Output Encoder for RL-D / RL-S

We supply 2 options of encoders for our joints / joint arms.

Option 1 (our Standard before HMI 2017): Motorencoder plus Ini switch for 0-point reference on the joint output (PRT bearing)

Option 2): Output encoder on the PRT bearing of the joint. This is our own development, we use a magnetic ring plus Encoderchip on the output with an aditional magnet and Hall Sensor as reference point. Please find attached a description of the output encoder attached in GER and ENGL. Advantage: less cables, higher resolution, more accuracy for the arm.

DOWNLOAD section:

output encoder DEU: RL-D Sensorik Doku (#3)

output encoder ENGL: RL-D Sensors Dok (E #3)

strain wave gear (RL-S) vs. cycloid gear (RL-C)

The strain wave gear is available as a product in the size RL-S-17 and RL-S-20. RL-S-30 is a prototype and still in development.

The cyclo gear can be an alternative in future and is not available as a product yet. The sizes 17 and 20 are currently in development.

Both types of gears contain a coaxial in- and output axis (different from RL-D worm gears), they consist of three similar components:

  • An outer (static) toothed ring
  • An inner toothed ring (rigid in the cycloid gear, flexible in the SWG)

  • A drive (an excentric in the case of the cycloid gear, the wave generator in the SWG)



strain wave gear with flexible inner ring                  cycloid gear with excentric ring



RL-D different versions, pricing

We have defined 3 different quality standards for our robolink D joints and I want to explain the background of this issue. The 3 qualities are:

  • “low cost”,
  • “standard”,
  • “high end”

The main performance differences are stiffness, friction, precision (reverse play) and on the other hand cost. For size -20 and -30, the price difference between low cost and high end is ~factor 2, for size -50 it is ~factor 1,5. standard version ~ in the middle.

The high end version contains of our lubrication free worm gear with worm wheel made of iglidur J and worm shaft made of aluminum (hard anodized), it has ball bearings for the axial shaft load and for the back side (only version 102). The outer bearings are our PRT-01-xx (= high end rotary table made of aluminum with sliding elements made of iglidur J). Housing and inner connection parts are made of moulded plastic parts (our RN33), screws and nuts are stainless steel.

Most parts of the standard version are the same, but the back side has a sliding bearing (iglidur J) instead of the ball bearing (only version 102) and the PRT itsself is version PRT-02-xx-AL, which is a low cost version of PRT-01-xx. It has more plastic parts and thus is much lighter. Compared with PRT-01 is is a bit less stiff and a bit less precise. In a performanmce comparison of the to joints, we see no big differences for most applicaations as long as we do not get to the limits.

The low cost version of our RL-D in comparison contains a moulded plastic worm shaft and sliding axial bearings instead of the ball bearings. Also the PRT is not build with an aluminum outer ring but a moulded plastic outer ring (PRT-02-xx-LC). Friction is higher and precision worse than our “standard” version. It should be used only for “easy applications” as for example hand adjustments.  



For size -20 and -30, all versions are available. For size -50, only version “high end” is available, as PRT-02-50 is yet under construction. We will have it in ~OCT 2015.



robolink® dummy with pneumatic muscles

I want to present a very ambitious project from our customer the automotive research and test centre CARISSMA, TH Ingolstadt. Project leader Igor Doric and his team had the goal to build a humanoid pedestrian dummy for autonomous emergency braking tests with vehicles.

This dummy shall not contain any metallic parts, especially no electric motors. Their concept is to use pneumatic muscles in combination with our wire driven robolink joints in order to achieve dynamic human-like movements. The dummy has 21 degrees of freedom for the motion of his head, arms and legs and weights less than 21kg! The dummy is carried by a 6D motion system (product name “M=6D target mover” developed by the project partner company MESSRING, www.messring.de). 6D represents 3 translational and 3 rotational degrees of freedom -> forward/backward, left/right, up/down, pitch, roll and yaw. All control parts and algorithms are developed by the TARGET team itself.

The video shows the movement of the dummy.

For more detailed informations please contact Igor Doric. (=> igor.doric@carissma.eu)

meeting Igor Doric at the “safety week” in Aschaffenburg

more robolink D informations (HMI interviews)

I would like to share 2 interviews “live” from Hannover trade Show. They might explain more about our ideas and the product robolink D Joint kit. The first is in “English” (=germanenglish) and the second in german. please find some more written informations below.

in german:

I want to explain the basic idea of our Hannover trade show news:

# igus offers mechanical components for automation solutions, for example also joint arms.


# The main components of our kit are “joints” consisting of a PRT slewing bearing table, a plastic worm gear and a plastic housing. These joints exist in 3 sizes (-20, -30 and -50). These joints can be equipped with igus motors as an option. Standard motors are our stepper motors NEMA17, NEMA23 or NEMA23XL. In addition, INI switches can be used as Zero signal outputs.


# These joints can be combined freely (in principle) and as a result represent joint arms with different kinematics. Currently, max. 4 axis can be configured, up to 6 axis are planned. The shown joint arm (on the Hannover show as well as in our mailings and advertises) is a 3 DOF kinematic. This design with 3 different robolink D joints (one of each size -20, -30 and -50) of the new generation will be shown at Hannover Show in April for the first time in public as demo unit. The connecting parts between the joints are produced as SLS (selective laser sintering) parts in this case. On request, igus may share the STEP data for these parts, so that customers may “print” or “sinter” them by themselves as 3D parts. On request, igus may also modify, produce and offer these parts. As a “cheap” solution, these connting parts can also be produced as folded metal sheet parts (see second part of the interview videos).


# As a result of this, it is possible to design or create a cheap 3 DOF robotic arm, either with igus components (joints and motors) or as a ready mounted arm (like in the picture). The choice of joints and motors is depending on the application data given (as payload, precision, speed,…).


# In general, igus offers a mechanical design for robotic applications. Control components as well as further “intelligence” (like force or torque sensors,…) is not part of our offer or our scope of delivery. In order to control such joint arms (in the case of using our stepper motors), at least stepper motor controls are needed. In addition a superior control makes sense. In our demo unit we use an ARDUINO controller as main board, many other different control concepts are possible, as for ex. SIEMENS SPS, WAGO or BECKHOFF controls,….


# performance data of the joint arm we will show in Hannover can not be announced currently, as this is a prototype design! We will reach with this constellation a payload of about 1 kg and a precision (or repeatability) of about 1 mm. Higher loads can be reached by using a stronger motor in the 2nd axis (NEMA23 instead of NEMA17).