How to Convert Monoprice Select Mini to Laser Engraver

I was asked to write up the process of how I converted my Monoprice Select Mini V1 into a laser engraver by the lovely folks down at r/MPSelectMiniOwners. Since I had some trouble finding relevant resources while putting this together, I had no idea if it would end up working or not, which is why I didn’t do a very good job at visually documenting the process and why this instructable will be sort of light on the pictures and finer details of the assembly. But it’s chill, you’re definitely a smart guy and if you’ve already made it this far, you’ll be surprised to know that you possess the ability to make it through some of the hazier details and slight shortcomings that probably exist in my write-up and see this conversion to completion. So I must take a moment to formally apologize in advance that I won’t be able to spoon-feed you every meticulously microscopic detail. With that being said, let’s hit the ground running.

I’m sort of a visual/lazy learner so I ended up gaining most
of my insight for this conversion through various youtube videos and this Google Doc from the Monoprice Select Mini Wiki, I figure I would share with you all the same resources that helped me.

I’m going to be paraphrasing a lot of the main points from
this instructable from Jake's Workshop since the overall procedure is universal to all 3D printer to Laser Engraver conversions. You may want to review his youtube video as well before proceeding just so that you’ll be familiar with the overall process by which we will converting the MP Select Mini.

BTW: This conversion method is compatible with both the Monoprice Select Mini V1 and the Monoprice Select Mini V2

Step 1: SO WHATS EVEN THE POINT ANYWAYS? / Things You're Gonna Need

Well, that’s a great question. Hmmm, I suppose my inner existentialist cries for relevance and purpose as it passes through the sequentially unfolding eternity. Lol, jk. Many of the haters will have you believe this modification is ultimately useless and/or dangerous. While the latter may be true, let me illustrate how this is actually cool as hell and totally worth it.

PROS:

- No need to change firmware or perform dirty invasive 3D printer surgery

- Super easy to create designs and export to gcode

- Really decent quality engravings which make great last minute gifts to people you want to like you, and your dad might even respect you!

- Ventilation is not really an issue since the MP Select Mini is light enough to pick up and take outside to your patio for lasering the laser, just don’t forget an extension cord!

- Portable, since the printer only requires 12V DC, so technically you could use something like a car or motorcycle battery to power it anywhere (shout out to all you aspiring entrepreneurs out there who like to sell cool custom wooden trinkets at the farmers market, eh? *Wink, wink*).

CONS:

- I have not yet streamlined my Zeroing/Calibration process, so starting up can take a little while

- You need to make sure your designs are the correct size and are oriented in the right location because the limit switches tend to be ignored by the printer and it will keep chugging along despite any physical barriers imposed by its infrastructure (this can most likely be fixed if you use a better CAM application (Computer Aided Milling/2-D Slicer) to produce your gcode, or if you edit the gcode exported from the Inkscape laser Plugin to take this into account).

- No enclosure with ventilation system, which means it should be operated outside/well ventilated room

- You’re going to have to wear the proper laser protection goggles when operating, unless you build an enclosure for the engraver

What you're going to need:

- Monoprice Select Mini 3D Printer

- Separate 3D printer to print out a Mounting Bracket

- M3 Machine Screws (can't go wrong with these)

- Laser Module, Here's the one I used

- Laser Goggles rated specifically for the wavelength of your Laser Module, since mine has a wavelength of 445nm, I went with these.

- 2 mm Hex Key (Allen Wrench)

- 3 mm Hex Key (Allen Wrench)

- Phillips Head Screwdriver

- Small Zip Ties

- Handful of Rubber Bands

- Little bit of persistence

- 2 pieces of heat shrink

- Soldering Iron

- Calipers/Ruler/Length Measuring Instrument (Here's the super cheap one that I use)

- CAD Software or bribe a friend with CAD Software

Step 2: Remove the Old Hardware (hot End, Hot End Thermistor, and Cooling Fan)

- Take off the small metal clips that hold the cooling fan assembly to the moveable hot end mount

- Remove the PTFE Tube used for feeding filament to the extruder

- Free the hot end/cooling fan assembly from the X-Axis gantry. This can be done by removing the metal clips that hold the cooling fan and shroud, then use small 2mm Hex Key (Allen Wrench) to loosen the two grub screws holding the bowden tube and extruder nozzle and wiggle each part off of the heat sink. If you perform this step correctly, the hot end assembly and cooling fan+shroud should be danglin’!

If you would like more help with this, I mainly followed the hot end removal procedure done by Dave Wirth (you only need to watch from 2:06 – 3:30ish)

- Lay the printer down, face-up on a table

- Remove bottom plate, disconnect the LCD connector, hot end, hot end thermistor, and cooling fan connectors from the motherboard

- Take off top Upper Chassis Front Panel to access the wires (you’re going to need to remove the 3 screws on top of the printer, and the 3 screws on the bottom-inside of the printer)

Once again I must stress the importance of the Google Doc when removing the correct screws for removal of the Upper Chassis Front Panel

- Cut the zip ties that are holding the wires together

- Slowly untangle the factory installed spiral cable tidy to free the wires

- Pull the hot end, hot end thermistor, and cooling fan wires out from 3D printer’s chassis

- Since the design I’m working off relies on the laser being controlled by the fan port on the motherboard, we’re going to need the fan connector (I think it’s just a standard 2-Pin connector?) from the original cooling fan. If you already have one of these laying around, then you won’t need to cannibalize the old cooling fan. Cut the positive and negative cooling fan wires at a reasonable length (long enough to comfortably reach the laser module at the highest Z-Axis location and farthest X-Axis location) and solder each respectively to the positive and negative leads of the laser module, don’t forget the heat shrink!

- Route the newly lengthened laser module wires into the top of the MP Select Mini’s chassis down to the motherboard and plug it into the Fan Port

- You’ll then want to close up the bottom panel temporarily with a couple of its screws and stand the printer back upright

Step 3: Removing the Heat Sink

At this point you should have a dangling laser module, a full-frontal view of the insides of the MP Select mini (since Upper Chassis Front Panel has been taken off), and an aluminum heat sink fixed to the moveable extruder mount on the X-Axis.

- Start by removing the X-Axis belt tensioner, this can be done by compressing it and wiggling it off of the timing belt

- Since the belt is loose, navigate to the back of the X-Axis gantry arm, take the 3mm Hex Key (Allen Wrench), and kinda wedge it between the timing belt and the back of the extruder mount (right behind the aluminum heat sink) . You’ll see that the heat sink is mounted to plastic moveable extruder mount via 2 M3 Machine Screws

- This will be the hardest part of the entire process: carefully wedge the 3mm Hex Key between the timing belt and the back of the extruder mount and loosen the M3 machine screws to release the heat sink

Step 4: Fixing the Laser Module to the Moveable Extruder Mount

Now, you should see the two threaded ends of the M3 machine screws sticking out the front of the moveable extruder mount. You might be wondering why I have not included a thingiverse file for this bracket; I must admit this is because of a few different reasons. Due to all the different cheap Chinese manufactured laser modules on the market, not all laser modules are created equal. So you’re going to have to draft and print your own bracket. The good news is, if you’re anything like me, if you mess this up, it should still be okay since there are a couple of ways to make the best of your bracket, despite imperfections.

This is what I used for the initial inspiration for my bracket.

This is also the ONLY mentioning of a laser engraver modification being done on a MP Select Mini that I was able to find on the internet.

DISCLAIMER: DO NOT PRINT THIS FILE, the hole placement and exterior dimensions are incorrect for some reason. I’m thinking somehow the scaling of the part got messed up through their drafting of the part.

- Use some calipers/length measuring instrument to measure the precise distance between the holes that the M3 machine screws on the moveable extruder mount are sticking out of, center to center. Then write this distance down.

- Measure the location of 2 of the mounting holes on the laser module and write them down

- Draft a bracket in a CAD software of your choosing

- Print out this bracket on a separate 3D printer, if you do not have another 3D printer by this point, shame on you. Also, you could definitely use a 3D printing service to make this bracket, or rely on the kindness of the friends or the internet to fabricate your bracket.

- Since most cheap Chinese laser modules use M3 machine screws for mounting, grab 4 M3 machine screws and screw the into the bracket to fix the laser module to it.

- Now we can position the laser module + Bracket assembly in place of the previously mounted heat sink and yet again, wedge that 3mm Hex Key between the timing belt and moveable extruder mount on the back of the X-Axis gantry and screw each screw into the holes of the bracket. If you’re really good at reverse engineering, or super lucky, the threads of the M3 machine screws will nicely grab onto the holes of the bracket. If not, you can do what I did. Get SUPER frustrated, grab a dull screwdriver, brutally widen the mounting holes, and super glue M3 Nuts in their place so that the threads could be tightened.

NOTE: If you mess up this process, don’t freak out too much, you’ll still be able get this to work.

- Just get some rubber bands. Stretch the bunch of rubber bands around the midsection of the laser module and hook them onto the little nubs located on each side of the moveable extruder mount; you’ll remember that these are the same little nubs that the two metal clips that held the fan in place connected to. The tension from the rubber bands will do a decent job of holding the laser in place.

Step 5: Putting It Back Together

Okay, by now you should have a pretty much assembled laser engraver. All that needs to be done now is some cable management through reinstallation of the spiral cable tidy, and the application of some zip ties to the ends of the cable tidy and the wires running through the inside of the MP Select Mini chassis. I did my best to match the zip tie placement to their original locations.

- Do the zip tie/cable tidy stuff I mentioned above

- Lay the printer back down on a tabletop and take off the bottom panel again

- Slide the Upper Chassis Front Panel back into place on the printer, put the 3 screws at the top, and 3 screws on the bottom-inside to close it up

- You can reconnect the LCD to its associated port on the motherboard as you close up the bottom panel

- Install the belt tensioner in its previous location, the back of the X-Axis gantry. I’m not going to lie, this was pretty difficult as well! You’re going to want to set on side of the tensioner onto the timing belt, then you’ll need to compress it while moving the belt on its opposite side onto its respective wire-hook thing on the tensioner.

Step 6: Time for Testing!

- Connect your MP Select Mini to your computer/Octoprint Server/Pronterface/Anything that will let you turn the fan on and off from your computer

- Since the laser module was plugged into the motherboard’s Fan Port, we can now turn the laser on and off via the cooling fan’s gcode commands

- Put on your laser safety goggles (special goggles rated for the wavelength of the laser module), and cover the MP Select Mini’s print bed with a piece of card-stock or cardboard to prevent the laser from hitting the print bed. Over time, little mishaps will occur where the laser accidentally goes over the print bed and will quickly eat through any painters tape that might still be covering it from before and will expose a very shiny layer of metal below. Supposedly, it’s pretty dangerous to a person’s eyes and even the ceiling of a house when the beam from the laser is able to be reflected off this exposed metal at an unpredictable angle. So you’ll want to be aware of this when operating such a device, PROTECT THE BED!

- Set the Z-Axis height to its midrange and quickly turn the laser on and off to check if the intense dot projected by laser module is a fine point rather than a blob with a diameter greater than 2mm. If it is an unfocused blob, raise the Z-Axis height until things improve.

- Play around with Z-Axis height a few more times to feel around for the focal point of the laser, this should occur when the smallest/finest point can be attained. I tend to keep my Z-Axis height roughly 5-10 mm from the top of the Z-Axis limit. Once this has been completed, keep the Z-Axis at this location.

Step 7: You’re Done!!! Just Kidding, It’s Time for Software…

Since I’m a man of uncreative pursuits who’s aware of the fact that flattery will get you everywhere, I followed the software process shown by Jake's Workshop because it’s free and pretty easy to use. You can go to his instructable to read about what he did, or you can continue to read this one to get a watered-down version of pure paraphrase.

- Download and Install Inkscape

- After this has been done, download the J Tech Photonics Inkscape Laser Plug-in

- Insert the contents of the J Tech Photonics Inkscape Laser Plug-in .ZIP File into the Extensions Folder [located in the directory: Local Disk (C:) --> Program Files --> Inkscape --> share --> extensions]

Step 8: Using Inkscape + J Tech Photonics Laser Plug-in

- Open Inkscape, and start a new drawing

- Click on “File” then select “Document Properties” and adjust your Width and Height to the correct Cutting Bed Size. I would suggest setting these parameters a good 10-20mm under the actual print bed dimensions of the MP Select Mini so that the engravings are more forgiving to the printer in the wake of any mishaps; such as the motors trying to push the X or Y Axes beyond the confines of their limit switches. You should also save this as a template for future drawings.

- Grab a simple black and white design from Google Images and paste it onto your canvas space, once you’re happy with the position, go to “Path” Tab and select “Trace Bitmap”

- Here you’ll be able to adjust the parameters that define the paths that the laser will travel to recreate the pasted image. This is going to take you a little while to get the hang of, be sure to check the “Live Preview” box to see how your parameter changes will affect the path design. Click “Ok” when finished.

- You can then go to the “Extensions” Tab and hover your cursor over the “Generate Laser Gcode” option to then select the “J Tech Photonics Laser Tool” extension.

- It’s here where you can make adjustments to the speed, number of passes, and depth before generating the gcode for your engraver. I also use M106 as the gcode command to turn on and off the laser since it's the same command that controls power to the fan port on the printer's motherboard.

- Click "Apply" to output the gcode that you can then load onto a MicroSD card

- Load your MicroSD card into the MP Select Mini and power it on

- You will be able to go to the "Print" option on the User Interface of the MP Select Mini and select the gcode file you just created to begin engraving!

Step 9: You’re All Done (for Realz This Time)! and I’m Very Tired

If you have gotten yourself up to this point, congratulations! You are now a part of one of the most exclusive societies centered on the cutting edge of groundbreaking modifications being applied to a small faction of popular Monoprice products. You should have a somewhat functional laser engraver that, like each and every one of us, is neither perfect nor elegant, but gets the job done. Anyways, I think this completes my timid attempt at documenting my laser engraver conversion process. You are now free to explore the possibilities, use different software, try new configurations and path optimizations, as well as make your own engravings.