated with robotic machine tending.”
“This includes a matrix for the Fanuc R-2000iB robotic system to make decisions for itself, with the help of sensors, a function to carry out our own traceability engraving and recording and a simple function like the sounding of a buzzer to alert an operator that the component trolley needs to be attended to. Due to the relatively long machining cycle time, this would give us the option to reload timeously and run 24 hours of unattended machining when required.”
“However, we had to design our own removable storage trolleys for holding the rough machined components and a separate trolley for the final machined components, in the same location of the cell. Effectively removing components from the trolley proved to be one of the most challenging aspects of the automation project. Before a robot can grip and remove a component, it must first determine the component’s position. Each trolley contains a row of four components. The robot must know not only the component’s X-Y location in a row, but also its exact height before gripping it.”
“Sensors help the robot to accurately locate the component before removing it and also to deposit it after machining. A laser sensor mounted on the robot determines the X-Y location of the component it is attempting to pick. Once that component has been located, the robot probes the top of the component to determine its true Z level. It then positions its grippers above the component and closes them to secure and remove the workpiece and then place it accurately in the chuck on the machine.”
“The removable trolleys lock into the cell and have been designed to accommodate various size components as well as the same component.”
“As the Doosan Puma SMX 3100S has a main and sub spindle, the robot was programmed to be able to load and offload from the different spindles, depending on the stage of manufacture of the components.”
The DTH drill bits are manufactured in two versions – a 165mm and a 171mm diameter in QL60 and DHD 360 shanks
“There are some other duties the robot has to perform that requires no human interference, such as the opening and closing of the machine door and the brief rotation of the component so any excess cutting fluid or chips are discarded.”
Due to complex movements during the loading and unloading cycle, the project team decided to break it down into a series of subprogrammes which simplifies the manual operation, programme optimisation and fault finding.
“The project began in July 2020 and was commissioned by mid-December of the same year. Further optimisation and improvements followed and the project went into series production by April 2021.”
“The cell features an intriguing layout and interesting mix of technologies. The machine-tending robot also takes advantage of advanced sensor technology. We have had to be creative and introduce new thinking for the grippers to accommodate for the different dimensions of the products before and after machining.”
“We are now competitive with international processes but still have obstacles to overcome. The steel for example is not manufactured locally and has to be imported, which attracts import duties as where the complete manufactured DTH drill bits imported from China has no duty is payable even though the same drill bits are made locally.”
“Done incorrectly automation can introduce more problems than it solves. Robot arms, pallet systems and other forms of automation are designed to replicate processes established by humans, so before introducing an automation system, manufacturers need to ensure that their processes are solid.”
“Nonetheless, applications to date demonstrate the extent to which automation in general is expanding to include the previously impractical or impossible.”
For further details contact Vula Drilling on TEL: 011 845 3031 or visit www.vuladrilling.co.za
