Students Experimenting with Tension/Compression Joint Articulation

Students Experimenting with Tension/Compression Joint Articulation

Date: 3.1.17
Goal: Use Vex gear to simulate different joint articulation options based on a steady cam.
Location: Logan HS
Time: 3rd hour DE class
Students: Mason, Alex M. and Vaeng

Students were given some research illustrations on different types of Exo Arm assemblies. We were attempting to scale it down and replicate the movements to determine if we could used it as a possible solution for the Exo Arm. Students used Vex parts to quickly put together a section and then used springs and rubber bands to determine resistance and tension forces.

Alex, Mason and Vaeng at work.

Measuring a spring to test on the assembly.

Spring appears to hold the assembly in a neutral position.

Testing out the assembly with rubber bands.

Testing out another assembly with springs which were cut to a specific size.

Work Day on Exo Arm Base and Joint Articulation

Work Day on Exo Arm Base and Joint Articulation

Date:2.28.17
Time: 8:30 AM - 2:00 PM
Location: Logan Welding Shop
Students: Alex M., Mason, Alex R., Trenton, Ben, Andy, and John.
Instructors: Johnston and Pitz

Students came in on their day off to work on the Exo Arm. We built a base to support the linear rail and braced it up. We also spent quite a bit of time working on the joint articulation on our test model. Alex and Mason tried a number of spring combinations to see if they could get the arm to move in the direction they wanted to while mitigating the load. Results were mixed. We looked at other options for the joint articulation. Progress was also made on the shoulder joint and 2" slew ring bearing. A receive had to be turned down on the lathe to accept the slew ring bearing.

Test base for linear rail system

Testing arm motion

Discussing block movement on linear rail system

Turning down a receiver for the slew bearing.

Mason and Alex testing the spring and joint motion.

Test Arm Build to Simulate Functionality of Exo Arm

Test Arm Build to Simulate Functionality of Exo Arm

Date: 2.20.17
Location: Logan HS
Goal: Build a small test platform for the Exo Arm to begin simulating functionality.

A test arm platform and support structure was fabricated to begin testing the articulation of the joints for the prototype Exo Arm. The staff at Fastenal found some smaller rod ends and yokes with clevis pins to begin attaching the joints. We hope to take these parts and begin experimenting to determine balance, arm reach, joint movement, live and dead loads, etc... We need to determine if an additional linear actuator needs to be added to support the grinder or if springs will work just as well.

The test platform is welded together with tube stock and a threaded rod to attach the rod ends. We also attached a counter balance to test and see if this would be an effective method to stabilize the arm. The support legs are cut and welded at 30 degree angles. We are not sure if this will need to be changed or if additional supports need to be added. The entire platform for the full size prototype will be on wheels in the end.

Sketch of Exo Arm Joints 2.16.17

Support test platform for Exo Arm. Notice the threaded rod with rod end attached.

Different view of support test platform for Exo Arm.

Guest Speaker on Touch Screens

Mike Wettstein-Guest Speaker on Touch Screens

1.31.17
Logan HS
3rd hour

We asked Mike Wettstein (Industrial Automation) to come in and talk to the class about implementing touch screen technology. We have not used a touch screen on previous projects and wanted to see what it would involve.

Mike brought in a industrial grade touch screen, PLC, and power supply for us to look at. He demonstrated the Ignition software and how the PLC interfaced with the touch screen.  Mike noted that in creating an interface we should offer language choices other than English, and both words and graphic images to represent the function we wanted to control. He also mentioned touch screens are rated for specific temperatures.

Mike Wettstein talking to the class.

Grant with the interface he created for the linear actuator. We are looking at replacing the switches with a touch screen.

Some Parts Have Been Delivered

Some Parts Have Been Delivered

1.30.17
Logan HS DE

We have received some of the parts we need for the Exo Arm build. A BIG thank you to Schaeffler Group USA, Inc for donating the parts and Motion Industries, Inc for facilitating the ordering and parts. Jesse and Bill have been great to work with in getting the right parts ordered. We appreciate their time and consideration.

The linear rail which will be the "backbone" for the Exo Arm looks like it will work well for supporting the rest of the assembly. When we looked at the bearing rail block that rides on it on the rail it was incredibly smooth motion. You can tell it was well designed and built. We originally were going to take a smaller piece of metal square tubing and put it inside a larger tube, drill holes and allow this to be our adjustment for shoulder height. The linear rail will provide a much smoother movement than we anticipated.

Concerns are that the single linear aligning block and bearing will not be enough to support the arm structure. The block will hold about 320 lbs of dynamic force which should be enough to support the load, however, the blocks are small and we need more surface area to attach a plate for the shoulder joint. We are therefore going to double the block.

Marcus and Andy inspecting the linear rail and other parts.

Parts Ordered

Parts Have Been Ordered!

1.9.17
11:22 AM
LHS

Just a quick update to let everyone know that the parts (bearings) are in the processes of being shipped. Schaeffler has kindly agreed to donate the bearings used in this project. Motion Industries has been working closely with them to get the parts shipped to LaCrosse from Germany. Right now it looks like we will have some of the parts later this week. Other parts will not be here until mid February. Depending on what parts come in and when, we can hopefully start work on building the prototype soon.

The programming and controls for the linear actuator that will raise and lower the arm has been completed and bench tested. Now we just have to scale it up and test it on the actual arm.

Business/industry Professionals Suggest Bearing Options

Business/industry Professionals Suggest Bearing Options

Date: 12.3.16
Location: Logan HS

The following information was sent to us from our contacts at Motion Industries, Inc. and Schaeffler Group USA, Inc. Earlier this fall the students had a conference call with Schaeffler reps to explain and trouble shoot the Exo Arm joint articulation problems. The result of that conversation is the information you see below.

      For the main support bearing mounted at the top of the support leg we suggest a 2” slewing ring bearing. The slewing ring will allow 360 degree rotation and will accommodate axial and radial thrust loads. This is a low friction bearing with many balls internally. I have attached a basic drawing that Al Bower has created which shows a possible way for mounting the bearing on a stepped shaft. This part # is CSXA020-HLE.
•         After much discussion regarding the bearings for the arm, we are recommending rod ends. The rod ends that we have suggested have a 25 mm bore and will connect to threaded rod. We envision the bore of the rod end being connected to a clevis which could then be connected to another rod end and rod. The rod ends will allow for some misalignment by the user, but will help to ensure that the arm stays relatively rigid while grinding. We had explored using a ball joint (as discussed during our previous call), but Schaeffler  does not offer a product which we felt would meet your needs for this application. This part number, which would require 3-4 depending on if we will connect a rod end to the grinder, is # GIR25-UK. Threaded rod ends with the necessary length would need to be ordered. I believe Motion can assist with this.
•         We are unsure of if you are planning on adding additional support framing around the arms or if you would just use the rod.
•         Going back to our previous discussion, will you be installing a spring between the upper arm and forearm instead of an actuator? We feel this could minimize your costs/complexity and may accomplish much of what you want to do with the actuator.
•         For the adjustable height feature of the exo-arm we currently recommend a round shaft system with open bearing and housing.  This would make it easy to assemble.  To drive it, either look into a belt system, an acme screw (of which they’d have to source elsewhere), or manual adjustment.  We also discussed drilling a hole and placing a pin into the shaft to keep the height where the user would like it to be. In reviewing your initial drawing, it appears that this may have been what you were considering as well. These are part numbers TSNW16, KSO16, and KSN016.

First sketch of Exo Arm