Timber as a mould making base

Hi All,

I needed to fill in 30 mins so thought would explain how I used to make lure moulds prior to 3D Printing - Unfortunately I don't have any photos of the process so hopefully I can provide enough detail so you can visualise it.

Why use timber instead of clay, I found it much simpler to get a 100% flat face on each mould half to minimise seam lines compared to using clay.

Tools Required

Lure stencil.
Drill.
jigsaw.
Hot air gun.
Blue Tack.
Plasticine.
Small el cheapo paint brush with a brush width of about 5 mm.
Clay modelling tool kit - buy at most Toy stores for about $10.00
5mm , 8mm & 10mm drill bit`s.
Piece of 20mm thick timber - Thickness / type optional but I used to use pine.
Timber to make walls for mould and as additional base plate for mould.
Wood sealant or Top Coat clear in aerosol can.
Bolt that is 5mm in diameter on the non threaded section of the bolt.
Hacksaw.
Metal file.
Ruler & Pencil.
Hot melt glue gun.
Mould release spray.
Silicone or Urethane moulding selection.

OK now to test the memory :

Stage 1 : Place your lure stencil on the timber and work out just how big the piece of timber needs to be, as a general rule I use to allow a minimum 2cm clearance from any part of the stencil to the edge of the timber - cut timber to size and then position and trace around lure stencil.

Stage 2 : Within the outline of the stencil, drill a 10mm hole through timber to allow you to then use jigsaw to cut out stencil - NOTE : Cut along the actual line of the stencil, not inside of the line as this slight increase in stencil scale will help later in the process.

Stage 3 : Take note of the highest point of your lure stencil as this will become your filling and vent port for injection and expansion of your choice of lure composition material - Resin or Expanding foam.

Stage 4 : Draw a line from the highest point of your lure stencil to the edge of your timber and go over the edge to mark the side of the timber. Now clamp your stencil to another piece of scrap timber and where the line is marking the highest point, drill a 5mm hole through the join in timber pieces to your stencil, this saves a lot of filing later on. Then using the 8mm drill bit, drill some holes closer to the edge of the mould then to the lure, generally 4 to 5mm deep is more then ample, these holes will now become your alignment points for the two completed mould sections.

Stage 5 : Coat timber mould base in sealer or top coat, then once dry place mould base on top of another piece of timber that is larger than the actual piece you are using for the mould base. Use plasticine to fill in enough of the lure recess so that when the lure is now pressed down, the eyelets are resting on the flat face of your mould.

Stage 6 : On a flat surface, roll some plasticine until it is 1 to 2mm thick, you then place the rolled plasticine the whole way around your lure and use your finger to press it firmly against the lure / mould faces as the warmth of your fingers will make the plasticine more malleable as its going to be your sealant as such between the two faces.

Stage 7 : Set hot air gun to roughly 60 degrees, and then select one of the flat faced attachments from your clay modelling kit, and place in front of hot air gun for approximately 10 seconds, then slowly scrap away at the excess rolled plasticine that is around your lure & mould base. Only do small sections at a time, continue to reheat modelling tool and remove plasticine in layers, don't try to remove all at once as this will only ruin the seal between lure and base - Been there done that.

Stage 8 : Measure the length of bolt shaft that you will need to place inside of the groove that you drilled earlier, cut and file bolt section, then place very small amount of blue tack on the underside of bolt and press into the recess in your mould and fill any gaps with rolled plasticine as explained in stage 7.

Stage 9 : Once you are completely happy with the seal between lure and mould base - WALK AWAY - go have a coffee, can or whatever and come back to your mould base 30 minutes later, then recheck your lure / mould seal is good and there are no stray bits of plasticine on your lure. I always take this moment away as the majority of the time when you come back and look at your mould you will notice that tiny bit of plasticine where it shouldn't be, or that you don't quite have a flat seal between lure and mould faces - Which is why I am actually typing this post to fill in time before rechecking a 3D printed mould before I pour the urethane into it.

Stage 10 : Ensure there is no plasticine inside of the lure eyelet`s so that when you make your mould you will have a decent position / fastening point for your eyelet`s - this is why we positioned the lure with the eyelet`s resting on the timber base section, holds everything in place for when you are actually filling your mould.

Stage 11 : With mould resting on top of a larger surface area piece of timber, cut to size pieces for your mould sides, and then use hot melt gun to attach mould to timber base and to fill in the joins at the corners of you mould sides.

Stage 12 : Spray the inside of your mould with a release agent so that all surfaces that will come in contact with your silicone or urethane moulding rubber have been coated, then calculate volume required of rubber, mix well and pour very slowly into the mould. Once you have a layer that is about 10mm thick, submerge the small paint brush into the rubber and VERY slowly trace around the outline of your lure body, it is extremely important to do this step very slowly as it will lift any air bubbles away from your lure to provide a perfect seal. Pour remaining rubber into mould and then repeat paint brush step, if you move the paint brush too quickly it will actually create a vacuum effect and pull air down into the rubber as it fold`s behind the paint brush.

Stage 13 : Once rubber has been fully cured, turn mould over and remove excess plasticine that was used to suspend lure earlier. Once the lure body is exposed, place some pressure on the lure itself as you separate the rubber from the timber. If you do this step carefully enough, your lure will remain in the 1st half of the mould you have poured and therefore give a perfect seal when next section is poured.

Stage 14 : Pretty much a repeat of stages 11 & 12, glue mould walls into place, spray with release agent, slowly fill and use paint brush to remove any trapped air bubbles on the surface area of your lure.

Well I had spare 30 minutes and its taken me about an hour to type all this so that it hopefully makes sense. I no longer use timber for a base as can 3D print them, however I still use the plasticine to minimise seam line in finished lures.

Hopefully this can help anyone new to mould making or at least provide some tips before diving straight into it.

Cheers
Steve