Posts Tagged ‘ manufacturing

Day 13: Prototyping, Manufacturing & Design

Prototyping

Today, the prototyping group worked extensively on the minibot.  After the addition of a fourth stabilizing roller, the bot was able to climb the pole very quckly.  The prototype is improving.  The next step is to brainstorm alternative methods of pole climbing, test the alternative methods and compare the results.

Manufacturing

Today, the manufacturing team was working very hard on pieces for the drivetrain.  The CNC was running all day cutting the sprockets for the drivetrain.  After the drivetrain sprockets were done, they moved on to the front and back rails of the chassis.  The manual machining team continued milling parts for the bumper supports.

Design

Today, the Design team worked primarily on the arm design.  The team worked to design and begin detailing a symmetrical gearbox that will use two motors to independently drive both sets of rollers.  We are very happy with the progress made on this gearbox.  We also worked to finish detailing the drivebase and all of the remaining parts were sent to the manufacturing team.

The grabber with roller gearbox.


Day 12: Prototyping, Manufacturing & Design Progress

Prototyping

Today, the prototyping group continued to work on prototypes for the Minibot.  Their prototype successfully latches onto the bar, but does not have the proper weight distribution and contact with the pole to climb.  With weight added to balance it, it can climb a few inches before popping off of the pole.  More tweaking will happen tomorrow to try to improve the design.

Minibot Prototype

The Minibot Climbing the Pole

Manufacturing

The machining for the frame side rails was completed today.

Completed Side Rails

Furthermore, a separate team worked hard to cut and mill the bumper mount pieces.  These should be completed tomorrow.

Half completed bumper mount pieces.

Design

The design team was working on the arm today.  Progress is being made on the design.

Current concept for the tube grabber.

The design team also finalized the mounting of the motor to pivot the arm within the carriage.  The whole motor is mounted to a plate that slides vertically to tension the chain.

Motor mount in the carriage.

Day 11: Design, Manufacturing & Prototyping Progress

Design

Today was our 2011 Preliminary Design Review.  We met as a whole team at the lab to discuss our game objectives and the direction we are going in with the robot.  Everyone seems to approve of the design and we will move forward to finalize the design in the coming days.

Manufacturing

The manufacturing team was working hard today on various pieces for the drivetrain (1110500).  They worked on the bumper support pieces and the siderails.  We plan to have the frames ready for welding on Monday.

The Manufacturing Team Working on Bumper Supports

Prototyping

The prototyping group received our shipment of Tetrix parts from FIRST Choice Today.  They started to put together a prototype for a pole climbing minibot mechanism.  The prototype shows promise but is not close to being complete and will be perfected over the coming days.

Day 10: Prototyping, Manufacturing & Design Progress

Prototyping

Today, a prototyping group met to finish the roller prototype that was almost complete yesterday.  Round belt pulleys were fabricated and round belts were added so that one motor could be used to power both wheels simultaneously.  The prototype was made mobile and we tested picking up tubes off of the floor and spitting them onto pegs.  It works very well but has issues picking up the corners of the triangles.

Manufacturing

Today, the wheels were finished.  The first operations were performed on the chassis siderails which should be completed tomorrow.

Completed Wheels

Design

The design is coming along great.  The baseplate is almost complete and the spool gearbox is nearing completion as well.  We are on track to be finishing the robot design within a week.

Spool Gearbox

Day 9: Rollers Prototyped, Wheels Complete & Preliminary Electronics Layout

Rollers Prototyped

Today, our prototyping group finished putting together a jig for testing tube intake rollers.  The prototype was very successful and successfully picks up and holds tubes.  Furthermore, we were able to rotate tubes within its grasp by rotating the two rollers at different rates.

The design still needs to be tweaked for optimum tube grabbing performance.

The initial roller prototype. Driven by drills, the prototype is very effective at sucking tubes in and holds them quite well once they are in its grasp.

Manufacturing

After several days of hard work, the drivetrain wheels are finally complete.  During machining, there was an issue with the original CNC code where the spokes were not being milled deep enough.  This was resolved and the problem wheels were fixed.

Completed Wheels

The wheels look great and are visibly much smaller than previous wheels, as shown in the image below.  The wheels will be anodized by sponsor Pacific Coast Metal.

The Evolution of Cheesy Poof Wheels. From left to right: 2006 6" Wheels, 2008 4" Wheels, 2010 4.5" Wheels, 2011 3.5" Wheels.

The DXF CAD drawing for the gearbox sideplates was created and sent to Mike D of Team 233 for Manufacture.

Design

Today, the design team worked on the electronics layout, the spool gearbox and preliminary design for the minibot.  The electronics board is coming along great.  We are happy with the positioning of most of the elecronics but are still not clear on where we want our compressor.

Preliminary Electronics Layout

A second team worked on CADing the spool gearbox.  An issue arose where one of the needed gears was not available, so we had to modify the gear ratios slightly.  The design for the gearbox is coming along and should be finished tomorrow.

A third team started to analyze the parts available for the minibot and started to develop preliminary ideas for how to efficiently lift the small robot to the top of the pole.  Work will continue into the next week.

Day 8: Design & Manufacturing Progress

Design

Today, we worked on space claim analysis and tried to figure out how we could even fit a roller claw onto our elevator and still have room for a minibot while building a nice looking robot.

Space Claim Analysis Sketch for the robot. The minibot is housed on top of the horizontal elevator support and can slide out backwards to attach to the pole.

Next, we started to analyze what our tube grabber could be shaped like.  We knew that one of the major issues would be getting the tube grabber over the bumpers to pick up tubes on the floor.  To solve this problem, we thought about creating an arm that would come down from the elevator carriage and have a second roller below it.

A second issue we were worrying about was depositing the tubes on the rack.  Our experience with the 2007 FRC game as well as the 2011 VEX game led us to believe that simply spitting the tubes out of the rollers could result in unpredictable scoring.  To eliminate this issue, we thought about having the two rollers separate with a pneumatic piston so that the tube could be gracefully released and deposited on the rack in one fluid motion.

The tube grabber in pickup position.

The Raised Tube Grabber. The grabber would be able to raise to perfectly vertical so that the tubes can be carried entirely within the volume of the robot.

We also talked some about the speeds for the elevator.  We decided that we could use one BaneBots 775 Motor and one Fisher Price Motor on the spool gearbox to still leave enough motors for the rest of the robot.  We decided to gear for a faster cable speed than either of the elevators we have built (for comparison, the 2007 robot’s elevator moved at 3.6 ft/sec and the 2011 will move at 5 ft/sec).

The gear ratios for the 2011 elevator. The first stage will use 32DP gears and the other two stages will use 20DP Gears.

Prototyping and Testing

We decided to build some prototypes to test how much force would be needed to keep the tube grabber closed.  We built a jig to hold two wheels at a specific angle and allow us to apply force between them.  It was found that with the tubes, once the wheels had passed the diameter of the tube, the frictional force was so great that the tubes could not be freed from the grabber.

Testing using two wheels as a tube grabber. With static wheels, once the wheels pass the diameter of the tube, the tube cannot be freed from the grabber by pulling.

Another issue we addressed was the tendency for the tubes to rotate in the grabber.  By putting a metal tube behind the tubes, it improved tube centering on most tubes.  Problems, however, arose when testing on the corners of the square and especially triangular tubes.

On the corners of the triangle, the wheels cannot get past the major diameter of the tube, causing more difficult tube retention.

To allow the tubes to still be held on the corners, we tried applying various amounts of force to the top of the lever.  We found that after about 12lbs of force, it was extremely difficult to dislodge the tube from the grabber.

Manufacturing

The machining of the wheels is coming along very well.  The first operation is complete on almost all of the wheels.  We hope to complete the wheels tomorrow.

The wheels with the first operation completed.

Last year, we had an issue where the hole in the wheels created by the rotary hex broach was not big enough for the hex shaft. This year, we have purchased a new hex broach to fix this issue. The wheel fits very nicely on its shaft.

Aluminum Chips after Milling the Wheels.

Day 7: Manufacturing Progress, No Build Meeting

Today, the FRC Build group did not meet at the lab.  However, progress was still made in the manufacturing and materials procurements area.  We were able to pick up the raw aluminum from Coast Aluminum in Hayward so that wheel construction can begin soon.  Furthermore, Cory started setting up the CNC Mill at the lab so that we can start milling wheels soon.

Tomorrow is the VEX Tournament and the team will be meeting tomorrow night after the tournament at the lab to continue with the robot design.

Day 6: Prototyping, Programming, Design & Manufacturing Progress

Prototyping

Today, we had a large group of students working to prototype mechanisms for subsystem 2 (tube grabber.  One group was working to construct a jig for testing roller prototypes.  The other group worked to think up alternate solutions for tube grabbing.

Several Team Members working on a prototype.

Ryan and Erik "Prototyping"

Programming

The programming team met today to refine the control of the robot during teleoperated mode.  Progress is being made.

Design

Today, several team members were working on the CAD Design of a part for the elevator carriage.  Furthermore, later in the evening, we continued working on the mounting interaction between the elevator and the drivebase.

Manufacturing

The machining of the bearing housings is finally complete.  After five long days of machining, all of the parts are done with machining.  After they are deburred and polished, they will be ready for anodizing.

Completed Inner Bearing Housings

Completed Outer Bearing Housings

Day 3: Field Construction, Programming, Design & Manufacturing

Field Construction

The field construction team was hard at work today working on the two elements of the game field that we are building this week.  We have constructed a shopping list and hope to buy the remaining materials tomorrow.

Programming

The programming team was working hard today on teleoperated and motor control code.  They have designed an interface to separated the control system (joysticks, arrow keys, etc) from the code so that the robot can be easily modified to be driven by a variety of controllers.  Furthermore, they performed experiments to measure how linear the Victor Speed Controllers are in their outputs.  Using MatLab, they will be able to analyze this data and derive a function to linearize the Victor outputs.

Design

The design team was hard at work today.  The first order of business was the drive gearbox.  After the gear ratios were finalized last night, we were able to move forward with the drive gearbox CAD which his now completed.  When doing the design, we were able to develop a new way of retaining the shifter shaft between the bearings to ensure that we can shift reliably.  Without motors, the wheel and bearing housing, the gearbox is less than two pounds.

Drive gearbox as of tonight.

In addition to working on the gearbox, a group of students worked to design and CAD the drivebase frame.  After careful review of the bumper rules, we decided on a design that would support the bumpers all along the back while still being extremely lightweight.  We added a heavily pocketed baseplate and put the whole thing together for a design that weighs about 30 lbs.

The drivebase design as of today.

Manufacturing

Production continued on the first operations of the bearing housings.  We hope to finish the bearing housings by Wednesday.

Lab Improvements

Today, the wired network between the lab computers was completed so that they can all share printers.

Day 2: Drivetrain Design & Manufacturing

Today, at the lab, a group of team members met to continue designing the robot drivetrain and continue manufacturing bearing blocks.

Networking & Lab Improvements

We started by networking all of the upstairs computers at the lab together.  This will allow us to share printers before the computers.  We were able to connect all of these using a switch generously donated by our sponsor, Vivid-Hosting.  The networking will be completed tomorrow.

We also procured two power strips which were wired under the floor to provide power to two upstairs tables for laptops.  Previously, the lab did not have a good place for laptops to work.

Manufacturing

Manufacturing on the bearing blocks continued today.  Progress is being made and the manufacturing will continue into the next few days.

Design

Today, we discussed and decided on several key aspects of the drivetrain.

The first topic of discussion was wheel size.  Several team members brought up the idea that with such a flat game field, we could potentially go to wheels even smaller than 4″.  Although we quickly ruled out 3″ wheels due to lack of ground clearance (~1/4″ clearance), we were interested by the prospect of 3.5″ wheels which would lower our center of gravity slightly and could decrease drivetrain weight by more than one pound.  Furthermore, because less gear reduction is needed with smaller wheels, the weight of the spinning components could be decreased by up to 20%, leading to a potential significant increase in robot acceleration.  However, some team members had reservations due to the decreased ground clearance in the move from 4″ to 3.5″ wheels.

To come to a consensus, we created a weighted objective table to weight some of the pros and cons of each design.  After much deliberation, the table resulted in almost a tie so we continued to discuss.  In the end, it was decided that any problems caused by the decreased ground clearance (1/4″ lower) of the 3.5″ wheel system could be avoided so we decided to move forward with the lighter 3.5″ wheel design.  This caused the outer bearing blocks to need edits so that they would not interfere with the newer, smaller wheels.

Benefits of 3.5″ Wheels

  • Lower Center of Mass
  • Less Weight
  • Increased Acceleration
  • Smaller Gear Reduction Needed
  • Less material means less cost
Benefits of 4″ Wheels

  • More familiarity with the design
  • More ground clearance
  • Less Tread Wear

The second topic of discussion was robot speed.  After yesterday’s strategy session, the whole team was in agreement that having a fast and maneuverable robot would be key to successful performance in Logomotion.  After deciding on small, 3.5″ diameter wheels, we also knew that these smaller wheels would not require as large of a gear reduction as has been present in past robots.

With the ability for a smaller gear reduction, we started with our gear ratios from last year and worked with them to both speed up the robot and minimize the use of large gears to decrease robot mass and increase acceleration.  In the end, we found a set of ratios that we liked that will both allow for the fastest 254 robot ever built and for smaller and lighter gears while still maintaining a slower low gear.

Finalized gear ratios for the 2011 robot. Robot speeds are estimated for 3.5" wheels in ft/sec at 100% and 80% efficiency. The first line represents the common reduction. The second and third lines correspond to the secondary reductions for High and Low Gear.

Finally, today was our deadline to finalize the gearbox shafts to be sent out for manufacturing by sponsor Pacific Precision.  All four of the shafts were updated and finalized by a team of students.  All drawings were checked by team leaders and mentors and were sent to manufacturing.