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Author Topic: Are wood patterns obsolete?  (Read 759 times)
Bernie Perch
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« on: April 01, 2017, 02:22:46 AM »

On Wednesday I visited a modern foundry with a pattern for CNJ 113.  It is yet possible for them to do one off wood patterns but was informed basically that they were not really interested in that type of work or not using wood patterns.  What they really wanted was a computer disc where they could 3D print the sand molds and cores.  One of the people I talked to suggested that if I wanted to save costs would be to get some knowledgeable volunteer with access to the proper computer to write the program for the part.

He also went on to say that their pattern shop did not make patterns anymore, just did repairs and modifications.

I know that Jason is fully cognizant of the process of 3D sand mold printing, so what I am saying is not new to him.  What I am leading to is this:  is it really necessary to make wood patterns for our locomotive 11 project if they are going to be used a few times and then forever stored and never used again?  I am hoping that the currently finished patterns made by Allen, Howard, and myself will be used but if we wait too long, will they be obsolete?  

On my visit to the foundry, I was showed the machine that did the 3D printing and a large mold that was just done.  Even though I was aware of the process, I was shocked by the precision of the mold.

I was just wondering if it would be better and cheaper and more time saving if we just went totally to the new processes to get our parts cast.  Probably the only foundry that I know of that will probably continue to use the old methods is where Wayne got the castings made at the Cattail Foundry.  Their choice of metals is somewhat limited.

Any more thoughts?

Bernie

Edit:  It's been a while since I started a post.  I wasn't paying attention to what I was doing.  Thanx for moving it.

B
« Last Edit: April 01, 2017, 03:59:10 AM by Bernie Perch » Logged
Mike Fox
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« Reply #1 on: April 01, 2017, 01:04:40 PM »

I woll say I would rather look at your wood patterns than some kind of 3D creation. It will be a lost art, but now we have these great patterns we can use, and also show that this is how it used to be.
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Gordon Cook
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« Reply #2 on: April 01, 2017, 05:54:29 PM »

This is like CNC machining. Because of the economics, eventually the expertise to do it without the computer is lost in the commercial world.
Sounds like we may not be able to continue to use patterns. Even if a preservationist group is able to collect the the equipment, expertise, and materials to continue using the traditional process, the costs may be prohibitive.



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Stephen Piwowarski
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« Reply #3 on: April 01, 2017, 08:35:07 PM »

From an engineering standpoint, it may be more economical and easier to do CNC printed molds.

However, preservationist in me does not accept that this is the end for wood patterns though. If people had accepted that same reality at dieselization, there would be no steam locomotives running today.

Your work and time spent is invaluable- certainly the techniques of using the such patterns should be preserved as well. Many museums have already made a substantial investment of time and money into patterns. How can we protect that investment of time and money while also preserving the skills of traditional sand casting?

This sounds like the time to partner with a organization that is interested in preserving traditional casting techniques. Everyone wins.
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Joe Fox
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« Reply #4 on: April 01, 2017, 08:53:34 PM »

Bernie, the patterns you make are beautiful and make for great show pieces and it is amazing to see what the patterns look like, visualize the finish product, and the creativity involved in making the patterns.
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Wayne Laepple
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« Reply #5 on: April 01, 2017, 09:28:32 PM »

I think some folks who view the patterns made by Bernie, Alan, Harold and others miss the point. While their patterns are works of industrial art, by the time they are used at the foundry they become dirty and battered pieces of wood. In fact, back in the day, it was not uncommon for patterns to end up in a stove. Bernie is simply asking the same question that was asked by someone else regarding making parts off-site for No. 11. In that case, the reply was that it makes more sense to water-jet cut the steel and make the rivet holes and then bring everything to Sheepscot for riveting. It saves man-hours of volunteer time. The same might be said for 3-D computer aided pattern making, especially for the more complex pieces that may require multiple cores, etc.

Bernie's other point, which he may not have emphasized sufficiently, is that modern foundries cannot or will not use wooden patterns due to the labor cost involved in the moulding process. A computer-assisted pattern can be made so precise that no hand work is necessary, for example. The foundry that he visited told him that their pattern shop is no longer producing wooden patterns, only making repairs. Wood pattern casting is becoming extinct, and as much as we'd like to preserve the technology, it may not be cost or manpower effective to do so.

The Cattail Foundry that Bernie mentioned above is operated by an Amish family, and is thus exempt from many labor and safety regulations. It is literally a step back into the 19th century. But they are limited in the quality of what they can produce by the technology they employ. Every piece they produce requires some hand labor to grind off parting lines and other imperfections due to the type of molds they can produce and the pouring they can do, and they are also limited to casting only gray iron, aluminum and bronze. At least some of the parts we will need for No. 11 will have to be manufactured elsewhere, at a foundry that can produce cast steel, and you can bet that place will have all the modern bells and whistles.
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Harold Downey
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« Reply #6 on: April 02, 2017, 02:17:40 AM »

Wayne, do you have any pictures of our patterns after being used at Cattail?    I probably don't really want to see how battered and dirty they end up, though.
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Benjamin Campbell
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« Reply #7 on: April 02, 2017, 03:19:09 AM »

As an antique dealer I have seen and owned many wood patterns which were in remarkably good condition. They tended to be painted black(varnish tinted with lamp black) so don’t appear dirty until handled. The damage generally appears to be from poor storage practices – probably after they have become obsolete. Some patterns can be slightly chewed up from having wood screws partly threaded into them to act as handles for removal from the sand molds. Wood patterns which were intended to be used repeatedly generally had several metal ‘rapping and drawing’ plates let in to them and flush with their surface. These served the dual purpose of providing a hard and durable surface to ‘rap’ on the pattern when molding it in the sand and their tapped holes where used to insert handles for pattern removal. Patterns were often made of cast iron, zinc, or other metals when many castings were expected to be made. An initial pattern was made of wood – cast in the metal of choice – often machined – and then good to go for multiple castings. The original pattern had to take into account two cycles of metal shrinkage – one for the metal pattern and one for the final product.

I was using a foundry in Nashua NH to have castings made in the 1990s. They had one old timer left who they could entrust with molding loose patterns.  The castings I was making were relatively simple and capable of being cast in two part molds. The foundry’s preference was for split patterns which could be mounted to boards with the addition of sprues – gates etc. I painted my patterns the traditional black but they were always returned in silver paint which I told was a special anti stick formula to facilitate withdrawal from the sand. They used a fairly coarse sand so the surface tended to be rough. It is my understanding that back in the hand molding days a smoother surface could be achieved by sifting fine sand over a pattern before adding the coarser.
« Last Edit: April 02, 2017, 03:21:43 AM by Benjamin Campbell » Logged
Jason M Lamontagne
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« Reply #8 on: April 02, 2017, 01:14:16 PM »

Bernie, Wayne, all,

The printed mold approach has definitely been chosen as an appropriate candidate for no 11 in some instances.  The boiler dome saddles (bottom flanges) for both 10 and 11 are being made this way, as one off castings that would have required truly unwieldy patterns.  As ASME certified steel castings, this instance will provide a great test of the printed mold casting industry and concept.

My feeling is that wood pattern making will eventually become commercially obsolete, and be relegated to preservation environments.  It's another reason why this country so desperately needs an operating industrial museum.

That said, I don't see the transition being instant.  There are still too many circumstances where you don't want to make a mold for every individual casting required, and in circumstances where you know you want multiples (coach seats for us) or might want repeat castings in the future (loco 11 wheel centers for other projects) that making patterns still makes sense.

Even at that, there will be foundries slow on adopting new technology.  

We've explored a lot of these foundry approaches.  We've found companies who deal almost exclusively in printed molds, and companies that have never used one.  We found a company who will supply us with a printed mold, which we then own.  We've also found a foundry willing to use such a supplied mold.  

We really want to get through this boiler dome saddle process as a proof of concept.  After that, we know we want to print molds for some components (no 11 cylinders for example), but as to whether we move other components in that direction, we'll have to look at a number of factors, including foundry willingness to work with wood patterns, pricing and quality of castings from printed molds, availability of volunteer labor for wood patterns, etc etc.  

I suspect we'll end up deciding on a mix of printed molds and wood patterns for years to come...  Any existing wood patterns for 11 are getting used, and we'll still need more, for sure.

See ya
Jason
« Last Edit: April 02, 2017, 01:19:34 PM by Jason M Lamontagne » Logged
Wayne Laepple
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« Reply #9 on: April 02, 2017, 11:01:28 PM »

Harold -- I have not taken any photos of the used patterns. However, I still have the patterns for the flanger dies here in Lancaster, so I'll try to get a photo tomorrow and post it here. The fellows at Cattail Foundry always comment how nice our patterns look when I deliver them.

All -- Jason's approach as explained above makes perfect sense to me. Obviously, as we proceed with the No. 11 project, we're all going to learn a whole lot more about the foundry process. I look forward to it.
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Rick Rowlands
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« Reply #10 on: April 05, 2017, 12:31:47 AM »

As Jason said, various foundries are going to do things differently depending on what they make and what their customers want.  Jobbing foundries are getting even harder to find.  Not many industries require limited run castings anymore.  One of those industries is the heritage rail industry. 

Frankly I am looking forward to widespread acceptance of 3D printed sand molds.  Is it easier to find someone who knows CAD and Solidworks than it is to find a traditional patternmaker.  If it can be drawn up, the casting can be made at a cost probably cheaper than if I had to get a wooden pattern made for it first.  And even better, there are no bulky patterns to store.  Just a computer file. 
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Rick Rowlands
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« Reply #11 on: April 05, 2017, 02:32:30 AM »

If anyone needs an example of how widespread 3D printing has become, they are now building rocket motor parts via 3D printing.
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Jason M Lamontagne
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« Reply #12 on: April 05, 2017, 02:43:35 AM »

In college I had an industrial history class in which we had to write a paper which postulated whether our current technological advances could still be considered a part of the "industrial revolution" or whether it is a separate "informational revolution." 

Maybe there's no clear answer to that question; it all seems to blend together...

see ya
Jason
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