Hot water method for straightening resin parts doesn't work

[Salamander]

I'm trying to straighten a resin gun using the hot water method, and no matter what I try, the part will return to its banana-like initial state, making me suspect it was molded in that state.

Any solutions besides scratchbuilding a replacement? Asking the manufacturer for a replacement is out of the question, as the kit is a vintage event-only kit from Japan.

[Ziz]

Can you build a jig to hold the part after you flex it back into shape? What's probably happening is that it's not flexing/stretching enough to counteract the way it's molded so as it cools, it shrinks/flexes back to its original state. Making a jig will force it not to flex as it cools.

[Salamander]

Can you build a jig to hold the part after you flex it back into shape? What's probably happening is that it's not flexing/stretching enough to counteract the way it's molded so as it cools, it shrinks/flexes back to its original state. Making a jig will force it not to flex as it cools.

Right now it's in my fridge with something heavy on the tip. If that doesn't work I'll try the jig.

How long should I let it cool, by the way?

[Ziz]

You're on your own. Depends on the size of the part, amount of flex you're trying to correct, how hot you get it to un-flex it to start with, what kind of resin was used, how old or new the part is (how long it's been cured in the distorted state) - too many variables to even guess at something like that.

Trial and error.

[Johnnycrash]

How hot was your water, and how long was the part in there?? As Ziz said, too many variables to give a complete solution.

Try HOT hot water, as in boiling. Just get it in there, and then take it out again. Depending on how big/thick the part is, changes the soak time. Not much time is needed to get it all soft and bendy though. You should still be able to hold it with your hands.

As for cooling times... Not long at all. At room temp, the part should be ready to handle in about 5 minutes or so (again, depending on size).

One thing to try as well, when bending it to straighten it, bend it PAST the point you want it to be at. There will almost always be some flex back, and this should take care of that.

And the jig idea is good too.

[Salamander]

Used really hot water (too hot to put my hand in for more than 1-2 seconds), let the part soak three minutes, pulled it out and held it bend in the other direction for five minutes => almost straight for a few minutes, then returns to its initial warped state This resin sucks.

Banana-like gun it is.

[tonyG2]

Last resort trick.

Hot water. Soften. Bend back to straight. Drill into the end lengthways whilst still straight. Let Cool

Cut a length or brass rod to the right length.

Place part in hot water. Soften. Bend back to straight. Insert brass rod. Driible in superglue. Use a rig to hold shape. Let glue set and resin cool....

[Salamander]

Last resort trick.

Hot water. Soften. Bend back to straight. Drill into the end lengthways whilst still straight. Let Cool

Cut a length or brass rod to the right length.

Place part in hot water. Soften. Bend back to straight. Insert brass rod. Driible in superglue. Use a rig to hold shape. Let glue set and resin cool....

I thought of doing that, but that would require I drill a 10 cm deep hole lengthwise through a beam rifle that's no more than 3 mm wide in the problematic section. Might work if I can drill the hole and then use piano wire or a carbon rod, but I do not trust my skills in drilling holes well enough to try that. I prefer the banana-shaped part to trashing the part while attempting to fix it.

[Tankmodeler]

Sounds like it really did take a set when it was made.

If you want a straight barrel (and who doesn't!) I think scratchbuilding is probably your only hope.

If you have a lathe it's not that difficult.

Paul

[Stu Pidasso]

Can you post a pic of said gun?

[aussie muscle]

have you tried after removing it from the hot water, hold it in shape and dunk it in cold water? (cool it very fast).

[gsb5w]

I personally have never tried to straighten resin with hot water but have had excellent success heating the warped parts with a hair dryer. I've done this at least 10-15 times. If the part is small I recommend using tweezers to hold it while you apply the heat. Take your time and keep checking the flex of your part as you heat it up so you don't melt anything.

[CR]

if it doesn't work out, sell your banana gun to the banana guy.

http://www.buzzfeed.com/patricksmith/po ... le-carryin

if it is the barrel that is warped, then slide it into a pvc pipe after you heat it up. (probably have to cut the sights/sites off then reglue)

it come out less warped and it might get stuck and you use your dremel to
cut off the pipe.

keep using smaller diameter pipes till it gets straight - pvc pipes are easy to cut off if your barrel gets stuck inside.

cr

[kenlilly106]

To expand on the jig idea above, I'm thinking there might be enough residual stress in the gun that even heating and bending the affected area might not be enough, you may have to effectively anneal the entire gun.

I used to work in metal fabrication and sometimes we would have parts that would warp and twist after welding and machining, the only way to get it to hold the true shape would be to firmly restrain it in a jig and then bake it in an annealing oven until all of the stresses had been baked out, once it cooled it would hold the correct shape.

In your case you'd have to:

• Construct a sturdy and heat resistant jig that can firmly hold the gun in the correct position.
  
  Dip the bent part in boiling water long enough for it become flexible enough to bend into shape to get it to fit into the jig.
  
  One gun is in place and firmly restrained submerge the jig with gun into boiling or near boiling water and remove the water from the heat source and let it cool to room temperature with the jig still in it.

Hopefully at this point all residual stresses are gone and it will hold the new shape.

Ken