A common problem faced when using 3 phase AC motors in multiple lane packaging equipment and conveyor systems is motor drift. The Sydney company was using a 415V AC 3 phase 0.37Kw motor that had a 1380 rpm output driving through a 115:1 right angle gearhead. The motor is driven by a PLC which commands 60.5mm moves on a conveyor but without a true absolute closed loop positioning system, over the course of the day the AC motor system would develop a drift of a few millimetres with respect to other components on the machine. The AC motor and drive system employed was using a relative step positioning system that on paper was able to deliver the required position resolution, however it is the motor and drive system accuracy that leads to drift or offset when hundreds or even thousands or repetitive moves are carried out over the course of a day. maxon were able to offer a solution using a brushless DC servo system and a DC motor position controller that conducts absolute movement based on high accuracy optical encoders. The motor is a 3 phase 60mm diameter 0.4Kw 48V brushless DC type fitted with an 81mm 93:1 180Nm planetary gearhead and an additional 1.5:1 stainless steel right angle transfer gearbox rated at 238Nm peak. The three phase DC motor controller EPOS2 (easy to use motor positioning system) has the unique feature of being able to conduct absolute moves measured directly from the load by using a dual encoder loop function; Whereby the position is taken from a load mounted absolute SSI encoder and high speed motor regulation is taken from a second encoder mounted directly to the rear shaft of the dual shaft motor. A stand-alone motor control system was required via a customised keypad. To set up the motor control system with an application unique human machine interface maxon recommended the local Sydney company Robotic Systems who have in-depth knowledge of mechatronic systems. Robotic systems chief engineer and CEO Adam Amos has conducted many successful custom motor control implementations using maxon motor products. The successful relationship between Robotic Systems Pty ltd and maxon motor creates a full solution service from hardware, firmware, and software to programming and support.
Contact Brett Motum from maxon motor Australia Pty Ltd on +61 419 020 233 or Adam Amos from Robotic Systems Pty Ltd on +61 424 624 578
© 2013 by maxon motor Australia Pty Ltd
maxon motor Australia now carry a range of general purpose shaft couplings and power supplies in stock from the Sydney warehouse.
Flexible couplings that are compatible with a majority of maxon DC motor shaft diameters from 2mm to 12mm are carried in both stainless steel and aluminium construction. They are offered to our customers only at cost to support fast and easy implementation of motor and gearhead servo systems. The cost of the shaft couplings ranges from as little $12.00. In addition to the motor shaft couplings we also now carry a range of DC power supplies. The power supply range has also been selected to suit the maxon DC motor range with typical voltages of 12V, 24V and 48v and power levels up to 750W. The power supplies are also intended for maxon motor customers only and are passed on at cost as a support service. The power supplies have also been specifically researched and tested for use with the low inductance windings of maxon DC motors. Both brushed and brushless DC motors with low inductance windings can allow large short-term inrush currents that often send low quality power supplies into foldback or hiccup mode. Careful consideration of the output capacitance and circuitry must be automation or robotic application. Ph:+61 2 9476 4777
Something different: For this week’s motor of the week article we are talking encoders.
Small encoders for DC motor positioning and speed control applications are easy to find. With the range of MR incremental encoders for maxon rare earth brushed and brushless DC motors and the new Easy line of encoders for the DCX permanent magnet brushed DC (PMDC) motors, there are many choices for small and miniature encoders. In fact, these encoders are so small they can’t be supplied separately. They rely on the DC motor housing and shaft for their own mechanical structure. When you need a very small encoder to mount with the load or any other rotating component the standard incremental encoders will not suffice. Another interesting requirement for the use of small encoders is very high resolution positioning of DC motors that are fitted with gearheads. The backlash in the gearbox can often cause a positioning error in the system. To counter this the new EPOS2 miniature position controller has an advanced functionality whereby two encoders can be used. The first encoder is used on the rear of the motor for speed regulation and the second is mounted directly to the load for positioning. This results in the need for a small externally mounted (structurally independent) incremental or absolute encoder. Two such encoders that were specified for a robotics application this week were the Gurley R112 and A19. Both of these encoders are tiny, with diameters of 12mm and 19mm. Both have 3mm hollow bore shaft inputs and mounting flanges. The R112 has a 500 counts per turn incremental output and the A19 has a 12bit absolute SSI output. Either of these tiny encoders can be used with maxon brushless DC motors and brushed DC motors in a dual encoder loop to achieve accurate position control via the EPOS2 position control devices. matching the truly tiny proportions if the DC motor and controllers from maxon these miniature encoders offer solutions previously unattainable with standard products.
Contact maxon motor in Sydney for further information or assistance on how to match Gurley encoders with maxon DC motors and positioning systems. Ph: +61 2 9476 4777
The Austech exhibition is now wrapped up and we are back at the office following up on the new contacts we made. This year we launched the new DCX motor with many visitors interested in the ability to configure custom motors online. The exhibition was also an opportunity to exhibit KAG motors for the first time in Australia. These motors were particularly interesting for industrial automation engineers looking for robust high quality solutions.
Brushless DC servo motors are an effective solution for applications in harsh environments.
A major factor for the selection of a DC motor in an application is the environment that it is intended for. maxon motor offer a wide range of IP rated brushless DC motors however factory IP ratings can some-times have undesired side effects. Take for example Figure 1: which is a 250w continuously rated 45mm brushless DC motor. This motor is assembled with a 52mm Ceramic Planetary Gearhead. The Gearbox is fitted with rubber sealed bearings and a rear cable exit housing for the encoder, motor and hall sensor cables that pass through rubber sealed grommets. This solution offers effective IP54 sealing for the of the DC motor but it is easy to see that the sealing method is quite bulky and possibly not suitable for many applications with tight mounting constraints. The good news is there are many other sealing solutions. maxon brushless DC inrunner motors do not require any airflow through the motor itself to maintain operating temperatures in the winding. Many unsophisticated brushed and brushless DC motors do however require convection cooling of either the windings or brushes. The inrunner design of maxon brushless DC motors combined with the ironless rhombic winding also allows the rotor to be thermally bonded to the housing and completely conduction cooled. Meaning the motor requires no airflow through it, allowing the motor to be inserted into a tube or extrusion housing to protect it from the elements. In many applications the size and cost of factory IP rated motors has resulted in the selection of smaller non IP rated motors with simple modifications like rubber or Teflon sealed bearings. Often the simple addition of an external v type seal on the shaft is sufficient. Figure 2: is an example of this style of modification. This brushless motor is only 30mm in diameter and with the addition of a Teflon seal and the motor being mounted in a tube housing gives a small, well cooled, sealed brushless motor at a fraction of the cost for factory IP solutions. This motor is used in an aerospace application where the weight of the motor is obviously critical and this solution offered a major advantage weighing only 270 grams. Additionally maxon also manufacture specialist motors for extreme applications. For example downhole drilling or deep sea remotely operated vehicles. In these applications the motors see extreme pressures whereby sealing is impossible and an alternate approach of letting the motor flood with oil is adopted.
Contact maxon motor in Sydney for further assistance. Ph: +61 2 9476 4777
These small DC motor combinations are perfect for robotic applications where weight is a premium.
When Australia’s leading automotive parts manufacturer builds robotic assembly equipment they turn to the leading manufacturer of small DC servo motors. “Power density”, this is a particular buzz phrase in the robotics and automation industry at the moment and motors and drive controller technology are at the core of this requirement. This flat or “pancake” brushless DC motor when used in conjunction with a high reduction planetary gearhead gives very high torque levels for the motor and gearheads combined length, diameter and mass. In the application on a cyclic basis the servomotor combination delivers up to 6.5Nm with a motor and gearhead length of only 61mm, a motor and gearhead diameter of only 32mm and a mass of just 240g. These features make it suitable for any automation application where the mass of the motor is located on another moving actuator. When designing robotic arms for example, if you start with higher mass components on the end you have a cascade effect of increasing motor size towards the base of the unit. This critical power density criteria also flows onto the motor control electronics. The less efficient the servo motor is the higher the current draw for a given load, the higher the current draw the heavier the cables, and motor controllers also need to be larger to cope with the additional power. Recently servo motor controllers have become so small and efficient that designers and engineers are mounting the controllers close to the motor on the moving parts to reduce the number of cables on the arm section of the gantry or robot arm. Indeed this was the main reason for the selection of the ESCON (Easy to use Servo Controller) 36/3 servo motor controller specifically for brushless DC motors. The controller can be used anywhere between 10 VDC and 36VDC it can deliver up to 9A on a short term basis and up to 3A continuous. The motor control unit has very fast response and weighs in at a mere 36 grams. With dimensions of 55x40x19.8mm when combined with the servo motor at the point of the robotic joint the total servomechanism is achieved at a tiny 276 grams.
Contact maxon motor in our Sydney office for further information +61 2 9476 4777
This custom brushless DC servo motor supplied this week for a customer in New Zealand is a real powerhouse.
The featured DC motor supplied this week displays technology that delivers an outstanding power density. Power density is a measure that compares the output power of the motor with its volume. This DC motor weighs in at only 300 grams and delivers an amazing 15Nm of torque and 200rpm on a cyclic basis in its aviation application. The motor is a four pole brushless DC that has several distinguishing features. Traditionally the front and rear flange of a DC motor is swaged or bolted to the body. But in applications with extreme vibrations and high shock loading these methods are inadequate. On the 30mm brushless 4 pole from maxon motor the end flanges are double laser welded to the body. The laser welding is not a spot or pulse method but a continuous flow system with unrivalled penetration. The process for the weld is fully automated and uses advanced visual software to monitor the quality of every weld. The centrally shaft mounted rare earth magnet allows for proportionally large and robust bearings of the same size on both the front and rear of the motor. This means the DC motors rotor can withstand impacts that traditional designs cannot, it can be balanced for high speed operation up to 25,000rpm and can operate here with very low noise. The motor is coupled with a 32mm high power planetary gearhead This gearbox has large dual preloaded stainless steel bearings fitted with a seal to prevent any ingress form the harsh environments the motor is intended for. The standard gearbox is supplied with a 6mm hardened stainless steel shaft however the heavy duty gearhead is fitted with a large 10mm shaft and keyway. Interestingly, for this application maxon motor have tapped a threaded bore along the axle of the gearbox shaft to comply with unique mounting requirements by the customer. The servo gearmotor is fitted with a high resolution 4000 quad count three channel encoder and the motor is used in a positioning system also supplied by maxon. The overall gearmotor, encoder, controller package is of the highest power density available on the market today.
DC Gearmotor specially customised to suit novel wheelchair design.
The challenge in this application was to allow the adjustment of the wheelchair seat height to allow the easy access to workbenches of various heights. Kitchen work surfaces and workplace areas that are normally very hard to access from a wheelchair. Also required from motors in wheelchair applications is the need to independently control the gearmotors for manoeuvring. Challenges faced during the design of a wheelchair are the minimum amount of space for the motors, the weight of the motors and the high torque requirement for users that are heavy. For this application KAG had developed a new custom DC gearmotor based on the M 48 DC motor and the PM 52mm planetary gearhead. They have manufactured a unique cable and connector that allows for very easy connection and they have also manufactured the 52mm gearbox with an extra long shaft. The shaft has been machined with a groove along its length for easy installation with a linear actuator that pushes the seat up and down. For the traction drives on the wheelchair they have used x2 DC gearmotor assemblies with noise optimised gearboxes and backlash reduction customisations. The motors are fitted with noise reduction circuits for compliance with the motor drive and power supply. This style of brushed DC gearmotor is robust both internally and externally. It can withstand high short term overloads and the rigours of use outdoors.