Skip to main content
12 votes

Silicon and silicones

Silicon forms bonds in a similar way to carbon, and has a similar outer-shell electron orbital configuration. Carbon, as you may well know, has the ability to covalently bond with up to four lone ...
do-the-thing-please's user avatar
8 votes

Silicon and silicones

Starrise gave an answer describing silicone from an engineering/chemical perspective, but I disagree that this is the reason for silicone to be so widely used. The real reasons why it is used so ...
rumtscho's user avatar
  • 180
8 votes
Accepted

How are protective sheets attached to plastics?

The material is called "Electrostatic Protective Film". It is manufactured by letting the plastic film cool in a strong electrostatic field: there are high-voltage electrodes on top and bottom of the ...
jpa's user avatar
  • 1,943
8 votes

Why not build container ships from plastic?

In short, because steel is less expensive on a strength per dollar basis of anything else, and for large structures, it's less expensive to work, again on a strength per dollar basis. That's why ...
TimWescott's user avatar
  • 2,682
8 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

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 ...
fred_dot_u's user avatar
  • 7,132
7 votes

Why not build container ships from plastic?

Anything is possible and lowering the lightship weight (LS) of ships will save fuel, but the key issue would be any change must not reduce the seaworthiness of ships. This question is very broad. ...
StainlessSteelRat's user avatar
6 votes

Difference between 'plastic yielding' , 'plastic yield strength', plastic strength' and 'plastic stress'?

All these terms refer to the effect of loading on the deformation of materials. Let us assume that we start with zero load and zero deformation. Elastic deformation If you increase the load you ...
Biswajit Banerjee's user avatar
6 votes

How would I put a barcode of other scannable code on a coffee cup?

A few different marking processes are available to accomplish your objective. Glass is a good choice, for reasons of durability. Etching One creates a mask or stencil with the desired graphic. In ...
fred_dot_u's user avatar
  • 7,132
6 votes

PTFE sheet vacuum forming

Don't make them, just google "ptfe stoppers", and buy them. (You've asked an XY problem.)
D Duck's user avatar
  • 391
6 votes
Accepted

What does 50% RH mean?

DAM means "dry as manufactured" or "dry as moulded", i.e. the material is in its moisture-free state immediately after manufacture. The DAM moisture content is typically less than 0.2%. "50% RH" ...
alephzero's user avatar
  • 12.5k
5 votes

Why not use fire-retardant plastics everywhere?

Fire retardant fillers are pretty cheap; often cheaper than the base plastic (Alumina Trihydrate for example). Like anything in engineering though, there are always exceptions and functional reasons ...
ericnutsch's user avatar
  • 8,176
5 votes

How do I cut a crack into a polymer/plastic?

Since you used some specific words in your question, I will respond a certain way. Cracks are generated by mechanical action, and cannot be machined in. They may, in certain brittle materials, be a ...
tillmas's user avatar
  • 241
5 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

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 ...
Solar Mike's user avatar
  • 15.8k
5 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

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 ...
MTA's user avatar
  • 221
4 votes

How to create an airtight connection between Stainless Steel and PTFE?

You're going to struggle to get a reliable gas tight fit with that design. For a start it would be better if the two connections were separate so they aren't fighting against each other in terms of ...
Chris Johns's user avatar
  • 15.2k
4 votes

Shear strength polymers

The reason it is impossible to give you figures is that nobody has run the tests to verify the shear strength. Why? Wouldn't it be easy to get a block of polypropylene and run a test? Well, that ...
Mark's user avatar
  • 5,333
4 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

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 ...
NMech's user avatar
  • 24.4k
3 votes
Accepted

Why there are grooves at inner side of plastic nasal spray cap?

that part was injection molded in an unscrewing mold which allows fully-formed threads to be molded into a part. Ordinarily, the resulting undercuts would prevent the part from being extracted from ...
niels nielsen's user avatar
3 votes

How to create an airtight connection between Stainless Steel and PTFE?

If you have to use the Teflon for some reason(s), you can bond the Teflon part to the SS by first etching the Teflon with a special etchant designed for Teflon and then you can use a high temp epoxy ...
William Hird's user avatar
3 votes
Accepted

Push button design for small gadget

You can get switches designed to be soldered onto the edge of a PCB and actuated from the side. It's your responsibility to make the buttons. Get some cheap electronic watches and tear them down, ...
TimWescott's user avatar
  • 2,682
3 votes

What plastic material is best for a snap-fit design?

I have designed parts which are snap-fit using Polypropylene. They work well, but the best advice I can give make one (or a few) in one or more material and do some life testing to figure out which ...
am304's user avatar
  • 1,841
3 votes

How to select the correct Bolt/screw Torque for sealing?

Use a dial gauge and an adjustable torque wrench / screwdriver, then measure the compression of the seal compared to the torque applied - keep increasing torque setting until compression is sufficient ...
Solar Mike's user avatar
  • 15.8k
3 votes

What is the composition of Arizona Ice Tea 1gal plastic bottles stamped #7 OTHER and PP COMPATIBLE?

Many times manufacturers make bottles from coextrusions of plastics (see... coextrusion blowmolding). Think of blowing a bubble with two or more thin layers of virgin material (without mixing the ...
Jim Clark's user avatar
  • 496
3 votes

What is the composition of Arizona Ice Tea 1gal plastic bottles stamped #7 OTHER and PP COMPATIBLE?

I can tell you this is a five layer bottle with polypropylene plastic. I was one of the first engineers to use 7 and 5 layer containers for food it was for Coke and Tropicana orange juice. The Arizona ...
Russell Young's user avatar
3 votes

Increasing torsional-stress resistance of an Auger at its motor-shaft joint

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 ...
user33187's user avatar
3 votes
Accepted

How well does epoxy bond to PETG / ABS vs Wood?

I have had good luck with plastic specific consumer grade epoxies. Both JB Weld Plastic Bonder and Loctite Plastics have worked well. I have not performed any structural tests with them, but in my ...
ericnutsch's user avatar
  • 8,176
3 votes
Accepted

How to design stiff plastic sheet

"... while minimizing the thickness of the end plate. I don't care about how much material I use." Those statements are in conflict with each other. If the end plate must be flat on the ...
fred_dot_u's user avatar
  • 7,132
3 votes
Accepted

Is there any difference between an-elastic and visco-elastic materials?

Anelastic is a material that exhibits a delay in the deformation with respect to the loading. figure 1: Anelastic material bevahiour (left: wrt to time, right: stress vs. strain) (source Princeton) ...
NMech's user avatar
  • 24.4k
3 votes
Accepted

Is this shape possible with injection moulding?

Yes it is, in fact the part in your picture was almost certainly made this way, as follows. An injection mold can be made to accept those metal pins, which are positioned in the mold so that when the ...
niels nielsen's user avatar
3 votes

Create a mechanism to support a speaker in the upper part of an enclosure

That is a piezo-electric transducer. ("Speaker" usually means a device consisting of a device with a paper or plastic cone driven by a voice coil.) Heat staking of the part is an excellent ...
Transistor's user avatar
  • 10.8k

Only top scored, non community-wiki answers of a minimum length are eligible