Injection Molded Hard Baits - Thermo Plastic Choices

[CNC Molds N Stuff]

I've been playing with hard baits lately.  I've made a few solid resin casting molds.  They are ok, but have some limitations in my opinion.  Not hand carved stuff either.  That's not my thing.  I have hand carved a couple baits, but it takes a lot of time and care I just don't have these days.  I might machine carve a few wood baits.  I've got a machine that mostly sits idle which would be good for it, but I want to look at a more production oriented solution.  Not to do production, but to make what I want quickly (once I'm set up) and take it fishing.  I'm of course taking cues from my favorite commercial baits like any "beginner," but I have some ideas of my own as well.  

I'm looking at hard thermos plastic injection.  I've already got a piston plunger injection machine, and I'm about halfway through the build of a more serious pneumatically operated auger piston machine.  Neither is primarily for anything to do with bait making or tackle making.  Well that wasn't the intent to acquire/build them anyway.  I had the opportunity to make a bunch of "other" parts for an unrelated endeavor and stepped in to do it.  Now I have the capability and I plan to use it for my passion too.  

Its obvious that some production baits are 3 piece plus hardware.  Left side, right side, bill, & hook hangers.  Some are two piece.  Just a left side and a right side.  I suppose its possible some might 2 axis spin cast out of resin, but that's not where I am going with this particular project.  The plan is a glue or fusion clamshell type shop made blank. 

My hold up isn't really the injection machines or the mold making.  My hold up is plastic choices.  There are a lot of them.   I have a couple schools of thought and a few splintering of those ideas.  Initially I'd like to make some with an integrated bill.  The bill is part of the body.  There are a few I can think of off the top of my head.  Storm(tm) Thin Fins(tm) and Wiggle Warts(tm) have a bill made of the same opaque material as the body.  Bomber(tm) also makes the Flat A(tm) with a clear body and clear bill obviously all one part (per side).  I'm leaning more towards clear.  I could color laser print an insert close the halves, and fish with it.  No painting, no sealing, just add hooks and go fishing.  This is where I get into a bit of a quandry.  The most common clear thermos plastics are acrylic and polycarbonate.  There is also a clear plastic sold as clear PVC pipe.  I am sure there are others and there are plenty that are semi clear. 

The two I am most familiar with are acrylic and polycarbonate.  The most know differences are that acrylic is more scratch resistant, less flexible when solid, and more likely to shatter when subjected   to hard stresses.  Acrylic may also be more prone to shatter from impact when cold, but I do not know that definitely.  Polycarbonate is stronger (by a lot) but more formable when cold and scratches much easier.  Polycarbonate takes some pretty extreme forces to shatter or break. Its more likely to deform.  Even when used as bullet resistant glass the punctures are more of a distortion and tearing when a high enough power round is used.  The formability of polycarbonate can be good or bad.  I have a piece of 1/4" for the windshield of my small boat that I cold bent in the old Tennsmith(tm) sheet metal brake.  Made for a good looking rigid windshield.  I can imagine that for something like a crank bait it might sag or deform when left in a tackle box in a hot boat compartment in the Arizona sun.   For my own use (which this is really gear to) I am leaning towards acrylic.  I have had a Bomber Flat A break when fishing on a cold winter day, but to be fair it was old and had caught a lot of fish before one swam away with the back of the lure.  

I'm hoping for some experienced feedback with thermo plastics for this sort of application.  I know this may not be the right group for technical material science knowledge, but there are some members with widely varying backgrounds and experiences.  

An opaque plastic is not out of the question, but I would hope for something better than the easily heat deformed plastics Storm and some other tackle makers used.  

**  I do not want to "duplicate" any of the baits named in this post.  They are just good examples for illustration.
 

Edited June 18, 2020 by CNC Molds N Stuff

[whitaker201]

I can't help you with the plastic choices but good luck on your endeavor!

[Vodkaman]

There is no ideal solution to this dilemma. Acrylic is hard, scratch resistant, but shatters under impact. Polycarbonate is soft, easily scratched but it can take the impacts.

Fishermen, the customer base, can put up with the scratches. What they cannot abide is breakages.

For me, poly would be the way to go every time.

I wish I had the funds to develop and prototype my triple point lure, funds and materials are holding me back, otherwise I would be tempted to throw it your way for a limited production run. What I need is my own 3D Printer.

As for design, all the materials available have roughly the same density, around 1.2g/cm2, so interchange of materials is not an issue.

Dave

[CNC Molds N Stuff]

… and injectable in the same machines.  Just slight adjustments in temperature and/or pressure at most. I figured I'd test with ABS.  Easily injected, and takes paint fairly well.  

[Vodkaman]

ABS would be my first proto material for sure. Cheap, readily available, same density.

Dave

[CNC Molds N Stuff]

In another group somebody mentioned clear ABS.  I had to research it.  Like Clear PVC pipe I didn't even know it was a thing until I looked.  From what I read clear ABS is less impact resistant than even regular ABS, but I don't know what that means in the grand scheme of things.  

I think I'm just going to make some using different materials and conduct an exacting scientific stress and wear test, but tying them to a stick and beating them on the sidewalk.  

[Vodkaman]

The worst a lure has to endure is casting into rocks etc. I would find an empty car-park (4am) and cast there a dozen times.

Slapping on the sidewalk would be too severe and unrealistic - funny though

Dave

[CNC Molds N Stuff]

I would expect testing to failure would generate more useful information than just testing to "good enough," even if "good enough" is the goal.  Much like destructive crash testing of automobiles.  I think it would allow me to choose my compromises rather then being stuck with them.  

 

Edited June 19, 2020 by CNC Molds N Stuff

[Vodkaman]

Good point.

Dave

[mark poulson]

I can tell you repeatedly casting a PVC crank into the side of a concrete pier eventually taught it to break.   Just wanted to save you the trouble of trying that particular test.