This is just a loose collection of my experiences with using phenolic urethane resin sand binder for mould making in a small non ferrous foundry environment. The guy I'm learning from has used it since the 1980's and at the time it had such clear cut advantages that he stopped using green sand completely. There were a few special conditions at the time that made it practical: there was enough domestic foundry demand from manufacturing for the resin to be imported in decent quantities to be fresh and for the supplier to be willing to sell small quantities. These days there's no real importer and any company importing the stuff wants to sell a minimum of two x 1000 litre IBC containers of a product that degrades within six months on exposure to moisture in air and probably UV light too. So the local demand is not there for an expensive product with a short shelf life. The other local advantage was access to high quality super pure silica sand from a mine that supplied Mitsubishi with it's sand for glass making and foundry purposes. Originally the sand was loaded by barge onto the ships and it was possible to get a cheap barge load when barges came South for maintenance at the local shipyard. A barge load would fill a vacant lot and require a dozen or so 10 tonne tip trucks making multiple trips to unload, taking care not to fill the truck's bin more than a quarter of it's volume as the weight would blow the tyres if completely full due to the 1.5 specific gravity of the dry fine sand (it was often wet). The advantages are that it's fast: cycle times can be as low as two minutes from mixing to tipping the cured mould out of the pattern. There's no need for flasks, even those snap flasks when pouring the metal. You can make as many moulds as you have resin and sand for and they will store for quite a long time, years in fact if undisturbed. The resin has three components all of which are subject to age, temperature, humidity and in some cases retarded by sunlight, so a small test batch is made and cured every session to get the exact ratios correct. For a given session, two components are mixed into a one reservoir and the third component into a second reservoir. The only special equipment are the two metal can reservoirs that gravity feed two glass bottles with a simple hand made lever valve on each bottle: one lever position taps the reservoir to fill the bottle to a predetermined amount, the other lever position dumps the resin into the sand mixer bowl below. A scoop batches the sand and the patterns have the number of scoops required marked on it in felt pen. There is a simple paper table on the wall showing the amount of resin vs scoops of sand to get the correct mix. The resin looks like motor oil in colour and viscosity, one component gets dumped into the sand via the bottle lever valve and is thoroughly mixed in, then the second component is dumped in using it's lever valve and a digital egg timer is triggered. The two components blend with the sand for about two minutes and once the egg timer goes off the batch is dumped into a small sheetmetal box under the mixer bowl via a central hole in the mixer. The sand is dumped into the pattern and a second timer triggered: if you are running a fast resin blend and don't get it into the pattern and tamped down with a brickie's trowel and screeded off in time, the sand grains will no longer stick and the sand is dumped off the table under the floor, this is rare and the excess is used to make pouring cups. There is no ramming of the sand whatsoever, just tamp it down lightly and tap the sides of the pattern and wait for it to cure. That's probably the most frustrating part of going back to green sand after using resin sand and easily takes the most time compared to resin sand: no need for vibrators, ramming or jolt and squeeze machines, just tamp it down, screed off and wait a bit for the cure. The pattern gets a few light raps on the side before cured to ease the extraction of the partially cured mould. Ideally you want the get the mould out of the pattern while it's slightly flexible so any pattern imperfections don't catch and so the mould can be assembled on a flat table to allow the two mould halves to conform to each other and prevent molten metal leaks. So that's the PUNB process in a nutshell, the used sand moulds are not recycled as that would involve cooking in an oven and crushing. It's my understanding after reading some product sheets that the resin is designed to break down over time into CO2 and water vapour and the suggested disposal is to use to cap off land fills with it. It goes into a bin and is sent to a specialized land fill and any metal spills must be removed before going into the skip bin. I'll try and find some relevant photos and add them later. Resin sand mixer, originally used to mull green sand, the resin batching system is out of sight:
Here's an earlier description of using the resin sand moulds which shows the layout of the foundry and some moulds being poured. https://forums.thehomefoundry.org/index.php?threads/sand-casting-session.738/
Mark, Too bad that material is not more accessible to us peons. It looks like very very nice binder and the molds produced have so many advantages. It sounds like it may be pretty similar to using AIr-Set and similar Furan binders. It would be so delightful to be able to practically use Air-Set or PUNB. I do appreciate your taking the time to write it up. Denis
The sand disposal sounds like a rough thing for a small shop, everything else sounds great about it. I have seen PEPset and a few others used. The fumes/smoke from the no-bake binders can be pretty noxious. The capability is unmatched, however.
It does have a few downsides, as Rocketman mentioned there's a lot of nasty burning resin fumes to contend with when poured. I suspect molten iron would be so hot the smoke would be greater and could lead to complaints nearby, we pour on a weekend in an industrial area to minimize the smell effects. As far as I can tell, a quality sodium silicate has all the upsides and few of the downsides, especially if you build a gas manifold into the pattern with small holes everywhere to ensure an even, consistent gas reaction. You can see a 20 litre can used as a rubbish bin beside the sand mixer in the photo: it's the original 1980's Pepset from a company called Ashland Croder and it could be tuned to cure speeds faster than you could get the mix into a pattern. I can't find much mention of the company now, it probably got merged or bought out over the years and all you can get are similar products from places like Germany.
I only use gas when I am in a big hurry for a core these days. I use NaSilicate catalyzed with propylene carbonate 95% of the time and wait three hours for it to set up. It probably would be ok to strip in less time, but there is enough detail in my cores that require pretty solid binder to draw perfectly. I do reuse the core sand by mulling it in my general casting sand and adding proportional clay and coal. I’ve not tried casting silicate molds without flasks. I suspect it would work ok but might require increasing silicate to 7.5% rather than my standard 5%. It is interesting to hear about the practical aspects of PUNB. Denis Clay Planet sells (well, maybe used to sell as I don't see it listed at their store now!) Chem Bond 210 (propylene carbonate)
I took a few more photos today: here's a punb mould for 4" tabletop gemstone diamond saw housing: the casting will get the runner cut off, a hit with the 2" belt linisher and then sand blasted. There are pre-cast dimples where holes need to be drilled and tapped and after a coat of paint it's ready to use. These are going back into production after a long hiatus as secondhand samples are selling for $800 or so.
With iron, at least if the volume of metal in it is chunky enough, the gasses escaping from the vents can be lit to burn off, which is much cleaner. Aluminum doesn't have the same temps/btu's in it. At the now-defunct iron foundry I worked at, when I made my way out onto the floor on pouring days my first job was a skimmer. Use a steel bar with a crook at the end to make a dam in the ladle spout until the pouring cup was full. The gas would erupt out of the core vents on certain molds, it was my job then to wave the hot end of the steel through the gas to touch it off. Wild stuff. I had posted a thread on the old BYMC forums with pictures of that foundry, I have them buried somewhere on an old drive, if I run across them I'll toss them up here
I was looking through some photos on the hard drive and found a photo of the original resin drum. A search of Ashland Pacific reveal they are still in business and there's a website for the parent company: https://www.ashland.com/about/about-ashland the website appears to have been written to make it hard to work out they are a chemical company and use a lot of words like "passionate, tenacity, stakeholders" etc. but is short on company history. If you search for Pep Set, you find the company ASK chemicals: https://www.ask-chemicals.com/company/history Ashland oil company bought Archer Daniels Midland in 1967, a foundry supply company and formed Ashland Chemical and by 1989 they made Novathane a phenolic urethane no bake resin for foundries. Novathane is what Peter always refers to the resin as and this is the first time I've heard of it mentioned elsewhere. Peter mentioned that when they first bought the stuff, a tech representative arrived at the foundry one day after flying from the USA to show them how to use the product. The tech rep said they were the first people in Australia to start using the stuff, this would have been in the early 1980's, yet the company timeline says 1989 and Peter has the photos from 1983 at least using resin sand moulds and he started the foundry in 1977. Current Pepset page: https://www.ask-chemicals.com/foundry/no-bake-binder-systems/our-brands
Interesting to hear about ADM (started locally in the early 1900's) de-vesting in chemicals in the 1960's. https://www.adm.com/en-us/about-adm/ ASK-Chemicals has quite a portfolio in foundry materials.
It's interesting to read between the lines of their acquisitions: starting off by supplying linseed oil with additives for foundry use, later on develops a petroleum oil binder process, then gets a bentonite mine. By 1970 the first Pep Set hits the market (missed that entry earlier). At the same time they sell the bentonite mines and bet the future on Pep Set. I count about 16 company mergers or buyouts. So Ashland just bought ADM's chemical division not the whole company like I mentioned a few posts ago. So I wonder what connection Ashland has with ASK (1975) which has Ashland as the A in it's name, maybe Ashland spun off the foundry part of the business into ASK at some point and just focused on chemical supply.
Here's the diamond saw casting from the earlier punb sand mould along with the brass spindle bearing housing to suit. The iron compatible resin has to be dug out with power tools so there's a small dent in a rib where I missed with the rock hammer. If it was the old novathane intended for aluminium it just would have shaken out of the mould as the sand disintegrated. The original pattern was pencil cedar (white straight grain softwood) and was later upgraded to aluminium sheet. There's no draft on the base of the pattern so the casting will sit flat without machining it: all the draft is on the inside.
Thanks but I can't much credit apart from the pour, you can see the glue residue so it's not even sand blasted, that's the "as cast" finish with a runner and vent bits cut off. That casting still has to be poured hot and fast to succeed as it's 1/8" thick in places, in the second photo you can see the round dots around the edge which are the remnants of the bike spoke drill bit making vent holes in the sand, on the surface there were scratched grooves under the clamps and aluminium plate and the aluminium even ran 3/4" along the scratches in contact with the aluminium clamp plates so it was nice and hot. Laurie, the guy who made the pattern actually did his apprenticeship as a patternmaker during WW2 before going on to become a manufacturing engineer. Peter was telling me that Laurie used to work on patterns in his spare time every week with a lot of them still in storage. Not every product was a winner but enough succeeded to pay the bills. I was using a casting off the scrap pile as an impromptu zinc ingot mould which turned out to be part of the case for a military encryption device in the 1990's.
BTW, Mark, I used your diamond-point wire drill idea to drill holes in sand cores and it worked very well. In my case I had 1/16" steel TIG filler rod handy rather than a bike spoke. So, I just ground 3 or 4 steep pyramidal facets on the end of an 8 or 10 inch piece and chucked it up. Pinching it between finger tips stabilized it as you indicated and it drilled neat clean holes quickly----much better than using a stiff 1/16" twist drill. Thank you. Denis
Here's some more photos of some bronze LG2 alloy castings today in resin sand. The locomotive name plate is the second attempt as the uneven halves and lack of venting in the first attempt caused a cold shut and failed casting. This second attempt had the two halves mated while still green so they matched, then two venting holes on top and several lines scratched in the mating surfaces. You can see some sand burnt into the metal in a few places from a hotter pour but it'll clean up fine. The small bronze anvils were cast from left over 10 year old resin sand moulds made from the old super fine silica sand. The pattern goes back a fair way and was for a Canadian national farrier competition trophy and is based on a Peter Wright anvil.
Got the plate sand blasted today, there some roughness that needs sanding on the F of "Fowler", the 2 of "No2" and the 5 of "1952" where the sand was broken when pulling the pattern original. The second photo shows the original plate painted in silver aluminium mould release agent.
