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How to build a 50k ton forging press

construction-physics.com

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Re: How to build a 50k ton forging press

#131

Post by kragen »

bacon_waffle wrote: post #129
kragen wrote: post #123

Earlier quoted context omitted.

yes, i agree. what i was trying to express is that rebuilding a motor is generally strictly easier than building one from scratch, because it's building a motor from something more than scratch. i don't think i expressed it very well (i mean, if all the parts of your engine are trashed, you are going to have to machine replacements for them, and that might actually take you longer. but it's clearly achievable given t…

Ah, that helps, thanks. It's a bit academic, but set theory doesn't really apply to such fuzzy human things as knowledge and experience. Repairing and designing are different pursuits which might have a lot of similarities, but I wouldn't presume that a design engineer could competently do the work of a technician. Just consider that any particular field of engineering as might be described by a lay person, can be fa…

there's something to that, for sure; there are plenty of design engineers who don't know nearly as much as they think they do, and who depend heavily on the expertise of their technicians to get anything done in the real world. they could never build an engine on their own! but there are also others who are eminently capable at the technical level, and i think their designs benefit from that

repair and design have in common that they require a lot of hard thought about the causal relationships involved in making the artifact work, tracing the causal chains through until they break, then patching them up. but they both also certainly involve other skills that the other does not; design also requires figuring out how to make new things happen, which involves imagining things that have never happened, while repair also requires knowing how not to bust your knuckles or spill the gasoline

Re: How to build a 50k ton forging press

#133

Post by libria »

kragen wrote: post #124
wizardforhire wrote: post #111

Earlier quoted context omitted.

This is exactly what dyneema is only with hdpe.

no, dyneema is not hdpe; it's uhmwpe, and it isn't just strain-hardened, it's gelspun

Assuming these terms are all correctly spelled, this has to be the shortest sentence I've understood the least of on HN.

Guess I've got some googling to do.

Re: How to build a 50k ton forging press

#134

Post by kragen »

libria wrote: post #133
kragen wrote: post #124

Earlier quoted context omitted.

no, dyneema is not hdpe; it's uhmwpe, and it isn't just strain-hardened, it's gelspun

Assuming these terms are all correctly spelled, this has to be the shortest sentence I've understood the least of on HN. Guess I've got some googling to do.

they are! sorry to be telegraphic

Re: How to build a 50k ton forging press

#135

Post by NavinF »

libria wrote: post #133
kragen wrote: post #124

Earlier quoted context omitted.

no, dyneema is not hdpe; it's uhmwpe, and it isn't just strain-hardened, it's gelspun

Assuming these terms are all correctly spelled, this has to be the shortest sentence I've understood the least of on HN. Guess I've got some googling to do.

UHMW = ultra high molecular weight. Each molecule is literally heavy because they have a lot of atoms.

PE = polyethylene. The most popular plastic on this planet.

HDPE = high-density polyethylene. One of the most common plastics. Milk jugs, glue bottles, etc.

Stick some UHMW tape on anything that needs to slide easier. Its surface is quite slippery

Re: How to build a 50k ton forging press

#136

Post by bobeboph »

abe_m wrote: post #110
hwillis wrote: post #20

> Forgings have the added advantage of variable grain direction which generally can be tailored to the stress patterns of a specific design. This is a super underappreciated fact! It's often repeated that forging is just stronger, but just squishing steel does NOT make it stronger. Forging a part is so much more than just smashing it into a shape. Steel cable is made of pretty ordinary steel which is stretched 100s o…

I'd really like to see some backing of these claims. I've seen "grain flow" claiming big gains for years in various enthusiast magazines (bike, motorcycles, cars, etc) as to why components are forged. Then I started working in engineering, and I can't find any support for these claims. For sure when a steel bar is worked down to become wire for a steel rope, it cannot be pulled to an elongation of 100x increasing str…

MIL-HDBK-5 [1] is a good publically-available source for strength allowables for several aerospace alloys, including multiple directions relative to the grain for some of them.

The first relevant example I found was on page 3-86, extruded 2024, 2.250 - 2.499 inch cross-section. For ultimate tensile strength, F_tu, the L (in the direction of extrusion) allowable is 57 ksi, while the LT (perpendicular to the direction of extrusion) allowable is 39 ksi. That's a 30% drop in strength.

[1] http://everyspec.com/MIL-HDBK/MIL-HDBK-0001-0099/MIL_HDBK_5J...

Re: How to build a 50k ton forging press

#137

Post by hackit2 »

mannyv wrote: post #86
advisedwang wrote: post #77

This should be a lesson for free-market advocates, especially those who see the US economic boom as a result of laissez-faire economics. In reality there are opportunities the free market doesn't take, and wise government intervention can yield enormous benefit to the public.

In reality what we call 'capitalism' is unstable and requires continual intervention to survive.

That is a very simplistic perspective of 'capitalism', it is a bit more nuance than that. It typically requires intervention to prevent it from destroying the economy because of insider trading, liquidity, and monopolist practices. The only criticism you say about it mirror aspect of our-selves that we don't like to admit. It isn't perfect but people are not perfect how-ever based on how fast we're pull people out poverty, you have to admit its pretty good!

Re: How to build a 50k ton forging press

#139

Post by shiroiushi »

bluGill wrote: post #32
bee_rider wrote: post #4

They talk about machining, casting, and pressing. Mostly with casting and pressing in a good light, machining not so good. As somebody who knows absolutely nothing about this stuff, I wonder—casting, I thought, was generally a lower quality option (like cast iron doesn’t have fantastic high-performance material qualities, and I had some crappy cast pewter toys as a kid). Are there different, higher quality casting pr…

Which cast iron? There are many different grades/alloys with different properties. Sometimes cast iron (some specific grade) is better sometimes it is worse. And of course you can cast things other than iron, cast steel does exist (rare outside the feed to a press, roll, or some other process, but you can cast steel into a specific shape if you want to). There are trade offs. The topic is so broad we cannot even star…

>Cast iron is fantastic for building machine out of - while it isn't as strong, it is stable against vibration. There is a reason engine cylinder selves are often cast iron.

I thought it was because cast iron had very high resistance to wear.

Re: How to build a 50k ton forging press

#140

Post by shiroiushi »

margalabargala wrote: post #80
shepherdjerred wrote: post #45

What strikes me is how great of an investment this turned out to be. Does the US invest in manufacturing like this anymore? Tangentially, if there were a war today would the US be able to produce as much as it did in WW2?

We didn't have any of these presses in WWII. We have several of the article's presses still operating today. Furthermore, all presses mentioned in the article have been surpassed by a 60,000 ton press that opened in Los Angeles, in 2018. People with agendas will happily feed others narratives about the US not investing in manufacturing anymore, but it isn't true. US manufacturing output has been steadily increasing s…

>People with agendas will happily feed others narratives about the US not investing in manufacturing anymore, but it isn't true.

It's a matter of perception. Most people don't directly see (or buy) the stuff manufactured in the US these days. Normal people don't buy nuclear power plants, aircraft engines, commercial aircraft, etc., and certainly not military hardware which the US makes a lot of. They do buy clothes and various consumer electronics, and they see "Made in China" (or for some clothes, places like Bangladesh or Vietnam or Cambodia) printed on all those, when 50 years ago all that stuff had "Made in USA" printed on it, or for the nicer consumer electronics 30-40 years ago, "Made in Japan". People still might be getting a CPU for their laptop computer manufactured in the USA, but the chip will probably say "Made in Malaysia" because only the silicon was made in the US, and was then shipped somewhere else for packaging.

>However, manufacturing does represent a lower percentage of our GDP with each passing year, despite the absolute value increasing.

I'd say that's probably a bad sign: what other sectors are increasing? Likely they're things that aren't actually productive, such as healthcare (the value received does not represent the price paid in the US by a long shot, compared to other advanced economies; most of the money goes to insurance companies and waste), legal services, ever-increasing real estate valuations, etc.

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