Recycle Scrap PLA With This Compression Mold

Totally Unique Gridfinity Bins!

Use up your printer poop and other scrap PLA in this compression mold to make the coolest Gridfinity bins in the drawer. 

Video Instructions & Examples

Print The Mold

The mold is 4 parts: Two inner compression mold parts and two outer shell parts. 

• Mold_Top and Mold_Bottom must be printed at 100% infill in at least PETG. The higher heat resistance the better - if you can print in PA or PC you totally should. 

• Shell_Top and Shell_Bottom material doesn't matter, I'm using PLA. 

  • Shell_Bottom must be 100% infil

  • Shell_Top must be solid until you reach the big square pocket

    • I achieve this by changing the bottom shell to 30 layers, but double check!

Assemble The Mold

Hardware is required:

I encourage you to buy all of this at a local hardware store

• 8X Stainless Steel 1/4-20 X 3.000 Bolt

• 8X 1/4 washer, any material

• 8X Non-Stainless Steel 1/4-20 Nuts

  • Stainless-on-stainless is nearly guaranteed to sieze

• 12X M3 X 10MM SHCS 

• 2X M3 X 12MM SHCS

• 12X M3 Washer

• 14X M3 Nuts

Assembly Instructions:

Use washers at the head of each bolt unless otherwise stated

• Trap two M3 nuts in between Mold_Bottom and Shell_Bottom in the outer-middle hex pockets

• Fasten Mold_Bottom to Shell_Bottom using 8X M3 Nut/Bolt

• Put two M3 X 12MM in the outer-middle holes on the bottom

  • The bolt tip should be flush with the inside of the mold, no washer needed

• Fasten Mold_Top to Shell_Top using 4X M3

• Screw two 1/4-20 bolts directly into the plastic of the outer-middle two holes in Mold_Top

  • Screw until the bolt is flush with the surface on the inside of the mold

  • No washer needed

• Fasten a nut on a 1/4-20 bolt and spin it all the way to the head to prepare for the next steps. Do this for two bolts.

  • Put these bolts in the outside-middle holes (not the corner holes)

  • Fasten a second nut on each bolt until its completely engaged, but not much more

    • Pull the bolt to trap this second nut in the hex pocket

    • Now unscrew the first nut to pinch the plastic and lock it into place. 

    • A good target to shoot for is making the bolt flush with the cut-away surface of Shell_Top when its pinched, but this isn't critical. 

• Press-fit four 1/4-20 nuts into Stell_Bottom slightly (not a tight press fit, its okay)

  • Reminder, don't use stainless bolts on stainless nuts or it will seize up. 

• Put four 1/4-20 bolts into the corners, screwing into the press-fit nuts

  • You can tighten this slghtly to snug the nuts up into their pockets, but as long as they don't fall out when picking it up then it's doing its job. 

  • Undo this last part when you use it!

Use The Mold

Tools Used:

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• Firm Silicone Bowl https://amzn.to/4wA6AAS

• Firm Silicone Spatula https://amzn.to/4wy9DcH

• Heat-proof Gloves

• Silicone Spray

• A toaster oven which will never be used for food again

• Tools to fasten hardware above

  • (I used hex head bolts, so I used a socket bit, but to use this with a power drill I needed a Socket Adapter Set)

  • I've also used socket wrenches, works but definitely recommend power drill

Method:

• Melt 65-70 grams of PLA in a firm silicone bowl at ~400F until melted

  • Use more than 1 color for unique results

    • Forming it into a ball may help transfer to mold in next step easier, but don't mix it up too much

• Spray mold with silicone spray release agent for best results

• Transfer PLA to mold

• Compress by hand slightly

• Finish compression by tightening corner screws evenly with a power drill (recommended)

  • Take your time ensuring you are tightening evenly

  • Can be done by hand but not recommended

• Wait an hour to cool

• Unscrew 4 corner bolts

• Move outside-middle top-nuts back to top of bolt

• Tighten these jack screws evenly so it pushes against the bottom half, separating the two halves. 

• Tighten the inner-middle bolts evenly to eject the part

Modify the Mold

The OnShape files can be found here!

https://cad.onshape.com/documents/4b0a44577e8d9a575e788e8d/w/4b83fb24ed32e1600ca2e29a/e/81c4e83dda937a75dd290b72?renderMode=0&uiState=6a09171180c6824b475c47cc

Beware

• These Gridfinity bins do not stack like they should because they have the "live edge"

• They rock slightly in a grid & the more you use a mold the more it rocks

  • The bottom half bows-outward if you overheat PLA (easy to do) which is the mail culprit of the rocking. Maybe make the bottom thicker, add 2 more compression screws, or don't use PETG. 

  • This didn't bother me, most of my bins are free-reign and grass-fed anyway

• May not save more plastic than it uses

• The reason for the unused center hole in the shell is to make it modular-ready with a 1x1 bin, but unlikely I get around to that

• Theres a small chance the part gets stick to the bottom half instead of the top half, hence the M3 x 12's. If this happens you'll need much longer M3 bolts to get it out. But most M3 assortment kits has everything you need. 

• Make sure you melt PLA in a properly vented environment 

• If you try to melt PETG and use it in a PETG mold it will never come out

  • Any PETG poop mixed in at all runs a risk of permanent-sticking to the mold

  • You can probably melt PETG if you print the mold in PA or PC