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https://www.appropedia.org/Open-Source_Grinding_Machine_for_Compression_Screw_Manufacturing

Design Files: https://osf.io/ev6ta/

BOM: https://osf.io/tvsqd/




We build our own!

Status: build in progress


Changes to original design:

  • Wood thickness: 12.2mm 
  • Conduit_OD: 20mm (we use stainless steel rods)
  • Threaded rod for linear motion:
    • M10 instead of 3/8"-16
    • pulleys need to be adjusted due to different pitch (see below)
  • 6mm GT2 belt (instead of 8mm), easier to source (not printed)


Github repository with adapted design: https://github.com/ProjectFabMX/ExtruderScrewGrinder

Materials

ItemAmountWho takes care?StatusPurposeComment
Wooden pieces
Blue0ceandone

3D printed PLA pieces
done

Belt GT2 2mm, 225 teeth, 6mm width1Andreas Kahlerarrivedbelt to connect threaded rod and chuck pulleys

https://www.ebay.de/itm/162387133939

Steel rods 20mm140cmarrivedRails for the X and Y sliders to move on
Fastener: M8 x 30mm hex head bolt28arrivedAxle and secures M8 Bearings
Fastener: M8 Nylon Insert Locknut28arrivedSecures M8 Bearings
Fastener: M7 x 16mm Hex head bolt8arrivedMounting the flange bearings
Fastener: M7 Hex nut8arrivedMounting the flange bearings
Fastener: M3 x 12mm36arrivedFasten 3D-Printed parts
Fastener: M3 Hex Nut36arrivedFasten 3D-Printed parts
Fastener: 5/16"-18 x 1-1/4" Grade 5 hex head bolt ???1

Mounting angle grinder (dependent on angle grinder used)Need to decide on angle grinder
Linear Motion: M10 threaded rod100cmarrivedMoves X-slider for right-hand thread compression screws
Linear Motion: M10 nuts9arrivedMoves X-slider for right-hand hex nu compression screws
Linear Motion: M10 threaded rod (left-handed)100cm
---Moves X-slider for left-hand thread compression screwsignore for now (only do right handed crews)
Linear Motion: M10 nuts (left-handed)9
---Moves X-slider for left-hand thread compression screwsignore for now (only do right handed crews)
Hardware: 10mm Self Aligning Pillow Block Flange Bearing4Andreas KahlerarrivedSecures threaded rod and chuckhttps://www.amazon.de/dp/B073L2LWN4/
Hardware: 3-16mm Drill Chuck with SDS-Plus Shank1Blue0ceandoneHolds the stock material being machined
Hardware: 608 ZZ Bearings24arrivedLinear motion, stock supporthttps://www.amazon.de//dp/B07RZ651J7/
Fastener: Flat Head Wood screws 3x20mm36arrivedSecure individual pieces of plywood together
Fastener: Flat Head Wood screws 3x25mm4arrivedSecures the plywood sub-assemblies






Angle Grinder1arrived
see below

Calculation of teeth count

  • Extruder screw pitch: 8mm
  • Threaded rod pitch: 1.5mm (M10)
  • Gear ratio: 8/1.5 = 16/3 = 144/27
  • Chuck pulley: 144 teeth
  • Threaded rod pulley: 27 teeth

Calculation of pitch angle

The pitch angle of the screw to be made is equal to the angle the grinding wheel needs to be rotated

  • Extruder screw pitch p=8mm
  • Extruder screw diameter d=12mm
  • tan(α)=p/(d*π)
  • tan(α)=8mm/(12mm*π) → α = 11.98°

Angle Grinder

The original design uses this 4-1/2" battery-powered angle grinder: https://www.milwaukeetool.com/Products/Power-Tools/Metalworking/Grinders/2680-20

The metric equivalent is a 115mm angle grinder

We decided to use this one: Bosch GWS 18 V-LI

Grinding Wheels

The paper recommends "Type 27 Ceramic 4-1/2", 1/4" thickness" grinding wheels:

  • Type 27: these are not flat, but have a raised hub
  • Ceramic: ceramic cutting material, e.g. aluminum oxide
  • 4-1/2": 115mm diameter
  • 1/4" thickness: 6.25mm

These discs may be suitable:

TypeBuyfor which materials
Metabo FLEXIAMANT SUPER 115X6,0X22,23 INOX, SF 27Metabo Shop No. 616739000steel, stainless steel
Metabo FLEXIAMANT SUPER 115X6,0X22,23 STAHL, SF 27Metabo Shop No. 616275000steel





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