In this system’s configuration, we're utilizing two separate servo motors to drive the X and X’ axes. This is due to the fact that they are so far apart. If the X and X’ axes were closer together, we could utilize one single servo motor with a linkage shaft between them to drive both axes. We need to do this so that the axes will move synchronously to keep the system from mechanically binding. Imagine having a large motor on the end of this actuator and a linkage shaft that acts as a coupler to drive both of these axes.
What we have here is a five-axis gantry system utilizing Parker Hannifin’s HMR belt-driven actuator series. We have the sizes 24, 18 and 11 of the series. Valin has sized these actuators specifically for our customer’s application. In addition to the mechanics, we have even helped size Parker Hannifin’s P-series servo motors along with their PV series gearboxes. We have the HMRB series size 24 that is holding a bracket with the HMRB size 18 side-mounted on this bracket. We can also do other configurations, depending on your application requirements, with these side-mounted and this horizontally mounted or even both side-mounted depending on what your application calls for. Here we have the HMRB 18 side-mounted on our X and X’ and off of the HMRB 8 we have the HMRB 11 mounted straight to the axis. Here we have the HMRB 11 on the gantry system and we've customized a bracket to hold our Stober gearbox and mount our motor to provide our customer with the Theta axis. In order for our cabling to get here we have also included a bracket to hold our cable management system for the brake and encoder feedback cables to the motor.
A very important factor to keep in mind when sizing your gantry system is the cable management and cable lengths you'll need. We're going to need cables to span throughout every axis of motion starting with the Theta. We have to go through the Z-axis, through the Y and then even through our X to get to our end. This is because the cables are going to be bending and flexing with every axis of motion and it's very important to have organized cables. With these cable carriers, we're able to keep the cables organized. And utilizing high-flex cables, we're able to help increase the cables’ life. When doing our custom cable management systems, one of the things that we're able to account for is additional cables that our customers may have. In this particular case, we are adding extra space in the system, so our customer can run an air hose system to their custom end-effector.
The HMR series is able to come as a belt-driven actuator or a screw-driven actuator. We know these are belts based on how the motor is mounted to the actuator itself. If this actuator was a screw-driven actuator, the motor would be mounted in-line with the axis of motion right off the end or it would have a wrap-around in parallel with the axis of motion. In belt-and-pulley actuator applications, most of the time we have to utilize a gearbox to match the inertia that is reflected back on the motor due to the low mechanical advantage that the belt actuator provides us. If these actuators were ball screw driven, we would not be able to back drive them but because we're utilizing belts, I'm able to move them around freely. You'll notice though I cannot move the Z-axis. This is due to the fact that when sizing this axis, we added a brake to our servo motor. This is because this is a belt-and-pulley vertical application and if there were any power failure we want to make sure that the load that our customer is utilizing does not free fall with gravity.
These actuators are able to come with internally mounted sensors or externally mounted sensors. We chose the externally mounted sensors with the quick connectors so that our customer can adjust the limit switches on their system. The actuators come with a T-slot so that you can adjust and move your limit switches wherever you may need them in your particular application.
When we size, select and design gantry systems such as this one, we have to make sure that we take into account the whole framing that this is going to be mounted on. Is that framing going to simply-support the actuators at just the ends? If so, we might get some deflection and vibration caused by the moving of a load or even just the weight of the actuator itself. Or is that frame going to support that whole actuator underneath or just various points along the way? We have to make sure that we ask these questions and take that into account when we're sizing these actuators on top of all the sizing and selecting of the frame and everything else we've talked about.
We also have to think about the logistics, especially with a gantry of this size. Is this gantry going to be assembled in a warehouse and then shipped? Is it going to be put on a frame and then shipped? Or are we going to assemble this at the application’s site? In a gantry of this size, we have to think about the transportation of the gantry, the way that we're going to pick the gantry up, and the way that we're going to get the gantry out of the building it into the building. Are the doors big enough? Is the forklift big enough? Is the crate big enough? Who's going to lift it into place onto the frame? These are all the logistical considerations we have to take into account once we've designed the system and are figuring out how to actually implement it.
When designing the gantry, we also pay attention to the controller and what the controller's capabilities are and what the application needs are. Is this going to be a point-to-point application where the actuators are moved one direction at a time just back and forth? That's a very simple application. Or is there going to be interpolation where there may be a circle that is moved in which case we have to coordinate the axes with higher level math. Those are different capabilities that we have to make sure that the controller has or doesn't have depending upon the application.
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