Recycled Cardboard Claw

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About: Design Technology Teacher at UWCSEA

In this Instructable I'm going to copy a readily available syringe powered 'robot' arm using Autodesk's Fusion 360, then disassemble the CAD model and lay it out flat. Using the orthographic feature in Fusion 360, I will output a plan of all the parts as a 1:1 scale PDF file.

I take the PDF file and import it to a graphics package that can use the vectors as a cutting path for a laser cutter, however, you can use the plan as a cutting template for CNC milling or just cutting by hand with a craft knife (although there's quite a bit to cut!).

Using recycled Cardboard I will laser cut the components and assemble them with glue and wooden kebab sticks. Later adding the Syringes and Silicone Tubing will then test the outcome.

I have produced a video that accompanies this Instructable and have linked it here.

Please enjoy!

Supporting video can be found here:

https://youtu.be/Bq7LBM09H08

Step 1: The Parts, the Plans and Getting Started

To start work on the Recycled Cardboard Claw, you'll need the plans. This are located within the Instructable here. <Claw Drawing v1.PDF>

The plans were created by looking at images of commonly seen syringe assisted 'robot' arms and modelling them in CAD, I used Autodesk Fusion 360. Each component was constructed from pieces that could have been flattened.

Once the claw CAD model had been disassembled it was turned into a PDF output at a 1:1 scale. I have added a link to the original CAD file should you wish to play around with it and improve the design. (It seems to be a little off balance favouring the front)

https://a360.co/2FRRekT

For this project you will need:

PDF plans

Craft Knife (and or Laser Cutter)

3mm thick Cardboard(preferably recylced due to the title!) - Any thicker and the slot in the plans will need to modified.

Modelling Glue

5mm (Internal Dia 3mm) Silicone Tubing(Polyurethane Tubing seems to offer too much resistance for the Cardboard to cope)

Wooden Kebab Sticks (I used bamboo)

10ml Syringes (You can use bigger but you'll need to accommodate the tubing and look at the plans)

Tools:

Needle Nose Pliers

Side Cutters

Step 2: Cutting the Pieces Out

Doing this by hand is going to be a nightmare due to the nature of corrugated cardboard, I used a laser cutter so I'll be focussing on this method.

Adjusting to the material

Because you're not always able to choose the best piece of recycled cardboard for the job, it's important that you understand how to use your Laser Cutter's accompanying software. Creases, tears and cuts in the material all means adjustments to the cutting plans are going to be needed, look at the card board, work out where you can cut and adjust the PDF plans accordingly.

Careful!

Corrugated Card board, layers of paper a cluttered laser bed are all potential threats to having a safe day with your friendly Laser Cutter. The air flowing through the card's core, the potential warping of the material all lead fiercely to fire hazards, so clear the junk from the laser cutting platform, try and get the card to lay as flat against the bed as you can and don't leave the laser cutter for one second. (I sound like someone who's witnessed something.....)

Islands

Many of the parts in this plan have centres that will need cutting out. Try to get you Laser Cutter to cut these first, if the centres drop out there's no real problem, if the main pieces drop out before the centres are cut, the laser will attempt to cut without being properly focused, this equals fire hazard and or a charred mess.

Soot..

On a successful cut, you want to clean the component edges somewhat, that card board soots up pretty badly and mixed with modelling glue can leave your walls and doors in a bit of a state. If anyone has any advice for this, I'd be very happy to hear it.

Step 3: Assembly

With everything needed gotten, it's about that time to get going.

Syringe Housings

The place to start is in creating the housings for the 8 syringes, the 4 holed interface (The part that houses the syringes YOU touch) will be under a fair bit of stress, you'll want to make that strong. I used amples of glue and let it secure to the base completely before pushing the cylinders through all the way. The 4 other housings are all separate but are identical with the pivotal hole and syringe hole located perpendicular to each other. The current hole diameters are so accurate to a 13mm Dia Syringe, there was no need to add any glue. The syringes here were slid into the housing until just past the front taper (about 1-2ml mark). The next part is the end plates, these are the parts that are pushed by the response syringes. there are 4 in total, the square end connected to the claw itself is left until last, the other 3 are round and be glue to the remaining 3 freely housed syringe plungers (the part your thumb touches).

The Claw

Although complex looking, the claw is very simple to work through, start by gluing the claw grips, then fix the pivotal points to the claw chassis. I used bamboo skewers which complicated things hugely, you can use nuts and bolts. Next comes the square syringe end plate and join it to the two links, spread the claw apart to allow accessible space to connect the linkages to the moving pivot point of the claw levers. It should now work to the touch.

The Pillar

This central part is the most dubious, everything is connected to the pillar and its only held together with a thin bamboo 'tooth pick' you may want to adjust this if you're planning on using it long term. M5 nut, bolt and washers should do the trick.

The Arms

The arms are straight forward, the notched arms connect to the claw, the shorter connect to the pillar, best to look at the CAD diagram for this, not the Video CAD version, the Video real version is good to reference to though.. (phew thats confusing!)

Tubes

Sorry to be gross but I licked the ends, I know!! And I feel dirty, but it really does help getting the tubes onto the syringe ends. In the photos here, I'm holding two types of tubing, the clear one is Polyurethane, the cloudy tube is Silicone, you want the later and about 1m (3 foot) of the stuff. Polyurethane works but it's resistant to movement, not much but enough to rip your card board to bits if you're unlucky.

Step 4: Operation

Pushing the syringes is fairly straight forward, things start to move quickly after a moment of 'stickiness', this is the rubber on the plunger loosening once the pressure has been applied. Pulling the syringe however doesn't work so well, the air in the syringe will give you a spongey elastic feel as you start to pull back on the thumb grip. I thought about replacing the air with oil, but bleeding these effectively would mean removing the cylinders from the card board housings and that would be a pain!

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