Install Apeiros Servo Gripper Kit

Introduction

Please follow this installation guide if you have purchased the Apeiros Servo Gripper Kit.

Tools Needed

You will need to have access to the following list of tools.

  • Mini Phillips head screwdriver (eyeglass size)
  • Small Phillips head screwdriver
  • Small adjustable wrench or 3/8" nut driver or socket set

Prerequisites

This guide assumes that you have already purchased and setup your Apeiros Robot as per the Initial Setup and Configuration guide on the Lessons page. In preparation for installing the servo gripper kit, you will need to compile and upload the Apeiros_Servo_Gripper_Setup example sketch. Go ahead and launch the Arduino IDE and then select File -> Examples -> Apeiros -> Apeiros_Servo_Gripper_Setup.

Lay Out Servo Gripper Kit Contents

Go ahead and unpack the servo gripper kit parts, so that we can begin the assembly and installation process. 

Assemble Gripper Gears

Remove the protective paper from both laser cut gripper gears.

Also need to remove the round white servo horn from the HS-81 servo. Use a small Phillips head screwdriver in this step.

Use the truss Phillips head #0x1/4” screws to attach the active gripper gear onto the round servo horn. We call this the "active" gripper gear because it attaches directly to the round servo horn and will be driven by the HS-81 servo. Find a set of (3) holes on the servo horn and use the middle hole to attach the active gripper gear to the servo horn as shown below. Use a mini Phillips head screwdriver in this step.

NOTE: It is important that you use the middle holes on the servo horn because they dictate the orientation of the active gripper.

Use a #2-56x3/16” machine screw to attach a compression spring to the active gripper gear. Install the screw in-between two coils of the compression spring as shown below. Use a mini Phillips head screwdriver in this step.

NOTE: The #2-56x3/16" machine screw must be installed as shown below. If you install the machine screw from the opposite side, then it will interfere with the plastic robot body when installed in a later step!

Slide one of the rubber caps onto the compression spring that was installed in the prior step. Be sure that the rubber cap completely covers the head of the #2-56x3/16" machine screw.

Install a compression spring onto the "passive" gripper gear as shown below. We call this the passive gripper gear because it is driven by the active gripper gear. Secure the spring with a #2-56x3/16” machine screw.

NOTE: The #2-56x3/16" machine screw must be installed as shown below. If you install the machine screw from the opposite side, then it will interfere with the plastic robot body when installed in a later step!

Install a rubber cap onto the passive gripper gear as shown below. The rubber cap needs to completely cover the head of the #2-56x3/16” machine screw.

Install a #10-24x5/8” truss head screw into the center hole of the passive gripper gear and thread on one of the #10 nylon-insert locknuts as shown below. Gently tighten the locknut until you are unable to rotate the gripper gear relative to the truss screw. Then loosen the locknut just until you can freely rotate the gripper gear. Use an adjustable wrench, 3/8" nut driver or socket set along with a Phillips screwdriver in this step.

NOTE: The passive gripper gear must be free to rotate on the truss screw. If the passive gripper gear is resistant to rotation, then it can cause damage or premature failure to the HS-81 servo!

Bottom view of installed #10-24x5/8” truss head screw and #10 nylon-insert locknut. Note the installed orientation of the nut in that the nylon locking element is visible.

Remove Apeiros PCBA from Robot Body

We need to remove the Apeiros Printed Circuit Board Assembly (PCBA) from the plastic body, so that we can install the HS-81 servo and passive gripper. From the image below you will see which (4) #3-24 screws need to be removed. You also need to unplug the left and right motor connectors from JP2 & JP3. Use a small Phillips head screwdriver in this step.

After removing the (4) #3-24 screws and unplugging the left and right motor connectors, your robot should appear as shown below. You will need to feed each left and right motor connector through its respective hole within the Apeiros PCBA. Then proceed to gently remove the PCBA from the plastic body.

After removing the Apeiros PCBA, place it upside down on a secure Electrostatic Discharge (ESD) safe surface. Now you should be able to see inside your Apeiros Robot.

We need to mount the passive gripper to the plastic robot body using the hole identified in the image shown below.

Insert the threads of the #10-24 truss head screw through the mounting hole in the plastic robot body as shown below.

From the top side, thread on a #10 nylon-insert locknut as shown below. Do NOT over-tighten the locknut, otherwise you might crack the plastic robot body. Use an adjustable wrench, 3/8" nut driver or socket set along with a Phillips screwdriver in this step. Note the installed orientation of the locknut in that the nylon locking element is visible.

NOTE: The passive gripper gear must be free to rotate on the truss screw. If the passive gripper gear is resistant to rotation, then it can cause damage or premature failure to the HS-81 servo!

Install Rubber Grommets & Bushings

Install (2) rubber servo grommets into the mounting holes of the HS-81 servo as shown below.

Install (2) flanged bushings into the previously installed rubber grommets as shown below. Note that the bushing flange must be installed so that it is facing away from the top of the servo as shown below.

Mount HS-81 Servo to Plastic Robot Body

Mount the HS-81 servo to the Apeiros plastic robot body using (2) #2-56x5/8" machine screws as shown below. First, insert the #2-56x5/8" machine screws into the holes in the robot body as shown below.

NOTE: You will need to hold the HS-81 servo in place as you insert a screw.

 

Install (2) #2-56 rectangular push nuts onto the #2-56x5/8" machine screws. Be sure NOT to overtighten the screws. Otherwise you might damage the servo mounting tabs or the Apeiros plastic robot body. The rectangular push nuts are curved. You must install both rectangular nuts with their dome side facing up (refer to image below) and away from the servo grommet. Use a small Phillips screwdriver to tighten the machine screws in this step. Ensure that you tighten both screws equally. Meaning that you should end up with the same number of threads showing on each #2-56x5/8" machine screw.

NOTE: You can push the rectangular nut onto the machine screw threads in order to get started. Then tighten the corresponding machine screw.

Connect HS-81 to Apeiros PCBA

Connect the 3-position female connector of the HS-81 servo to the 3-position male connector, JP5, on the Apeiros PCBA as shown below. Note the wire color and PCBA connector labels shown in the image below.

NOTE: Improper connection of the servo connector can result in damage to the HS-81 servo and/or the Apeiros PCBA!

Install Active Gripper Gear

Before installing the active gripper, we need to compile and upload the Apeiros_Servo_Gripper_Setup sketch. This sketch will properly position the HS-81 servo to the fully open position, so that we can attach the Active Gripper as shown below. After uploading the sketch, be sure to wait for the servo to move to the fully open position. Next, power off the Apeiros PCBA, so that you can install the Active Gripper onto the spline of the HS-81 servo. If you accidentally change the servo position while attempting to install the Active Gripper, then simply remove the Active Gripper, power on the Apeiros PCBA, wait for the servo to move to the fully open position and then turn off power. We recommend removing the rubber end cap and spring from the active gripper prior to commanding the gripper closed.

When ready, you can command the servo gripper closed by pressing BTN-1 on the Apeiros PCBA. The Apeiros_Servo_Gripper_Setup sketch will incrementally close the gripper and then revert to the open position again using incremental moves. After verifying that the gripper properly closes and opens, you can reinstall the compression spring and end cap on the active gear. Don't forget to install the black colored servo horn screw.

NOTE: You need to match the installed orientation of the Passive and Active Grippers as shown below. Failure to do so can damage the HS-81 servo! We also recommend removing the rubber cap and the spring from the Active Gripper. You can reinstall the spring and rubber cap once you have verified proper gripper closing and opening. When properly installed, the servo gripper will move to the open and closed positions with a smooth motion and will hold position until commanded to move again. While the servo is holding in the closed position there may be slight hum. However, if the humming sound is loud then it is a sign that the servo may be overloaded. Immediately turn power off, remove the active gripper from the HS-81 and repeat the above step.

Be sure to check out Lesson 7: Commanding Apeiros Servo Gripper!