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  1. #1
    3D Printer Noob
    Join Date
    Mar 2018
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    20
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    Convert a CubePro over to Smoothie hardware (open source stuff)

    I will put information here for others that might be interested in following a similar path.

    Background

    I bought a CubePro Trio fairly cheap, knowing that it was a closed system with lots of limitations. However there seemed to be recent activity to unlock a few of the restraints and thus allowing such a printer to be used more economically in a home environment and also keep up with the constant stream of improvements in the 3D printer space. Unfortunately after spending more time then I am willing to admit I feel it was time to throw in the towel, gut the machine and install some new hardware that would open the printer up and let me get on with printing.

    Plan

    Choose a hardware and software project that is active but stable, high performance and with a decent design that I might even be willing to work on the code and make some changes or improvements if necessary. The original board has 8x microstepping TI DRV8818 chips and the system was almost all 24V. I needed to match this or do better.

    The Smoothie project with the Smoothieboard is built on a 32 bit ARM platform along with 32x microstepping drivers. It offers ethernet, USB as well as several LCD displays. Going a bit deeper I decided to select the MKS SBASE board that is designed to work with the Smoothie firmware because it uses TI DRV8825 chips that support 8x, 16x and 32x microstepping, it has all 5 channels populated along with ethernet and it all works off a single 24V supply. The MKS SBASE also uses very resonable JST connectors, unfortunately they where not the same series (pitch) as the original CubePro JST connectors.

    Details

    I happen to have a CubePro Trio, that means it has 3 extruders. However the smoothie by default is designed for 5 axis, that includes the 2 extruders. So first i am going to give up one extruder but I am fine with that. What I really want to do is have some material in one and support in the other. So 2 is good enough for now.

    The CubePro uses a chamber heater (hot air) and the heater runs off line voltage (120V) or mine. So we need to switch this with a relay, just as the original factory board does, more below.

    The Smoothieboards have FETs to switch or pwm DC loads, in the case of the Smoothieboard it has 6 where the MKS board only has 5. I decided to use mine FETs to control the devices that needed PWM capability. So I am using only 3 currently for the two extruders hotends and the parts cooling fans (mine has 3 fans).

    To control the heater AC, chamber LED lighting and the cooling fans on the hotends I used a 4 relay board that was originally design for Arduino type projects. The board has 4 relays with 5v coils and can be driven from logic level signals. I only needed 3 relays for now.

    I removed the circuit board mounted on the extruder assembly and won't be using the filament sensors. I removed the third extruder assembly.

    All the fans in this printer are 12V, so I kept the two under the PCB wired in series and connected to the power supply. I wired the two for the hotends in series and switch them with a relay. I wired the two big LEDs in the chamber for lighting in series. I wanted to keep all 3 parts cooling fans and they are not very strong, so I used a cheap 24V to 12V buck converter for a 12V supply. I tied the output negative common with the smoothieboard and I one of the FET inputs to PWM the three 12V fans that are wired together in parallel. This is a hack and you have to make sure you understand the schematic and know that this will work for what ever board you choose. The LED light that is under the extruders also runs off this 12V supply and is always on for now.

    Results

    I was committed to making this work as quickly as possible without a way to back out, so I cut the original connectors of and crimped on new pins for the JST connectors used on the MKS board. I cut off all the original connectors one wire at a time as I had traced them out and knew where their new location or functionality would be. This only took a few hours to complete a majority of the connections.

    There where a few sticky points. The chamber air temperature uses a thermistor mounted on a PCB with an amplifier. I removed that PCB and used the factory wires for a standard 10k RTD. I used all the wires in the harness that ran up to the PCB mounted next to the extruders for the fans and LED light. I left the original connectors that where 0.1" pitch and created an adapter using header pins soldered back to back to cross wire from one connector to the many fan connectors. I had to work out which extra pins could switch my relays.

    Pretty much everything worked the first time I powered it up. I got the steps per mm from the factory xml config files. I verified that they where all correct, I adjusted them for 16x microstepping.

    I used a thermal-couple to work out the calibration points for the thermistors in the nozzles. For some reason these are using 250k devices and they need some calibration to make them accurate at high temperatures.

    I had to calibrate the feeder steps.

    I needed to work out the Z homing and offset number.

    The final piece was to tune the acceleration for the axis and determine some reasonable velocity limits and choose current limits for the motors. I was able to push the acceleration parameters way beyond what the factory board seemed to be running and I still never had a skipped step. I could really shake the printer hard without skipping a step, so I backed off to some reasonable numbers.

    Conclusion

    Overall I am so far pleased with the results. I printed some test cubes to prove that the system works. Next I printed some mounting adapters to mount the new boards to the original factory holes. My next project is to print spool holders to keep the spools inside the printer like the factory did. I am printing PLA right now and it looks pretty good. I tried Nylon but failed. I need to spend some time coming up with the right settings for each material.

    I did discover one limitation of the Smoothie hardware/software. I was going to only use the web interface only, however once you start printing the web interface is useless. It didn't want to add a local display on the printer because I rarely use them. I might need try OctoPrint running on a raspberry Pi.

    IMG_0879_scaled.jpg

    Board in the upper left is the MKS Smoothie board. Board in lower middle is the 4 relay board already mounted. The board slightly above it is the 24V to 12V converter. The 24V power supply is on the right with the cover removed. I will upload a finished picture as soon as I stop printing.

  2. Thanks TommyDee, bolsoncerrado, papptacsi thanked for this post
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  3. #2
    3D Printer Noob
    Join Date
    Oct 2018
    Posts
    1
    Post Thanks / Like
    Hello!
    Thank for this post!
    Not long ago I have a CubePro Duo and I think of a similar thing.
    I would be grateful if you shared more pictures. And what are the experiences since then?
    Best!

 

 

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