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K40 Motorized Z axis

This is a motorized Z axis for the popular chinese K40 Laser Cutter using 3d printed parts and the most common hardware.

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This is a motorized Z axis that I designed for the popular K40 Laser Cutter. My goal was to create one for under $50 using the most common materials and mostly with stuff we already have lying around. It might cost you more however depending on what you have on hand.

The final version is much more polished. Photos of it along with more details are below!

Note* I started this project with an already modified K40. We cut down the exhaust intake to give us more room in the Y axis. If you want to use this design then you will likely need to do the same, or remove the part of the exhaust where it is closest to the bed of a stock K40. If you don't, you should still be able to make this work, however you will have to trim the aluminum to different sizes, and get a different belt length.

Parts

Hardware

(Note that these are the exact parts that I used to model this, so if you use parts with slightly different dimensions, then you will need to modify the 3d models)

1/2" X 1/16" thick aluminum angle (8ft long - Menards, Home Depot, etc)

These are the sizes that each piece will need to be cut to.

  • 3 X 300mm long (X axis)
  • 2 X 120mm long (X axis)
  • 4 X 160mm long (Y axis) These may need to be different if your K40 wasn't modified like ours
  • 4 X 100mm long (Z axis)

8mm linear rod (At least 450mm in length)

(I used chrome plated rod, but drill rod will work just as well for this application. You won't use the Z axis as much as you would in a normal cnc application)

  • 4 X 110mm long (You can get some cheap chrome plated stuff Here )

M8 1.25 Threaded rod (At least 500mm in length)

  • 3 X 110mm long (This is basically what I used for Threaded Rod X 2)
  • 1 X 140mm long (this is if you want the manual override knob)

M3 Threaded rod

(This was kind of a last minute addition. I used this for the belt tensioning mechanism, but there are better ways of doing it)

  • At least 300mm in length

8mm Bushings

  • 4 x 8mm i.d X 10mm o.d X 10mm long bushings. (I used these exact 8mm bushings. If you use any others than you will need to adjust the 3d models accordingly)

GT2 Pulleys

  • 4 X 20 tooth 8mm Bore (I bought them Here )
  • 1 X 20 tooth 5mm Bore (I had one lying around but it can also be bought Here )

608 Bearings

  • 8 X 608zz ball bearings (You can get a pack of 10 Here )


C clips

  • 4 x 7mm C clips (These will attach to the bottom of the threaded rods)

Heat Inserts

(these are used to add threads to all the 3d printed parts. I just used a soldering iron to press fit them)

  • Aprox. 40 X M3 5X5mm heat inserts (I bought mine Here )
  • At least 2 X M5 heat inserts (not sure of the exact diameter used, but the wholes are 8.2mm in diameter, so your insert must have a slightly larger diameter than that)

Screws

  • 2 X M5 x 28mm (26 - 28mm should be long enough. I had to cut some to length)
  • At least 30 X M3 x 10mm (I would just buy some in bulk, but 10mm should be long enough for everything. If you plan on drilling and tapping the aluminum angle though, then you will need more than 30)
  • 4 X M8 1.25 Nuts

GT2 Belt

(This is the one critical thing where the exact length does matter. We are using a closed loop belt, so I had to order an exact size. Getting one too large will increase the amount of slack, and getting one too small will make it useless) Remember that I started this with a modified K40, so you may need a different belt length depending on your K40!

  • 1 X 6mm wide 1210mm long GT2 closed loop belt (This is the only source that I could find)

Nema 17 motor

  • 1 X 34mm long Nema 17 motor. (The length of the body is somewhat critical for clearance issues, so I wouldn't get one any longer than 34mm) This one will work.


Endstop Switches

  • 2 X SPDT switches (I used these but I would not recommend them. Basically any similar micro switch will work)

Aluminum Bed

  • 1 x 350mm X 250mm bed. (I used this, but it is almost overkill for this application. Pretty much any expanded aluminum or laser bed material will work)

3d Printed Parts

All of the STL files can be found Here

I have also provided the STEP files in case you need to modify the 3d models at all.

I printed all the parts in PETG with 3 shells and a 20% infill.

You will need to print

  • 1 x Knob.stl (for manual adjustment of the Z axis)
  • 2 x Bed Mount.stl (This is what the aluminum bed attaches to)
  • 2 x Bed Mount Mirrored.stl
  • 2 x Bed clamp.stl (this is what clamps the aluminum...
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  • Improvements

    haqnmaq05/09/2017 at 22:35 0 comments

    I recently updated the instructions to clarify some changes that we made to our K40 before I designed this Z axis. It affected the way I designed this, so the Z axis may need to be modified depending on your z axis. However if you have a stock K40, it should be easy to modify it. We essentially trimmed down the air intake for the exhaust fan to give us more room in the Y axis.

    The Z axis has been working flawlessly at River City Labs ever since I built it. I did notice that I haven't been able to get the full z axis length out of it, but it hasn't really been a big problem. The belt starts to slip when it gets to about Z-40mm, but no one at RCL has needed to engrave something that is larger than 40mm so it hasn't been a problem. I am not entirely sure why the belt slips, but if I ever created a second version of this, I would adjust the belt path to hopefully eliminate that and allow the pulleys to get a stronger grip on the belt.

    I also just added a new Z min endstop holder called "Z min endstop holder Longer.stl" to the github. It allows the Z min endstop switch to stick out farther allowing you to home the z axis to the top of your material. This makes it easy to get your material at the proper focal length. Essentially we home to the top of the material, and then move the z axis down a known amount to the proper focal point for our lens. You can then move your material anywhere else on the bed knowing that it's at the proper distance from the lens. (assuming your bed is fairly level) This is an example of our homing G-code in Laserweb4

    G28.2 ;home all move z-1 (the z-1 is set up in the smoothie config)

    G91 ;relative positioning

    G0 Z7.0 ;move z to focal point (the focal point for our lens with the Z-1 already taken into account. Your focal distance will likely vary)

    G90 ;absolute positioning

    I also added a new .stl file on the github for some 3d printed pegs that can hold down materials (leather, fabric) or help align materials by pushing them through the 1/4" holes in the aluminum bed. They are press fit, and they work great! Normally people use magnets, but since I chose an aluminum bed, I had to come up with a different solution, and I think they work even better than magnets.

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GrayPillow wrote 05/13/2017 at 08:45 point

Nice Project!

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