Fine-tuning & Increasing Performance of your gMax Printer

#1
After owning the gMax 1.0 and converting it to the gMax 1.5 XT+ I have come to understand quite well how this printer works, and what it needs to print incredibly well. The gMax printer is a very well made printer. If you take the time to understand what the printer needs, and fine-tune it, it will reward you with even more reliable and stunning quality prints.

Below are shown some critical high performance areas that once fine tuned, the print results will leave you smiling in satisfaction.

I did not want to develop each topic below as it can be pretty extensive. However I have dealt with all of the topics while upgrading the printer. I'm not showing or suggesting something new here. In fact all of these topics have been covered throughout the internet extensively. However this information can be found in scattered places and there is not one spot where all can be addressed at once. Perhaps this can be a good place to start.

So if anyone is interested in developing either topic, I would be glad to share my knowledge with you.

Addressing some of the topics below will give you dimensionally accurate and smooth prints (of course depending on your slicer settings as well).

Thank you

Topics for Discussion

1. Squaring the X, Y, Z axis


2. Making your Z axis Level to the frame


3. Acurizing / Calibrating steps per minute X, Y, Z


4. Extruder Filament Calibration – Extruded Length


5. Calibrating Filament Extrusion Multiplier - Calculating the Setting


6. Acceleration X&Y Jerk Settings - Ringing Reduction


7. Calibrating Your Heater Block Thermistor – PID Auto-tune (E3D V6 or J-Head)


8. Surveying & Mapping your Heated Bed for Thermal Gradient (cold spots & print warping)


9. Modifying Marlin Firmware & Updating to your Ramps 1.4


10. Mounting the E3D-V6 Extruder


11. BluTouch Installation and Calibration- setting your Z offset


12. Stale Filament - Drying your Filament - Popping filament & not sticking to bed



.
 
#3
Re: Fine-tuning & Increasing Performance of your gMax Printe

4. Extruder Filament Calibration – Extruded Length

I typically use Symplify3D Machine Control Panel for this one as it has some short cut buttons on the jog controls that makes life easier. In case you do not have Symplify3D you can use any Communication port like Repetier-Host etc. All will do the same to input commands.
Heat up your extruder to the temperature that you print for the type of filament that is in the extruder (example PLA 205 C).

1. Measure 150mm with calipers and place a mark on the filament as shown in picture.
2. In Symplify3D Machine Control Panel click on the Extrude 100. If you do not have Symplify3D type in the command line:

G92 E0 then send
G1 E100 F90 then send

Note: You can do the same as above from the LCD panel. Go to move Axis, choose Extruder, move 10 times 10mm. I have found this to not be as accurate as with thr command line or Symplify3D Machine Control Panel (it can be off as much as 1~2mm.)

The filament should move 100mm. Measure again the mark to verify as shown in picture. If it is within 0.5 ~ 1.5mm it is close enough (personally I prefer it to be less than 0.5 mm). If not, do the following:

Go into either the Marlin you uploaded or from the LCD screan, under Control, motion, Esteps /min and read the current value, for example 96 steps/min. This is your existing steps/min

S= Steps
S=((What we asked for) / (what we got)) x (existing steps/min)
Example if your extruder measured 99.51mm and you asked 100mm then:
S=((100 mm )/(99.51mm)) x ( 96 steps/min) =96.47 steps/min

This is your calibrated new steps per unit value.

If you have enabled EEPROM in your Marlin you can store the value from the LCD directly.

if you want to enable EEPROM in Marlin, in "Configuration.h" file remove the "/" before the "#define ":

Example
"................

#define EEPROM_SETTINGS
//to disable EEPROM Serial responses and decrease program space by ~1700 byte: comment this out:
// please keep turned on if you can.
#define EEPROM_CHITCHAT

.............."

if you do not have EEPROM enabled then you will have to go to go to Marlin under the “configuration.h” file and modify the following value highlighted in black bold below. Then you will have to upload the firmware to your printer in order to store it into memory.

Example
"................

//for gmax 1.5 + Uncomment below
#define DEFAULT_AXIS_STEPS_PER_UNIT {80.377, 80.370, 406, 96.47}

..........."

If you do not want to upload the Marlin firmware you can type the following in to your command line and it will save the value into EEPROM:

To see what is the value of the extruders steps per minute type "M501 E0" and press enter
To change to the new calculated value type "M92 E96.47 M500" and press enter

That should save the values to the EEPROM

I hope this helps
 
#4
Re: Fine-tuning & Increasing Performance of your gMax Printe

6. Acceleration X&Y Jerk Settings - Ringing Reduction

This is not as straight forward as plugging in numbers.
What I have found to influence ringing in prints usually boils down to the following:

1. Large mass of components. In this case the extruder and the Y print table
2. High x/y jerk settings
3. High acceleration values
4. High print speeds
5. Stretched X/Y belts
6. Loose X/Y belts

Each printer is different and you have to look at all of the above points one by one. There is not much you can do for the mass of the print head and print bed, unless you redesign it. It is what it is as this printer is huge so even a redesign is not going to help that much because of size. So that leaves you with tuning in all the other values.

Try printing with speeds below 30mm/sec on the outer layers. You can go faster in the inner fill layer but not by much. Make sure your belts are tight and print a “Z” clip that actually helps absorb some of the vibrations. The default X/Y jerk for this printer is rather high so I reduced it to 8. The accelerations for the X/Y are fine at 600mm/s.

To test your printer settings and calibrate your filament multiplier, speeds, jerk and acceleration you can design a test print with 1mm thick walls as shown in the picture and use it as a calibration print. If you need it let me know as I can make it available.
 
#5
Re: Fine-tuning & Increasing Performance of your gMax Printe

One thing that helped me reduce, and in some cases remove the ringing was to replace the Y print bed belt with a wider one. I went from the original 5mm to a 9mm GT2 belt. Now the bed moves are crisp and solid. I believe that this upgrade is a must for the heavy print bed of this gMax printer. I am vary please with the results.
 
#6
Re: Fine-tuning & Increasing Performance of your gMax Printe

Any chance you can tell me what printing speeds you're using for your "other" section on S3D? I'm having issues where some prints are great while reprinting with the same settings on the same model has given me failures.
 
#7
Re: Fine-tuning & Increasing Performance of your gMax Printe

flrock said:
Any chance you can tell me what printing speeds you're using for your "other" section on S3D? I'm having issues where some prints are great while reprinting with the same settings on the same model has given me failures.
In S3D for:

For PLA and PETG

Default 35mm/s
Outer 50%
Solid 50%
Support 70%
x/y 50
Z 50%

Also,
Do a filament diameter measurement and calibrate your multiplier.
 
#8
Re: Fine-tuning & Increasing Performance of your gMax Printe

PianoPrint said:
Do a filament diameter measurement and calibrate your multiplier.
My multiplier was off by a measure of 12mm for an extrusion of 100mm. I'm unable to save the changes as EEPROM is disabled and the firmware I downloaded from gCreate (gmax 1.5+ single extruder with BLtouch) is kicking back error codes that aren't involved with the changes of enabling EEPROM, CHIT_CHAT, and default PLA temps. As of now I'm manually inputting the changes.

Is there a way to download the firmware from the actual printer?
 
#9
Re: Fine-tuning & Increasing Performance of your gMax Printe

The multiplier is changed in S3D and the firmware is downloaded from the PC to the Ramps 1.4 through the Arduino interface. You save the multiplier into the profile of S3D exclusively for each brand and type of filament.
 
#10
Re: Fine-tuning & Increasing Performance of your gMax Printe

PianoPrint said:
The multiplier is changed in S3D and the firmware is downloaded from the PC to the Ramps 1.4 through the Arduino interface. You save the multiplier into the profile of S3D exclusively for each brand and type of filament.
Just so I am clear. I command 100mm to be extruded, it actually extruded 88mm. That gave me a number of 1.13 is this what I am to add in the multiplier in S3D? If so, why would I need to multiply it by 96 steps/min?
 
#11
Re: Fine-tuning & Increasing Performance of your gMax Printe

flrock said:
PianoPrint said:
The multiplier is changed in S3D and the firmware is downloaded from the PC to the Ramps 1.4 through the Arduino interface. You save the multiplier into the profile of S3D exclusively for each brand and type of filament.
Just so I am clear. I command 100mm to be extruded, it actually extruded 88mm. That gave me a number of 1.13 is this what I am to add in the multiplier in S3D? If so, why would I need to multiply it by 96 steps/min?

Did you use this formula?

S= Steps
S=((What we asked for) / (what we got)) x (existing steps/min)
Example if your extruder measured 99.51mm and you asked 100mm then:
S=((100 mm )/(99.51mm)) x ( 96 steps/min) =96.47 steps/min

What are your current steps/min of your extruder?
 
#12
Re: Fine-tuning & Increasing Performance of your gMax Printe

Did you go through the process as explained in the section that was posted earlier in the this thread?

4. Extruder Filament Calibration – Extruded Length

I'm asking so that I can understand which part I can explain better in order to get you going.

Let me know.
 
#13
Re: Fine-tuning & Increasing Performance of your gMax Printe

Here is an example of using a 3% infill, 0.20mm layer height no internal support printing with red PETG. Personally I am very impressed with the results. Keep in mind the circles that you see on the surface of the print were present in the CAD model. So what you see on the model surface is the actual detail as intended. I could never imagine this type of quality when I first put the printer together. Now I am incredibly happy with the results.
 
#14
Re: Fine-tuning & Increasing Performance of your gMax Printe

PianoPrint! +Rep for this thread! I hope to be able to add some more knowledge when possible.

Im still tuning my gCreate to output a good quality for me. I've been into 3D printing since 2010, at first the powder typ printers from zCorp, and the last year I've been printing 24/7 with two Prusa i3 MK2 (BETA - testing the multi color upgrade on one of them), so I see myself as experienced with 3D printing, although there are four things with the gCreate gMax that I'm still struggling with, I would be extremely happy if you could give your short view on this matters.

1. First layer / Start of print


On the prusa my process are: Slicing with 80-100% first layer height for 0.2mm layers
When the printer starts i turn down the speed, and use a Live Adjust Z feature which gives me the possibility to change the Z offset, to get a good squeeze for PLA (or less squeeze for flexible filaments for example). When its set I can print prints after prints since the Live Z adjust is stored. If I switch filament type I might need to slightly adjust it.

When I got the gCreate I downloaded the profiles and I was chocked by the first layer settings in S3D, extreme over extrusion! The first tests looked like a mess honestly. I understood after contact with the support that it's a way to handle un-flat spots in the acrylic plate which is the default plate, so I started to tune the settings closer to what I'm used to.

I always need to adjust the Z offset with babystep Z at the start of the print, even though Im at 100-150% first layer height. Otherwise it will pretty much drag the nozzle. Also I still think the first layer is crazy over-extruded I'm not even close to the perfect, smooth first layer that the Prusa achieves. Also having some issues from time to time with adhesion, and if I print an object that covers either front-back or left-right side of the bed, it can be too squeezed in the front and not sticking in the back. Sometimes not sticking in the center, but squeezed in the back/front. Havnt been able to reproduce this, I'm just moving the print around, restart, adjust Babystep Z until I get a complete first layer.

I think I might need to lower my BLTouch just a bit (half of a turn on each screw?), so I will probably do that as the next step. I will also calibrate the extruder to see how off I am. I've settled on the Colorfabb Economy PLA and Colorfabb NGEN for 80% of my prints, so I'll calibrate for both of those.

If you have any other idea or tip regarding the first layer please let me know!




2. Surface finish


I cant say that I'm satisfied with the surface finish of the prints, it doesnt matter if I print at 0.2mm layers or 0.38mm layers, i see a lot of horizontal lines, ringing/ghosting etc. Attaching example image (0.2mm layers, speed 30mm/s)

I have adjusted my Z axis (had to loosen the bolts holding the X axis parts that connects the X axis to the Z rods to be able to move it all the way up without skipping) and X axis (had too adjust the eccentric bolts a bit to get a smooth X movement.) And I'm printing slow in general.

I'm printing a lot of 3D hubs orders, and I cannot use the gMax for that yet because of the poor surface finish I'm getting.

Groot printed with 0.36mm layers, the first image 0.2mm






4. Nozzle drag / Vertical Lift not working?

Especially during the first layers I'm experiencing some heavy nozzle drag when the nozzle moves from one side to the other (typical retraction moves to me), but it seems like the Vertical Lift doesn't work like I'm used to. This problem is enhanced by the over extruded first layer but the nozzle does not lift when it should (imho). I've tried Vertical lift from 0.5mm to 2mm without any noticable difference. After about one month of printing, and many prints I've seen a Vertical lift ONCE, after finishing some supports, but that's the only time I've actually seen it. All I hear from the printer is the nozzle scraping when doing retraction moves. This brings us to the next issue:

4. Layer shift / bad surface taller objects

I bought this printer mainly to print 500mm tall objects in a race car project I'm involved in, I've done some tests with the standing minigroot model and some other models, and at around 430-450 mm Z height I always get a massive layer shift. It looks like the nozzle crashes into the print because of lacking Vertical Lift. And the print moves/vibrates as well from the Y axis movements. Is it recommended to turn down the acceleration for the Y axis to get a more smooth movement? Thats the only thing I can think about, I'm NOT printing fast.. the last fail I turned the speed down to about 20mm/s just to be sure, took like 10 hours to finish 20cm of the model before it failed. If I dont get layer shifts, I get some heavy lines on the outside, like the outer outline misses the line pretty much (se photos).





UPDATE: Just checked my extruder, and it extruded 93mm when I sent the command to extrude 100mm, so I'm under extruding according to that, which is the opposite of what I was hoping for :) Old steps 96, so my new steps is 102.7, trying to update it through OctoPrint terminal but it doesn't bite...Where do I find the configuration.h file?

UPDATE 2: Trying to print a 350mm x 20mm x10 mm long part now, tried to both print it on the left side of the bed along the Y axis and on the front side of the bed along X axis, but I have to adjust Babystep Z in a way that the one side is almost skipping since the nozzle is too close, to get the other side ok. And even then it warps...
My front left corner is aparently lower / leaning down. Shouldnt the Probing deal with that?
 
#15
Re: Fine-tuning & Increasing Performance of your gMax Printe

OK. So I read all your post. There are a lot of things going on here and it will take some time to address them all. With that said I had the same issues for some time until I systematically eliminated them all. The gMax printer is a good printer, but you need to understand it in depth where the machine is, what it can offer and how to get there.

In general as configured by gCreate the machine is meant to print big, slightly rough and bulky, as its size dictates that. However, with some fine tuning you can get small and detailed. I have two other printers I put together that were mainly for smaller detailed work, but now I exclusively use the Gmax as it produces perfect prints.

If you have the patience I am confident that we can solve all your printing issues.

Do me a favor though, on the fist page of this thread tell me what have you already done so far from the long list of impovements?

Have you done the:

5. Calibrating Filament Extrusion Multiplier - Calculating the Setting

I would start from there. If you are not familiar with the process I can a share the information.

Also, I would like to understand your printer baseline as far as what equipment you have. Do you have the new upgraded bed with the heated pad and borosilicate glass? Or are you using the acrylic bed with buildtack on top?

What hotend do you have? I have used both the Jhead, and now the E3D V6 in 4.5mm. Let's start form there first.

Also, I do not use any more the BabyZ as I think it is a waste of time once you level mechanically your bed and set the Z height thorough Marlin and adjust with the Bltouch sensor height adjustment screw. The rest is handled by Marlin and the Bltouch sensor.

I typically print in 0.20mm layer height. If I change to different layer heights I do not mess any more with the baby z or the Bltouch height screw. The only thing I change is the % height for the first layer. I use S3D as a slicer.

Typical setting for first layer height for 0.20mm:

First layer speed 25%
Bed temperature 78C for PETG, and 60 for PLA
First layer height 138%
Fist layer width 100%

On the "Other" tab, in S3D, the general printing speed is set between 30 to 45 mm/s. I like to print around 35mm/s, outside layers to 65% and inner layers to 75. X/Y movement set to 50mm/s, and z to 100%.

Sure the prints take a little more time, but the results are flawless.

What also helped the gMax printer bed quite a bit, as the glass and silicone heated mat are heavy and tend to sag in the middle, was to add an adjustable leveling screw in the middle of the print bed. The bed is big and in need to stabilize it in the middle, thus the leveling screw. I'm not sure why gCreate has not implemented something like this yet, but I'm sure they are thinking about it. Any way, it took a little of drilling and taping, but once you set it you pretty much forget it. Now the bed flatness is leveled to 0.008" (0.20mm), and I did that with a filler gauge. Now by setting the first layer height slightly above that, say 140% of 0.20mm takes care of any variation or what is left over from the bed flatness. Now I never have any first layer issues. The fist layer is flat, consistent and crisp. I just push print and walk away.

Below you can see a picture of the middle of the bed leveling spring screw. It has helped tremendously.

Best,

Eric
 
#17
Re: Fine-tuning & Increasing Performance of your gMax Printe

Thank you for your answer!

Looking at your tall print there at the end tells me that I'm pretty ok with surface finish. I'm just used to a baby skin like surface up to 200mm prints on the Prusa's I have.

To answer your questions:

Yes I've calibrated my extruder and I've updated the E Steps / mm through the LCD (havnt had time to dig into how I write it permanently, will do that later when I find some time.

I have one e3D hotend, and I've just installed an e3D hardened 0.8mm nozzle, trying to tune in the settings atm.
I'm in direct contact with Kyle as well, I've been running some tests for him, we'll see what he thinks, but its pretty clear that my bed is a bit higher on the right side than on the left side.

After I installed the new nozzle, I did auto home, I used a very thin paper and lowered the nozzle to Z 0.0, it was a bit high, so I turned both screws on the BLTouch one quarter of a turn and did auto home again, this time it just touched the bed when I lowered the Nozzle to Z 0.0.

I have a heated glass bed with Buildtak on that, which I'll replace with PEI in a week or two. Not a big fan of the buildtak, personal preferences probably though, and since I've been using PEI on the Prusas for a long time I know all the tricks to increase (and decrease) adhesion for certain filaments.

Printing the 0.6mm layerheight model now with my own set up profile, will try the one gCreate offers from here next test, because this works pretty bad :) I'm having feeding issues since it cant reach my set temperature when the partcooling fan is turned on more than about 70%, when the fan is on with full speed it cant reach a temp above 205 degrees C, when I turn it off it reaches 235 degrees in like 10 seconds. I've now set my nozzle to 255, and raising the fan 10% at a time. When I reach 80% cooling the temp drops, at 70% fan it stays at 246 degrees, but cant reach 255 again.

And it seems like Im stuck at about 30mm/s if I dont want Extruder skipping.
 
#18
Re: Fine-tuning & Increasing Performance of your gMax Printe

Some more examples of prints and first layer print quality. The RC printed plane has a 60cm wingspan. The layer is rather course at 0.20mm layer height. Since my nozzle is 0.4 in diameter it will print best in increments of the nozzle diameter. For example the layer height should be in multiples of 0.04, 0.08, 0.12, 0.16, 0.20, 0.24. I could have printed in twice as good as a resolution as what is shown for instance 0.12mm. But there is no value for me due to the time involved to printing the items.

In your case, with a 0.8mm nozzle I would limit your layer height to the following 0.16, 0.24, 0.32, 0.4mm. Anything more than that it would be difficult for the extrude to push the filament fast enough (most likely will be skipping steps if you do not extrude less than 30mm/s). The 0.8mm thick nozzle is made for quick non detailed work. The corners of parts will not be sharp and details will be get lost in the thickness of the extrusion. To expect good detail and surface finish out a 0.8mm nozzle would be unreasonable due to its physical limitations.

On the E3d V6 are you using the blue silicone hot end boot? It insulates the head and create a stable temperature. Did the E3D V6 come with the printer or did you installed it later? It could need a PID auto-tune for the temperature in order to get calibrated. I had to do mine ( I did not buy the printer with the E3d, but installed it later).

What material are you printing that you need to run 255 C? For PLA I run 208 C with 70% fan, for ABS 240 C with 0% fan, and PETG 241 C with 70% fan. On all filaments when bridging I use 95% fan for that layer.

The aluminum print bed it could have been hit during transport. I had a small issue with mine. Place a straight edge on top of each side of the aluminum bed (after removing the glass and heated silicone mat from it) and bend slightly as needed in the opposite direction of the bend to straighten it. Then do a mechanical bed leveling with a filler gauge and the nozzle on top of each bed corner (fully assembled with the glass and silicone mat). That is all you have to do for the bed. Then set the height with your Bltouch and you should be fine.

As far as the extruder skipping that is a function of the nozzle being too wide in diameter (0.8mm), the heat extrusion temperature, the filament extrusion rate (expected print speed), and the appropriate voltage setting on your extruder stepper motor driver that is plugged on top of the RAMPS board. You can adjust all of the above to obtain favorable results. Are you familiar how to increase the voltage input by turning the pot screw of the stepper drive? Keep on increasing in 5 degree increments while printing until it stops to click.
 
#19
Re: Fine-tuning & Increasing Performance of your gMax Printe

Hi!

Yes im aware of the "issues" with a larger nozzle, but I'll be printing alot of models where the surface finish is not of priority, layer bonding is more important.

I'm printing alot of Colorfabb NGEN, its recommended to print between 220-240, but to get a good flow without any skipping I had to turn the temp up to 250-255 as well as lowering the speed to around 20-30mm/s

The printer came with the E3D hotend, I havnt done anything with it hardware wise yet. (except the nozzle switch)
My E3D hot end did not arrive with the silicon sock, although I have a few laying around, I will mount it and see.

When I print at 20-30mm/s with NGEN and 0.6 layers I cant increase the fan more than to around 30-40% before the temp starting to drop.

I'll soon replace my buildtak with PEI, ill take a look at the aluminium bed then.

I tried to mount the soc but it cant grab the heatblock, I had to modify it a bit, hopefully it will stay.. we'll see.
 
#20
Re: Fine-tuning & Increasing Performance of your gMax Printe

I have another question for you, printing a 500mm tall model now.

I have some skipping happening but at the exact same two positions during the layers each time, and it has no effect if i print at 220 or 270 degrees, nor if I print at 20mm/s or 50mm/s.

Any ideas regarding that?