Giant Foam Companion Cube Walkthrough

This was supposed to be a proper tutorial, until I realized I was doing everything wrong. Learn from my mistakes, children.

Pictures are included where possible. Stopping work to pick up a camera breaks flow more than I predicted, so I hope you are not expecting good photos. Click on any photo to see larger version on Flickr.

Cube 2.0 vs. Cube 1.0

Materials

  • 16" cube of high-density foam
  • Piece of 1/2" high-density foam (I used ~30"x45")
  • Piece of thick upholstery batting
  • 1 can of upholstery spray adhesive
  • 1 yd (60" wide) dark grey double-velour fleece (aka Polar fleece, Arctic fleece, etc)
  • 1 yd (60" wide) light grey double-velour fleece
  • 1/2 yd pink fleece
  • matching thread in all 3 colours
  • 48" black zipper
  • 9 pieces of 1"x1" black velcro (both hook and loop sides)
  • large paper (at least 18x18) for patternmaking
  • pencil
  • ruler
  • pins

Tips if you are building your own

  • Foam tends to be expensive at retail, and a big cube likely needs to be custom ordered. If your local foam shop cannot/will not order in a big cube, you can laminate smaller pieces using spray adhesive. (If you've never laminated foam before...uh...good luck.)
  • Bulk zipper chain can be bought by the inch/meter at some fabric stores and upholstery shops. This way you get the exact length you need.
  • Fabric stores have seasonal displays; you will likely have the widest selection of fleece in fall/winter. Prices may be lower in the spring.
  • You can use other fabric types, but this pattern is designed for low-to-moderate stretch knits. Woven fabrics will fray, and the pattern is not precise enough for good results with non-stretch fabrics.

Things I will do differently next time

  • Applique corners and circles before inserting foam. (Leave openings on inside of cube for foam.)

  • Add shaping seams to corner pieces to preserve 3D look at edges. Preferably have fabric edges turned under for sewing.

  • Suck it up and do proper appliques. Oh who am I kidding, this will never happen.

Patternmaking

  1. Draw a square the size of one cube face

    Draw a square

  2. Draw midlines from each side to mark the center

    Draw midlines through square

  3. Using the center of the square as a pivot point, draw two circles inside the square

    Drawing circles using makeshift protractorInner and outer circles drawn

  4. Make edge piece: Draw lines from edge of square to outer circle, about 3/4" on either side of each midline

    Companion Cube Walkthrough

  5. Make corner piece: Draw lines from edge of square to outer circle, about 1" from edge piece. Extend lines 1/2" outside square

    Draw corner piece
  6. Approximate size of heart

  7. That looks about right. Time to make patterns!

    Pattern draft finished

  8. Trace half heart on a separate piece of paper. Cut on fold to make symmetrical. This is the heart pattern. Mark with Cut 6 PINK

    Heart pattern

  9. Trace edge piece. Extend 1/4". The edge piece as drawn is only half the pattern--cut on fold to make symmetrical. This is the edge pattern. Mark with Cut 9 LIGHT GREY

    Edge pattern, extended and cut on fold

  10. Trace corner piece three times with edges touching, as shown. Add 3/8" seam allowance on all sides. This is the corner pattern. Mark Cut 8 LIGHT GREY

    Corner pattern
  11. Trace center circle. Add 3/8" seam allowance around outside. Mark the circle pattern Cut 6 LIGHT GREY
  12. Trace edge pattern piece. Add 3/8" seam allowance around three sides, leaving one curved edge the same. This is the bottom edge pattern piece. Mark Cut 6 LIGHT GREY

  13. Trace corner pattern. Trim both "legs" as shown. This will be the bottom corner underside pattern. Mark with Cut 4 LIGHT GREY

    Patterns for light grey fabric
  14. Trace the center circle again. Do NOT add seam allowance. This is the circle pattern for foam. Mark Cut 6 FOAM

  15. Trace three separate corner pieces off the original drawing. Label the first one Corner 1 - Cut 8 FOAM. Cut 1/2" off one outer edge of the second piece. Label Corner 2 - Cut 8 FOAM. Cut 1/2" off BOTH outer edges of the third piece. Label Corner 3 - cut 8 FOAM

    Patterns for foam

Cutting

  1. Trace all foam pattern pieces onto 1/2" foam using a permanent marker. I find this to be the most efficient layout. On each of the corner pieces, mark whether it is corner 1,2, or 3. In retrospect this would be a good time to mark the 1/2" extended side on each corner 2 piece. Cut out.

    Companion Cube: 1/2" foam layoutFoam pieces cut out

  2. Cut 12 rectangles of batting, approximately the size of the edge piece pattern.

  3. Cut out all fabric pieces according to pattern directions. Also cut the following:
    • Square with 1/2" seam allowance on all sides (17"x17") Cut 6 DARK GREY
    • 1/2"x17" Cut 12 PINK
    Fabric pieces cut out

Gluing

  1. Each corner will be constructed with one each of corner 1,2, and 3 foam patterns.

  2. Line up a corner 2 with a corner 3 piece. The corner 2 will have a 1/2" extension on one outer edge. Glue will go there and on the corresponding edge of the corner 3. (I prefer to do this in batches.)

    Preparing a batch of foam pieces for gluing

  3. Mask off areas you don't want glue on, then spray both pieces lightly with adhesive.

    Using a magazine to mask unglued areas

  4. Depending on the brand of glue, you may have a few seconds or a few minutes before the glue dries. Match up each set of corner pieces and press to make sure the glue has bonded well

    Pattern 2 & 3 pieces glued together

  5. Repeat with corner 1 pattern and the long flat edge of the combined corner pieces.

    Gluing final corner piece

  6. Now you should have eight 3-dimensional corner pieces.

    Completed 1/2" foam pieces

If you have never used spray adhesive before...

  • Assume glue will never wash out of anything, ever. Do not wear nice clothes. Do not use near furnishings that you care about. Use plastic sheets to cover your work surface. Paint thinner or similar products may remove glue overspray, provided the surface can stand up to it.
  • Glue is probably toxic. Use in a well-ventilated area. Do not point the nozzle at your face.
  • A little spray adhesive goes a long way. The glue works when it dries to the "tacky" stage, so if you soak the foam it will not stick.
  • Use cardboard or scrap foam to protect areas you don't want glued. The spray pattern from the nozzle is much wider than this little project, so the masking will be important

Sewing

  1. Sew each heart in the center of a grey circle. If you are feeling ambitious, use proper applique techniques. I took advantage of the fact that fleece does not fray and just used a straight stitch 1/8" from the edge.

    Preparing to sew heartsCheaping out on the applique

  2. Pin pink strips across the middle of each dark grey square. Sew in place. (See previous step re: applique.)

    Preparing cube sides

  3. Fold each corner piece diagonally in half, so the two legs of the notch line up. Sew notch.

    Corner fabric, before sewingCorner fabric, folded in half
  4. Repeat with bottom corner undersides, keeping in mind that the SHORT side is the notch.

  5. With right sides together, match up each bottom corner underside with a regular corner piece. Align edges and seams.

    Lining up bottom corner & bottom corner underside

  6. Sew bottom corner pieces together along outside edges. Repeat for all four.

    Bottom corner completed

  7. Match up two bottom edge pieces with right sides together. Sew three sides, leaving open along the curved side without seam allowance. Repeat twice more.

    Sew together bottom edge pieces

  8. Trim corners and edges if necessary to reduce bulk.

    Trim and turn bottom edge pieces right side out

  9. Place foam circle over center of each dark grey square. Pin fabric circle in place over top, aligning heart with one of the midlines.

    Placing circle foam and fabric for sewing

  10. Sew circle in place. An edging or zipper foot on your sewing machine may make it easier to sew next to the foam. Repeat for each side.

    Cube side finished

  11. Pin two sides along one edge with right sides together, making sure hearts are pointing in the same direction. Align pink strips. Sew.

    Sewing cube sides together

  12. Sew two more sides on in the same manner, then join edges to make a tube.

    Companion "tube", before top & bottom added

  13. Pin another square to top edge of tube, matching corners to seams and aligning pink strips. Make sure right sides are together. Sew all four seams...

    Sewed on the top...oops, that was the bottom

  14. Shit. I did it upside down. Ahem. Making the best of it... Place inside-out over foam cube. Pin zipper into place around three sides of bottom. Remove from foam cube.

    Pin zipper on to three sides of bottom seam

  15. Sew zipper into place through all layers. Sew across ends of zipper. (Turns out this part is easier to do before sewing the top on the cube. Now you know!)

    Sew over ends of zipperSew zipper through all thicknessesCareful when sewing corners

  16. Use a seam ripper to unpick seam above zipper.

    Unpick bottom seam with seam ripperSeam over zipper successfully unpicked

  17. Pin the final square to the last open side of the cube. This really is the top. Sew.

    Sew on the top...for real this timeA cube! Not quite a companion cube yet...

    Here is where things get stupid. There is a reason the official plush cubes are not made like this--it is far easier to sew details and appliques onto flat pieces and join them after. However, I like the look of this design enough to suffer for it. If you attempt to follow my methods you will likely curse my name before you are halfway through.

    You have been warned

  18. For each edge that does not have a zipper, line up the midpoint of one edge piece with the seam. Align the center of each curved side with the pink stripes. Sew down three sides of edge piece.

    Applique three sides of normal edge pieces

  19. Insert one piece of batting through the open side. Make sure it is lying flat and even. Sew up final side.

    Sew final side after inserting batting
  20. For three zipper edges, insert piece of batting into each bottom edge piece.

  21. Line up midpoint of bottom edge piece with zipper. Align open curved edge of edge piece with pink stripe on side. Other half of edge piece should be dangling past the zipper. Sew three sides, up to but not over the zipper.

    Sew 3 sides of bottom edge piece after inserting batting

  22. Slide foam cube inside cover, with right side out. Place foam corner pieces on each top corner, and pin fabric corner pieces in place over top.

    Placement of corner pieces
    NOTE:

    Next time I would do this step differently. See instruction for bottom corner pieces.

  23. Remove foam cube. Sew each corner piece into place, along all edges. (Leave one edge open to insert foam, if following suggestion above.)

    Sewing on corner pieces with foam inside
  24. Pack up and move across town. Unpack. Attempt to find sewing supplies.
    NOTE:
    This step is not required; in fact, I would recommend against it. It remains my excuse as to why this took so long to complete.

  25. Slide foam cube inside cover, right side out. Place foam corner pieces over bottom corners, and trace in chalk. Remove foam cube.

    Trace bottom corner pieces onto sides

  26. Align bottom corner pieces with chalk lines. Shorter underside piece should be to the inside. Fold back top portion of corner piece to get it out of the way. Line up seam on corner underside to cube edge seam. Pin underside in place.

    Bottom corner underside pinned in place

  27. Sew bottom corner underside into place.

    After sewing bottom corner underside
  28. Fold bottom corner piece up into place. Pin into place along chalk lines.

  29. Sew bottom corner piece into place along edges, up to but not across zipper. Leave a section open to insert foam. For the two pieces on the sewn edge of the bottom (ie not across the zipper), continue sewing that edge onto the bottom panel.

    Bottom corner sewed on

  30. Insert foam corner pieces. Sew up open edges.

    Preparing to sew final edge after inserting foam

  31. Sew hook side of velcro onto inside of each edge and corner piece that hangs over the bottom. Sew through all layers.

    Sewing velcro to edges and corners

  32. Slide foam cube back into cover. Do up zipper. Pin loop side of velcro into place to match each hook piece you have sewn on. Remove foam cube.

    Placing opposite velcro piecesVelcro pinned in place on bottom flap

  33. Sew all velcro into place on bottom flap.

    Sewing velcro on bottom flap

  34. Insert foam cube. Fasten zipper and velcro. Trim all threads.

    Companion Cube version 2
  35. Sing Still Alive. You know you've been thinking it.