To get the best possible CNC driver / firmware setup, in combination with the CAD and CAM programs that are required, I tested the following setups with the Indymill hardware:
1) Reprap 3.3 & the Duet2wifi. STL’s are made with OpenScad and then converted either online or with Estlcam to Gcode (.nc files). The Gcode is then uploaded via Duet webinterface and run on the local reprap driver board. Not chosen by me beacause it proved impossible to run a gcode stream online from the PC to the USB interface of the Duet2wifi board. It is, however, possible to attach a serial handwheel to the Duet2wifi and manually control the CNC setup. And dual axis squaring is also easily made possible. Actually, the Duet reprap CNC setup is very mature and customizable. I still have this setup as backup and by switching the connectors from the Indymill over, I can easily switch to this setup. Some advantages of this setup are a.o. the webinterface and the ease of having an automatic squaring gantry on the 2 Y axes with individual endstops. I also learned that Estlcam can generate Gcode that I can then send via the webinterface to the Indymill CNC machine which works very well. (I make my designs in Openscad and save this as .STL files. Estlcam can then convert these .stl files to .nc files…, using the machine configuration to get the code properly generated for the Indymill’s dimensions and hardware settings)
2) GRBL, Estlcam & Openscad, Marlin & GT2560 (A) board; This is also working out of the box and emulates a GRBL driver board. The main reason to NOT use this is the fact that the GT2560 board just has not got enough pins available onboard for things like a handwheel and other outputs for accessories. The second thing that prevents me from going this way is the fact that it proved impossible to have a functional LCD attached that shows things like position, speed, status et cetera.
3) Mach3, FreeCad & USB CNC ‘barebone’ . This is actually a very solid and reliable solution BUT I could not get it to do any way of squaring my dual Y axis setup. Still investigating this…
4) GRBL, Estlcam & Openscad & MKS DLCV2.1 board with TFT 3.5 “; Also for this setup: No option for squaring the dual Y axis setup. But- this is a very neat solution for smaller machines. or larger, if you use external drivers. The nice option of this setup is the 3.5 inch LCD that also comes preconfigured for CNC. I use this for my small 3018 CNC.
5) GRBL, Estlcam& Openscad & Mega2560 & RAMPS 1.6 shield. Firstly, I must admit that this option was initially NOT on my list bacause I felt this was a pure hobby-like option. BUT- as my requirements list grew and other options got less and less, I ordered a Ramps 1.6 shield and plugged one of my Mega2560 boards under it. Then- the search began to get a working fork of GRBL for arduino that both accomodated the Mega 2560 and my requirements list. On this list: GRBL, Squaring my gantry, LCD with useful data, Handwheel connection, Preconfigurable buttons on the handwheel (stop, define as zero, probe here, et cetera). The fork that does this all is: GRBL-Mega-edge. The last comment is of April, 2020 and the fork was updated last in 2019. But- it works straight out of the box and the documentation is very well maintained.
Since it works under the Arduino IDE and has its own library, I foresee little problems in the future. Everything is freely configurable and it might even be possible to put an Arduino Due in place of the Mega2560 in this setup, with some tweaking of pins and speeds. And- tweaking is required for the hardware as well. The Ramps boards were never designed for 24 Volts, so this needs to be taken care of. One might of course use 12 Volts and use external driver modules, but I intend to keep everything very small and make use of an external PSU, and a small handwheel-like box for the Mega2560, Ramps, drivers, LCD, buttons and handwheel knob. By the way: For getting my designs I already had from my 3d printer background towards the CNC I bought Estlcam (CAM program). This really does a great job at converting it to Gcode and sending it to my Grbl- Mega 2560/RAMPS setup.
Afterthoughts 2021-06-22: When connecting Estlcam to the Mega2560 and RAMPS1.6 shield, Estlcam can program the RAMPS / Mega2560 configuration, including dual X and Y axis. This works straight out of the box including endstops. Actually this is easier than first compiling GRBL on RAMPS with Arduino’s compiler. BUT- it seems that autosquaring does either not work or I did not install Estlcam’s options correctly since the endstops on the dual axis appear to function in parallel instead of indicvidually per axle.
Another option for Estlcam is to program the Mega2560 without RAMPS shield and connect everything directly to the Mega2560 with jumpers. If this is done, Estlcam can steer almost everything. I will, at a later stage, try this as well.
DUET2WIFI clone Mellow FLY-CDY-V2:
To get the Indymill running, at first I first chose to use the Duet2wifi and reprap3 as base. Since I am very familiar with Reprap and with the Duet, I want to try this anyway. In the end, if it is all installed I need to have software to design and get a file with Gcode and this will be sent to the Duet2wifi controller via wifi, using the Duet’s webinterface that is been developed for CNC in Beta (DWC for CNC). The Duet2wifi is my favourite solution because I can standard use sensorless homing on any axis. And- because I need to home 2 independant Y axis and I have a lot of experience in making this work very smooth I will first go for this solution. And- if you get a good enclosure for the Duet2wifi, use 24 Volt PSU and good driver cooling blocks, you can push the Amps to over 2 Amp continuously. Should work with my Nema23 steppers. 2.5 is max but we don’t want that, I have some experience with cloned Duet2wifi boards that now have burnt driver chips. Still awaiting repair.
I am currently using reprap boards from Mellow, since they use the raprap firmware that is ported to the STM core that the Mellow boards use. On top of this, on the esp you can mount the Duet’s DWC software and thus also the DWC CNC software. I have this currently running on a test setup with a FLY-CDY V2 board and TMC2209 drivers. The nice thing about these Chinese boards is, that you can mount any driver you like, and this means that external drivers is also possible. So, also the external add-on drivers that do closed loop control can be used. I was thinking to make this my additional project: Try to do sensorless homing on the Y axes with this, use very low power and switch off the Closed loop during homing.. If I can get this to work, you will read all about it!
For the Duet, a setup has been made to use an original pendant handwheel unit and use an arduino nano or micro to make a serial interface to connect to the Duet! That would be great. I already ordered me a pendant to perform this surgery.
MACH-3 with a generic USB-CNC converter
I also have an original USB Mach3 interface with a. o. a handwheel unit. This works very straight forward but needs a PC to keep a stream of Gcode commands running to the USB controller. I am not very fond of this solution since a little mishap will destroy your objects that is being carved. But- this appears to work very well for many people so I have set this up after I had the FLY-CDY-V2 with the reprap 3.3 and the Duet webinterface running, to get to know the differences. I must admit it works straight forward without any problem. I decided to have this setup available next to the GRBL Mega2560/GRBL shield solution. The thing that keeps me from the USB-CNC solution is primarily the fact that this setup cannot auto-square my dual Y axis gantry. The Mega 2560/GRBL shield solution does this squaring very well.
GRBL with MKS-DLCV2.1 and the TFT screen
And- the most in use hobbyist solution: The GRBL boards like the above shown setup from MKS. I have this running on my old 3018 CNC milling machine and it always works well. This particular setup utilizes the preconfigured KMS DLC 2.1 board and the preconfigured MKS TFT for CNC. All is very neat and since the drivers can be adde externally as well as interanlly, it is possible to drive real high currents if you want that. These boards don’t do sensorless homing and usually put the 2 Y steppers in serial. This means that you will never be sure that they are well aligned.
RAMPS shield for Arduino UNO and Mega2560 (and DUE?)
GRBL can also be done via Arduino boards like the UNO or Mega (2560). With a proper GRBL RAMPS shield, connecting the steppers and limit switches is rather simple. BUT- 24 Volts connecting is not possible just like that. I removed D1 and powered the Mega2560 with a 9 Volts PSU, and the shield seperately with 24 Volts. For the Arduino DUE, dedicated RAMPS boards are already available (Smart ramps that compensates for the 3.3 volts in/out Voltage of the Due)!.
The Indymill’s Z-axis uses a lead screw by design , and not a ballscrew as I would like. But- that will be changed later.
For now, the lead screw solution will be OK because I will first build the Indymill machine and use the 500 Watt DC engine I already have for my CNC3018 setup.
The leadscrew of the Indymill is an 8mm leadscrew with a brass nut mounted in a 3d printed part that is mounted on the vertical rear of the Z-plate.
And- the drive stepper motor is mounted hanging on a horizontal plate on top of the Z-plate.
The required motion is exchanged to the leadscrew with a pair of 8x10x22 treehed wheels that are coupled with a GT2-10 mm wide 200 mm long belt.
The change I made to the original setup is to use an original 8mm lead screw bearing on top, under the horizontal plate.
I did not particularly like the original setup with an 8mm bearing in a 3d printed holder, and an 8 mm lockup ring under and above this bearing.
I had to machine the pro-bearing to fit the Indymill’s mounting holes and get the threaded drive screw nicely centered.
Under construction-still trying to find out how to do this.
I intend to use the same method as with the Y-axes so drop the 3d printed parts as much as possible and re-use the available bearing blocks and nut holder.
For the red nut holder I only need to make a flat extension plate to connect the nut holder to the Z-plate.
For the end bearing block BF12 to the right, this is no problem. I can mount it easily on the sideplate’s outside.
The push/pull bearing block BK12 is more difficult to re-use, I will try and find a small enough connection block that is 3d printable to shape the BK12 in, and still fits in between the 2 horizontal aluminium profiles that shape the X-axis. It will be very tight so I might have to make something myself, possibly I will just mount the BK12 on a in-between piece of 2040 and first I can mill a hole in the center of the 2040 piece so the end of the 1605 ball bearing screw can gain access to the BK12… Or something like this, will try and report how it goes later!
2021-5-24: Found a possible solution with an adaption of the same Nema23 to BK12 housing as is used for the Y axis. I am printing this fast with PLA on the Ender pro, will cut off some flesh of the NEMA23 top and bottom flange and will then fit this between the 2 lengths of 2040 extrusions and see how it works! The screw holes will have to be saved, but 4cm in the center will be removed, some 4 mm wide om both top and bottom.
Today I made the last solution fit the X axis and got all related components to fit the X-axis. During this I found that the left bottom ball bearing slider cannot move along the BK12 block.. So, I machined some material from this block’s side bottom. That doesn’t hurt but it does impact my planning a bit. And- during the process I destroyed a piece of the PETG BK12 holder that connects the BK12 bearing block to the stepper motor and the in-between side plate. I already directly printed a new ABS part to replace the PETG and wished I had started with ABS like I dit with the Y-axes. But- look at the bright side: Now all 3d printed parts will be ABS red: like the steel plates!
You must know that I elaborated quite a lot on how to print the Neam to BK12 couplers and fount that it is not good to print these withh the face to the Nema23 motor DOWN. Instead- I printed them flat, with the side that faces the stepper motor to any side but down or up. This gives great strength to the 2 pieces that carry the mounting holes for the BK12 bearing so they won’t break during use.
And I found that ABS in my case (both ABS red and PETG vblack are Sunlu products) works better for this build because the PEG breaks under strain and ABS flexes a little but does nor break..
In this post, you can see how I changed the original Indymill to more rigidity by using the original 1605 aluminium nut holders for the 1605 ball bearing screws of the Y axis, and how I made use of the BK12 and BF12 ball bearing blocks instead of the 3d printed parts like in the original build.
When building the frame, make sure that you do not initially screw anything tight. Follow the steps that apply to any build:
- Make the footprint square by measuring either with a good 90 degrees angled measuring hook OR measure the diagonals against each other and make them alike. Then, tighten all corner screws .
- Re-measure the footprint’s left against right length and also front/rear length. If there is any difference here, a) take everything apart and b) make sure you have equal sizes for your build where this is required. OR, if you have a non-standard build, make sure you build according to specs sizes. The, do 1. again.
- For a lineair rail: use a ruler that is specifically made for your type of rail You can 3d print one or buy two aluminium ones. ALWAYS use at least 2 rulers! With the rulers in place at 20% from left and 20% from the right, after you have installed the rail loosely with the screw in the nuts, tighten the screw a bit but not too stiff.. We will get back to these screws at a later stage.
- Put the connecting piece on the motor’s axle (8mm side) and tighten this well. Preferably, use some loctite on the axle but don’t overdo it. Be aware that you need to testfit the BK12 first. make sure that the connecting piece almost touches the BK12’s nut!
- Put the stepper motor and the BK12 connector together, using the 3d printed thin NEMA23 adapter plate between motor and steel plate. Do not yet tighten this too much.
- Make an original aluminium 1605 nut holder block shorter to fit exactly. See the picture.
- Fit the aluminium nut holder block including the entire assembly of the 600 mm long 1605 ball bearing screw on the machine, and superglue the block in the correct position. Let it dry so it won/t come off. Demount verything except the steel sideplate and the glued aluminium nut holder.
- clamp the nut holder to the steel plate with a grip vice, just to make sure it all keeps together.
- Drill 3 new 4mm holes through the steel plate’s lower part , drill through the aluminium block as far as possible. 2 holes on the lower side and 1 just between 2 of the top 3 holes, NOT where the existing hole of the aluminium nut holder block exists.
- Get the nut holder block loose, if it has not already come off.
- Tap M5 in the holes of the nut holder block. You will have come through the big center hole (for the nut) with 2 holes, make sure this gets cleaned up on the inside.
- Drill the new holes in the sideplates with 5.5 mm drill (to give you mounting clearance)
- Place the sideplate on the 2 bearing blocks of the linear rail with 4 outer M3 x8 (or x10) screws.
- Put everything loosely together
- Mill an end baring block to fit the 1605 ‘s screw end at the front an mount this at the exact center of the small front plate.
- Now, connect your nema 23 engine to a motor steering device so you can test the setup. First, turn the screw by hand and it should run smooth.
- Since you want to have an even height of the side plates, do not alter these unless it needs to be done on both sides equally.
- Your fixation point is the only non-movable position, at the rear of the frame.
- Move the carriage to the rear and now, see if you have slack on the M3 screws of the slide bearings AND on of the 3x M5 screw the rear of the aluminium nut holder. If so, first tighten the M3 screws. Then tighten the M5 screws. If not, loosen ALL of the linear rails screws ans move the rail a little. If this is possible, tighten the M3 screws of the linear rail’s bearing blocks. Then, try to get as much clearance on the linear rail’s movement up/down as you can and tighten the 3x M5 screws of the nut holder block.
- Now, tighten 1 screw only of the linear rail, at the position above the nut holder.
- Move the carriage entirely forward position.
- Tighten the linear rail’s M3 screw that is exactly in position above the nut holder (of the ball bearing screw)
- Now, tighten all screws of the linear rail.
- You’re done!
- Check the other side and if the linear rail’s height differs from the other side, the only thing to do is to start over again, where your slack is in the 5.5 mm holes of the steel plate’s screw holes for the nut block. If you play with this, and then adjust the linear rail’s height, you can get it all even. At least’eventually I got mine right but it took some time. Have fun!
Things to bear in mind: You don’t want anything out of parallel like a linear rail that is uneven to the aluminium profile on which it is mounted or a ball bearing screw that gets under tension. There is also another way to see what is happening while you are tweaking the hardware/frame: take the front bearing off and see what happens to the end of your ball bearing screw in the hole up front when you move the carriage. It can tell you much about what is happening… It should always stay perfectly centered but I’ve seen it up, down and all other directions.. -)
And- I must say, this build goes quite well. The materials are OK, and the guideline from the build description was very good. Although I never use it anymore. The build is quite self-explanatory once you start building the Indymill CNC machine. I also cahnged quite some parts, and made alterations where I felt this would improve the machine to fit my purpose better.
The required iron plates were not available in ready- to use state at the time I needed this, fortunately I could buy the plates as a kit with all of the drilled holes already in it, non-painted. And- all of the thread tapping still needed to be done. Since I am also making changes to the design of the millling machine, some holes will be altered and this is best done when the plates are not yet painted.
The raw streel for the Indymill. I put small colored circles where the thread needs to be tapped.
I am in the process of developing a router for my plasma cutter, since the cutter works very good but it will be way more effective once I can machine my designs with a router for this cutter.
My design differs from others because i will use only existing affordable parts that require no additional machining.
For the Y axis I will use a complete accessory from AliExpress with ball bearing 1604 and an effective way of 600mm, including a Nema23 stepper motor.
Mounted at a 90 degrees angle on the carriage of the Y axis by using extenders, the X axis will run with an effectice way of 400 mm but you could enlarge this to 600 mm.
The Y axis will get 4040 aluminium mounting feet , one of 400mm on each end of the Y axis, these are required for stability.
The plasma cutter ‘head’ will get a mount on the end of the X-axes.
The electronics will be added at the front of the Y-axis in a 3d-printable box. (or you can buy a ready-made box HERE).
Electronics will be an Arduino UNO with standard GRBL shield, or THIS as a better all-in one solution, including local router managing. At the beginning and end of each axis, a limit switch will be mounted. Switches, cabling and mounts are available on Aliexpress HERE and HERE.
Firmware for the Arduino comes from the widely available GitHub and the GRBL community. GRBL software is available for Windows PC and MAC as well. Designing can be done in any way, and the most simple way will be the online Cad solutions like Tinkercad .
The power supply for the Plasmarouter will be a 24 Vols 8 Amps portable power supply like THIS one.
2021 05 13: Yesterday I received the iron plates for my Indymill from Nikodem Bartnik, and it was all very well packed and quickly delivered!
As I always do on any build, I first check the separated axis for best fit and possible improvements. I started with the Y-axis. In the below picture, the left side of the macine is shown, being the left Y-axis. The rest of the machine is not yet attached.
The Y-axis is somewhat limited in its drive towards the rear of the Indymill CNC machine, due to the bridge plate for the X-axis. This bridge plate is blocked in its movement towards the rear because it hits the bearing block (orange part) that holds the ballscrew in place. By removing a small and unused part of the bridge plate, the movement can get about 6 cm extended towards the rear. The pictures are attached to this post, please see how I made this.
I used the plasma cutter to cut the parts out of the 6mm steel plates and after this was done, I used the lamel grinder to make it smooth. Although I used a guiding rail for cutting, the power was apparantly a bit too much so it is not a very beautiful cut… -) No worries because all still fits very well.
In my search for the best affordable CNC motherboard for my new to build Indymill CNC machine I finally chose the GT2560 from Geeetech as best compromise. At least for now, and maybe later I may change to an RRF3 board with a good remote CNC interface like the Mellow Fly-CDY-V2.
The board has a budget price and utilizes an atmega chip with great performance.
The board does not come with the CNC GRBL firmware installed, you can get the required arduino library HERE for the Arduino Mega with the add-on RAMPS 1.6 board and HERE for the GT2560 integrated board!
The nice thing about this board is that it can be flashed with the arduino IDE, and I like the board especially because I can plug in the NEMA23 closed loop stepper motor cables directly in the driver connectors of the GT2560 board. By doing so, I don’t need the lumpy seperate 6600 driver units and I never miss a step. These closed loop drivers get attached to the rear of the Nema23 stepper motors and use the 24 Volts from the wiring to the GT2560 driver socket. The max Amps is 4 Amps per unit and this is enough to have good CNC results. I also added the tiny LCD’s into the closed loop units, this makes it possible to perform local management like the initially required one-time calibration of each stepper without the need for a PC. And= the display also shows the status of the stepper motor (errors, missed/corrected steps etc).
The required Gcode can easily be made with Esticam. I first make my design in Openscad, export the design as .STL file in the highest resolution ($Fn at 128 or higher) and import the STL file in Esticam. Then I use Esticam to send the Gcode via a USB cable in the GBRL format to the GT2560 board. BUT- it is also possible to save the CNC file output from Esticam and put it on an SD card. The LCD unit that is attached to the GT2560 accepts SD cards (formatted as FAT 32) so you can work independantly of a PC.
Or- you can connect your Mega2560 to a Raspberry PI and use the Raspberry PI as webinterface , to control your CNC machine via wifi from your PC or phone/tablet.
Since Corona is still around (May, 2021) , I have some time available to spend on other things than just work.
I already have an upgraded 3018 CNC-machine with a 0.5 kW spindle motor,
and a simple GRBL 3- axis board that works very well. But- it would be nice to make a CNC machine that can really work with aluminium and possibly also with copper and brass. I have already done some research in the past about what sort of CNC machine would be right for my goals. And the IndyMill CNC macine was already on my mind for over half a year. So-last week I ordered the manual and the steel plates
for the build and ordered some other parts from Ali. I also have quite a lot of parts on stock, from my 3d printer supplies. The Nema23- motors and the extrusion, motherboard, drivers, power supply, switches and probes are already available.
The required printed parts are being printed right now (early May-2021). I am printing all the upgraded STL’s, latest version as these are freely available on Thingiverse (just search for IndyMill) . And then you see the power of sharing: the design was already great, and with the upgrades it got even better. The upgraded versions of the mounts for the linear bearings are really a lot sturdier than the original design and the new endstop holders are very handy to have.
I roughly calculated the costs for building this machine and it was a lot cheaper than buying a similar CNC machine of this size. If you purchase wisely, the costs for all materials can be just under Euro 1000, if you follow the original BOM and including the 1.5 KW air-cooled spindle motor with regulator…
If you want to install another board than the standard Arduino UNO with the standard Arduino CNC shield, this can set you back an additional amount of 120 to 500 Euro’s. I use a FLY_CDY_V2 with Mellow’s original TMC2209 stepper drivers. DO NOT FORGET to set the switches on the underside of these steppers to ON if you want to use sensorless homing!
My add-ons to the original build:
- Currently I use a 10 Amps detachable 24V PSU, will become a 30 Amps one.
- Sesorless homing with the use of a FLE-CDY-V2 motherboard and TMC2209 stepper drivers. This works awesome!
- Original mounts and usage of the ball bearing screw nut’s holder, and of the BK12 nd BF12 original bearing holders to keep the ball bearing screw from moving the wrong way.
- Altered Z axis setup with a better nut holder, and a better top bearing
- Closed loop NEMA23 stepper motors drivers MKS Servo57A V1.0 will be fitted to the rear of the steppers, still to be mounted but will conflict with sensorless homing
- 10 mm GT2 200mm belt between the Z motor and the Z-leadscrew with GT2 10mm wide 16-teethed wheels
- Add a ‘CNC pendant’ manual control device.
- On the Duet support website a project is available to convert such a device to a serial interface, with a programmed Arduino (pro) mircro or -nano built-in the device:
- Solid connection plate between the rear side of the upper and lower linear rails of the X-axis. Still to come.
- Piezo-probes on all axes’s start- en end positions, instead I have for now setup the FLY CDY V2 reprap board with TMC2209 and sensorless homing.
- Coolant mist installation and fluid gathering-, pump, reservoir et cetera is ordered
- Independantly driven (and independantly finetuned homing) Y-motors to prevent any possible problems between left and right. This works flawless with the FLY_CDU_V2 reprap setup but it took me quite some hours of finetuning to work woth the 3.5 kilogram heavy spindele motor…
- 2080 profiles all around (also front and rear) with 4 extra-wide corner brackets underneath. I chose to implement this differently with 3 additional bottom connections and corner brackets, since I need the front of the frame to be low and give way to the spindle vacuum hose.
- Smart enclosure with Scheppach vacuum cleaner connection like this example from https://www.shophacks.com/cncenclosure.html#/ THIS IS REALLY NEEDED!
- Protecting guards for all leadscrews and linear rails (ordered in China)
- Later if possible: Wheels on the rear or on 1 side and a handle on the front (or other side) to stow and store the machine easier
- Easily detachable control unit(s) with solid connectors
I started with a FLY_CDY-V2 reprap board to experiment with reprap CNC and the webinterface that has been developed for this setup.
This is achieved with smart dual homing of the dual Y axes, and gives me a lot more control on the machine. It is also already possible to just send GRBL-based Gcode to the USB port of the machine and use the reprap FLY board simply as gcode-interpreter to steer the machine. But for now I use the webinterface to upload and run any gcode.nc CNC file, which works perfect!
Picture of the CNC-adapted and already available webinterface for reprap, especially tailored for CNC (by Sindarius, work ongoing):
Pictures are already published about this build!
My Chinese lasercutter which I bought back in 2014 has been upgraded over the years. As many others do, I got the cooling system for the laser tube inside the casing, added some LED lights inside and also added an air pump for the laser head.
All in all the machine works fine now but the relatively small working area remains the bottleneck for using this machine for real interesting projects.
Mid-2020 I used the laser cutter for a couple of projects where I needed series of cut acrylic. The machine handled this flawlessly, but I did put it outside to prevent any smoke from entering our home.
I do have some ideas about upgrading the machine with a larger workspace and put the electronics and water cooling system in a seperate housing. No materials are needed for this, except 3 linear rails and some aluminium profiles. But- (status May-2021) I will start this project only if there is some work to be done with the machine since it is already working fine as it is, although the workspace is limited.
I use Inkscape (freeware) for making designs in SVG and import these .SVG files in K40whisperer (also freeware) which then can send the required Gcode to the K40 lasercutter. This all works very well and fast, you don’t need a fast computer for this. I use a 10 year old dedicated HP laptop for this.
In future use I want to make this lasercutter use the same board as I am using with my big LED laser cutter, so I can use GRBL on both.
As you probably know, a K40 or any other CO2 lasercutter can cut a specific kind of materials while a common LED lasercutter can cut other kind of materials better, due to the used kind of light on both which differ in wavelenghts.
The CO2 cutter can cut acrylic easily and the LED laser cutter can’t.
The LED cutter requires some sort of substance in the to be cut material to work properly.
Be aware that the security goggles you need also are specific for either macine.