These sound like good options. Is it an issue for calibration having the bed higher with the steel and magnetic layers? I guess you just move the probe higher up? I suppose you could also just clamp the steel sheet with some bulldog clips.
Prusa I3 on a budget
No issues with calibration as the probe will get contact with the metal sheet instead of the bed
The probe assembly and distance need to follow the original Prusa i3 instructions. Because the probe as a sensing distance of 1.2 to 2.4 if my memory is correct
The first things when you turn the printer on is send m119 this will give you the endstop state
http://marlinfw.org/docs/gcode/M119.html
And you need to make sure that each endstop change state when pressed the probe should behave as an endstop and you can trigger it with a screwdriver or any metal pieces for tips the probe the led light on the prod should be on when not triggered and off when triggered
Listen to this video for the probe setup I found it really helpful
Ps: other video on his channel are useful too
I’m back carrying boxes now will follow up tonight if I’m not too exhausted
Thanks Laurent. I will probably keep bothering you with questions but I still haven’t finished my build yet so no big hurry.
Hi @laurent_muchacho, hope the move is going OK. A few more questions for you.
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Did you print out nut traps for the aluminium frames? the M3 nuts are too small for the slots in the two triangular frame parts. If not I can print some when my printer is up and running.
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I’m a bit wary of setting up z calibration because I don’t want to damage my board. My pinda probe is working - it triggers when close to metal and its LED goes out. I’ve set up the probe following the Prusa instructions - I have set the height of the probe when the nozzle is just touching the board. Now I think I will have to edit the Marlin config to make the probe hit the sensors on the MK42 board - there is a Chris’s Basement video about this. What I’m not sure about is making sure the probe works as an endstop. I don’t want the nozzle to scrape the board. Can I now go ahead with homing the z-index or do I have to set a z offset on the LCD, or in Marlin?
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It seems like we need some 3mm filament to help with the cable management - was that part of the order or do we still need to get hold of some? Maybe I could use two strands of 1.7mm instead…
Move went ok I’m pretty exhausted and an place full of boxes at the moment.
- No nut trap are available for the aluminium frame. You need to put a washer and a lock nut, it’s not ideal but this is how it’s designed to be assembled
- Sorry buddy but if you went on your own this is the risk you have to take without my guidance. Unfortunately you can not use the printer without setting up the auto probe calibration.
–my tips is when you trigger a command if you are scared/unsure keep an finger on the power button
– when testing the motor direction initially alway home each of the axis individually and keep your finger on the power button e.g when you press “home X” in pronterface and the motor is moving to the right instead of going to the left toward the endstop switch off the power automatically
– when homing the z you can trigger the probe with a piece metal like a screw driver way before it get close to the bed that will re-assure you that it is working as expected - there is plenty of 3mm filament in the space have a look for some red translucent taulman bridge and grab a bit you don’t need more than a meter
Hopefully this answer a few of you question
First print, woohoo!
Thanks for the help @laurent_muchacho
I have some helpful tips I can contribute for the other builds, after learning a few things the hard way 
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Hi Daniel,
Do you mean the Marlin config? I tweaked a few things - first of all when using the lead screw instead of the threaded rods, the z-axis steps per unit had to be divided by 10. So this line:
#define DEFAULT_AXIS_STEPS_PER_UNIT { 80, 80, 3952.5, 459 }
became
#define DEFAULT_AXIS_STEPS_PER_UNIT { 80, 80, 395.25, 459 }
I also have the MK42 board so I had to change the bed size values. I then changed the values to hit the 9 sensors in the board when probing, in these lines:
// Set the boundaries for probing (where the probe can reach).
#define LEFT_PROBE_BED_POSITION MIN_PROBE_EDGE
#define RIGHT_PROBE_BED_POSITION (X_BED_SIZE - MIN_PROBE_EDGE)
#define FRONT_PROBE_BED_POSITION MIN_PROBE_EDGE
#define BACK_PROBE_BED_POSITION (Y_BED_SIZE - MIN_PROBE_EDGE)
I ended up hard-coding a few of these for better accuracy.
I also enabled baby-stepping in configuration_adv.h as it was useful for adjusting the z probe offset using the LCD option under ‘Motion’.
That was the main stuff I think - Laurent’s settings are working well otherwise.
An IMPORTANT thing to be aware of is with the RAMPS board. The Q3 MOSFET, which is for the heated bed, runs really hot. You need to make sure it is not touching the plastic header connectors for D8, D9 and D10. Bend it away from there. I strongly recommend adding a heatsink to it. And make sure never to run it without the fan on the electronics box cooling it.
When I was doing my build I thought my RAMPS board wasn’t working at all, as my bed wasn’t heating, so I got a replacement. That one worked but it went into meltdown because Q3 wasn’t properly cooled. Then I had another look at the original one and noticed that the main power header had an unsoldered pin. So i soldered that and everything worked OK.
But on the replacement board I got Q3 was touching the plastic header and there was a lot of smoke when it melted it - probably would have gone on fire after a bit if I hadn’t powered it down. Be careful!
Hi Mike,
Thanks for the info. One question about configuration.h. For the LCD controller, the line uncommented in the firmware, as downloaded from dropbox is
#define REPRAP_DISCOUNT_SMART_CONTROLLER
Is that what you went with?
I see a line further down
//#define REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER
and wondering if that should be used instead?
I didn’t edit that line, just used what was set there.
Hi guys,
I was wondering if I can join you on the builds (your builds ?). I’m not sure if you all are building a printer collectively or each one of you is building one for themselves. If it’s the latter - I wouldn’t mind making one for myself.
I see Electronics Night in the calendar for tomorrow and I’m thinking off swinging by. Anyone is planning to be in? I have some general questions before committing to the project.
Anyone who have started the project, lost the motivation and now interested in buyout? 
I think @laurent_muchacho might be considering running another build project after this one is finished? We are building our own printers but Laurent has ordered all the parts and printed various required bits for the builds. You are welcome to sit in on the build sessions when they are running again.
Hi all just came back from trip to France and sorting through this
See you this Tuesday evening for the follow up to the build everyone welcome
Hi all,
Quick msg to confirm tomorrow evening build will start again. Should be there by 7
@dsikar
@dermot
@Esther_Gladstone
@peter_hellyer
@mikekelly
@Calum_Nicoll
@Vagwin
@david
I’ll be there