We have a new project kicking off and my employer will be supplying a large but local small engine company our tooling and molding services

These are the brand new mold halves hanging in a 625 ton press ready to sample

The array of water lines are for mold temperature control....this one runs about 180 deg





Each sub 60 second cycle will produce two tops and two bottoms to be ultrasonicly welded together in a secondary operation to form 2 complete gas tanks ready for shipment

The initial sample was a success but we had an area that was trapping air/gas and not allowing the cavity to fill as we want

A normal mold vent is milled or ground near the molding edge at a very controlled depth of about .0005 to .001 deep to allow the air inside the sealed cavity to escape but no plastic to flow into these areas

This would not work in this area so we broke out a special product in the injection mold industry called Porcerax

Porserax is a steel with pores all the way through it that allow air to pass through. In this case we opted for .0007 pores

It is quite expensive at $14 per ounce

This picture shows the end of fill and the marked up area I will vent with the porcerax

I will use an EDM machine to "burn" a 1.250 x .675 pocket in the 50-52 RC core

First I mount graphite to 20mm EDM tooling holders and grind roughing and finishing sized electrodes

These need to be undersize to allow for the overburn or rather...spark size or spark gap

A higher setting is used for roughing but leaves a very rough crattered surface

This is followed by a finishing electrode to size and leaves a smoother finish

.018 spark gap for roughing

.006 spark gap for finishing

Grinding the electrodes mounted in EDM tooling



After the electrodes are made I can set up the block and get it ready to machine

All indicated strait and electrode located I have set a depth and this leaves us with little to do but close the hatch doors and flood the tank with dielectic fluid to start the burn



Tank flooded and the roughing electrode at work pulling about 15 amps





This will be monitored until the depth has been reached but leaving about .005 of stock to smooth and finish size

.

After the .018 spark gap electrode has reached the set depth I then switch electrodes and machine power for the .006 finisher electrodes

The tank no longer needs to be flooded as the chance of fire is greatly reduced with a low power electrode

This will finish the pocket for size and leave a finish that will work for this application



This is the finished pocket

I need a socket head cap screw to hold the porcerax insert in place from the back side of the block so now I will EDM a .201 hole through the block with a long round copper electrode and then flip it all over and EDM a counterbore for the cap screw head with a simple round graphite electrode

The pocket machining done on both blocks and the clearance hole burned to hold in the inserts it is time to finish grind the porcerax inserts I have rough squared on the knee mill

First joe block the pockets to gauge the size the inserts need to be ground to



Then grind them both to fit with no more than .0007 clearance and then off to the knee mill to rough in the molding area

The porcerax needs to be EDM'd to allow the pores to open up

I will mill away most of the excess area before final EDM using a 4 flute carbide end mill at 1200 rpm

the angle is about 2.8 degrees so a .0025 x .050 stepover is used to creat the rough molding wall







ready to go back in the EDM machine for the final burn shot

We will need a couple more electrodes

As before one rougher and one finisher....graphite mounted on 20mm EDM tooling



The finish will get no polish so it can breath through the open pores. There is a hole under the insert that allows the air to pass out

For this picture I have put a small amount of oil on the porcerax and shooting a small amount of air through the pass hole

Air passes through the .0007 pores but the nylon will not

see the oil foam with the air



This allowed the parts to fill completely on the next sample

These are cutaways of before and after porcerax

My apologies to those offended by this being off the forum topic

Just a share for those who machine

quote:

Originally posted by ted thorn:
My apologies to those offended by this being off the forum topic

Just a share for those who machine

All I can say is WOW!

You may be off topic but that was a neat tutorial. Thanks for posting!

Great post. Please post this on The Hobby-Machinist forum. There are many there who would love to see this. Having worked in a similar environment for many years it was good to see this. Thanks for posting.
Gary

Very neat stuff!

Thirty years ago I worked at a place in Tampa (I had two full-time jobs) that did injection molding but as I remember our biggest injection machine was 100 tons and our machine shop consisted of two ancient Bridgeports and a Clausing lathe. Got to be fun to work in such a place as yours.

I too find this amazing. When I served my aprenticeship back in the 60's we never heard of this stuff and I missed out. Really would love to have had some exposure to CNC stuff. I am strictly a manual machinist type.

Neat stuff yes.

But seems like such a waste when all of that machinery and the skilled operator could be making custom mauser actions instead.

It doesn't matter if it is guns or gizmos. This stuff is always very interesting to see. It gives us a better understanding and appreciation for what modern machinery can and cannot do. It also proves that even the most complex and intricate tooling requires a man behind the controls. Man is the master, machines the slave, and man will never be replaced by machines. Thanks for sharing, Ted

Ok,, this stuff is like rocket surgery, and all the machining I do is like early bronze age technology.

It looks like the video doesn't work

I will upload it again

Porcerax is a mind blowing steel. It isn't strong at all and requires a pocket that gives support from at least 3 sides or it will break off. It is amazing to see air pass so freely through what would appear to be solid.

The EDM is a 1978 model Charmilles D10 manual sinker

The video has been fixed

quote:

Originally posted by ted. ... It is amazing to see air pass so freely through what would appear to be solid.

Remarkable; folks have made the same observation about my head!

Ted,
I told you that the members would like it. It should give some a better respect for your machining skills and knowledge.

quote:

Originally posted by Toomany Tools:

quote:

Originally posted by ted. ... It is amazing to see air pass so freely through what would appear to be solid.

Remarkable; folks have made the same observation about my head!

Great stuff Ted! You have all the cool toys.

So you have the skill to machine a couple parts, but do you have the skill to insert a 286 grain 9.3 bullet into the heart/lungs of a Colorado bull elk?

Nice job! I hope you get some extra pay from the mould manufacturer since you obviously fixed their design problem!

Awesome stuff, thanks for sharing!

quote:

Originally posted by graybird:
So you have the skill to machine a couple parts, but do you have the skill to insert a 286 grain 9.3 bullet into the heart/lungs of a Colorado bull elk?

We will have to get closer than 650 and 450 yards this year

quote:

Nice job! I hope you get some extra pay from the mould manufacturer since you obviously fixed their design problem!

Now that's funny.....the molding is what makes us money

We typically give almost all of the tooling time away....free....to secure the molding we even maintain the mold for free

quote:

Originally posted by ted thorn:

quote:

Originally posted by graybird:
So you have the skill to machine a couple parts, but do you have the skill to insert a 286 grain 9.3 bullet into the heart/lungs of a Colorado bull elk?

We will have to get closer than 650 and 450 yards this year

I'm up for it! I'll be in shape this year!

Very impressive, Ted!

That porcerax is cool stuff all right!

I think everyone who tinkers with a gun has a secret desire to be a machinist.

I visited a friend two weeks ago in Houston who is a hobby machinist. He is also an astronaut but has converted his whole garage into a machine shop/laboratory. He has lathes, an electron microscope, a whole bunch of tools. Neck turns his cases on a lathe. He is absolutely brilliant; he can make and fix anything. When I asked him about wearing a pressure suit he brought up Boyle's law. When the compressor broke on his beer fridge (he brews his own) he fixed it himself. He is currently reading a college textbook on cell biology and growing some ferns as an experiment.

Sorry, little hero worship going on...

A Journyman Toolmaker can make anything

There are two ingredients.....time and money

I can helical flute a bolt but I send mine to Twisted Barrel

Time is money and I won't do it for $60

Thanks for posting this Ted. Way beyond my ken. jc

Is Mike Hart still around on AR? Aerospace machinist.

Cool stuff - not that I understand even a tiny bit. This is not sociology!

But I do appreciate the real old school craftsmanship of old English rifles and the current stuss as well.

Great stuff Ted.
Thanks for sharing.
Most of the machining I've seen was on small stuff like medical and electronics.
The big stuff moved out of the Bay Area about the time I started in the trade.
It was fun walking through the shop like Delaval back then and seeing pistons the size of 30 gal garbage cans.

Molds are elementary

Truly amazing work!

quote:

Originally posted by AnotherAZWriter:
I think everyone who tinkers with a gun has a secret desire to be a machinist.

In my experience, the best gunsmiths were, or are, above-average machinists.

Wow , nice stuff !
How do they make porcerax ? It's made with metal powder ,sintered and obviosly carefully controlled to givconsistant density !
There isn't much that those machinists can't make. Even more fun with modern tools !

I dabbled in building injection molds for a couple years and doing lots of servicing of them in processing plants. I am in awe and not worthy! I am curious about the plastic. Shot size? Temperature? Back pressure? Hold time? What kind of runner or X plate? How was it gated? Hope that's not too many questions. I see these things and it takes me back to problem solving and I admire how other toolmakers fix them. The ugliest and most troublesome mold I ever had to vent was shooting some kind of nylon that would flash at .0002". The tool actually had stand-off built into it to prevent flashing all over the place. When the stuff was at its melt flow it was thinner than water. The only machine tools at my disposal at that processor were Bridgeport mill, some junk lathe, and a surface grinder that had seen better days. The processor didn't want to outsource the repairs and told me to figure it out. The day shift foreman wanted to close up on a core pin held by hand in the edge of the tool, because "We do it all the time". I convinced him that was a really bad idea. I decided the only thing I could do was use a craytex/BrightBoy stick and hand rub a "vent" in the areas where the part was burning. I got lucky as it worked. I was very happy with myself. Knit lines, well that was another issue.

Beautiful molds man!

Wish I could find a mold shop in Texas that would take me as an apprentice. I'd give up a lot money to start over. I hate working for the govt.

What I still don't understood is chilled "A" side with hot tips when running LDPE.

TNT in my screen name is part of my email address. The mold maker I was working with insisted I get an email address. He suggested TNT-Toolmaker N Training. I am still learning.

Andy B