Casting for Woodturning

By David Bell

Biography

Reside in the beautiful scenic town of Elora, which is home to the Tooth of Time on the Grand river.

Belong to the AAW, the Thames Valley Woodturners Guild and the Grey Bruce Woodturners Guild, which I am currently the elected President.

Some of my passions for woodturning include, pens, bowls, goblets, vases and many other projects.

Introduction to Casting

Safety

Casting Principles

Mold Design

Casting Resins, Pigments, Dyes and Paints

Casting Materials and Preparation

Casting Tools

Post Casting

Projects

Casting Process

Safety

• Latex Gloves

• Safety Glasses

• Safety Shields

• Respiratory Protection

• Gloves

• Safety Boots

• Hearing Protection

• Apron

• GFCI

Casting Principles

What is casting? (Wiki definition)

Casting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting materials are usually metals or various cold setting materials that cure after mixing two or more components together; examples are epoxy, concrete, plaster and

Casting Principles

clay. Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods.

Casting is a 6000 year old process. The oldest surviving casting is a copper frog from 3200 BC.

Mold Design

Parts of the mold.

1. Cope – Upper Mold half

2. Drag – Lower Mold half

3. Riser – provides liquid due to shrinkage.

4. Sprue – passage for the liquid to flow.

5. Core – The cavity that will be filled.

6. Pouring Cup – Where the liquid is poured into.

Sand Cast Mold

Mold Form and Design

Solid Form – The core material is solid and held in place by means of an adhesive or a bridge material. The casting resin fills all of the voids. Simplest form of mold design.

Cored or Hollow Form – The mold consists of two or more pieces that follow the contour of the core material. The basic shape of the mold is similar to the shape of the core material. The casting resin flows through the mold to fill open voids. This is the most complicated mold form design and requires the most time to build.

Loose Form – The core material is allowed to float or remain suspended in the casting resin. Usually requires some sort of cap to prevent overflow of the resin. Simple mold form design.

Mold Form and DesignSolid Form

Mold Form and DesignSolid Form

Mold Form and DesignSolid Form

Mold Form and DesignSolid Form

Mold Form and DesignSolid Form

Mold Form and DesignCored or Hollowed Forms

Mold Form and DesignCored or Hollowed Forms

Mold Form and DesignLoose Forms

Mold Form and DesignLoose Forms

Mold Form and DesignLoose Forms

Mold Form and DesignLoose Forms

Mold design con’t

Mold Materials

• Silicone

• Hardboard

• Pine

• PVC

• UHMW

• Delrin

• Rubber

• Plastic pails

• Plastic cups

Resins or Casting Mediums

• Alumilite – Alumilite Corporation

• Epoxy – West System

• Polyester Resin – Clear Casting Resin

Casting Dyes and Pigments

Dyes are an additive that colour the resins.

Pigments are additives that give the colours a pearlescent reflection of light depending their platelets that are reflected.

Oil base paints provide a colour effect similar to dyes, except they do no cause bleeding.

Casting Materials

• Wood

• Paper

• Pine Cones

• Chola Cactus

• Corn Cobs

• Coffee Beans

• Rice

• Pasta

• Brass

• Aluminum

• Sparkles

• Just about anything

Material Preparation

• Drying – 200 F max. 0% moisture

• Cleaning – wire brush

• Stabilizing – Cactus Juice

• Material Sizing – depending on the project, everything from the mold size, resin quantity and pressure pot size need to be taken into account.

Casting Tools

• Pressure Pot

• Toaster Oven

• Wire Brush

• Mold

• Chuck/Faceplate

• Mixing Paddle

• Pigment Spoon

• Measuring Spoons

• Cordless Drill

• Bandsaw/Tablesaw

• Wax Paper

• Masking tape

• Oven Thermometer

• Timer

• Air Compressor

• CA Glue

• Accelerator

• Tape Measure/Rule

Casting Tools

• Pencil

• Compass

• Mixing Cups

• Paper Towels

• Latex Gloves

• Turning Tools

• Sanding Medium

• Log Book

• Drop Sheet

• Acetone

• Aluminum Foil

• Level

Post Casting

Cleaning – as soon as your cast is under pressure, wipe down the mixing paddle or spoon. Check your work area to make sure that no resin spillage remains. Dispose of the latex gloves, paper towels and mixing container.

Acetone will help remove any resin that is spilled. Wear appropriate gloves, a respirator and safety glasses.

Projects

Lets Cast a Project

Casting Process

1. Prepare and dry the core material. 0% moisture is optimum.

2. Does the core material require stabilization?

3. Prepare the mold for the core material to be cast and determine what mold design will be used.

4. Determine the amount of resin that will be required to perform the cast.

5. Determine what resin will be used, what dyes, pigments and/or paint will be used.

6. Which recipe will be used to cast the resin? New or old?

7. Is your Casting Log Book filled out?

8. Place the core into the mold and secure it. Place into pressure pot and level mold.

9. Prepare the pressure pot for casting. Is the pressure pot level? Is the Pressure regulator set to the proper pressure? Is the baffle plate ready ? Is there any pressurized air in the compressor and is there enough to charge the pressure pot?

10. Prepare the resin for casting. Which resin will be used? Are both parts A & B on hand? Is the dye on hand? Is the pigment on hand? Is the oil based paint on hand? Is the cordless drill ready and fully charged with a spare battery? Is the spoon and paddle ready? Is the digital scale ready and set to grams? Latex gloves ready? Paper towels ready? Is a disposable work surface laid out to mix the resin upon?

11. Pour equal parts by weight (grams) A & B into the mixing cup. Mix resins until they are clear. Add dye/paint and mix until uniform throughout. Add pigment and mix until uniform throughout.

12. Pour resin mixture into mold cavity slowly and uniformly.

Casting Process

13. Place baffle plate into pressure pot without disturbing the mold from being level.

14. Place lid onto pressure pot and secure immediately.

15. Pressurize the regulator side of the system. Slowly open the valve and charge the pressure pot to 40-50 psi.

16. Close the valve when the pressure pot regulator reaches the desired pressure. Disconnect the air line from the pressure pot.

17. Set the timer for 60 minutes.

18. Clean the mixing paddle and spoons free of resin and pigment.

19. Record your casting information in the Cast Log Book.

20. Go for Coffee.

ResourcesAlumilite

Plastic World - http://www.plasticworld.ca/

* Some hobby shops will carry this.

Epoxy

Lee Valley - http://www.leevalley.com/en/

Artistic Wood and Tool Supply - www.artisticwoodandtoolsupply.com

Polyester Resin

Plastic World - http://www.plasticworld.ca/

Michaels - http://www.michaels.com/

Pigments

Wyndham Art Supplies - http://www.wyndhamartsupplies.com/

Art and Craft Stores

Paints – Oil Based

Hardware Stores