Building the Anet A8 - my experience

@SixDegreesOfFlight - Never mind. Stupid me. When I extracted the Zip I only took the Skynet folder, I didn't even see the documentation folder. As you say, it's an excellent guide and gives me what I need. Doh!

@Archie
Hi from sunny Melbourne!

The very first time I set mine up it did exactly like you describe - several mm above the bed and squirting filament making a pretty little bed nest

I did look at Maker Noobs approach but decided to go with the step by step instructions inside the Skynet3D documentation folder. To be frank, when I first looked at the manual I thought it might be too finicky or technical for me so I searched on YouTube for ages for a clear explanation. Unfortunately, I didn't find anything useful so I went back to the Skynet documentation. It is actually quite easy to follow. The bit where I kept going wrong and maybe you are too is reading the -z offset - I was reading the value from the wrong line (page 13) Look very carefully at the image attached here from the documentation. If your value is like 10.23 then you are reading the wrong line.

Have another look in the Skynet3D documentation/tutorial folder and follow along. I did have to get a copy of Cura 15 (which I think is in the Skynet zip) to use the 'command line' to send the M commands to the printer. Take your time going through each step.

Good luck

Thanks, @SixDegreesOfFlight

Yeah - Once I read the documentation it all sank in. Not tested this but I am certain I am using the wrong technique to enter my probe offsets, so any correction is not going to be applied to the hotend. I now understand why my nozzle is so high, so I will fix it all tonight and report back.

The 4mm sensor I have is awful. It's like 0.5mm above the bed before I get a steady trigger. 8mm sensor is on the way.
(I use the normal bed with Kapton/Kaptan tape) so I think the sensor is just bad as even with the loss in sensitivity from Aluminium it should sense better than it does.

I'll report back....

@Archie
If you get the one that I purchased then all you need is a 1N4148 signal diode - much easier than resistors. I removed the z axis micro switch and cut off about 100mm of the wire from the end so I had the socket and the two wires. I only needed one wire so I wrapped the other free wire around itself just in case I might need it in the future. I then wired the sensor to the 12V power supply directly.

In summary: two wires directly to the power supply, and the signal wire with the diode (reversed) into the z axis socket.

All the best

Will do. I can't recall the sensor model number I have, but I already wired the resistors to drop down the 12V - But do agree the diode method is the best option. Mine was odd in that I had to disable the resistor pull-ups in the firmware to get the Zmin to register the sensor.

I also ordered the Anet A8 official sensor (ROKO version of the TRON-XY) but I think it was DOA as no matter what I do I can't get the thing to light up, so I went back to the cylindrical proximity sensor.

I'll write it all up once I get it all sorted

@noorbeast

Connect your A8 to your pc via USB and have Cura 15 running
Start the Arduino IDE that comes in the Skynet zip file. Don't use the one on your pc if you have already installed it.
Chose the configuration.h file you are going to use and copy into the main skynet folder
Make sure the IDE detects your printer connected to a COM port
Load a test cube .STL (not really necessary but ensures Cura is working correctly. You can get one from Thingiverse)
Click Print from the Cura menu (this brings up the command window and the circular image to control the XYZ axis)

These are the steps in summary but explained in detail in the Skynet documentation (case sensitive):

Heat your printer up to your printing temperature and allow a few minutes for it to expand and settle
Reset the existing Z-offset to zero: M851 Z0
Home all axes: G28
Move the nozzle to the middle: G1 X110 Y110
Move the nozzle down so it is just gripping a piece of standard printer paper (use the circular interface on Cura)
Mark this position as Z zero: G92 Z0
Use the sensor to probe the middle of the bed (where we just set Z0): G30 X110 Y110
Take the Z value of the bed from the screen and put a minus sign in front; this is the Z-offset. e.g. 1.23 becomes -1.23
Set the Z-offset: M851 Z-1.23
Store it to the EEPROM: M500

As you can see once you have the IDE, Cura and the A8 are running/connected you can whiz through these steps in a few minutes if it doesn't quite turn out as you like. Uploading the skynet sketch to the Anet Arduino board takes about a minute. Tip: when I issued each command above in red, I had a finger on the power supply off button - just in case you screw something up and the hotend hits the bed.

@Archie
Skynet allows you to turn the Arduino pullup resistors on/off in the configuration.h file. I didn't have to change the default PULLUP settings for my sensor.

...and one more tip - I am using good 'ol Bear Brand masking tape ($1.50 roll) that I purchased from Bunnings and it works fine. It is only 12mm wide so I put on 8 strips with a very small gap between each strip. Then rub over with Metholated spirits. I heat the bed to 60C for PLA and it sticks fine without the need for a scraper to get the parts off

@noorbeast - This was the part that has been throwing me, I have been looking at the LCD and subtracting the numbers to get my offset. It will never work.
Once you look at the output in the Printer Control software (terminal window), then that is the value you need (negated), as @SixDegreesOfFlight points out

Also, be sure to use CURA or Simplify3D to adjust the nozzle. Repetier Host adheres to Software Endstops so won't let you drop the hotend below 0, which of course when you are trying to level initially is not helpful

You'll have fun building the Anet A8. It really is a great printer!

man, i guess this thread is the best a8 resorce in the web... really i have loocking a lot for things like this.. thanks again

fer

@Archie - I hope you mean that the resistors drop the voltage down to 5V Otherwise you are going to fry your Arduino. Reading your quote again, I think this is what you mean

Yes - I get 4.95 volts at Zmin.

@noorbeast - @SixDegreesOfFlight did an awesome job of summarising the setup - I'll just put what I had to do for completeness and to assist in case anyone has the same issues.

First, these are the changes I made in my Configuration.h file and are very specific to the mods I have, so may not apply. I use a different X axis holder and have also printed tool holders which affect my Z height by a few mm's.

// Travel limits after homing (units are in mm)
#define X_MAX_POS 220
#define X_MIN_POS -15 <-- Centres my nozzle perfect on the bed at the start of a print.
#define Y_MAX_POS 220
#define Y_MIN_POS -15 <-- Centre my nozzle perfect on the bed at the start of a print.
#define Z_MAX_POS 210 <-- Took 30mm off to give clearance at the top of printer for tool holders.
#define Z_MIN_POS 0

Enabled the M48 command to test that my probe is doing the right thing and I can "repeat" the bed level at anytime to check the matrix.

// Enable Z Probe Repeatability test to see how accurate your probe is
#define Z_MIN_PROBE_REPEATABILITY_TEST

Set the offset of my probe so it's prefectly centred (again using a different x-axis / hotend carriage)

#define X_PROBE_OFFSET_FROM_EXTRUDER -33 // X offset: -left +right [of the nozzle]
#define Y_PROBE_OFFSET_FROM_EXTRUDER -29 // Y offset: -front +behind [the nozzle]
#define Z_PROBE_OFFSET_FROM_EXTRUDER 0 // Z offset: -below +above [the nozzle]

Reversed the logic of my Probe so that it's triggered when the Probe light comes on. (Zmin looking for pull down - absence of 5v)

#define Z_MIN_ENDSTOP_INVERTING false // set to true to invert the logic of the endstop.

And same for the endstop as well.

#define Z_MIN_PROBE_ENDSTOP_INVERTING false // set to true to invert the logic of the probe.

Then just follow what @SixDegreesOfFlight put. My process was:

Heat your printer up to your printing temperature and allow a few minutes for it to expand and settle
Reset the existing Z-offset to zero: M851 Z0
Send M500 to store new value

Home all axes: G28 <--- Test your Senor before you do this with M119 - This will show you the "switch" states
You want all to be "open" when they are, ..well... open and TRIGGERED when closed.

Move the nozzle to the middle: G1 X110 Y110
Move the nozzle down so it is just gripping a piece of standard printer paper
Mark this position as Z zero: G92 Z0
Use the sensor to probe the middle of the bed (where we just set Z0): G30 X110 Y110 (NOTE THE G30, not G1)
Take the Z value of the bed from the screen and put a minus sign in front; this is the Z-offset. e.g. 1.23 becomes -1.23
My offest was 0.57
Set the Z-offset: M851 Z-0.57
Store it to the EEPROM: M500

Ensure you add G29 into your Start Script AFTER the G28. Running a G28 will reset any bed level matrix configured by G29.

Let G29 do it's thing (3x3 matrix) so nine probe points, and enjoy nice - level - prints!

This is my start code:

M107 ; stop fan <---- Stop Part cooling fan, just in case it's still running
G21 ;metric <---- All moves / sizes in Metric.
G28 <--- Home ALL axis
G29 ; AutoLevel <---- Do the magic bit
G1 X0 Y20 Z0.15 F3000 ; get ready to prime <--- Move extruder to edge of the bed, ready to print a straight line.
G92 E0 ; reset extrusion distance <--- Reset Extruder count (metres of filament used)
G1 X200 E20 F600 ; prime nozzle <--- Run a 20cm line across the front of my bed to prime the nozzle.
(Go along the X axis 20cm, extruding 20cm of filament at a speed of 600 (60% of max)

That last line lets me print without an "outline/brim" as the filament is already waiting in the nozzle and good to go.

Enjoy!

@Archie
Thanks for adding that extra detail. I am sure it will help others who come searching here

Credit to you @SixDegreesOfFlight - Without your initial post about the documentation and not worrying about the sensor height, I'd still be scratching my head!! YouTube is full of crap advice on how to do this. After reading the doco I was up and running in less than 15 minutes!

The prints I am getting now from this little machine are awesome.
Everything just sticks to the bed as I know now that 0.15mm anywhere on my bed is now 0.15mm and not affected by warp/tilt etc.
(I print at 75% of 0.2mm for the first layer)

I was able to print a brooch for my daughter that I could just not get to stick to the bed before this.
This is the brooch. It's quite a complex slice.
https://www.thingiverse.com/thing:1440267

@Archie
That's great news. Glad I could help in some way

Rather than start a new thread I thought I would write a short post on how the Vertex bed mat worked out. The mat is a replacement for the tape or glass that you use on the printer bed to make the parts stick. It is slightly bigger in one dimension than the Anet A8 bed so when you fit it a small strip needs to be cut off using a razor blade. The mat is adhesive on one side (peel off waxed paper) and on the top surface the plastic is slightly textured (think plastic shower screen). It is about the thickness of heavily weighted paper but not as thick as light cardboard. It cost $37 posted to Australia (from the UK). That was the cheapest I could find. Unlike glass which will last indefinitely, the Vertex mat has a limited life and will need to be replaced depending on how much printing you do. That is, you will eventually put a scraper through it.

Fitting it only takes a minute. I cleaned the bed surface firstly with eucalyptus oil to remove the sticky residue left by the masking tape I was using. I then used glass cleaner to remove the oil, and finally Methylated spirits to give it a final clean. I peeled off the backing paper and started on the left hand side of the bed gradually working my way to the right, smoothing out any air bubbles as I went. I used a razor blade to trim off the 20mm strip on the right hand side.

I run my PLA settings as 60C on the bed and 210C at the hot-end. I printed my first part a small plate for my linear actuator. Hmm - it was very very hard to remove it. I didn't want to rip a hole in the new mat so it took nearly 5 minutes of working my around the outside before I get the scraper underneath and remove the print. The second part I printed with the bed not heated at all and that was great. The printed part was still very firmly stuck but it only took around 10 seconds to get it off. I did not see any warping at the corners which is what I was getting when I printed on glass. It works great with my auto bed leveling sensor too!

I also fixed the strange pause that seemed to start when I added my Bowden setup. Basically, the print would pause at some random point during the print and wait for a button press on the panel. Actually it wasn't random it was when the print got to 5mm high. So for low profile parts it never happened. Once I pressed the front panel button it would proceed to finish. What was causing this wait? Without boring you with my fault finding adventures, it comes from two plugins supplied with Cura 15 - 'Pause at height' & 'TweakAtZ'. I simply moved them from the Cura plugins directory to the desktop and restarted Cura. Problem fixed.

Edit: The official name of the mat is: Velleman Buildtak 3D Print Bed Surface for K8400

Edit2: I found that you still need to keep the mat clean of finger prints by using alcohol - I use methylated spirits - not sure what it is called in other parts of the world but it is nearly 100% alcohol with some additive to prevent it being consumed. The other thing I noticed is that for parts with very low surface area in contact with the bed you should heat the bed to help with adhesion otherwise the parts tend to come off. For larger parts leave the bed unheated.

so, what about the vertex, does it worth what it cost, what do you think?

@ferslash
It is a bit on the expensive side. Time will tell if it works out better/cheaper than painters tape. It is better than glass, though, especially if you want to do auto bed leveling. It definitely is superior to glass for stickiness and preventing curled corners. Because the bed doesn't need to be heated you can start the print quicker. I haven't tried with PETG or ABS yet.