sand squeezer do's and don't s question

[todd goff]

Well, I have a good question for everyone once again and need some guidance on something. I was using a match plate pattern on a sand squeezer machine and disaster struck; I need to figure out what the h--- is going on. The squeezer plate made a rather sudden movement and I thought that oh well, maybe it was due to the fact that it was the right plate for the flask (12x16) and I figured that it had just jarred it. I made the mold and then went to make the drag half and found out what had happened; it seems that the pattern had split slap in two. My question is this; this is not the first time that this has happened but why is it happening? Should I ram the mold by hand to get a little cushion for the mold and then squeeze it or is it permissable to ram it by packing a layer of sand and then another and keep squeezing it? I honestly don't know why this happened but this is definitely causing problem after problem?

[RONALD]

Todd, you do not say what the match plate base is made of? Most match plate bases that I have are made of aluminum, but if yours is not metal, then it should be made of plywood, and I would use not less than 3/4" plywood.

[todd goff]

Sorry about that; these are made of aluminum and they are about 1/4 inch thick (maybe a little thicker). Man, it is breaking these things like it is nothing and I don't have a clue as to why. I know that these machines have some force behind them but is it really that much? I have basically given up on the squeezer machines and started using a pneumatic rammer. Sad part of it is that some of the patterns that were broken were very nice and I don't know if I should try to salvage them by repair or say the heck with it and melt them; if anyone has an idea please let me know.

[steamin10]

Patterns once lost or broken are hard to replace. I would advise to make serveral runs on the broken pattern, trying to duplicate it, and save the best one for the 'new' pattern.

I personally have not heard of a squezzer breaking patterns, that just seems wrong. I hand ram and have a pneumatic rammer. It always seemed rough on the pattern.

[ghornbostel]

Todd, Hopefully you have a Jolt/Squeezer. When you make the drag half of the mold you only jolt it (molding machine lifts the mold several inches and drops the mold) and hand ram the sand around the outside of the flask. Then you fill the drag half with sand and put the bottom board on it and turn the flask over. Then you put sand into the cope half of the mold and jolt the mold again. Then you ram the sand around the outside of the flask, fill it with sand and put the squeeze board on top and squeeze the mold. You then remove the sprue pin and vibrate the match plate as you remove the cope. Then you vibrate the match plate as you it from the drag. Cut your gating if it isn't on the match plate, blow out the loose sand, set your cores if any and put the cope back on the drag. You can only do this with a jolt/squeeze machine. Anything else you will have to have a very thick match plate as just the act of hand ramming will distort it. If when you get the mold made and it looks as if the pattern has been double struck you have tried to get the mold too tight. Slack off on the ramming or jolting. Sometimes your sand has too much bond and will bridge in spots and look that way too only in spots. Natural bonded green sand mulled correctly feels like silk to me in my hands. Over mulled feels course or grainy.
Regards
Greg Hornbostel