A plastic molding reality check...how crude can it be and still work?

[DDoug]

Lead and oakum? I always used oakum and tar.

I watched This Old House doo it that way (oakum & lead)....to connect to the old cast iron soil pipe
running out to the sewer.

And your planning on using your oakum & tar all throughout the house ?

 

[Joe Gwinn]

It could be there is an excess of draft on those cores, so much so, that in usage, the fitting is loose on the pipe at the mouth end.

Unless the pipe is sized to just fit into the open end of the fitting. Then, solvent plus a whack with a hammer will ensure a tight seal.

 

[DavidScott]

I found a video showing the rest of the operation, including the grinder.

Digger, I didn't watch it on tv, I did it. And if it leaked I would be the one coming back to fix it, so I made damn sure my work didn't leak, considering what was leaking out. Oakum and tar make a pretty good seal. This was sealing the pipes going in and out of septic tanks, all new construction thank you.

 

[DDoug]

Unless the pipe is sized to just fit into the open end of the fitting. Then, solvent plus a whack with a hammer will ensure a tight seal.

Doo you think the glue line is in the face of the counterbore ? Many times the pipe cut is not square.

Buy all the cheap Pakistani fittings you want, I'll stick with proper expensive fittings.

Oh, and make sure the cheap Pakistani pipe too....it comes with a little hammer...

 

[bryan_machine]

An economic observation. Cheap? Sure. Very low labor rates? One can presume. But while clever, also very poor productivity compared to a modern plastic injection molding setup.

The point being that a big part of our wealth and well-being in the 1st world is about more complicated, more elaborate, processes that are on a per part basis much more productive. (At least for physical goods.)

 

[Joe Gwinn]

Doo you think the glue line is in the face of the counterbore ? Many times the pipe cut is not square.

Won't matter. And the plumber will de-flash and trim if needed.

Buy all the cheap Pakistani fittings you want, I'll stick with proper expensive fittings.

In Pakistan, yes - plumbers are cheap. In the US, plumbers are expensive.

Oh, and make sure the cheap Pakistani pipe too....it comes with a little hammer...

Nahh. Need BFH. Any big lump of iron will do.

 

[DDoug]

Won't matter. And the plumber will de-flash and trim if needed.



In Pakistan, yes - plumbers are cheap. In the US, plumbers are expensive.



Nahh. Need BFH. Any big lump of iron will do.

Please move TO Pakistan.....

 

[Joe Gwinn]

Please move TO Pakistan.....

Nahh. No booze.

 

[SVFeingold]

I always get a kick out of some of the comments in threads like these. "Hyuck hyuck, that ain't even gonna make parts as fast as a modern $300k servo-driven injection molding machine!"

Yeah, who would have thought!?

This is clearly being done in a developing country. People do the work they can do and that they have access to until the country becomes developed and prosperous enough to make/afford better equipment and better working conditions. Also, not every developing country exists for the sole purpose of stocking your local Home Depot. You wouldn't think it needs to be said and yet folks feel the need to make it clear that "I'll buy nice fittings instead, thanks!" These probably aren't meant for you. The world doesn't revolve exclusively around supplying you. There are entire countries full of people that also have their own needs and may not have access to the best of everything. Us in the USA really take for granted the fact that we lead the world in access to pretty much every possible product and more often than not at the lowest cost.

There's a difference between meaningful discussion and a circle-jerk about how "haha other people are poor." This method isn't being chosen because they're all stupid. If everyone had access to modern facilities and equipment - most all would use them. The superiority complex is a bad look.

 

[surplusjohn]

Sv. I agree. The other side to consider is that i understand that the Pakistan government would actually discourage productivity efforts since they are trying to keep everyone fed. I dont know if thatis still try but that was my understanding several years ago.

 

[bryan_machine]

Riffing on this. SV has it right. I don' t know about SurplusJohn's observation, but such ill advised policies are rife throughout human history.

Of course it's not as productive as the $300K machine - if it was, nobody would buy the machine.

Rather my point is that such plants help us understand why an entire population is poor. If all of the output of the economy has his very low productivity, it won't produce much, therefore people will have little to consume -> poverty.

Such videos (there are lots of them) illustrate that people in general are clever and persistent in seeking ways to make a living (duh), and that relatively crude methods can be made to succeed in at least some circumstances.

 

[richard newman]

I'm sure that at some point in our country's history we had similarly "informal" production methods. Except that here the work was done by people we kidnapped from Africa, packed into boats like sardines, and enslaved. Great way to keep costs down.

 

[ViktorS]

Bryan said that a part of the reason (or so I read it atleast) that our 1st world countries have wealth is because of greater machines.

I'm still not convinced. Chinas rapid growth (and other countries as well, not exclusivly china) tells a different story, if I was to look at the evidence I have in my mind.
I will make a prediction now, call it scientific.
I think that as china accumulates wealth and they use progressevly more expensive machines and better conditions etc., as our societies does, the economic growth will slow down.

And I predict that the reason for that is that people will always buy the cheapest they can get that still works for the application. So as asia slows down some other will take their place as a low-cost-producer of different goods.

People in the first world will try to maximize their profit by buying cheaper material for construction, home shop, raw stock etc. etc..
A flaw in the capitalist mindset if you will.
We're shooting ourselves in the foot in a way.

 

[DouglasJRizzo]

Here's a link to a Youtube video I just watched, that is a nice reminder just how crude a plastic injection mold and plastic injection molding can be and still make some sort of usable part.

Why go for "crud" when you can have "crude?"

 

[Scottl]

I'm sure that at some point in our country's history we had similarly "informal" production methods. Except that here the work was done by people we kidnapped from Africa, packed into boats like sardines, and enslaved. Great way to keep costs down.

Actually, most of the work in early America was done by white people, often either indentured or bound by an apprenticeship contract. Methods of work were often crude and labor intensive but they managed to produce items for sale. Blacks brought here as slaves mostly performed agricultural work in the fields.

There is an arrogance here in the modern USA about sophisticated and expensive production methods. What is seen in the video is how much of the world operates, with methods that seem crude to us but get the job done. I'm sure the local craftsmen know how to use these fittings and if there is a lot of draft they probably have (crude by our standards) tools that taper the end of the pipe to match, probably something like the tenon cutters used in rustic joinery.

 

[SVFeingold]

I will make a prediction now, call it scientific.

IMHO you're about 10-15 years late on this prediction, this has been happening for a while now. China, for all its problems, managed to lift several hundred million people out of poverty in the span of a decade. An unprecedented feat. As people get access to higher paying jobs, better living conditions, etc. they also start to demand less scrappy and higher quality products and services. It's been happening for years and years in China. Most of the really low-cost stuff (e.g. textiles) has either left and moved on to cheaper countries already, or is in the process of doing so. In 2018 they stopped importing the world's recycling and garbage to be reprocessed, because it wasn't worthwhile to do it anymore and because the local environmental impact is severe. Which is right around the time people in the US started realizing "Oh wait, recycling isn't actually all it's cracked up to be." They're not investing enormous amounts into renewable energy because the Chinese government are exactly tree-huggers, after all.

Once people stop living as humans did for almost the entirety of our existence - e.g. a daily struggle to stay alive - they start to demand higher pay, better living conditions, better products, cleaner air, etc. and start transitioning from economies based on bottom-of-the-barrel cheap labor into economies based on advanced manufacturing and services. Just as we've done in the US. There is still plenty of cheap manufacturing in China but likewise there is also a lot of advanced manufacturing, and a lot of manufacturing talent. The number of experienced tooling engineers in China probably dwarfs that of the US at this point. Remember where most of those Speedios and Robodrills end up, after all.

Of course the crimes of the government put a damper on the enthusiasm, but I'm not the one to advise anyone what to do on that front...

As for the greater machine theory, the machines themselves are just one tiny part of a rich tapestry of fields, industries, services, people, etc. that comprise a modern industrialized nation. For the most part there's no such thing as just dropping an advanced machine, or production facility, or power plant, or whatever, into a destitute country with a largely uneducated populace, and thinking it's going to solve anything. You need people who know how to run the machine, you need people who can run mold flow simulations to take full advantage of its capabilities. You need other machines to create the molds. You need experienced tooling engineers who know how to do that. They need to run CAD. They need modern computers. The machines require tooling, maintenance, lubricants, spare parts, clean stable power, nice sturdy flat floors to sit on, etc. It goes on and on as most of you know better than I do.

Without the enormous breadth of skillsets and industries to enable efficient use of that equipment, it's useless and will be out of service and stripped for material within a few years. It's not just "the machine." The machine arrives when it's needed and makes sense, and once that point is reached the people that ordered it will be properly positioned to take advantage of its capabilities and use them to further drive their economy/culture/nation/etc forward. All of these moving parts that make up a modern developed nation are heavily dependent on one another, a fact that doesn't get enough appreciation IMHO. Isolate any one of them - I don't care what it is - and it will become useless and/or fall apart in short order. 99% of the time.

 

[JST]

IMHO you're about 10-15 years late on this prediction, this has been happening for a while now. ..................

As for the greater machine theory, the machines themselves are just one tiny part of a rich tapestry of fields, industries, services, people, etc. that comprise a modern industrialized nation. For the most part there's no such thing as just dropping an advanced machine, or production facility, or power plant, or whatever, into a destitute country with a largely uneducated populace, and thinking it's going to solve anything. You need people who know how to run the machine, you need people who can run mold flow simulations to take full advantage of its capabilities. You need other machines to create the molds. You need experienced tooling engineers who know how to do that. They need to run CAD. They need modern computers. The machines require tooling, maintenance, lubricants, spare parts, clean stable power, nice sturdy flat floors to sit on, etc. It goes on and on as most of you know better than I do.
................................

It was going on in china in the mid 90's, which is the last time I was visiting factories in china. Wages were going up rapidly, so that we "had to" move production elsewhere.

And, it takes at least one generation, usually more, to finish the job of industrialization. You have to build up a potential workforce of people who have had access to industrial products, and have ingrained some of the skills and understanding. Just stuff like about how tight a certain bolt can be made, or what tool is best to do that particular job.

We don;t even think about that, because most of us already have a good understanding of things like that. But if you come off a really primitive farm, you have no clue. Our more modern farmboys had worked on tractors, etc in the 1940s and 1950s.. In china, not so much until much more recently.

And, china went anti-industrial during the"cultural revolution". That set them back. Anyone who was skilled had to go and work on a farm behind some buffalo to "re-educate" them acceptably. Many were permanently blackballed so they were not available to show the way.

They caught up pretty fast in the last decade or two.

 

[Nagol]

I disagree with "no pressure" look at a 2 story house, and that drops down to the basement, makes that 90, thru a trap, and thence out to the sewer.
And then it gets plugged.....24'-30' of head pressure.

You only get 1 PSI per foot of elevation with water. not that much pressure

 

[bryan_machine]

@SV...

As for the greater machine theory, the machines themselves are just one tiny part of a rich tapestry of fields, industries, services, people, etc. that comprise a modern industrialized nation. For the most part there's no such thing as just dropping an advanced machine, or production facility, or power plant, or whatever, into a destitute country with a largely uneducated populace, and thinking it's going to solve anything. You need people who know how to run the machine,

Yes.

There are certain donor orgs that sometimes acquire advanced machinery (sometimes weirdly specialized - things like CNC folders) and seem to "air drop them" into various places in developing countries in Africa. This is not helpful. I am personally actively hostile to this. The machine needs to come with supporting things (tooling, manuals, training) and be appropriate for circumstance. By ALL MEANS raise the game however you can, but keep touch with reality.

I am working to build an efficient back gauge, to allow cutting very thin droopy material with a stomp shear, that will be used by a factory in Uganda. If it works out, it will greatly improve their productivity. But we (I and other folks working on the project) spend a LOT of time trying to make sure these things will be applicable, that they will 'stick', that the folks using them will be able to maintain them. I am hopeful, but it is fraught. (I sometimes fear these things will work OK so long as I or one of my associates is around to support them - but after we're gone, they will fall into disrepair.)


@Viktor - actually, I meant good production processes in general, rather than particular machines - but machines are a big deal. As noted here they only matter in context. Remember that machines doesn't just mean fancy injection molding presses - the shop in the video is full of machines. A bicycle is a machine, arose in the 1st world, and can profoundly change transport and society anywhere it is used.

Likewise environmental issues must be in context - plastic never breaks down? That's a problem for things like plastic bags in landfills, but a feature for things like sewer pipes that you'd really rather not dig up.

 

[Mavika]

Hi All:
Here's a link to a Youtube video I just watched, that is a nice reminder just how crude a plastic injection mold and plastic injection molding can be and still make some sort of usable part.
Production of Pipe Elbow || Incredible Technique of Making Elbow || Pipe Fitting - YouTube

For all of us who've been moldmakers it's pretty cringe worthy because it's incredibly rough and violates most of the rules we learned about our trade.

For those who are Prima Donnas about how special they are, it's a nice reminder to the rest of us that the tenths they pretend to split are not always necessary tenths.

For those who really do build high end tooling, it's a nice affirmation of the vast gap between a "mold" and a mold.

I especially liked the process control around deflashing the parts and trimming the sprues...high end and OSHA approved if I do say so myself!

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

Do you happen to have a procedure or process for for machining molds? Is there step by step guide reference book somewhere one can use? I have a mold trying to machine. I have CAD done now trying to generate tool paths and wanted to get input from experts here. I know detail is last thing that’s all.