GMax 2 First Impressions (and some warnings!)

#1
Firstly, I've been happy with the support and a fan of the work being done at gCreate. My overall impression of the gMax 2 after having it for about 5 days is awesome but I've run into a few show stopping issues that I'm about to open support cases for but wanted to warn other about as they may lead to damage of your machine (or worse). I'll also say that these are mostly minor issues that can be resolved with new 3D printed parts so hopefully gCreate see this or my support ticket and point out the dumb mistakes I'm making or give us remedies for these issues.

1. Firstly, the clamps that hold the Acrylic bed are too tall and the BLTouch Probe (even when stowed) crashes into the clamp bending the probe (pictures below). I'm hoping this is some weird this with just my machine but I highly doubt it. It literally limits the safe Y-Axis travel to 415mm (not the advertised ~457mm), thats nearly 2 inches lost on the Y due to a poorly designed clamp. If they aren't able to offer a resolution for this I'm going to be returning the printer as 2inches is just too much to lose, I might as well get the Gmax 1.5XT instead at much lower cost.

IMG_20190526_201230.jpg MVIMG_20190524_113406.jpg

2. While attempting to level my X-Axis per the instructions in the provided manual, my extruder crashed into the edge of the acrylic bed putting pressure on the heater cartridge wires. I couldn't for the life of me understand how the leveling routine could possible level the X-Axis by going all the way to the right and then traveling down as far as possible (off the bed). Upon closer inspection I found what might be a spacer in the box. It seems like it fell off the right Z-Axis brace (picture below). Either way, this approach for leveling the X-Axis seems flawed and instead I just sent the X-Axis all the up the Z until both side were firmly against the top Z stop. Be careful using the included X-Axis leveling gcode routine as you risk extruder damage. Again, Im hoping I did something dumb here but this isn't my first printer and there is a similar spacer on the left side which seems to be what the X-Axis stops on.

IMG_20190524_113431.jpg

3. Wire Drag Chain chaffing heater cartridge cables (or any cable really). Where the wire drag chain meets the extruder it has 2 relatively sharp edges. After just 30 hours of printing I found a powder on the drag chain and then looked to find my heater cartridge cable was rubbing on the edger of the drag chain and making serious progress towards cutting through the insulation. I put a quick fix on tape to hold the wires away from drag chain's last articulated segment. The printer shipped with some extra zip-ties that were not called for in the manual, perhaps they new of this issue but omitted this advice in the manual? Either way, this poses a fire hazard so if you have the gMax 2 please check this and if you see any chaffing, add something to minimize it. If i get time, I'll design a quicj printable shroud for the affected area and share it here.

cable_fray.png MVIMG_20190525_160006.jpg

4. Acrylic Bed - Being a large format printer, I was expecting that the bed would be a bit challenging to level but after printing 10 single layer, nearly full bed calibrations. Ive come to the conclusion that the BLTouch's utility is severely limited for this printer (again, maybe just my) machine for two reasons: 1) The acrylic material has a high thickness variance (>1mm for the bed I was shipped). 2) The Bed's mounting system appears to only provide support at 4 points allowing for the bed to sag, this is made even worse if you have a large print which uses lots of material, adding weight over an essentially unsupported area. Maybe I'm wrong on this, I tried to look beneath the bed to see if the screw heads on the carriage had been strategically places for support but that didn't seem to be the case The result is that the number of probing points (6x6) is too few to compensate. A 10x10 or even better 18x18 mesh would be way better. (maybe there is a way to do this that I'm not familiar with and then have the firmware do better UBL into the standard mesh?). I'm really hoping that the heated bed system that was supposed to ship with this printer (pre-order) overcomes these issues. I'm fairly certain that I can manually tune the bed leveling mesh to make the entire bed usable and am hopeful to have that done sometime tomorrow to try my had at a useful print but it shouldn't be this difficult. The BLTouch should have done 90%+ of the work if mounting and surface were just a bit better. I'm happy to be wrong about all of this so please, someone, anyway, point out the hopefully dumb thing I overlooked.

IMG_20190524_130413.jpg

5. Min Temp Errors - I'm also getting random min-temp errors on the extruder which has led to several failed prints after running for a few hours. Seems the extruder thermistor is shot too.

Code:
Send: N8997 G1 X410.105 Y280.468 E210.1128*101
Recv:  T:225.25 /225.00 B:0.00 /0.00 @:80 B@:0
Recv: echo:busy: processing
Recv: ok
Send: N8998 G1 X411.044 Y278.037 E210.2809*111
Recv: ok
Send: N8999 G1 X412.439 Y273.374 E210.5950*102
Recv: ok
Send: N9000 G1 X310.802 Y171.736 E219.8696*109
Recv: echo: cold extrusion prevented
Recv: echo: cold extrusion prevented
Recv: Error:MINTEMP triggered, system stopped! Heater_ID: 0
Recv: Error:Printer halted. kill() called!
Changing monitoring state from "Printing" to "Error: MINTEMP triggered, system stopped! Heater_ID: 0 - Printer halted. kill() called!"
Changing monitoring state from "Error: MINTEMP triggered, system stopped! Heater_ID: 0 - Printer halted. kill() called!" to "Offline (Error: MINTEMP triggered, system stopped! Heater_ID: 0 - Printer halted. kill() called!)"
Connection closed, closing down monitor
 
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#2
gCreate has very quickly (next day) responded to my issues, including redesigning the bed clips. They shipped me some replacement and updated parts. I'll update this post once I get them and test them out.
 
#3
You can change the bed leveling settings in the firmware, also the temp hysteresis.
It uses Marlin firmware so you can Google for directions if you don't know how.
The rest of the problems are pretty bad for a brand new printer. Hopefully you got a bad one but...
 
#4
Which bed level settings are you referring to? Is it possible to change from 6x6 to 18x18? If so can you point me to the source file by chance? :)
 
#5
yes, you can probe as many times as your bed area will allow, with the probe offset taken into account of course.
I take it you're not familiar with Marlin?
It's all in the configuration.h file.
I'm using the bugfix 2 version on my printer so this won't be exact but youcan find the Z probe options around line 775, then the probing options around 1090.
You're looking for this line for number of probe spots:
#define GRID_MAX_POINTS_X 6
#define GRID_MAX_POINTS_Y GRID_MAX_POINTS_X
 
#6
I'm only familiar with Prusa's mk3 firmware and changing that from 3x3 to 7x7 was a pain in the butt. Does the gmax2 run stock Marlin or has gCreate made any modifications (like to the config file you mentioned). If so, where can I find the source for gCreate's fork/branch?
 
#15
Here is the zip file. But we will be unable to give any assistance on modifying or installing the firmware as this will fall outside the scope of tech support since the printer will no longer be in its stock format.
Thanks, I understand. I'm planning to just test 18x18 mesh for bed leveling and then revert to stock if it doesn't help. If it does I'll send you a PR as you may want to make this available to all customers.
 
#16
Here is the zip file. But we will be unable to give any assistance on modifying or installing the firmware as this will fall outside the scope of tech support since the printer will no longer be in its stock format.
The zip file you attached looks like it contains Gmax 1.5xt firmware no mention of gmax2 anywhere (any change logs or commit history). Can you confirm this is the correct zip (perhaps you guys just haven't rename/organized this branch for gmax2?).

Additionally the replacement thermistor you sent me doesn't work, it reads 0 all the time. It looks significantly different than the original thermistor so perhaps I need to change the thermistor in the firmware but zero info about this new thermistor (no packaging or markings on it) was included and given the uncertainty i have about the validity of the zip you provided I'm not comfortable flashing random thermistor values until i see which is the correct one.
 
#17
Wanted to give an update since gCreate has been awesome in helping me get up and running. Most of my issues have been solved. I'm just waiting on a couple more replacement parts since USPS lost the first package (doh!). It was a rough start but the team has given great support and my first GIANT print is well under weigh. I'll post the results in a few days once it finishes. Right now I'm limping along on a patched up thermistor cable.

The big root causes for me:
1. Bad thermistor
2. Nozzel that shipped with mine wasn't .5mm as advertised but rather .6mm which caused havoc with extrusion consistency because I was using .5mm j. Slicer.
3. The provided slicer profiles don't work when printing a large surface area. They need to be slowed down by about 20 - 25% to ensure consistent extrusion on long travels. Also highly recommend enabling z hop/lift.
4. Check your cables are not getting bound up in the drag chain, use zip ties or tape to keep them from the final articulation joint.

I'm currently running a print that will be 15inch x/y and 19inch z. :) ETA 73hrs if the thermistor patching I did holds up until the replacement comes.