AL5A Arm Assembly Instructions Rev. 2.1
| AL5A Arm Assembly Instructions Rev. 2.1.
Updated Dec 2014 Safety first! Wear eye protection and never touch a powered robot! This guide shows how to assemble the AL5A arm with either the SSC-32 or the SSC-32U servo controller. Take note of which version you have and follow each step accordingly, as the connections and configuration are different. Calibration of the arm is done using one of the following software:
Note: Loctite / thread lock can be used on the construction of the aluminum components, though it is not necessary if the nuts are properly tightened. However, don't use them with Lexan or plastic, as they are not necessary and may cause damage. |
 Image of complete arm (SSC-32 Shown). |
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| Lexan Preparation. The lexan pieces have a protective covering that needs to be removed before assembly. When the laser cuts, the covering melts into the cut edge which can make removal difficult. If you gently scrape the cut edge with a flat blade screwdriver, the covering can easily be lifted and peeled off. On smaller pieces the coverings can be more difficult to remove. If you have trouble you can gently scrape the cut edge, then use duct tape to lift the covering off. For further information on lexan, see this page. |
 Lexan Preparation. |
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| Step 1. Connect the standard "C" bracket to the large "C" bracket as shown. Use two 2-56 x 1/4" screws and 2-56 nuts.
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 Figure 1. |
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| Step 2. Install the mechanical dampening panels as shown. Use four 2-56 x 1/4 inch machine screws. Be sure to add the discs to the correct side and ensure the protective covering has been removed from the Lexan parts. Press down when screwing to ensure there is no gap between the Lexan and the aluminum, as the screw will be threading the Lexan.
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 Figure 2. |
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| Step 3. Insert the 4-40 x .5" Phillips head screw through the hole in the multi-purpose bracket as shown. Secure with a steel nut.
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 Figure 3. |
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| Step 4. Slide the large "C" bracket end of the bracket assembly over the screw as shown, and secure with a nylon insert lock nut. The amount of friction can be adjusted by tightening or loosening the lock nut. Start with the nut loose, and if the arm seems to wobble a bit, you can tighten this joint to correct the wobble. Caution - don't over-tighten this! If the arm is operated with the mechanical dampeners too tight, the servo WILL heat up and CAN be damaged!
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 Figure 4. |
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| Step
5. Figure 5 shows a typical mega-size servo with its default servo horn at center position. You will need to replace this black servo horn on the 755 servo with the round nylon servo horn included with the hardware bag. Remove the servo horn screw, being careful to not rotate the servo horn itself. Pull the servo horn off, then press the nylon servo horn in place, as close to the alignment shown as possible. Replace the servo horn screw. Make sure your large servo looks like figure 5. The arrows in the image point to the screw holes you will use. |
 Figure 5. |
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| Step 6. Attach the HS-755HB servo to the base bracket as shown using the 3mm hardware; follow the diagram below. Use two #2 x 1/4" tapping screws to secure the bracket to the servo horn. Route the shoulder servo wires underneath the servo. Plug the servo into channel 1 on the SSC-32. Carefully rotate the base to an extreme, and use a wire tie to take up the slack in the servo cable.
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 Figure 6. |
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| Step 7. Attach two of the tubing connector hubs to the short side of the "L" brackets, using four 2-56 x .250 screws and 2-56 nuts. Orientation is important; the hole in the tube should be as shown, so the tube will line up as in figure 8.
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 Figure 7. |
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| Step 8. Connect the hubs to the 1.50" tube using two 4-40 x .250" screws. Tighten these down tightly.
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 Figure 8. |
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| Step 9. Attach each of the ends of the tubing structure to two standard sized Multi-Purpose brackets as shown, using four 2-56 x .250 screws and 2-56 nuts.
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 Figure 9. |
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| Step 10. Insert the 4-40 x .5" Phillips head screw through the hole in the multi-purpose bracket as shown. Secure with a steel nut.
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 Figure 10. |
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| Step 11. Slide the screw on the forearm assembly through the dampening discs as shown, and secure with a nylon insert lock nut. The amount of friction can be adjusted by tightening or loosening the lock nut. Start with the nut loose, and if the arm seems to wobble a bit, you can tighten this joint to correct the wobble. Caution - don't over-tighten this! If the arm is operated with the mechanical dampeners too tight, the servo WILL heat up and CAN be damaged!
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 Figure 11. |
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| Step
12. Figure 12 illustrates a typical standard-size servo with its output horn (the round white part) at center position. Make sure your servo looks like the image. The arrows in the image point to the screw holes you will use. |
 Figure 12. |
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| Step 13. Attach the HS-645HB elbow servo to the bracket as shown using the 3mm hardware; follow the diagram below. Use two #2 x 1/4" tapping screws to secure the bracket to the servo horn. Route the shoulder servo wires over the servo. Plug the servo into channel 2 on the SSC-32.
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 Figure 13. |
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| Step 14. Attach the Little Gripper connector to the Short "C" bracket using two 2-56 x .250" screws and 2-56 nuts.
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 Figure 14. |
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| Step 15. Attach the short "C" bracket to the other Multi-purpose bracket as shown.
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 Figure 15-2. |
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| Step 16. Attach the HS-422 wrist servo to the bracket as shown using the 3mm hardware; follow the diagram below. Use two #2 x 1/4" tapping screws to secure the bracket to the servo horn. Route the shoulder servo wires over the servo.
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 Figure 16. |
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| Step 17. Attach the Little Grip to the Lexan as shown, using three 4-40 x .375" button head screws and acorn locking nuts. Only three screws are used (shown in the image) as the body of the gripper servo is in the way for the fourth. Make sure the HS-422 (a HS-322HD
may be substituted) servo is aligned to mid-position, and the gripper
is halfway open. Now the servo and gripper will be aligned correctly.
Remove the servo screw and horn. Slide the servo into the gripper from
the bottom. You may need to wiggle it a bit to get it seated properly.
Use the servo screw to attach the servo. Tighten this down, but then
unscrew it half a turn. Too much friction can bind the servo.
Step 18. |
 Figure 17. |
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 Figure 18. |
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| Step 19. Carefully bend the wrist servo back as far as it will go, and use wire ties to secure the servo cables as shown. Make sure to leave slack in the gripper servo cable, don't pull it too tight. |
 Figure 19. |
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Step 20.
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 Figure 20. |
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Step 21a (SSC-32 / Lynxterm).
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| Step
21b (SSC-32U / Servo Utility). Just like in the base instructions, we will use the SSC-32 Servo Sequencer Utility to test the servos and confirm they are all plugged into their proper servo channels and oriented correctly. If not done so before, download and install the SSC-32 Servo Sequencer Utility. Connect the USB cable and power the board using the on/off switch. Run the program. The SSC-32U is shipped with a baud rate of 9600. Ensure the baud rate towards the bottom right of the window is set to 9600 (not 115200). The software should automatically detect which COM port is connected to the SSC-32U, and have installed the FTDI (USB to serial) drivers automatically. Ensure Servos 0 4 are checked off in the software (and therefore accessible). You can now move the sliders to see each servo rotate. Verify that the servos are plugged into the channels as listed in Table 21. Easy does it; this is real time control, so be careful. For more information, please consult the SSC32 Servo Sequencer Guide. |
 Figure 21b (SSC-32 Utility). |
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| Step 22a (SSC-32 / Lynxterm). Click on the "All = 1500" button in LynxTerm. This will command the servos to hold center position. Your arm should look like Figure 22. If any joint is off by more than 15°, then you may have made an error in assembly. If you did not purchase RIOS software, please proceed to step 27.
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| Step 22b (SSC-32U / Servo Utility). Click on the "Calibrate" button in the SSC-32 Servo Sequencer Utility. A knob next to each servo will appear (figure 22b). This knob is used to fine tune the servo's center position. The knob is not intended to be rotated: click the knob you wish to rotate, keeping the mouse button down, and drag up and down to rotate the knob. Do this for each servo until the arm looks like figure 22, and angles are 90 and 180 degrees. If any joint is off by more than 15°, then you may have made an error in assembly. Once all servos have been properly positioned, click the icon "Calibrate" once again, and the offset values will be stored on the SSC-32 / SSC-32U. If you did not purchase the RIOS software, please proceed to step 27. |
 Figure 22b (SSC-32 Utility). |
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| Step 23 (RIOS Users Only). To use the RIOS Arm control software, you need to make one minor modification. Remove the servo horn screw from the elbow servo. Pull the servo horn off the servo, lift the arm two 'clicks' (30°) at the elbow and reattach the servo horn and screw. Note, the Hitec spline has 24 grooves, so each groove is 15°. |
 Figure 23. |
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| Step 24 (RIOS Users Only). At this point the arms is assembled and tested using LynxTerm. If your robot came with RIOS, we can now install RIOS and calibrate the arm to the software. For those using a different program such as FlowBotics or FlowStone, refer to the software's user guide. Use the RIOS Help File to calibrate and use the arm. Install RIOS, following the on-screen installation prompts. The serial number is on the back of the CD sleeve. Use the RIOS Help File to calibrate and use the arm, following Steps 1-7. When you get to Step 8 in the help file, please use the following instructions instead. Click on the "Arm" button, then click on the "Arm" button in the "Arm size" section, and then click on the AL5A arm image on the popup screen. Please take the time to do an accurate calibration. The performance of the arm will only be as good as the calibration. If the on screen virtual arm does not match the real arm this is a sign of an inaccurate calibration. After calibration please study the RIOS manual carefully to learn how to store and playback sequences for the arm. |
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| Step 25 (RIOS Users Only). To calibrate the arm's shoulder servo, click the "SSC-32" button. |
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| Step 26 (RIOS Users Only). Select the Shoulder, servo #2. Move the shoulder slider up to move the shoulder forward so that it looks like Figure 27-2. Set the Min Deg angle -90°. Right click on the slider to set this as the Min Position. Now the servo will not go past this value, and the program now knows this value is exactly 90° from centered. Now move the slider down to move the shoulder backward so that it looks like Figure 27-3. Set the Max Deg angle to 45°. Right click on the slider to set this as the Max Position. Now the servo will not go past this value, and the program now knows this value is exactly 45° from centered. The next step is to read and study the RIOS users guide. It is accessible by clicking on the help icon on the main screen or by navigating to the install directory (c:\Program Files\RIOS_SSC-32\) and opening the Help.pdf file. This manual explains in great detail how to use the arm. |
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| Step 27. To connect springs for load-balancing, replace the servo attachment hardware in the locations shown, following the diagrams below. Hook the springs together after they're secured.
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 Figure 27. |
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| Step 28. The arm assembly is complete. The arm is robust mechanically, but the servos can be damaged by improper use. An example would be if the arm was told to move to an unobtainable position, like the surface the arm is mounted to, or by crashing the arm into itself, or other objects. The elbow servo is the most vulnerable because it holds the entire weight of the forearm. Load balancing springs should be added to reduce some of this load. If you purchased FlowBotics Studio, FlowStone or FlowArm, you can proceed with the instruction guide(s) associated with those programs. People do not like holding heavy objects with their arms outstretched in front of them. Servo based robot arms don't like it much either. Remember, the most important rule for servo based robot arms: Park the arm when not in motion! When it's moving or at rest it's usually ok. When it's holding an object it should do so for the minimum amount of time required to do the job. You can always touch the servo case to see if it's getting hot. |
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