# Tag Info

24

TL;DR: Its not the air that's enclosed inside that creates the force, but the lack of air - or more precisely pressure. First of all some nomenclature (this is for the closed type, there is also the open type): When you press a suction cup on a surface what happens is that the air inside it is pushed out. During the compression phase of the cup the air ...

7

As your construction is 3D printed, increasing the strength at the point of current breaking will more likely transfer the damage to a new location. The obvious and possibly impractical solution is to solve the jamming problem, rather than to try to power through it. If it's not practical to prevent the jamming, consider to convert the jamming related ...

5

You might consider dealing with it in software. Sense the stepper motor current, and when it exceeds a certain threshold that indicates jamming, perform a high speed reverse rotation for one or more revolutions. Then proceed in the forward direction.

5

Build the auger around a stronger shaft which has a better connection to the motor shaft. Perhaps a carbon fibre or even a steel centre. But then consider what will be the next breaking point. Or make a joint between the auger and the motor that fails if the mechanism gets jammed - just make it easy to replace.

4

For me a good (compromise of a) solution would be to redesign the shaft with an rectangular slot (although I am still unclear as to the fracture type, so I suspect is torsional). Like so Then you can use a rectangularly shaped metallic shaft along the length, which will be able to transmit more gradually the torque. *Figure 2: rectangular shaft image ...

3

CTE characterizes dimensional change, with no load. It corresponds to a relatively fundamental physical principle, making it easy to use in a design calculation Heat Deflection test characterizes the deformation under heat AND load, which includes a variety of phenomena happening at the same time. The result is dependent on the particular geometry and ...

3

When you push that onto a flat surface it pushes most of the air out. The elasticity of the item makes want to flex and come off but the air pressure is pushing it onto the surface.

3

In machine tools where an auger is used to remove scrap metal chips, the current in the auger motor is sensed. If it exceeds a certain level due to jamming, the electronics temporarily reverses the auger direction which can clear the jam. Lubrication of the material-auger interface is very important with augers, which have a huge swept surface area.

2

TLDR: look at Viton / FKM PTFE has poor mechanical stability, would be careful whether to use it in most sealing apps (unless it has mechanical backup). Look at other fluoroelastomers, in particular Viton (FKM) or Kalrez/Chemrez (FFKM). The other common elastomer substitutes for NBR are EPDM and silicone (PDMS). Those are the most common ones you can usually ...

2

If you know the torque, or a close approximation of it, you can size the auger shaft more appropriately. From Machinery's Handbook the max torque T a shaft can handle is T= S_S* Z_P S_S = allowable torsional shear stress of material Z_P = polar section modulus (0.196 * diameter^3) Make sure your units are consistent. So you can either use a stronger ...

2

It won't help prevent swinging, and in all likelihood would keep the door swinging longer after an impulse force is applied. As the comments suggest, most inside doors have a guide on the floor (usually in the retracted region, not the doorframe itself). If you have a barn-door-type sliding door, there may well be a guide/stabilizer near the top of the door.

2

For a rectangular beam under a load, P, at the end the deflection is $$\delta= \frac{PL^3}{3EI}$$ therefore if you have the E as half you need to double the I of the part. In rectangular beams and roughly rectangular tabs: $$I= \frac{BH^3}{12}$$ So you ned a tab thicker by the ratio of $T_{new}= T_{old}*\sqrt[3]{2}$ edit if we are concerned with a yield ...

1

The coefficient of thermal expansion is the change in size of the material as the temperature changes, which is obvious when looking at the units: a length change per metre per degree. Heat deflection is not about a change in length.

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If I understand correctly you need the part to be able to rotate around point B, so that the AB section remains vertical, while the BCD rotates. In that case, the following is not really an answer, just a heads up, that there are other properties that will have a detrimental effect on the properties: The horizontal distance between the fulcrum and the ...

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