Mini Rambo 1.3a + mk42 aluminum clone Firmware

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neo
Posts: 3
Joined: Wed Jun 20, 2018 11:31 am

Mini Rambo 1.3a + mk42 aluminum clone Firmware

Post by neo » Wed Jun 20, 2018 11:42 am

Hello

I'm currently building a Prusa i3 MK2 Haribo with an Mini Rambo 1.3a and chinese MK42 heatbed (aluminum + PEI glued on) and a chinese inductive probe. I have a few questions regarding the calibration process with this choice;

1) xyz calibration will not work with the aluminum heatbed as the probe will have problems finding the calibration points, correct?

2) Mesh bed leveling should work without a problem, right?

3) Do I need to do any modifications to the Marlin firmware in order to calibrate the printer (marlin 3.2.1)?

4) How do I calibrate the printer if xyz fails obviously? Just z height/mesh calibration?

Maybe someone has experience with such a setp. Thanks in advance!

Stefan
Posts: 223
Joined: Thu Jun 15, 2017 12:46 am

Re: Mini Rambo 1.3a + mk42 aluminum clone Firmware

Post by Stefan » Wed Jun 20, 2018 5:54 pm

Hi Neo,
the probe will have problems finding the calibration points, correct?
An inductive probe will work with aluminum, but the trigger distance will be smaller.
Mesh bed leveling should work without a problem, right?
Mesh bed leveling will work as long as the probe is working properly.
Do I need to do any modifications to the Marlin firmware in order to calibrate the printer (marlin 3.2.1)?
(Note: Marlin is up to 1.1.8) Quite a few changes to "configuration.h" will be necessary. Tom has a good video on just this subject.
How do I calibrate the printer if xyz fails obviously? Just z height/mesh calibration?
All three axes have to be properly set (such as the number of steps per mm). Proper values need to be placed in Marlin and an inspection of the mechanicals. Don't get ahead of yourself, here. Let's see what the printer does.

As you progress, let us know how the build is going. Ask questions as they come up. So far, I don't hear of any red lights.

-Stefan

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Mini Rambo 1.3a + mk42 aluminum clone Firmware

Post by slippyr4 » Wed Jun 20, 2018 9:05 pm

Do you mean marlin, or prusa firmware (which forked from marlin a long long time ago)?

Marlin will work just fine with an aluminium MK42 lookalike, but the prusa firmware will not calibrate with one. It looks like a MK42, but isn't.
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

neo
Posts: 3
Joined: Wed Jun 20, 2018 11:31 am

Re: Mini Rambo 1.3a + mk42 aluminum clone Firmware

Post by neo » Thu Jun 21, 2018 4:04 pm

slippyr4 wrote:
Wed Jun 20, 2018 9:05 pm
Do you mean marlin, or prusa firmware (which forked from marlin a long long time ago)?

Marlin will work just fine with an aluminium MK42 lookalike, but the prusa firmware will not calibrate with one. It looks like a MK42, but isn't.
Actually I tried to use the Prusa fork of marlin. Or would you recommend straight marlin? (or will try, still waiting for the last parts to arrive)

I assume the calibration will not work because the clone MK42 has aluminum as base material and not FR4. With FR4 (original MK42) I assume the inductive probe would be able to detect the calibration circles (copper) during xyz calibration but with the aluminium base material the inductive probe would not detect the copper calibration circles on the bed as the aluminum would trigger it always. This is what I meant with "xyz cal fail". Just want to make sure I understand the problem with the aluminum mk42 bed.
Stefan wrote:
Wed Jun 20, 2018 5:54 pm
the probe will have problems finding the calibration points, correct?
An inductive probe will work with aluminum, but the trigger distance will be smaller.
Ok, I thought the probe will sense in the location of the copper circles/white silkscreen circles, where it actually senses copper and aluminium beneath. But should not be a problem so far. I will have to play around with the sensor height anyways.
Stefan wrote:
Wed Jun 20, 2018 5:54 pm
Mesh bed leveling should work without a problem, right?
Mesh bed leveling will work as long as the probe is working properly.
Ok, perfect.
Stefan wrote:
Wed Jun 20, 2018 5:54 pm
Do I need to do any modifications to the Marlin firmware in order to calibrate the printer (marlin 3.2.1)?
(Note: Marlin is up to 1.1.8) Quite a few changes to "configuration.h" will be necessary. Tom has a good video on just this subject.
I'll have a look at that. With the mk42 aluminum clone, would you actually recommend marlin or prusas marlin fork?
Stefan wrote:
Wed Jun 20, 2018 5:54 pm
How do I calibrate the printer if xyz fails obviously? Just z height/mesh calibration?
All three axes have to be properly set (such as the number of steps per mm). Proper values need to be placed in Marlin and an inspection of the mechanicals. Don't get ahead of yourself, here. Let's see what the printer does.

As you progress, let us know how the build is going. Ask questions as they come up. So far, I don't hear of any red lights.

-Stefan
I'm not concerned about any misalignments, I meand xyzcal fail in the meaning of; the printer can't find the calibration points, those are 9 copper circles on the surface of the bed, inbetween the heating traces. (same on original and clone mk42).

Tanks so far! I'd definitely come back to you when I can finally start to assemble it.

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Mini Rambo 1.3a + mk42 aluminum clone Firmware

Post by slippyr4 » Thu Jun 21, 2018 4:24 pm

If you use prusa firmware it almost certainly won't work for the reasons you've stated- it won't be able to locate the calibvration points.

Marlin is about your only remaining option really, unless you get an FR4 clone of a MK42
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

Stefan
Posts: 223
Joined: Thu Jun 15, 2017 12:46 am

Re: Mini Rambo 1.3a + mk42 aluminum clone Firmware

Post by Stefan » Thu Jun 21, 2018 7:10 pm

Hi Neo,

My clone uses an inductive sensor and an all aluminum bed with Marlin 1.1.8. This means I have no copper circles embedded in the aluminum and depend solely on the sensor detecting the bed. I use a 9-point bi-linear scan.

-Stefan

neo
Posts: 3
Joined: Wed Jun 20, 2018 11:31 am

Re: Mini Rambo 1.3a + mk42 aluminum clone Firmware

Post by neo » Wed Jul 11, 2018 2:42 pm

Pretty much assembled it. Disassembled and reassembled the extruder as the filament was rubbing against the PTFE tube a lot and it lost steps after ~5mm height. I turned the extruder current up to 1A, but will turn it down again with some testing probably.
I'm still facing extruder clicking/missing steps sometimes, but I guess this is caused by overextruding (filament is 1.8mm and appears to work with extrusion factor 0.9).
Currently running prusa firmware, just with the Z calibration, E step calibration and first level calibration but might change to stock Marlin. First layer cal works ok and I can see the Z steppers slightly adapting. Not perfect but it worked so far.
Stefan wrote:
Thu Jun 21, 2018 7:10 pm
My clone uses an inductive sensor and an all aluminum bed with Marlin 1.1.8. This means I have no copper circles embedded in the aluminum and depend solely on the sensor detecting the bed. I use a 9-point bi-linear scan.
Nice, would you mind sharing your Configuration.h file?

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Mini Rambo 1.3a + mk42 aluminum clone Firmware

Post by slippyr4 » Wed Jul 11, 2018 3:06 pm

If it's rubbing on the PTFE it's likely because the drive gear you're using isn't the same effective diameter as the one prusa use. IIRC tom's parts had a modified extruder body which offset the motor so that the filament path was correct when using a MK8 drive gear.

On my clone I'm using an e3d hobbgoblin and that's close enough to the stock diameter that it works fine - even with TPE/TPU
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

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