911 re pouring 3.5" carrot

[Denny Welch]

I've been trying to pour a ten cavity 3.5" carrot for the first time and I'm having a heck of a time.  I'm getting large empty places in most of the baits.  My first pour had 10 half full cavaties.  My next pour I was careful to void all the air out of the injector and still no usable baits.  I was using 4 oz of plastic so I added another couple ounces thinking the injector wasn't filling...actually got a few usuable baits.  The best I've done is 8, but that's out of 1 1/2 hours of pouring.

I preheated the mold and the injector...brought the plastic to 350 - 360 (infrared thermometer) and let it cool a bit before injecting...slow and steady injection...no clamping issues...for the most part the injected sprues are hollow. 

Any thoughts?  Thanks in advance.
 

[MicroSpoons]

loosen up just a little on your clamps. I have a mold that is like that. if I clamp it to tight it wont fill right but if I loosen it just a tad it works great.

[superharmonix]

Are you holding pressure for a couple seconds at the end of the injection?  I have a couple molds that love an extra "hug" at the end.  At first I was thinking your mold temp wasn't quite warm enough but it sounds like you've run enough hot plastic through there to get it nice and cozy!  Some molds do like it hot, but usually it seems to be the thicker plastic baits...
I've also had microscopic little whatchamacallits get stuck in the vents a few times and caused holes.  I usually hit the molds with compressed air before I inject to be on the safe side...

[Jason]

It should shoot like butter regardless of clamping or pressure.  I'll call you in a sec., I'm sure it's an easy adjustment.

Thanks,

Jason

[Jason]

All is good now.  When we re-did the Carrots we maxed out the cavities and they require topping off (or relatively cool plastic).  We could have opted for a bigger spru / runner, or less cavities, but ultimately went with max cavities and minimal waste. Hence, they need topped off.

An alternative is to release the clamps fairly quickly after injecting (requires great care).  This will allow them to draw air evenly as they shrink vs. just from the head.  Once the spru is solid you can then open the mold and de-mold as normal.

Denny, Let us know how they look when you get a chance.

Thanks,

Jason

[pjmcla]

The joys of the learning curve.  Sounds like Jason has you "fixed".
When I get hollow baits, it is usually on a "cold mold".  With a warm mold and 350 degree plastic and an injector nozzle that is warm, you should have all the ingredients to get a good bait.  If I inject too slowly sometimes I get a larger bubble or two in the head area of the lower baits: but not the very bottom ones;  or incomplete baits in the lower cavities ( tails missing ).  I found holding a little pressure for a little while after a medium quick injection is needed as this is a large volume mold and draw down will get you.  You can actually feel the plastic shrinking through the plunger.  Don't get discouraged: some one; usually me; has already fouled it up that way and the forum members help solve the problem.  That's what this forum is really good for. 

[Denny Welch]

Cancel the 911 call.  The last pour was 10/10.  I took some pictures with that camera I couldn't find and will now spend a considerable amount of time trying to download / upload and all that stuff.  Paul, it looks like you have some competition for finding ways to mess things up.  Thanks all.

[pjmcla]

Glad you solved your problem.

When I get it right;  my problem then turns into remembering what  I did to get it right  .  Especially if I take a nap. 

[kipbass]

I had troubles learning the croaker. The back of the feet would have holes or missing the whole heel. I have to inject really slowly and hold pressure for about 5 to 10 seconds, and top of the sprue. Every once in a while the gremlin creeps back in