Towards Automated Concrete Spraying

Operating a concrete sprayer is one of the most demanding tasks in underground mining and tunnel construction, and experienced and skilled operators are becoming more difficult to find. As a result, the quality of sprayed concrete application can vary critically from one operator to another.

Equipment manufacturers have been increasingly tasked to develop their products so that variations from operator to operator are minimized, and productivity and safety are increased. The SmartSpray System from Normet is one step toward developing a machine capable of fully automated concrete spraying.

Traditional control of a spraying boom means that every boom position is controlled separately by the operator in order to achieve desired movement. Spraying result, spraying quality and even durability of the machine can vary greatly between operators. The need for improved performance and result prompted Normet to begin design and development of a fully automated spraying system.

Normet’s Spraymec family of shotcrete sprayers is currently available with SpraySmart System as an option. This version includes two features to assist the operator; coordinated and point-to-point control modes which are built on top of the standard boom control system. This configuration allows for the machine to be operated in either semi-automated or traditional control configurations.

State-of-the-Art Sprayed Concrete

Staying ahead in R&D and innovation is a critical component toward accomplishing automated spraying. Recent developments in shotcrete equipment incorporated into Normet sprayers include low pulsation concrete pumping, constant flow accelerator dosing systems, and high voltage power systems. These advancements combined with operator training through simulators and other means promote best spraying practices and optimum hardened shotcrete characteristics.

During the past 40 years, more than 9,000 Normet sprayers and auxiliary equipment have been manufactured for use in small to large tunnel and mine headings across the globe. There are two categories of sprayers with many configurations offered. Five sprayer models are designed for mining and six sprayers for tunneling. Spraymec SF 050 and Minimec are designed for use in smaller cross sections while the Spraymec 8100 VC, Spraymec RM-series, Spraymec Alpha 1430 PC, and NorRunner 100/140 DVC are suitable for the largest mining and tunneling headings.

SmartSpray 1: The First Step Toward Automation

Normet launched its first version of the SmartSpray 1 system with a customer-delivered Spraymec NorRunner 140 at the World Tunneling Conference in Bergen in June 2017.

SmartSpray 1 is an extension of the NorSmart system which provides seamless control and diagnostics for all machine functions. These systems combined allow the machine operator to use computer assistance in operation of the concrete spraying boom and nozzle through coordinated control and point-to point control modes.

In coordinated control mode, the operator controls only the spraying nozzle with boom functions automatically controlled in alignment with nozzle position. Only one joystick is required to perform basic concrete spraying movements, as opposed to the traditional two to four joysticks. Spraying direction can be maintained automatically during the movements, if desired, using auto nozzle control feature, which simplifies the spraying task for human operators.

When using point-to-point mode, the operator defines a line between two points. After activation, the spray nozzle automatically follows this line. If the nozzle angle is locked, it is automatically retained in position against the tunnel profile. The operator only has to move the boom to the next position needed for spraying. Nozzle position can be fine-tuned and controls overdriven manually if needed. This functionality is useful for spraying large smooth surfaces.

The redundant nature of concrete spraying booms enables inclusion of some extra features to assist with boom control. In the current SmartSpray system, one such feature allows the middle point of the boom to be moved in three (3D) directions by the operator using one of the control levers while pressing an activation button.

The position of the boom can be controlled in order to avoid collisions or to prevent the boom from being driven to impractical positions. Operator-controlled movements of the middle point do not alter movement of the spraying nozzle.

A second feature allows middle joints (two joints) to be made rigid using an on/off switch. These joints remain in the position where they were during coordinated movement of the nozzle, which is useful especially in narrow tunnels.

In addition to these boom control features, the Normet SmartSpray 1 system has several smaller features, designed to make the operator’s everyday tasks easier. Included is a coordinated frame in which the control works can be re-oriented by pressing a button. This new orientation is set according to current orientation of the upper part of the boom. Essentially this only changes interpretation of the control lever signals, which define the velocity demands of the nozzle. It also includes an automatic back and forth rotation and tilting of the spraying nozzle. Choosing between on/off or proportional steering of nozzle turn and tilt are similar to those in direct manual control state.

SmartSpray 2: currently in development and testing

When speaking about “robotic spraying”, worries concerning incorrect thickness and inconsistent quality of sprayed concrete arise. These issues have been taken into account from the beginning of the SmartSpray development process.

Customers asked Normet to develop a system where distance of the nozzle is kept within a certain range from the wall to make sure that fluctuations of nozzle distance do not affecting final quality of the sprayed concrete. At this stage, however, it was still expected that the responsibility for other spraying parameters is left to the operator so that concrete spraying does not fully rely on equipment and technology. It was also requested that Normet develop a system to spray required thickness of concrete, more or less automatically.

Development work for this SmartSpray 2 System, with easy profiling (“area spraying”), is ongoing and already in the testing phase. In the near future we will have more elaborate software and measurement system developments available and ready to launch, allowing Normet to offer “semi-automated” spraying with thickness control.

SmartSpray 3: the next big step

There remains a long road to travel before a fully automated concrete spraying system is developed. Steps taken by Normet so far have shown that we are heading in the right direction and will achieve our objective.
Normet’s goal is to be number one in concrete spraying automation. This includes the utilization of select scanning features in our sprayers, in order to provide a fully automated concrete spraying system complete with accurate thickness control and reporting. Our customer’s benefit through improved productivity, quality of application and concrete utilization.

Total Wet Mix Shotcrete Process Ownership

No matter how good the equipment, if the rest of the process is not in place the shotcrete process could fail. Robotic spray automation is an important part of the process in providing best placed shotcrete at best value to our customers.

In addition to shotcrete sprayers, Normet manufacturers a complete line of concrete transport equipment, mobile shotcrete / batchplant equipment and services, designed to meet the application and logistics challenges of the mining and tunneling industries. Normet Construction Chemicals offers a variety of admixtures, shotcrete accelerators, fibers, and specialty products that are suitable to local cements and project conditions. We can also assist our customers in designing shotcrete mixes that will meet or exceed their shotcrete specification requirements.

Normet has the experience, knowhow and resources to create the highest possible value to our customer’s. For more information on this subject or Normet products and services please contact the author at lauro.lacerda@normet.com

Lauro Lacerda, PE, is Manager of Ground Control and Construction Technologies for Normet Americas Inc. and based in Salt Lake City, Utah.

Marjo Koivisto is a designer and marketing specialist for Normet based Helsinki, Finland.

EDITOR’S NOTE: This article was originally published in the Fall 2018 issue of Shotcrete magazine, published by the American Shotcrete Association (www.shotcrete.org). It is being reprinted with permission.

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