CNC Pen Lift

This instructable explains how to make a CNC pen-lift from an SG90 servo, two 4mm x 100mm nails, the spring from a ball-point pen, and a 3D printer.

The design accommodates pen diameters up to 14mm.

There is no pen-wobble when the pen is raised and lowered.

Construction is easy … all you need is access to a 3D printer, and basic workshop tools.

All STL and gcode files are supplied.

The estimated cost to build this pen-lift is less than $5.00 USD

Images

• Photo 1 shows the penlift attached to an experimental plotter
• Photo 2 shows a close-up of the assembled pen-lift
• The video shows the penlift in operation

All parts are shown in photo1 above.

The SG90 servo, complete with horn and mounting screws, was obtained from https://www.aliexpress.com/

The following items were obtained locally

• 1 only M4 x 20mm bolt
• 1 only M4 nut
• 1 only ball-point pen spring
• 2 only 4mm x 100mm flathead nails

The yellow items were printed on a Voxelab Aquila 3D printer using 1.75mm diameter filament and a 0.2mm nozzle.

The 3D parts were designed using FreeCAD 0.2.

The STL files were created using Ultimaker Cura 4.13.1

This pen-lift was inspired by https://www.youtube.com/watch?v=hkwSPbMtB84&list=PL3BbZZ9thFk58og0_ueqBFIlwoCzLGlwf&index=64

Significant differences include:

• Only requires a single bolt
• Uses a captive nut
• The V-shaped hole
• prevents round pens from twisting
• accommodates hexagonal pens
• The use of construction nails for the guides

The servo housing holds the servo and the two nails that are used for guides

The pen-up servo horn position is shown photos 4, 5, and 6

The slot in the side of the pen-holder takes an M4 nut.

Position the nut mid-way down the slot then insert an M4 bolt through the top.

Don’t over-tighten the bolt … a finger-twist is sufficient to hold the pen.

Step 1

• Shorten the nails such that they will just protrude from the base of the servo housing (photo 1)
• Remove any ridges with a file

Step 2

• Rewind the ball-point spring around a nail
• It must be a loose fit
• Adjust its length such that it will push the pen-holder to the far end of the servo-holder.

Step 3

• Before inserting the nails into the servo-holder ensure that each side of the pen-holder slides freely under its own weight along a nail.
• This may require inserting a 4mm drill into the slider-holes to improve the fit.
• Don’t get carried away with the drill… any unwanted movement here will affect your plotter accuracy.

Step 4

• Insert one of the shortened nails through the servoholder, through the spring, through one side of the pen-holder, until it protrudes through the bottom of servo-holder (photo 3).
• The nail is a friction fit at each end of the servo-holder but the pen-holder should move smoothly.

Step 5

• Insert the other nail
• The nail is a friction-fit at both ends of the pen-holder but should pass freely through the holes in the pen-holder.
• Adjust the pen-holder hole sizes slightly if there is any tendency to stick.
• Don’t get carried away with the drill… any unwanted movement here will affect your plotter accuracy.
• Done

All STL and gcode files are attached

The STL and gcode files were created using Ultimaker Cura 4.13.1

This instructable explains how to make a CNC pen-lift from an SG90 servo, two 4mm x 100mm nails, the spring from a ball-point pen, and a 3D printer.

The design accommodates pen diameters up to 14mm.

Construction is easy … all you need is access to a 3D printer and basic workshop tools.

All STL and g-code files are provided.

The estimated cost to build this pen-lift is less than $5.00 USD

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