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Spring 2016 3D SMD: Z-Axis Linear Slide Actuator

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By Henry Nguyen (Electronics and Control)

Introduction

For our Z-Axis actuator, we found that our thread drive will constantly cause our nozzle to shift towards the left when going down and towards the right when going up. This was caused by the two 4mm rods and the thread screw we were using. A slight solution was to attach a rubberband to our nozzle to prevent it from shifting. The following Youtube video shows the problem our nozzle has when going up and down:

https://www.youtube.com/watch?v=Rw_LVb8K-G4

We found that in order to prevent this type of error, we had to have a completely new design for our Z-Axis actuator.

Linear Slide Actuator

We found a cheap linear slide actuator as shown in the title picture on eBay. After purchasing this sliding unit, we found that the slide will be sturdy enough to attach our A-Axis stepper motor as well as keeping the nozzle in a linear fashion. I needed to design a new bracket that will screw into the sliding unit as well as attaching to our red nut on the lead screw.

Figure 1. Linear Slide Bracket Sketch

Figure 1. Linear Slide Bracket Sketch

For my bracket design, I would attach the linear sliding unit to the top of my bracket with the four holes. The red nut will go through the large circle in the middle. The two screws on the bottom will allow us to attach our A-Axis stepper motor bracket. The last screw hole on top of the A-Axis stepper motor bracket will allow us to screw into the red nut. This will keep the red nut in place and allow us to move the hole unit up and down.

Figure 2. Linear Slide Actuator Bracket

Figure 2. Linear Slide Actuator Bracket

For the bracket, I had to apply some silicone to the red nut in order for it to stay in place. The screw did help to keep it in place; however, I wanted to make sure the red nut is completely stationary.

Figure 3. Full View of Linear Slide Actuator

Figure 3. Full View of Linear Slide Actuator

Figure 4. Side View of Linear Slide Actuator

Figure 4. Side View of Linear Slide Actuator

I uploaded a Youtube video showing the linear slide actuator in action.

https://www.youtube.com/watch?v=UqnxF44cEr8

Conclusion

Overall, this linear slide actuator is a success. It completely eliminated all wobbling caused from our old thread drive kit from Makeblock. We are able to go up and down smoothly as shown in the Youtube link above. This will allow us to rerun all of our accuracy tests to ensure that we are as accurate as possible when picking up surface mount components.

Spring 2016 3D SMD: Z-Axis Beam

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By Henry Nguyen (Electronics and Control)

Table of Contents

Introduction

When running our accuracy tests, I found that the current beam on our Z-Axis would wobble. After carefully observing the wobbling, I found that this will be a major problem when we needed to assemble a PCB with surface mount components. The wobbling will cause our machine to be very inaccurate and may cause us to fail our machine.

Old Beam

Figure 1. Old Beam

Figure 1. Old Beam

Not only was our old beam wobbling because the holes where the 4mm rod went through were slightly larger than 4mm. This will cause the beam to lean forward due to the weight of our A-axis stepper motor. Now that the beam is being tilt forward, our Z-Axis stepper motor will sometime stall out because of the friction against the 4mm rod and the thread beam.

New Beam

Figure 2. Beam Measurements

Figure 2. New Beam Measurements

For our new beam, I decided to make it approximately 0.754 inches. This meant that our beam will be longer than our older beam. I believed by extending the length, we will be able to prevent the wobbling caused by the two rods. The middle hole shown in the figure above will be tapped for our thread screw. The two holes in the middle is to attached our A-Axis stepper motor bracket.

Figure 3. Z-Axis Beam Manufactured

Figure 3: Z-Axis Beam Manufactured.

I was able to get Z-Axis beam manufactured. I found that after installing this bracket, we were able to solve the problem of our Z-Axis stepper motor stalling due to the proper size hole that the rod is now able to go through perfectly.

Figure 4. Lubricant

Figure 4. Lubricant

It was also important to apply some CRC Heavy Duty Silicone lubricant onto the beam and the thread screw to allow smooth vertical movement of our new beam. The following link is a video of our new beam in action.

https://youtu.be/214bttIEprQ

Conclusion

It was very important to manufacture a new beam for our Z-Axis. Before we would have a lot of error caused by the Makeblock beam that came with our thread drive kit. The old beam would wobble a lot which is a major problem when we are trying to be as accurate as possible. Other times, the poorly manufactured beam would also cause our z-axis stepper motor to stall because it did not move up and down smoothly. By manufacturing this new beam we are able to increase our accuracy of our machine.