NXT Beer & Soft Drink Bottle Opener

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After seeing a couple of LEGO Mindstorms NXT Bottle Openers on the net, I decided to tackle building my own… The task turned out to be somewhat more difficult than I envisaged. The most difficult part by far was the Gripper Mechanisms, as they had to securely hold the Bottle and it’s cap in a manor that allowed them to be unscrewed.

LEGO Mindstorms NXT Beer & Soft Drink Bottle Opener

Multi-views of the LEGO Mindstorms NXT ‘Drink Bottle Opener’s’ are shown below.. For ease of viewing the important modules that make up the ‘NXT Drink Bottle Opener’, I have chosen to us CAD images. As I build mainly with Black, it makes photographing detail a bit difficult. I also couldn’t be bothered dusting off and setting up my Macro Camera Equipment I normally use. But I think you will agree that the CAD is a better choice.

Multi-views of theLEGO Mindstorms NXT Beer & Soft Drink Bottle Opener

A single NXT Brick controls the ‘Drink Bottle Opener’ Mechanism. It us 5x NXT Motors, 2x RCX Type Touch (+1 NXT Touch Sensor for Trigger) Sensors. To control the two extra NXT motor, I have used a Mindsensor Multiplexer for NXT Motors (NXTMMX-v2) . I must get around to purchasing a second NXTMMX, as they easy and reliable to use. The Motor requires an additional 9 Volt power Supply. Hence the 9 Volt Battery Box pictured. As this is a stationary Robot, I prefer to use a ‘Regulated’ 9 Volt Power Supply for all its energy requirements. This method is also great during programming and debugging the Robot. Saves a lot of battery swapping and charging time.

LEGO Mindstorms NXT Bottle Opener’s Conveyor System

NXT Drink Bottle Opener Loading mechanism consists of the Conveyor System that carries the Drink Bottle to the Bottle Clamp Claw module ready for uncapping. This chain of events is triggered via a NXT Touch Sensor which is used to start the NXT Drink Bottle Opener.

LEGO Mindstorms NXT Bottle Opener’s Bottle Gripper

Drink Bottle Opener’s Conveyor module is used to transfer the Drink Bottle to the Claw Mechanism ready for opening. The Mindsensor MotorMux is used to control the attached NXT Motor.

LEGO Mindstorms NXT Bottle Opener’s Piers with Rack System

A 8-Tooth gears attached to the NXT Motor drives a 24-Tooth gear, resulting a 1:3 reduction in the speed of the Conveyor Belt. Drink Bottle Opener’s Gear Racked Pier is what the ‘Control & Uncap Mechanism’ slide up and down into position with. (Note the CAD is a abbreviated version of the Piers I used).

LEGO Mindstorms NXT Bottle Opener’s Control Centre & Lift Mechanism

Once the Bottle is loaded into the NXT Drink Bottle Opener, the top assembly is lowered down so the ‘Cap Gripper Mechanism’ is touching the top of the bottle cap. Slowly the jaws of the Cap Gripper is closed around the bottle cap ready for unscrewing. Now that the ‘Cap Gripper Mechanism’ has gip of the bottle cap, the ‘Cap Gripper Mechanism’ is rotated six times to unscrew the bottle cap. The ‘Cap Gripper Mechanism’ jaws are loosened and the mechanism is lifted above the the cap so the bottle can be removed via the ‘Conveyor Belt’ ready for the user to drink.

LEGO Mindstorms NXT Bottle Opener’s Bottle Cap Gripper

Key to the success of the ‘Cap Gripper Mechanism’ is the ‘Adhesive Rubber Feet’ used too fix to objects to avoid the from scratching surfaces. I purchased a pack of 16 for around $1 a few years ago to attach to the black melamine board the large LEGO Base Plate is attached to. One ‘Adhesive Rubber Foot’ is attached to each of the Yellow Jaws, which Grip the Bottle Cap, as shown in the CAD drawings. They feet grip extremely well to LEGO, and with a little difficulty can be remove from the LEGO Parts. When removed they leave no sticky residue and can be reused several times, as I discovered whilst going through the prototyping stages of Gripper’s development.

LEGO Mindstorms NXT Bottle Opener’s Bottle Cap Gripper Pads

The ‘Bottle Gripper’ consists mainly as a gear train. It uses a clutch at the primary stage of the gearing to avoid damage like shown at the end of the project. The Clutch drive a second down gearing before the output goes to a dual out put Worm Drive. The worm directly drives two 8-Tooth Gear on each side of the worm. The 8-Tooth gears in turn drive a 24-Tooth gear on each side held in place via a set of Technics ‘Triangles’. The output from 24-Tooth gear’s shafts drive a train of three 16-Tooth gears on each side, with the final output driving a set of CAMs. These Cams push the Gripper Arm inwards, gripping the bottle. The ‘Bottle Gripper’ is driven via a NXT Motor controlled via the Mindsensor Multiplexer for NXT Motors (NXTMMX-v2).

LEGO Mindstorms NXT Bottle Opener’s Bottle Cap Gripper

The ‘Bottle Cap Gripper’ relies on high torque to produces the forces required to grip a bottle cap for unscrewing. Prior to entering the Worm Gears, the NXT Motor speed/torque is reduced by a factor of 1:15. The ratio is further geared down by a factor of 1:3 before moving the CAM that pushes the YELLOW ‘Bottle Cap Gripper’ arms. The total Gear Reduction used to drive the Gripper Arm Cams is 1:45. This produces very high torque, but with the trade off producing considerable speed reduction.

LEGO Mindstorms NXT Bottle Opener’s Bottle Cap Gripper

Directly driving the gripper arms can’t successfully be used without a barrow load of backup 16-Tooth Gears. The 16-Tooth Gears fail catastrophically (See Conclusion). Using the CAMs solves this issue. A ‘White Technic Clutch’ is used in the primary part of the drive-line to help protect the gears.

LEGO Mindstorms NXT Bottle Opener’s Bottle Cap Gripper

Drink Bottle Top Lifting Mechanism raises the ‘Bottle Cap Jaws & Unscrewing Modules. The mechanism lifts and lowers the ‘Bottle Cap Gripper’ into place. The mechanism moves on two piers ‘Gear Racks’. The Mechanism also carries the Bottle Cap Gripper and Bottle Cap unscrewing NXT Motor , as well as the NXT Motor that propels it up and down the Gear Rack. The NXT Brick also is attached to this mechanism.

NXT Drink Bottle Opener in Action

By far the hardest part of the Bottle Opener build, was gripping the bottle and cap in a manor that allowed the Cap to be successfully removed. Getting the ‘Drink Bottle Opener’ to work successfully needed a large amounts of torque in order to clamp the Bottle Body and Cap.

I found uncapping “Beer Stubbies” with their crinkle edged caps a far easier challenge when compared to the ‘Smooth Edged’ “Soft Drink Bottles”. – – When I moved onto the challenge of Soft Drink Bottle Caps, I started to see a lot of LEGO Parts flying across the room. During my prototyping I had a few Technics Shafts ending up as Cork-screws and a 16-tooth Gear redesign. In one piece most of the time. I note that a 16-Tooth Gear at high velocity hurts somewhat when they collide with your head. Leaving their imprint as a warning!

LEGO Mindstorms NXT Bottle Opener Produced Gear Failure

The Software to drive the ‘Drink Bottle Opener’ Mechanisms is written in RobotC.

Despite a lot of initial frustration, the Sun rise surprising me twice, and a lot of hair pulling. It was worth the building challenge.

I hope you have enjoyed discovering this project of mine. Please feel free to take full advantage of the supplied LEGO Digital Designer CAD files. The Video availability has been delayed due to Bandwidth issues, so check back in a few of days.

Download LEGO Digital Designer CAD Files:

RobotC Source Code:


Foot Notes:

I decide to submit the NXT Beer & Soft Drink Bottle Opener as part of the NXTLog ‘Rube Goldberg’ Crazy Contraption Competition. The ‘NXT Beer & Soft Drink Bottle Opener’ is Triggered with mechanism used in my NXTLog ‘Crazy Contraption’ Entry, with the ‘Bottle Opener’ replacing the Reading Lamp in the Chain of Events….

Many robots are designed to do simple tasks in an efficient way to make our lives easier. But what if robotic machines did simple tasks in an over-complicated way? This is the type of Machine that ‘Rube Goldberg’ envisaged for his weird world. This example of a ‘Rube Goldberg type Machine’ is an upgrade to the version built earlier which was used turn on a reading lamp.

Here is my Mark I version of a ‘Rube Goldberg’ Contraption. I have attempted emulate the crazy ideas of Goldberg’s, with my very own, over complicated LEGO Mindstorms NXT based Drink Bottle Opener’. Two LEGO Mindstorms NXT Programmable Bricks are used for this Contraption. One NXT Brick for the Initialisation and Triggering Mechanisms, using 2x NXT Motors, a Ultrasonic Sensor and 11x RCX Type Touch Sensors. A Second NXT Brick controls the ‘Drink Bottle Opener’ Mechanism, using 5x NXT Motors and a couple of RCX Type Touch Sensors.



My NXTLog ‘Crazy Contraption’ Entry using the Bottle Opener didn’t make it to the contest, thanks to the pedantic and secretive ways of the NXTLog Moderators. They stuffed me around for four days, telling my project didn’t match their criteria/rules. Yet they were unable to inform me to what was the the actual problem. They did supply a couple of extremely cryptic clues, which I’m still at a loss to thier proper meaning. But most of the time their response was “Status: Rejected “, giving no reason to why. I spent more time going through their Rules list, looking for the what I could have missed than I did putting the article together!

In future, if every I decide to enter NXTLog competition again, I will enter my project by the second week. They need to have far better communication than what exists, which is NONE! At least allow for two-way communication so one can find out what is the offending word, sentence, paragraph, or image is.


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