First LF Castings

I got a chance to try out the new furnace yesterday in between the rain showers and do my first LF castings. I owe a big thanks to Kelly as I followed all his post very closely and applied this knowledge towards my patterns/castings.

I used the pink Foamular 150 and some of the blue stuff I had on hand from other previous projects. One of my many other hobbies is electric R/C planes, so I'm quite familiar with working with foam, so it did help with doing this as well.

So from seeing the many patterns Kelly made using the over arm pin router, I decided to make a larger router table for foam pattern making and my many wood working project. My plan was to add a pin guide to the top to basically do the same. I first tried to make the parts out of red oak, but they still flexed more than I liked, so I figured this would be a good LF project and make them out of aluminum.

From my first inspection they turn out great with one exception, I had a small shrinkage on one part, but I'll clean that up and fill in with some weld.

I used spray contact glue for most of the joining and some hot glue for the rest. Melted paraffin wax for fillets. The drywall mud I used I was not too impressed with, I purchased a bag of mix with water from the local big chain hardware store. It seemed to not hold up perfectly in some areas as the aluminum pushed through. I think I'll look into the premixed stuff for my next attempt. I really thumped the sides of the buckets to try and pack the sand in good, but maybe I did not get it that good and contributed to it too. Will have to experiment a bit more.





This pattern is for experiment/testing for shrinkage. I will have a much more complex/complicated pattern/casting coming up later down the road. I need to finish the pin router to make the other patterns.





Packed in sand, had a bit of over spill on the first one.




Had a small blow out on the top of the runner, this was completely my fault and was an over site. I did not have near enough sand packed on top to keep weight on it. I was very up set when I saw the aluminum flow up. However after pulling it out of the sand I looks to have cast just fine, yay!



Circled in red is the spot that had a bit of shrinkage.

There was a nice breeze, so the smoke/smell was not too bad, the neighbor next door might not agree with me, but I don't like him anyway, lol.

Over all very happy with the results and just cant get over how you get such a good part using insulation foam, drywall mud and loose sand. This is going to be very addictive!!

 

I am surprised at the results people get with the lost foam castings.
If someone would have asked me a few years ago if this could produce a quality part, I would have said "No Way".
It seems they use this in the automotive industry for casting engine blocks too, so obviously the method is very useful.

.

 

If for not seeing it first, I would have said the same thing. I was just like wow, this works so easy, now I know why people love it.
I had found some videos on youtube where a company was using LF for casting the blocks and heads. They had one hell of a air collections system for capturing all that nasty burn off.

 

This will have to be added to my project build list. I do have a good air supply, but I like the idea of the eccentric mounted ones, I actually looked into something like this years ago to use as a vibratory tumbler type polisher. This way I can kill two birds on stone.

I used Loctite multipurpose, the key is to spray at a good distance and let it cure for it bit. The propellant is what really attacks the foam. I did not do any cutting or router after gluing, I remembered your advice in your other post that it did not work so well.

Next time I'm at the store I'll pick some up, I did just look online and they have a lightweight and a general purpose type, which one do you use?

Thanks Kelly.

Your suspicion would be very close, this actually going to be for a 351W which is in my brother-in-laws '93 Lightening. To my knowledge it was used on the 5.0 equipped with the GT40 intakes, not sure all vehicles that had them, but I know the '93 Cobra did. I'm a lot more knowledgeable on the modular Ford engines. This part will be for a complete upper manifold. The stock GT40 (welded version) just did not have enough plenum volume when he had it dynode, it has been stroked to 408cid, with Edelbrock aluminum heads and large cam. Years ago I made a part cast and sheet metal intake that increased the volume and gave it a noticeable improvement, posted over on AA. Now with the possibilities with LF I'd like to make a more stock appearance one with larger plenum and shorter runners than stock. The stock intake is too prized to cut up and weld.

 

Very nice Cojo.
The only thing I'll add is that I test the sand by punching in with straight fingers. When the sand is first placed you can stick to a certain depth. With successful compaction penetration may be only to the first knuckle. It's a feel that is easily developed and help with sub surface blowouts. Sometimes I get the sprue runout even with a soup can Kush head, but as mentioned, there is usually a nice casting below it.

 

I've watched several videos, yours and some on youtube, so I was ready for the flame and smoke bursting out, but was still a bit worried how it was going to go for my first attempt. Yeah, that took me a bit by surprise when it suddenly dropped. I always slow my pour towards the end so that I can pour the most while the casting is starting to cool/settle, so I had no problem there luckily. My first thought when this happened was I just had a blowout somewhere, dang it. When I pulled the casting out I was OK, that was strange as it looked good.

I was very happy to see what I thought was a failed casting turn out OK. Definitely learning more on this LF after finally attempting it.

I'll be prepared for my next attempt and wont freak out, lol.

Thanks. I'll have to give this a try next time I do a LF pour.

 

Thanks Kelly, I checked online and they still make that exact same one, only $14, fairly cheap. Its in stock at the local big chain hardware store, so I'll stop by and get me a bucket. The non setting stuff should work better for sure, the stuff I used I had to keep adding water to stop it setting so fast. When I removed the parts from the sand, most of the mud had come off, so I don't think it really helped like the mud that you use.

That's the one thing I like about this hobby, some of it is trial and error and some of it is just plane luck when something works out perfect.

 

To make the mud lay down on the foam and wax more uniformly it needs an additive (surfactant) to lower the surface tension. I use a couple of drops of Dawn in a pint of mix.

 

OK, I thought it was mostly sticking to your castings, that's why you submerge them in water. I'd say 80-90% fell off in the sand. I did dip them water also.

I did lightly sand the foam with 320 grit and the mud seamed to stick fairly good. What you said makes sense and I'll give that a try as it cant hurt.


Thanks everyone for your input.

 

Been busy with other things, so I haven't had much time to start cleaning up and machining the castings. However I did wire brush the intake spacer casting to check if I got the shrinkage rate correct. I'm happy to say that I nailed it first try, I was very happy to see that it is 99% spot on, I see no reason to change it. The only thing will be to reduce the outer edge down a bit as I got carried away and added a bit too much. I did try to cut the runners off of the casting, but the junk HF band saw blade snapped at the weld, barely used too and its the second one to do that. So I picked up a good Olson blade tonight, so I'll get them done soon. Here are some pictures of the intake spacer.



gaskets on the bottom


Pattern template verse the gasket

 

Thanks Kelly.
Yeah, I've been slowly getting more aggressive over the years with my casting experience. I believe the LF will really get me to get aggressive, hence the CNC router, lol. I did kind of side track a bit on it as I've started to build a couple hot wire cutters for the foam. In the mean time I'm purchasing the lead screws and electronics for the router.

Corey.

 

That's exactly what I needed to do, resize the stock. Hot wire seamed the way to go. I started making a LF pattern for my supercharger adapter intake, going to try and make it as one piece verse the two piece I did with green sand as I do not need a core with LF to do this. The top part is 1/4" and the foam only goes down to 1/2", so slice it in half with a hot wire should work.

Yes, just cutting the holes in the intake spacer with forstner bit made a huge mess. I have one of those HF dust collectors to use, was going to buy an extra bag for it to separate the foam particles from the saw dust. I have a wood burning furnace and the saw dust is a great starter, I don't want to burn any foam in it.

Haven't done enough LF, so I have not experience cutting any foam that I glued together. I will take your advice and how to deal with it when the time comes. Once I get the CNC router built my plan was to make all the pieces like a puzzle then glue them together to avoid this issue. We'll see how that works once I try it.

I really like the surface finish of the router'd foam, its so smooth verse the more uneven hotwired foam, I have steady hands, but hard to cut it smoothly.