3d-Printing on OiePoie!

Auto Tramming (or Leveling) for a Mamba3D 3dprinter

Sat, 19 Sep 2015 23:28:19 +0200

Before starting an print, every time i needed to level the print bed. But the micro-controller (minitronics) and software (marlin) are already prepared for automatic sensing the distance of the bed and compensating during print. What’s needed is an inductive sensor, a mount and a few small software changes in marlin to enable the feature.
The term auto-tramming is from the CNC world, where the mounting surface is made level to the CNC by running it over with a router in the lowest position. Since we don’t modify the bed itself, i prefer auto leveling, because the software is keeping the nozzle perpendicular to the print bed during printing. But it’s up to you how to call this.

Sensor mount

For the sensor mount, i did not want to bolt it on top of the ventilator, but directly on the aluminium of the extruder. The design was done in OpenSCAD en the hole thing is posted on Thingiverse.
When mounting the sensor, position it around 1mm above the extruder point, so it never touches anything on the print bed (the extruder is the lowest point). Be careful with your bolts sticking out above the print bed, use tapered bolts and countersink your holes. In my heated bed, i can’t make them level with the print bed, because the holes are to much on the side, but with a little effort they will be low enough so there is no danger for collision.

Electronics

I used a LJ12A3-Z-4/BX cheap proximity sensor (between €2 and €3 on Banggood). The sensor is powered from the permanent 12V connections on the minitronics board.(upper right in the picture where it says 12V output. And the sensor output is connected to the Z-EndStop connector (instead of the switch). Since the output voltage is to high for the 5V logic of the minitronics, i use a 8k2 resistor to ground and keep the internal pull up resistor active (that’s configured in marlin), so the level is either 5V or 0V. The wiring on the minitronics connector for the Z-endstop is input,minus,plus (plus is on the edge of the board, and we don’t use that one).

Software

There is not much that needs to be altered in the marlin software, all of it is in “Configuration.h”
const bool Z_MIN_ENDSTOP_INVERTING = true;
Since the logic of the sensor is the other way round as the physical end-switch.
And remove the comment before:
#define ENABLE_AUTO_BED_LEVELING
to enable the automatic bed leveling process.
You will need to define the probe points. Because the sensor has an offset from the extruder nozzle the right side probes need to be more on the inner side of the bed. After some tuning, these were the points i came up with:
// these are the positions on the bed to do the probing #define LEFT_PROBE_BED_POSITION 35 #define RIGHT_PROBE_BED_POSITION 195 #define BACK_PROBE_BED_POSITION 165 #define FRONT_PROBE_BED_POSITION 10
But for your first time it’s better to start with safe values, so larger numbers for LEFT_PROBE_BED_POSITION and FRONT_PROBE_BED_POSITION and smaller numbers for RIGHT_PROBE_BED_POSITION and BACK_PROBE_BED_POSITION. As you might have guessed the numbers represent millimeters.

Also define the offset of the sensor from the nozzle, with my mount on a Mamba3D this is:
// these are the offsets to the prob relative to the extruder tip (Hotend - Probe) #define X_PROBE_OFFSET_FROM_EXTRUDER 34.0 #define Y_PROBE_OFFSET_FROM_EXTRUDER -32.0 #define Z_PROBE_OFFSET_FROM_EXTRUDER 0
The Z offset is zero because we will fine-tune this in Slic3r.

Compile and upload.

You can see the sensor trigger because the LED on the LJ12A3-Z-4/BX will light up. The sensor has a sensitivity of 4mm, but thats for metal. For Aluminium is around half that value, so approximately 2mm.
Check with “M119″if the minitronics also sees the trigger output of the sensor. Turn all bed leveling screws so that the springs are completely compressed, or replace the bolts and springs with static spacers.
After that you can issue a G28 home command and a G29 command to start the auto-tramming routing. The default is a 9 point measurement process and now you should see movement in the Z motor during the print of one layer.

If you download the Slic3r setting from the Mamba3D website, you wil find a printer setting called Mamba3D_Autolevel. If you open the configuration and go to Printer Settings, you will see that G29 is in the custom G-code. In the General section you can enter the Z-offset, this is the correction for the position of the nozzle above the printbed. For me this came out to -0.7mm, and i am thinking of making it -0.8.
The way to determing this value is by heating up the nozzle, issuing a G28 Home command and a G29 to run through the leveling steps. Then a G92Z10 which tells the printer that it is now 10mm above the printbed. Now take your piece of paper and move the nozzle down through manual control with 0.1mm steps while moving the paper. When the paper still moves but an extra 0.1mm down would prevent the paper from moving, you are at the right level and can record the number of steps as the value in Slic3r. The complete procedure is very well enlightened in this video of Thomas Sanladerer.

Have fun!

Heated bed for my Mamba3D 3dprinter

Sat, 19 Sep 2015 14:02:34 +0200

After using my 3dprinter for i while i found out that large objects would have the tendency to warp from the bed while printing. The solution for this is to print with a large rim, or upgrade my printer to a heated bed. Having a heated bed would also allow me to print different filament, so thats what i wanted to do.

Hardware

I decided to replace the aluminium printbed with the heated version (this is the one i bought: 3MM MK3 Aluminum Board Heat Bed because it’s cheap (see the shopping list at the bottom of the article), it’s simple and it doesn’t add mass to the printbed like a silcone heater would do. My Mamba3D has a minitronics board which runs on 12V. But i wanted to use 24V as power source, because this would reduce the current needed to heat up the board and by having a separate power supply i wouldn’t risk scary stuff happening to my minitronics. So i bought a 24V/5A power supply from banggood. Next you need a thermistor so the minitronics computer can measure what the temperature of the heat bed is, and a a couple of electronic components which are used to switch the heated bed on and off.

For the electronics i decided to use a BUZ36 N-Channel MosFET which i had laying around. It can switch up to 22A but the most important fact is that is has a low “on resistance” (R-on) of 0.12 Ohm. This is important because this resistance together with the current will determine the heat it has to dissipate. By using the 24V power supply the current is 4.5A so that computes to 2.5W (P = I*I * R) and the BUZ36 can handle that without the need for extra cooling. But of course you can replace the BUZ36 with an other N Channel MosFET as long as it can handle the current and also has a low R-on. If you need to buy one, you could use the IRFZ44N which can switch up to 20A and has an even lower R-on according to the datasheet.

From the bottom picture of the completed PCB you can see i use copper foil to create low resistance paths between the heated bed power lines. It’s probably not really necessary, but i had this stuff lying around, so why not use it 🙂

When you replace you non-heated bed for the MK3 heated bed, i suggest you replace to 3mm bolts with countersunk versions and use a deburring tool to fix the holes on the MK3 bed so the bolts don’t stick out so much, this will come in handy when you add the auto-tramming option.

For how to fix the thermistor in the heated bed, there is a center hole in the middle where the thermistor fits. Be careful not to let it stick out above the bed.

I used which is heat resistant for temperatures up to 250 degrees celcius..
So the thermistor goes to the the “Thermistor HB” connector, polarity doesn’t matter. And the “Heated Bed” output from our minitronics goes to our circuit board.

Software

When everything is connected it’s time to modify our Marlin software so that you can use the heated bed. You will need the Arduino Integrated Development Environment (IDE) to program your minitronics board (most other boards are also arduino like boards and are programmed the same way). For the minitronics, the easiest way is to download Arduino IDE version 1.6.3 from Reprapworld with the board pre-configured. From the same location you can also download the Marlin firmware for the minitronics, but i use the version supplied by Michiel on the Mamba3D website.
Start up the Arduino IDE, and load the Mamba3D firmware (select File -> Open -> Marlin.ino and it will load all the files). Set Tools -> Board to minitronics, and Tools -> Port to the right port (for me that’s COM3, but it could be different on your computer).
Now switch to Configuration.h and find this spot:
#define TEMP_SENSOR_BED 75
If you use a thermistor that’s allready properly defined, you can just enter the correct number here. The banggood thermistor were not defined in this version of Marlin, so i changed the value to “8” and modified that type in “thermistortables.h” to represent my thermistor (B=3950) with the data i found on this blog.
Always document your changes, so you know later on what’s alterd, e.g.
// Ewald 20150831, because of heated bed old value: // TEMP_SENSOR_BED adjusted from 75 to 8 (and type 8 redefined in thermistortables.h ) #define TEMP_SENSOR_BED 8

For temperature control, you want to enable the PID regulator
#define PIDTEMPBED
This is a pulse-width type regulator that is also used on the extruder to reach the desired temperature quick en keep is accurately on that temperature. For the heated bed the precise temperature is not really necessary, but the power MosFET enables us to do so without heating up. If you decide to use a relay to drive the current to the heated board, you need to keep this commented out, so the bang-bang (on/off) style regulation is used. Next i changed:
#define MAX_BED_POWER 100
to “MAX_BED_POWER 255”, this allows to PID controller logic to drive the heated board at full power, so it’s quicker to heat up. You can see this behaviour in the LED on the minitronics board (and on our own driver board), the both light up continuously during heating up and start to flicker when to desired temperature is reached (that’s the PID regulator using PWM to keep on that temperature).
If you use 12V to drive the heated board (so double the current) or a solid state relay, it’s best to keep this value at “100” and check the heat dissipation on you components.

The parameters for my MK3 Aluminium heated bed driven by 24V were:
// ran autotune with this command: M303 E-1 C8 S50 #define DEFAULT_bedKp 179.27 #define DEFAULT_bedKi 30.40 #define DEFAULT_bedKd 264.34

But after compiling and uploading you should run the autotune logic yourself by specifying “M303 E-1 C8 S50” in the G-code manual entry of your repetier software, after this it will show the measured values for your setup.
The S50 on the end is the target temperature, i had to use that because my max-power was set at “100” during this tuning instead of “255” and therfore trying to reach 90 degrees timed out. But with max-power set to full (255), that’s not a problem anymore.

In “pins.h” there is a section for the minitronics board ( #if MOTHERBOARD == 702 ), you should check that your heater pins are properly defined there: #define HEATER_0_PIN 7 // EXTRUDER 1 #define HEATER_1_PIN 8 // EXTRUDER 2 #define HEATER_2_PIN -1

#define TEMP_0_PIN 7 // ANALOG NUMBERING
#define TEMP_1_PIN -1 //6 // ANALOG NUMBERING
#define TEMP_2_PIN -1 // ANALOG NUMBERING

#define HEATER_BED_PIN 3 //-1 //3 // BED
#define TEMP_BED_PIN 6 //-1 //6 // ANALOG NUMBERING

Last step is to edit thermistortables.h with the new definition for type 8, or you can download my version of thermistortables.h
When you have made all these modifications, click “Verify” in the Arduino IDE and it should compile properly.
After that upload the code to your minitronics and see if you get a reading on the temperature of the bed.
Next switch on the bed heating in the Manual Control window of repetier and it should heat up.

Last thing to do, is update your Slic3r configuration with settings so you can choose “Heated Bed” when slicing
an object. You can download the Mamba3D config for this, or edit your own. I mainly print PLA, and that’s just heating up the bed to 50 degrees (Celcius) and keeping it at that temperature untill the print is finished. Other materials require other bed temperatures.

So that’s all,
below is an overview of the components used.
Have fun!

Shopping list

item	price indication (on banggood.com)
3MM MK3 Aluminum Board Heat Bed	€12.50
24V/5A power supply	€12.85
thermistor	€2.50 for 10
Electronics board	€3.04 for 5
IRFZ44N Power MosFET	€1.27 for 2 (instead of the BUZ36)
Resistors	€2.83 for 600
LED	€2.04 for 100
total cost	€35.76

Pannendekselhouder uit de 3D-Printer

Tue, 26 May 2015 21:36:49 +0200

3D-Printer toepassingen

Ergens op het Internet zag ik een plaatje voorbij komen van iemand met plakhaakjes zijn pannendeksels aan de binnenkant van de keukendeurtjes te bevestigen. Slim idee, want dat is ruimte die je normaal niet gebruikt en je hebt meteen alle deksels overzichtelijk en voor het grijpen. De uitwerking van zijn idee is terug te lezen op instructables.
Plakhaakjes zijn natuurlijk leuk als je niets beters hebt, maar ik wilde “custom made” houders maken die specifiek waren aangepast aan mijn pannendeksels. Dat is steviger, rammelt minder en weer een goed excuus om de 3D-Printer te gebruiken :).
Het ontwerp is gemaakt in OpenSCAD, dit is een gratis programma waar je makkelijk objecten kan maken door ze samen te stellen van kubussen, bollen, cylinders, enzovoorts. Door OpenSCAD te gebruiken en te werken met variabelen zijn de houders eenvoudig aan te passen aan verschillende soorten pandeksels.
Met een beetje knutselen zag het ontwerp er als volgt uit:

In het plaatje kan je duidelijk zien dat het is opgebouwd uit drie delen, een (iets ingekorte) kubus, een taartpunt en een rechthoek. De kleuren zijn aangebracht in OpenSCAD om makkelijk te zien wat er met een onderdeel gebeurt als je variabelen aanpast, maar de uiteindelijke kleur wordt natuurlijk bepaald door het filament dat je in de 3D-Printer laadt.
Het OpenSCAD programma en het STL bestand om de houder te kunnen printen zijn te vinden op Thingiverse

De houder heeft een verzonken gat voor een schroef, dat is wat steviger dan dubbelzijdig plakband. Door in OpenSCAD de variabelen aan te passen, kan je het gat precies passend laten maken voor de schroef die je hebt en er ook meteen voor zorgen dat je niet door het kastjes heen kan schroeven (want dat betekent ruzie met de vrouw en dat willen we niet :). Na een kwartiertje printen ligt de houder klaar op de 3D-Printer:

Het is een eenvoudige print, want alles wordt opgebouwd vanuit een plat oppervlak, dus geen support nodig voor overhangende delen. De print is met 50% infill, zodat de houder wel stevig is en geprint op medium resolution op mijn Mamba3D

In perspectief is goed te zien dat deze houder precies past bij deze pannendeksel, voor je eigen deksel zal je dat dus moeten uitmeten en de parameters daarop aanpassen. Maar ik merkte al dat je met deze houders ook allerlei andere pannendeksel kon ophangen.

Iedereen heeft natuurlijk andere pannen en andere pannendeksels, maar op Thingiverse kan je door op Customizer te klikken heel eenvoudig de houder aanpassen naar je eigen wensen en maten.

En hieronder zijn de pannendeksel houders in actie zien (the proof of the pudding is in the tasting ;).

Have Fun!