Migbot Prusa i3 Unofficial Support Thread

+Gatornic: We also noticed that the offsets for the probe were way off. We were also annoyed at how long it took to Auto-Level. This is how we have the Leveling section set now. It seems to work quite well now and is way master. We have the LARGE BED... so please keep this in mind for the "// set the rectangle in which to probe" section.

//============================= Bed Auto Leveling ===========================

#define ENABLE_AUTO_BED_LEVELING // Delete the comment to enable (remove // at the start of the line)
#define Z_PROBE_REPEATABILITY_TEST // If not commented out, Z-Probe Repeatability test will be included if Auto Bed Leveling is Enabled.

#ifdef ENABLE_AUTO_BED_LEVELING

// There are 2 different ways to pick the X and Y locations to probe:

// - "grid" mode
// Probe every point in a rectangular grid
// You must specify the rectangle, and the density of sample points
// This mode is preferred because there are more measurements.
// It used to be called ACCURATE_BED_LEVELING but "grid" is more descriptive

// - "3-point" mode
// Probe 3 arbitrary points on the bed (that aren't colinear)
// You must specify the X & Y coordinates of all 3 points

#define AUTO_BED_LEVELING_GRID
// with AUTO_BED_LEVELING_GRID, the bed is sampled in a
// AUTO_BED_LEVELING_GRID_POINTSxAUTO_BED_LEVELING_GRID_POINTS grid
// and least squares solution is calculated
// Note: this feature occupies 10'206 byte
#ifdef AUTO_BED_LEVELING_GRID

// set the rectangle in which to probe
#define LEFT_PROBE_BED_POSITION -15
#define RIGHT_PROBE_BED_POSITION 170
#define BACK_PROBE_BED_POSITION 170
#define FRONT_PROBE_BED_POSITION -15

// set the number of grid points per dimension
// I wouldn't see a reason to go above 3 (=9 probing points on the bed)
#define AUTO_BED_LEVELING_GRID_POINTS 3


#else // not AUTO_BED_LEVELING_GRID
// with no grid, just probe 3 arbitrary points. A simple cross-product
// is used to esimate the plane of the print bed

#define ABL_PROBE_PT_1_X 15
#define ABL_PROBE_PT_1_Y 180
#define ABL_PROBE_PT_2_X 15
#define ABL_PROBE_PT_2_Y 20
#define ABL_PROBE_PT_3_X 170
#define ABL_PROBE_PT_3_Y 20

#endif // AUTO_BED_LEVELING_GRID


// these are the offsets to the probe relative to the extruder tip (Hotend - Probe)
#define X_PROBE_OFFSET_FROM_EXTRUDER -25
#define Y_PROBE_OFFSET_FROM_EXTRUDER 60
#define Z_PROBE_OFFSET_FROM_EXTRUDER -0.8

#define Z_RAISE_BEFORE_HOMING 4 // (in mm) Raise Z before homing (G28) for Probe Clearance.
// Be sure you have this distance over your Z_MAX_POS in case

#define XY_TRAVEL_SPEED 8000 // X and Y axis travel speed between probes, in mm/min

#define Z_RAISE_BEFORE_PROBING 4 //How much the extruder will be raised before traveling to the first probing point.
#define Z_RAISE_BETWEEN_PROBINGS 4 //How much the extruder will be raised when traveling from between next probing points

I would love to use the auto feature but if not then all good. as for my OS I'm using 7 atm while I figure out this issue.
I'm so lost with all the info so thought I would just ask, SOOOO Many posts on similar machines lol
thanks again guys

3DST I honestly wouldn't know where to start when putting info in my configuartion.h file, would you be able to help me out?

@3DST

Cool, yeah I changed to some similar settings with the regular bed. Differences are I set my travel speed to 9000. Then the BACK_PROBE_BED_POSITION has to be different due to the smaller bed length. Think mine is currently 150.

Only problem I found was if I wanted to use a larger grid points number like 4 (16 probes) due to an uneven surface I couldn't have the offset be 60. Had to be lower due to the error code catch during compiling.

#if ((Y_PROBE_OFFSET_FROM_EXTRUDER * AUTO_BED_LEVELING_GRID_POINTS) >= (BACK_PROBE_BED_POSITION - FRONT_PROBE_BED_POSITION))
	     #error "The Y axis probing range is not enough to fit all the points defined in AUTO_BED_LEVELING_GRID_POINTS"

So if you want 4 probes, 60 offset, 150 Back bed and -15 front bed => 60*4 >= 150-(-15) so 240 >= 165 ERROR!
So it throws the error that it can't fit all the probes in that size bed.

If I want 4 probes had to go much farther down to 41 offset.
41*4 >= 150-(-15) so 164 >= 165 OK!

Quote
rumjar86
3DST I honestly wouldn't know where to start when putting info in my configuartion.h file, would you be able to help me out?

rumjar you shouldn't really have to do anything to get your auto leveling going. Newest firmware should have bed leveling already enabled. Should just replace the G28 line in your gcode start to:

G28
G29   ;auto bed level

The only reason we were talking about changes to the firmware were a few things:
1. Why was the offset on the probe half the size in the firmware (30), MAY compromise accuracy (unknown). Should be about 60, but measure for yourself.
2. Probing was too slow, so increase probing speed. Increase to 8000 or 9000 and decrease raising amounts (don't decrease raising amounts too much it needs to be enough to untrigger the sensor).
3. Some people with a bad aluminum bed (warped) wanted to probe more to hopefully deal with uneven build plane. Thus the increase in grid points.

If you want to do any of those 3 then keep reading, otherwise just stick with the adding G29 code.



Open up your configuration.h file in the IDE. Then focus on the following lines:

Grid points is fine at 3 (will do 9 probes) unless your aluminum bed is bad and is warped. Then maybe 4 (16 probes)

#define AUTO_BED_LEVELING_GRID_POINTS 3

Depending on bed size these numbers will be different. but you shouldn't need to change them if you got the proper firmware from Leo (regular bed or large bed). These are the regular bed defaults

#define LEFT_PROBE_BED_POSITION -25
#define RIGHT_PROBE_BED_POSITION 175
#define BACK_PROBE_BED_POSITION 150
#define FRONT_PROBE_BED_POSITION -25

This is where you want to change your settings. With a caliper measure your exact x y offsets from the tip of your extruder to the center of your leveling probe. Mine was this:

// these are the offsets to the probe relative to the extruder tip (Hotend - Probe)
#define X_PROBE_OFFSET_FROM_EXTRUDER -15
#define Y_PROBE_OFFSET_FROM_EXTRUDER 60
#define Z_PROBE_OFFSET_FROM_EXTRUDER -0.8

lastly you can change speed here (by default it was 5000 speed and raise was 10:

#define XY_TRAVEL_SPEED 9000         // X and Y axis travel speed between probes, in mm/min

#define Z_RAISE_BEFORE_PROBING 4    //How much the extruder will be raised before traveling to the first probing point.
#define Z_RAISE_BETWEEN_PROBINGS 4  //How much the extruder will be raised when traveling from between next probing points

Edited 1 time(s). Last edit at 07/01/2015 06:53PM by gatorNic.

cheers gator. I know that I sound like a dumb ass at times, just need that little bit of you know mentoring, if you could point me in the right direction just to make sure I have everything setup correctly with me config, for bed size tracking etc. I have a 200 x 200 x 180 print size, or is the print size controlled by the slicing software when organising from stl to gcode?

Quote
rumjar86
cheers gator. I know that I sound like a dumb ass at times, just need that little bit of you know mentoring, if you could point me in the right direction just to make sure I have everything setup correctly with me config, for bed size tracking etc. I have a 200 x 200 x 180 print size, or is the print size controlled by the slicing software when organising from stl to gcode?

Gosh I feel really dumb today.

Quote
rumjar86
cheers gator. I know that I sound like a dumb ass at times, just need that little bit of you know mentoring, if you could point me in the right direction just to make sure I have everything setup correctly with me config, for bed size tracking etc. I have a 200 x 200 x 180 print size, or is the print size controlled by the slicing software when organising from stl to gcode?

Yes that is the regular bed size. The other bed is larger in the Y axis. So the numbers I posted above should work, as that is what I have. But like I said I would just try to get auto-leveling working with the default firmware, so just add the code to your gcode start file that will be located somwhere in whatever slicer you are using. As in Cura, there is a tab for Start/End-Code. Select start.gcode and replace the G28 line with what I posted above. There should of also been a image that came along with the printer that showed the same thing.

thanks oh so very much. i got it working just now trying to get the Proxy sensor correctly setup so I can get the first layer right. I am having issues with it just trying to print too close for the first layer and what not.. trial and error I guess

there was a good post by Invictus awhile back on the leveling of the sensor

Invictus sensor attchement

yeah I had a look and tried to get it to work. even have a set of Verniers to set the correct hight of the 2 mm above the print head... it is a pain atm...lol

Slowly getting this thing dialed in. Surprisingly it was pretty good with the out of the box settings. Just dialing it in to right temps, strings, zits, correct dimensions etc.

Here is an owl at:
.2mm layer, 190 temp PLA, .4mm nozzle, on painters tape. Simplfy3d

Couple issues still.
1. Small string on ears - possibly adjust retraction settings, maybe slight temp change.
2. Hard to see in photo, but some ghosting in between the toes. acceleration or jerk issue?
3. Some zits and reverse zits, more noticeable on the back or more so at lower res.
4. Under the beak overhang, is a little low res, jagged. Not sure what I can do there.

So this weekend I worked on reducing ghosting that I mentioned in the previous post. Hard to see in those photos but there is certainly some inbetween the toes and on the back near the wings. Ghosting is one of those things that won't show up on some models or many just don't care about because you are going to finish it some way. So up to you if you want to fix it.

Here's what I found. The default acceleration in the firmware is way too high for this printer with an acrylic frame. Too much vibration, the frame just isn't solid enough. The default is this:

#define DEFAULT_ACCELERATION 2650

I tried half that at 1325, with no real noticeable difference. It was only when I went under 800 it started making a difference. In the end the 500 seemed to clean it all up. I did also lower the DEFAULT_XYJERK by about half to 8, but there was less or no difference in changing that. I didn't feel like doing another test.

In doing this ofcourse you will slow your prints down some. The benefits may outweigh the negatives because in reducing acceleration (x/y vibration) it may actually help in other areas of your print. Also taking care of the acceleration issue may allow an increase in overall speed with less complications. That ofcourse would negate the acceleration slowdown. Would have to do some overall speed test to see. Just some spit-balling some thoughts here.

If I have a chance I'll post some comparison images.

Edited 2 time(s). Last edit at 07/05/2015 01:04AM by gatorNic.

Quote
Invictus
gatorNic,

I fixed the centering by setting the actual position in my start.gcode after homing and z-probing:

G28			;home all axes
G29			;detailed z-probe
G92 X-15 Y130		;adjust position so 100,100 is center of bed

Please post your results if you tweak your offsets in firmware. I plan to update mine, but haven't gotten around to it yet.

Don't really understand this, and I've got the same problem as everyone else with the print off-centre. Not a problem with small prints but will be with larger objects.
When homed, I've got X -15 and Y -45. Would I need to add those values to the G92 (with the ';adjust position so 100,100 is center of bed[/code]' added)' to get the bed to centre at 100, 100
And where would I add the line? Another G92 below G29 (above the G1)


G28
G29 ;auto bed level
G1 Z15.0 F{travel_speed} ;move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F200 E3 ;extrude 3mm of feed stock
G92 E0 ;zero the extruded length again
G1 F{travel_speed}
;Put printing message on LCD screen
M117 Printing...

Am enjoying the advice and tweaks everyone is throwing in. Changing the default acceleration speed in particular has improved the prints dramatically. If I can get the bloody bed centred I'll be pretty damn happy for a while.

cheers

Did a few mods to the machine..thought I would share.

First and foremost, and ON/OFF switch. It is a covered toggle, I like the look.


Put a fan over the electronics. I had a 90mm computer fan just lying around, so I put it to use. No fancy bracketry, just a couple zip ties.


Did you know there is a reset button on the LCD panel? Well, there is. You can download the model for the button off Thingiverse.


Let me know what you think. These are cheap (free if you the parts lying around) and easy to do.

Quote
steaneb
Don't really understand this, and I've got the same problem as everyone else with the print off-centre. Not a problem with small prints but will be with larger objects.
When homed, I've got X -15 and Y -45. Would I need to add those values to the G92 (with the ';adjust position so 100,100 is center of bed[/code]' added)' to get the bed to centre at 100, 100
And where would I add the line? Another G92 below G29 (above the G1)

I simply measured the position of the extruder relative to the origin after G29, and used G92 to set that position. You must not do it before G29 or you will crash into the side and front of your printer b/c the probing locations are hard-coded in configuration.h.

This is for people who haven't or don't want to update bed probing positions in firmware.

Migbots are printing well?

i don't know if this will help, but, i finally was able to get my prints centered in cura by adding "G92 X-15 Y120" right before the M117 command in the start gcode. for some reason in Repetier Host, its "G92 X-18 Y120". dead nuts center.

Hello all

I bought a Migbot Prusa I3 and the printhead is about 20mm left of the bed on the X axis and 50mm infront of the printerbed on the Y axis when homed. This causes the centre of the bed to be offset from the true centre.

Can anyone give advice?

My printer is different, but the concept is the same. The gcode below is placed at the start of every print. I use Cura Engine which is included in Repetier Host, so if you are using something else you will need to replace the lines dealing with bed and ext0 temps.

G90
G21
G28
{IF_BED}M190 S{BED}
{IF_EXT0}M104 T0 S{TEMP0}
{IF_EXT0}M109 T0 S{TEMP0}
G92 X-30 Y-2.0 Z0.0 E0.0 //make x and y equal to home values
G1 X5.0 Y5.0 Z0.0 E5 F500 //move onto the corner of your bed while extruding a bit of plastic.
G1 Z0.0
G92 X5.0 Y5.0 Z0.0 E0.0 //reset extruder position

Keep in mind that this only works if the home positions for X and Y are actually correct. You can figure out the true position by manually stepping in 1mm increments from the home position to the corner of the bed or glass (0,0). Whatever the distance is for X and Y is what you should put into the START G-CODE.

Edited 1 time(s). Last edit at 07/07/2015 06:49PM by jcabrer.

I'm not a IT person so, i just print these part and use, it work for me as my home is on the bed itself instead out of bed.

For the Y Axis link as follow

[drive.google.com]

for the X Axis link as follow

sorry X Axis endstop: [www.thingiverse.com]

Quote
rejaak
i don't know if this will help, but, i finally was able to get my prints centered in cura by adding "G92 X-15 Y120" right before the M117 command in the start gcode. for some reason in Repetier Host, its "G92 X-18 Y120". dead nuts center.

Geebers....both yours and Invictus G92 codes did the opposite...drove the head the opposite direction......time for some more trials. Other than that, prints are coming out pretty damn good. Pity it's taken 3 months to get the printer together and running with no help from Leo and his boofheads

I think the confusion might be in where each persons printer is homing. The traditional home position moves the extruder all the way to the left, and moves the bed to the rear. If your limit switch is on the right, then the X axis would be reversed.

Ok, so up to now I have only been printing small objects, so the bed centering issue which we are all having hasn't been an issue.
Today, I decided it was time to sort it out.

I tried the values from earlier in this post, those gave me a print roughly centred on the X axis, but way off to the rear on the Y
I am probing 36 points due to the "special quality" bed they sent me.

To get my prints to centre dead on, my start g-code has been altered to the following.
G92 X-2.75 Y201
Those values will probably be different depending on how many points you are set to probe, so take them as a guide to start from.

Another thing to note, I wonder if we are receiving slightly different size beds.
Mine is the large bed, and the actual plate is 225 X 280mm. I know this will only make prints out of centre by a few mm, but hey, I'm a printer engineer by trade, so I expect perfect registration.
Once I get a replacement Y carriage and plate, I will most likely have to adjust those values again, as I will probe hopefully fewer points.

So that was Cura sorted, now when I import the file into Pronterface, the graphic shows my print object off the grid by a long way.
In Pronterface settings options, I have altered by bed size to the correct dimentions, and set x offset at 0, y offset at -201
The graphic now shows the print in the centre of the grid.

My advice to all of you is to stop using Cura, Marlin, and Pronterface. Sounds like terrible advice, right? Hear me out.

The person's who selected this tool chain for you don't provide support for it.
Cura is for Ultimaker. Yes, it works, but CuraEngine is truly what you should be using.
Marlin is great firmware. One of the best in fact, but there is another choice. Repetier.
Repetier Host, Repetier Firmware, and CuraEngine (comes in Repetier Host) is all you need to use, and you will have all the support you need.

The problems with bed centering are caused by the fact that centering can be addressed in host, firmware, or slicer, and most of you are trying to get it done with just the slicer.

I will lend a hand if anyone is ready to take the plunge with Repetier Firmware. It has a web based configuration tool thats easy to use, and it should not take too much to figure out the right settings.

In the latest version of Cura, they have even removed the option to choose a Reprap type printer. There are only options for the various Ultimakers.

I'm game to try the Repetier firmware, I have just downloaded the latest Repetier Host, printer is currently doing a job though, so config will have to wait.
The wizard is currently at the point it wants to connect to the printer. Once this print is finished, I'll continue the configuration wizard and see what happens.

Is there any benefit to the Repetier firmware over Marlin?

I am sticking with Marlin for now, but I was using Mattercontrol and now Simplify3d.

I think its more a support issue. With Marlin, we are each others support.
I have emailed the Migbot suppliers numerous times, and the only way they ever got back to me was when I opened a Paypal dispute. They responded instantly then!
Got what I wanted sorted, took ages for them to send me missing parts, now, they are completely ignoring me.
I have requested what I need to convert my printer to the latest version with multi filament support, not a word from any of them.
There is no way I would ever deal with 3dprintersonlinestore.com again, and would strongly advise others to steer well clear of them.

Most of the issues with my printer are sorted now, partly from my own experimentation, but also with a lot of good tips from this thread.

FYI, no more Migbot! They closed up shop and took there customer support with them.
Here is the response from 3dprintersonlinestore;

"We understand that only for the customers we are here. Unfortunately Migbot shutdown the factory due to high competition and big loss.
Only they are responsible for after sales support."

Steve Nelson
Sales Consultant
3D Printers Online Retail Store
[www.3dprintersonlinestore.com]
-----Original Message-----

Whatever that means!