Andrew Burks

Tag: CNC

Vibratron Auger Testing

by on Feb.25, 2011, under RobOrchestra, Robotics Club, Vibratron

The initial iteration of the auger was just installed into the nearly completed structure.  Mike made some pretty creative parts that will be assembled in the near future.

These clips hold the door brush to the side of the PVC sheel around the auger.  The brush is critical because without the resistance of the bristles, the balls would just roll down the auger.  The clip on the left is different because it needs to clear the motors on the agitation assembly.

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These two waterjet parts were, as usual, provided by the generous Richie P.  The one on the left is where the 30 tubes of balls will plug into the agitation/distribution assembly.  The circle on the right is made of steel instead of aluminum.  It acts like a ring gear, and with rubber triangles along the perimeter, is driven to disrupt any balls that might be jammed at the entrance to one of the 30 holes.

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This video highlights the first time we turned on the auger after it was mounted in the main structure.  Besides showing the coolness of the auger, it also shows all the progress we made on the structure!

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Improved Key Unit

by on Dec.11, 2010, under RobOrchestra, Robotics Club, Vibratron

After several attempts at getting the 180 separate parts necessary for the previous vibratron key unit laser-cut, we finally found a feasible method for fabrication.  The father of a roboclub member offered to us the use of his large CNC routing table.  Because Acrylic does not machine well (it is much too brittle) some redesign was done to make the key units out of hardboard.

Design Changes

Hardboard - Key Unit

The biggest change between designs was the decision to not remove the material between key points, exchanging concave cutouts for straight lines.  Each new unit is made of five separate pieces of hardboard, connected by wood glue (instead of plastic welding).  Only two parts per unit are unique, instead of 3, which makes machining prep and assembly easier.

Circular Structure with New Key Units

Hardboard - Full Circle

The new key units attach to a horizontal 1/4” plate, just like the previous version.  The only difference is that instead of two clips and two colder pins, these units attach with just a colder pin.  Nothing else in the structure needed to be modified to accommodate the change.

Machining

All of the pieces for all 30 key units can fit on five sheets of 2’x4’ hardboard.  Hopefully these items will all be machined by the end of the winter break so focus can be shifted to the design and fabrication of the structure instead.  Below is an example of how the pieces fit on a sheet of hardboard.  The labels are engraved .02” into the board, and everything else is a profiling cut.

Cut Sheet 1

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Robotic Manipulation Cup Stacking

by on Dec.02, 2010, under Classwork

Challenge

For the final lab assignment in my Robotic Manipulation class, we were challenged to competitively stack cups.  We were given six 3 inch tall plastic cups, and were instructed to make a 3-2-1 pyramid out of them, then destroy the pyramid, as quickly as possible.  Before we even began working on the project the best team had already done it in only 12 seconds.

The robot arm is currently equipped with a descent pneumatic gripper.  Two big plastic pads squeeze the cups one at a time to contain them.  Stacking cups one at a time is inefficient, but teams were doing it.  Nico and I decided that we needed a some mechanical advantage.

Denso End Effector

Design Goals

The biggest design limitation was that the only way to actuate our device would be to integrate with the existing gripper.  This limits us to on-off control, which prevents us from picking up all of the cups at once and releasing them strategically.

However, the bottom stack doesn’t really need to be picked up, it only needs to be slid across the tabletop.  Also, picking up two cups at once for the middle layer saves time as well.  The top cup could even be optimized by dragging it into the stacking area initially.  If any of these goals could be met, it would give us an advantage over the other teams.

Interface

In our previous lab, we were able to use the gripper to attach our end effector to the DENSO arm.  However, because we rely on the actuation of the gripper to activate our mechanism, we needed an alternate means of attachment.  The T-slots on the end of the DENSO arm are the perfect size for a 1/4” nut, which is the standard size for a #4 bolt.  Attaching here gave us a reliable fixed reference point.

Combined

Fabrication

Using the robotics club CNC, I was able to build the 6 parts necessary for the device.  The only problem I encountered was bowing and vibration in the middle of the largest piece.  Because my piece (11.58”x3.68”) was near the maximum limits of the machine (12”x4”), it was difficult to secure the middle of the stock.  All in all, it took about 5 hours of machining to build the entire mechanism, half of which was slow-going CNC time on the largest piece.

Gripper

Performance

In the end, we were able to achieve a time of 5 seconds.  Nico and I are pleased with the results, and expect to have the fastest time in the class.

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