How To Simulate A 4 Axis Palletizer Robot In Emulate3D

You're probably thinking that marking up a 4 axis robot is a piece of cake! Or maybe that it will be quicker than marking up a more common 6 axis robot. It certainly sounds like it is less work but it turns out these robots are much more complicated and sophisticated than their 6 axis cousins.

Most small/medium sized 6 axis robots will have 6 revolute joints. Larger 6 axis robots capable of lifting bigger payloads will be fitted out with additional balancers.

By contrast a 4 axis robot will require a minimum of 10 revolute joints. Four of these joints will be driven by motors, hence the 4 axis. The remaining 6 joints are used to keep the robot tool parallel to the ground at all times no matter the position of the 4 driven joints. 4 axis robots are well suited to press tending and palletizing tasks.

In this blog post we'll be looking at the mark up of an ABB IRB 760 Robot. In addition to the 10 minimum joints it also has 2 balancers, one on the side and one on the rear. This brings the total joints up to 16!

The clearest way to demonstrate robot markup is by video. Below you can find a video of myself demonstrating a markup of the robot. I then connect it up to the Emulate3D Robot Framework and use it in a simulation model.

Robot Mark Up tips

1. Sort Out The Hierarchy

The very first thing you need to do once you've imported your robot into Emulate3D is clean up its' hierarchy. The easiest hierarchy to work with is a relatively flat one. I often aim to have all my robot parts parented to the base component. You should also merge all moving parts together. For the above video I merged the red ABB logo to its' respective part.

In the video above the mark up process is smooth as the hierarchy is simple and logically named. You don't have to follow this tip but if you do you'll find marking up your robot much easier.

2. Add A Mechanism To The Top Level Robot Assembly

The Mechanism Aspect stores joint information for any joints below it in the hierarchy. This information includes the joints location, axis and anchor points which will be stored relative to the Visual that contains the Mechanism Aspect.

By adding the Mechanism to the robot we will be able to reuse this robot much more conveniently in the future. For example, we’ll be able to copy and paste it, add to a catalog or simply move it to somewhere else in the model without the joints needing redefining.

3. Test Out Each Joint Before Starting The Next One

If you are a CAD Is The Model noob you'll definitely want to follow this tip! If you blitz through your mark up, as I did, and you make a mistake it is going to be much harder to know which joint has gone wrong.

1. Add your joint and set the Aspect Properties (Axis, Anchor, Base)

2. Set Mode to Inverse Kinematic

3. Reset and Run Model

4. Switch to Navigate Mode and LMB on the joint and drag it to move

5. Reset model and move on to next joint... repeat for each joint

6. Once all joints are complete set Mode to Forward Kinematic where necessary

4. Start The Markup in a Sensible Place

You should always start your CAD Is The Model Markup on a joint that is grounded. You can then work your way up the joint chain setting the base for the next joint as the previous one.