A planetary gearbox consists of a sun gear, planetary gears with planetary carrier and a hollow wheel.

These internal gears have different dimensions for the different Gearbox gear ratios.

In a single-stage planetary gearbox with a gear ratio of i = 4, the planetary gears are exactly the same size as the sun gear and can thus transmit the highest nominal torque.

With the other gear ratios, either the sun gear or the planetary gears will be smaller. The different leverage conditions in the planetary gearbox mean that the nominal torque is lower, even though the gearbox is the same size.

Article 2g of Machinery Directive 2006/42/EC defines a partly completed machine as follows:

“‘partly completed machinery’ means an assembly which is almost machinery but which cannot in itself perform a specific application. A drive system is partly completed machinery. Partly completed machinery is only intended to be incorporated into or assembled with other machinery or other partly completed machinery or equipment, thereby forming machinery to which this Directive applies.”

Accordingly, a motorised Linear Unit is classed as partly completed machinery.

According to Machinery Directive 2006/42/EC, partly completed machinery does not carry a CE mark. Consequently, a motorised Linear Unit does not carry a CE mark of its own. However, the electronic components (Motors, Controllers) do indeed carry a CE mark, as they must comply with the EMC Directive or electrical safety guidelines, for example.

Motors and Controllers also meet the requirements of the U.S. UL certificate and can therefore be used in the USA.

item MotionDesigner® software is a selection and design program that identifies the optimum solution for a customer’s needs. During the configuration process, the transport task is described in detail and the software uses the data that is entered to calculate the technical requirements for the Linear Unit, Motor, Gearbox and Controller. Based on the estimated service life and capacity utilisation for the system, the program works out which solution will best meet the customer’s requirements. It factors in a performance reserve that makes sure there are adequate reserves during operation without making the system any larger than it has to be.

The Support team at item are on hand to help throughout all the design stages, right up to commissioning. 

item MotionSoft® is a software program that non-experts can use to get their Linear Unit up and running automatically, but experienced technicians can also use it to execute a more detailed commissioning process. Automatic commissioning is supported by the intelligent item Controllers. The touch of a button is all it takes to launch a program that gets the item Linear Unit to measure itself and automatically calculate parameters that are then stored in the Controller.

Experienced users can utilise an expert mode to make detailed, custom entries for all Controller parameters. If any problems are encountered, specially trained experts are on hand to offer help over the phone or through a remote session.

item recommends the use of preconfigured power and data cables, which are available in a range of lengths.  As the connectors are conventional plug-in connectors, customers can also manufacture their own cables. However, experience has shown that one of the main causes of errors lies in faulty wiring and inappropriate shielding. item cannot provide any warranty against errors or faults caused by inappropriate cabling. 

Yes. When laying the cables in a drag chain, please note that the minimum bending radius is 7.5 x d.

If the cables are not being laid in a drag chain, please note that the minimum bending radius is 4 x d.

item currently uses only synchronous servomotors. Synchronous motors are robust, low-maintenance, overloadable, compact and high-performance. Synchronous servomotors are widely used and are a highly developed technology.

Stepper motors are a special kind of servomotor. They exhibit the following differences from other motors:

• Stepper motors are often run using an external controller. That means, they do not generally have a closed current control circuit or a closed speed control circuit. As a result, stepper motors don’t have a position or speed sensor either (as usual, the exception proves the rule).
• Stepper motors are run on a pulsed current. Each current pulse causes the motor to turn a specific angular increment. All other motors run on a continuous current.

If you’ve ever travelled in a car, you’ll know it’s always better when acceleration and braking manoeuvres are executed as smoothly as possible. This smooth action occurs when the driver depresses and releases the accelerator or brake pedal gently and not roughly. When braking, experienced drivers will slowly take their foot off the brake shortly before the car comes to a halt, thereby reducing the energy of the deceleration. Ideally, the car will then stop without “jerking” to a halt. During an emergency braking manoeuvre, when the braking distance needs to be as short as possible, drivers will keep their foot pressed down hard on the brake until the car comes to a stop. This causes everyone in the vehicle to be thrown backwards with force when the car stops, because deceleration drops from maximum to zero from one moment to the next.

The significance of jerk in automation.

If you want to move the carriage of a Linear Unit, you need to factor in jerk.

Jerk indicates the period of time t it should take to achieve a desired acceleration a.

Where 

The unit of jerk is  

If, for example, you want to achieve acceleration of  within 0.5 s, you will need jerk to be .

However, if you indicate that you want to start a motion with an acceleration of    and you do not enter anything under jerk, this means that the desired acceleration will be achieved, in theory, after an infinitely short period of time.

In mathematical terms, that is equivalent to dividing by 0: 

In such an instance, jerk would theoretically be infinitely large.

In reality, this is not possible, as performance limits and inertia mean the motor has to build up acceleration over a period of time that, although short, is always going to exceed 0. Thus jerk, although very large, is finite.

If the goods to be transported are sensitive or a liquid, inputting acceleration without stating jerk means they can be damaged or, in the case of liquids, can lap over the edge of an open container. Inputting a motion without stating jerk can also subject mechanical components to extreme stress, as all the components involved in the motion will attempt to provide the desired acceleration in as short a space of time as possible.

The benefits that come from indicating jerk include less strain on both the load being transported and the mechanism itself. Furthermore, a motion with jerk is less noisy than one without. The disadvantage is that the motion takes longer to execute and involves a longer travel distance.

Every mass is inert. That means it is naturally predisposed to preserve its state of motion (stationary or current speed). To change the speed of a mass, you need to accelerate it. This requires the application of force.

The same principle applies to masses that revolve. In order to change the rotational velocity of a rotating mass, you need to apply a torque to make it “spin faster”.

The more inert the rotating mass is, the larger the torque will have to be to achieve the same rotational acceleration.

Mass moment of inertia J indicates the amount of rotational inertia. The unit of measurement for mass moment of inertia is kg m2.

The mass inertia ratio λ (lambda) is the ratio of driven mass (rotating and linearly moved mass) to the mass inertia of the motor.

The bigger the ratio between the two mass inertias, the more difficult it will be to execute rapid changes in velocity with precision.

Here as an example: If a small car were to try and tow a truck trailer, it would have difficulty getting the trailer to move. It’s difficult to imagine how it could achieve dynamic acceleration. The same applies to braking. The lightweight car would not be able to bring the heavy trailer to an abrupt halt.

If we transfer these principles to linear technology, the motor of the Linear Unit would be the car and the load involed in the application would be the trailer.

λ can therefore be viewed as an indicator of how effectively a process can be controlled. item generally recommends aiming for  λ < 10. In the case of highly dynamic processes, an even smaller figure would be desirable. By contrast, when it comes to slow motions, mass inertia ratios of higher than 10 are also conceivable.

TIP:
The mass inertia ratio can be considerably reduced by using a Gearbox.

For example, if a Gearbox with a gear ratio i is installed between the Motor and the load, the following applies:

This means that using a Gearbox with i = 7 can reduce an original  .

item MotionSoft® software takes this option into account and also states the mass inertia ratio of the current application in the configuration documentation.

At every point in the design process, item MotionDesigner® indicates how many Linear Units are suitable for the application as currently defined. If you make an entry and this number drops to “0”, adjust the entries to ensure there are still a number of suitable solutions.

If you are unable to do so, please contact our technical support team or your customer advisor. 

Fundamentally, item Linear Units (like most linear units supplied by our competitors) are not suitable for direct use and contact with foods. Wear debris could cause contamination. However, safety precautions can often be taken to enable use in food production.  Appropriate measures must be developed on a case-by-case basis. 

Any dynamic element can stir up dust or generate wear debris. Consequently, when planning to use a solution in a cleanroom, it is crucial to carefully analyse and understand the installation scenario and relevant requirements. item recommends that customers contact the customer solution sales team to get a customised review and seek advice. Design measures and the targeted use of currents of clean air can often help ensure that an item Linear Unit can be used in a cleanroom.

Not yet. At present, item MotionDesigner® can be used to help configure multi-axis solutions as several individual axes, while item MotionSoft® commissions them as individual axes. 

The fieldbus interface to the Controller for your linear axis and PLC is relevant as regards compatibility with an overarching PLC. item supports the following fieldbus protocols: EtherCAT, Profibus, Profinet, CanOpen and actuation with the aid of digital I/Os.

If you have any detailed questions regarding compatibility between Controllers and PLCs, please contact your customer advisor or the support team directly so that they can clarify the issues with Product Management/R&D.

You can place an order with a customer advisor or directly via item MotionDesigner®. 

The product documentation supplied as standard includes:

• Documentation of customer requirements and the solution proposed by item
• Product manuals
• Datasheets
• Test log

Individual components are usually dispatched within 48 hours. The delivery time for a customer-specific solution is up to two weeks. 

Parameter configuration, or parametrisation, is the process of storing the following data in the Controller:

• Controller parameters (e.g. the parameters for a PID control algorithm)
• Characteristic data for the item linear motion unit® (e.g. stroke, load, gear ratio, motor data)
• Travel profile

If the “Preconfigured” option for Controller parameters is not selected when a solution is designed in item MotionDesigner®, the Controller delivered with the item linear motion unit® will feature factory settings.

If the “Preconfigured” option is selected, item will store the Controller parameters, characteristic data for the Linear Unit and, if appropriate, a motion profile in the Controller and a programmed Controller will therefore be supplied.

item recommends using item MotionSoft® to repeat the commissioning process in the final installation scenario and with the actual operating load. This will enable you to define Controller parameters that are as close as possible to the final operating mode. 

item supplies Linear Units that are preassembled, with timing belts adjusted to the correct tension. The tension will be suitable for the operating scenario and load profile stipulated in item MotionDesigner®.

item recommends that the timing belt tension is checked before the system is commissioned and at regular intervals thereafter (see maintenance instructions).

No. Simple sequences can be programmed without a fieldbus interface and without a PLC. The item Controllers have a number of freely programmable I/O ports that can be connected to buttons or proximity switches. item MotionSoft® can be used to easily program sequences that respond to the high or low level of the ports. The ports can also be switched as an output so they can trigger optical or acoustic signals. 

There are several steps involved in configuring and commissioning the overall system. The first thing to do is ensure there have been no errors when commissioning the “Linear Unit – Motor – Controller” assembly.

Use the reset button to reset the Controller and create a defined starting point. Next, use item MotionSoft® software to commission the Linear Unit, Motor and Controller without the fieldbus modules. If there is an STO module, connect it to the Controller. Check whether the configuration has been successfully concluded and whether the Linear Unit can be operated, e.g. with a simple motion profile.

Once the “Linear Unit – Motor – Controller” assembly has been successful commissioned, insert the relevant fieldbus module into the Controller and establish the connection with the PLC. From this point on, continue the commissioning process via the PLC, as per the instructions in the PLC product documentation.

Check whether the 7-segment display on the Controller is showing any error codes and, if necessary, contact the item hotline.

Sporadic errors can occur as a result of awkward cable laying and inadequate shielding, particularly with regard to Data Cables. Check whether Data and Power Cables have been laid separately and whether proper shielding (Shield Terminal Blocks) has been installed.

item MotionSoft® commissioning software has a function for doing precisely that. 

No. Apple and Linux operating systems are not currently supported. item MotionSoft® commissioning software works on computers running Windows XP Service Pack 3 and later versions of Windows operating systems.

item MotionDesigner® is used online through the item website. item will carry out software updates as required and these can be used directly. Users do not need to update anything themselves.

Users download item MotionSoft® onto their PC/laptop and run it on their machine. When launched, item MotionSoft® looks for an Internet connection and, if one is available, checks to see if there are any software updates. If an update is available, the user is prompted to install it.

The item Controllers have their own software (firmware) that is up to date at the time of delivery. There is no need to update this software. item will notify customers and partners of the availability and functional scope of any updates. 

The item Motors do not have any software (firmware). 

One option would be to reload the relevant configuration project stored in item MotionDesigner® and then place another order for the same Linear Unit.

Another option would be to give your item customer advisor the relevant order number and ask for another quote for the same order.

Use only original Power and Data Cables from item. Make sure the Shield Terminal Blocks for the cables are connected to the system and that the system is grounded (earthed). 

Make sure the Shield Terminal Blocks for the cables are connected to the system and that the system is grounded (earthed). 

The seven-segment display on the Controller is used to display operating and fault information. You can find a detailed description of the display and the error codes in the product manual, where you will also find instructions on how to proceed.

The error and status codes for the Controller are also displayed in the status bar of the item MotionSoft® commissioning software. 

Error and status codes for the Controller are displayed in the status bar of the item MotionSoft® commissioning software. You can find a detailed description of the display and error codes in the product manual and in the help function in item MotionSoft®.

For security reasons, the factory settings of Windows 10 do not permit users to install unsigned drivers. A guide to disabling driver signature verification can be found here:

You can find technical data for all item products in the product catalogues and on the item website. Documentation for the electronic products is included in the scope of supply.