My Recommendations For Printing at gMax Scale

Okay, so I have less than 3 weeks experience with my gMax 1.5 XL+ dual extruder printer with heated bed. But I have about 250 kg of printing experience over 4 years using many other printer types and brands. Now I’m excited to take full advantage of the relatively massive print volume of the gMax. But as I’ve prepped for designing and printing at gMax scale, I’ve been forced to re-examine many operational challenges that I’d previously mastered at smaller scales. It seems to me that many of the gMax challenges we face relate to the print bed... Its size, certainly. But also how flat it is, how to control temperatures, optimizing first layer adhesion, mastering slicing-related issues, and in some cases surface quality of the printed piece’s bottom.

I spent the months between the day I placed my order and the printer's delivery, and even more intensely in the 20 days or so since it arrived, developing, testing and iteratively refining operational best practices that will enable me to reliably, affordably and efficiently take full advantage of the gMax’s powerful capabilities. After a very concentrated effort, and with Kyle’s invaluable help, I’ve resolved a multitude of assembly-related issues, identified some solutions for improvements to the current design, and put together a set of best practices that fully address all my requirements with few compromises in the printed results. I describe my findings in this discussion.

Just to name it, these are practices and settings that work well for me and my requirements in my operating environment. Your requirements or environment may be so different as to render my conclusions useless — or worse. But it might be worthwhile to at least be aware of what I’ve found even if you have your own best practices that are working well for you in your shop. Take all this for what it’s worth, and ignore what doesn’t fit.

I’ll start with a summary of the requirements I have that are the drivers of these best practices.

* I have no intention at this point of hacking the fully-assembled printer that I received from gCreate. That said, there have been several missteps made in the assembly of my printer that Kyle and I had to think through and fix. I also made numerous changes and additions to evolve a Simplify3D profile for this printer that enabled me to meet my requirements.

* I need to be able to print using any supported filament type from any vendor of reasonable quality within the temperature range of the stock extruder, to include PLA, PETG, ABS, TPU and carbon fiber.

* I need support for dual extrusion using any combination of mutually compatible filaments. Meeting this requirement means that I must be able to slice a single job for fabrication using both materials.

* All jobs must fully adhere to the bed until the print completes. A raft should be necessary only when the surface area of the bottom of the shape being printed is insufficient for the piece to adhere when extruding the higher layers of the print.

* The print bed may be heated if doing so will improve adhesion and not adversely affect the printed object.

* I want to take FULL advantage of the entire gMax print volume. This means every corner high and low. The gantry cable mustn’t bump the object being printed. The extruders must have full freedom of movement across the entire area of the print bed — from the point that it begins printing the first layer until it completes the final layer 530mm above the bed.

* I need to get full fidelity in the first few layers of every print. So the geometry in the first layer of my designs must be represented in the printed object. As such, Simplify3D slices must succeed with a ‘First Layer Height’ ratio setting no higher than 150%.

The Print Bed Surface

My local hardware store here in Berkeley, CA is Orchard Home Supply (OSH) Then I buy a sheet of glass from them they'll custom cut it to my specifications at no extra charge. So I buy single sheets of double strength glass 36 inch X 48 inch, which is 3mm thick. From this sheet they cut six 16 3/4 inch X 16 inch pieces.

I print with a piece of glass clamped on top of the gMax print bed. I have a heated print bed. So the glass is clamped on top of the heated bed. But before installing the heated bed I simply placed the glass directly on top of the metal bed. Either arrangement has worked equally well for me.

I print using a number of different materials. So I keep several pieces of glass prepped and ready for use based on the print surface needed for the filament type being used.

[table][tr][td]Filament Material[/td]
[td]Glass Preparation[/td]
[td]Bed Temperature[/td]
[td]Durability (same print/place)[/td]

[td]Blue Painter's Tape[/td]
[td]~20 jobs[/td]
[td]1.88 in. is cheaper, but 2.83 in has fewer seams[/td][/tr]
[td]Blue Painter's Tape[/td]
[td]~10 jobs[/td]
[td]1.88 in. is cheaper, but 2.83 in has fewer seams[/td][/tr]
[td]Aqua Net Extra Super Hold Hairspray[/td]
[td]~40 jobs[/td]
[td]1 coat, let dry, then another coat[/td][/tr][/table]

Printing on disposable glass plates optimally fits my needs because custom cut glass is the right size, it’s durable, readily available, inexpensive, VERY flat, and both sides can be used before being cleaned up, then prepared for reuse over and over again. If a piece does break, the shards are at little risk of damaging the machine, though you obviously have to be careful cleaning up the broken glass. Broken glass is 100% recyclable. Just eyeballing it, I find the glass that I buy from OSH to be flat to within +/- 0.2mm across the entire 16 inches in each direction.

Below is a photo of my rig with a piece of blue tape covered glass installed. Note that the glass is sitting on top of a heated bed. Also note that I’m currently using binder clips to secure the glass to the bed. The chrome “handles” of the clips have been removed so that they don’t get caught up on anything while printing. My use of binder clips is temporary, as I plan to hack gCreate’s TPU clips that keep the heated bed in place above, but separate from, the metal bed. You can see these TPU clips in red in the photo below. My hacked version of these clips will be extended vertically so as to clasp the glass to the bed. (I’ll post the STL’s in this discussion.) This is necessary because the binder clips shown below actually do intrude slightly into the print volume, though the hacked TPU-based clips will not.

Placing glass over the printer’s bed (whether heated or otherwise) provides an easy means to level the glass surface simply by using doubly folded Post-It Notes inserted under corners of the glass. Based on my experience, each doubly folder note (so 4 layers thick) raises that corner of the glass by 0.6 - 0.8mm. The glass is rigid enough that it’s not necessary to insert additional shims mid-span. Those in the corners are sufficient. Notice the doubly-folded note in the bottom right corner of the photo.

Using Simplify3D To Slice Jobs

Simplify3D (S3D) is my slicer of choice — by a long shot. It’s been over a year since I had to use Slic3r, though I used to have to use it a lot before S3D arrived on the scene. My opinion when I was using it was that Slic3r is the absolute worst slicer still being worked on — by a long shot. If you care about the quality of your prints, I strongly encourage you to use S3D.

I didn’t find the gMax+ S3D profile that I downloaded from the gCreate website (v. 160520) to be usable when first installed. What would happen is that every job that I sliced using the profile would not progress beyond the initial heating of the extruder(s). However Kyle told me how to get past this hang and get my jobs to print…

[td]I have recently had a customer who used Simplify 3D with his Makerbot prior to using the gMax. When he imported the config files for his gMax 1.5+, an important setting for the printers firmware type was not changed. This is the setting labeled "Update firmware configuration" in the gcode tab.

Normally this is not enabled. Enable it, set firmware type to Reprap (Marlin), and baud rate to 250,000.

I was able to generate my first printable job once I made these changes in my factory file.

Sadly, at the time of this writing the download page on the gCreate site for this profile still doesn’t include instructions for changing these settings to overcome this job hanging condition as part of the profile installation process. Unfortunately, I have experienced numerous situations where Kyle and Gordon know how to fix a problem but don’t bother to update the site to inform users of fixes, updates and workarounds.

My S3D factory file can be downloaded from here. It includes processes for printing PLA, Ninjaflex or ABS on the latest version of the gMax 1.5 XL+. Know though that my version differs slightly from the approach taken by the gCreate team…

* The Layer tab for all filament material types has a First Layer Height ratio value of 150%. This setting is essential in order for the first layer of a print to be the same as the geometry in the STL. This is essential when printing pieces where the fidelity of the first few layers is important. In contrast, using the value of 300% as set in the gCreate profile results in a bottom layer of the printed object to be the geometry found around 0.5 mm from the bottom.

I should note that the value of 150% for the first layer height works for me because I print on the very rigid 3mm glass that I’ve described above. I’ve printed 490mm tall jobs in PLA with 0% loss of adhesion found when the job is completed.

Also note that dual extrusion jobs must have the same first layer height ratio values for both extruders, as different values between extruders could cause layers to be misaligned, which could result in the non-printing nozzle to hitting material being laid down in the current layer. This could damage the object, which often snowballs as the job progresses. Layer misalignment could also cause a loss of bed adhesion due to the knocking of an extruder against the printed object.

* My factory file adds support for Ninjaflex.

* Oozing by the non-printing extruder in a dual extrusion job is a significant challenge. Generally speaking, the larger the nozzle opening the greater a problem oozing becomes. TPU filaments ooze much more than ABS or PLA. There’s really no way to completely eliminate oozing using extruders like those found on gMax’s. But my Ninjaflex settings call for 12mm of retraction. The barrel of the stock gMax extruder is fairly tall. This allows for a lot of retraction without “breaking the seal” and introducing air into the barrel when retraction is reversed.

Double-Check, Triple-Check For Assembly Missteps

I bought my gMax pre-assembled rather than build it out myself. I made this decision based on quality assurances on the gCreate website and further assurances in direct email exchanges. But the unit I took delivery of 20 days ago was not up to the promised quality standards. Kyle and I spend literally weeks debugging the problems I was experiencing, which included…

* The install instructions for the S3D profile did not instruct users to confirm the proper Firmware settings in the Advanced tab. So it took 3 days before I was able to print my first job that I’d sliced myself.

* The Create Ticket button on the gCreate support page is non-functional.

* The two screws on the front left side of the gantry that are supposed to hold the belt firmly attached were loose to the point of almost falling out. The very loose belt tension that resulted caused major deformities in tall prints and poor surface qualify (referred to as “ringing”) at 3:00 and 9:00 of all prints. This took almost a week for Kyle, Gordon and I to figure out.

* The 3 screws behind the gantry hood that are used to attach the extruder to the gantry were also VERY loose. (Notice the pattern of problems caused by screws that were insufficiently tightened during assembly?) This resulted in uneven layering in single extruder jobs, and the failure of all initial dual extrusion jobs.

* The gMax is sold as a printer with fully automatic bed leveling. While the probe results in dynamic recognition of bed height, the hardware and firmware don’t currently include a means to actually level the bed. The operator much manually rotate individual Z-axis rods to compensate for different left and right bed heights. There’s no means that I’m aware of to compensate for differences in height between the front and back of the bed. The gMax is NOT a self-leveling machine.

The company’s assembly practices are evolving. Buy my advice for customers taking delivery of pre-assembled gMax units would be to question everything related to assembly. I consider myself very fortunate that the frame of the unit I took delivery of is very straight and rigid. But the state of your machine may be different — for better or worse.

What a GREAT Piece of Gear!

After spending about 100 hours “certifying” my gMax as meeting my requirements, I want to say that I’m very impressed with this rig. There are a lot of new challenges that need to be overcome in order to operate and maintain a rig able to print at this scale. I appreciate Kyle’s help and positive attitude while we debugged the problems I encountered in the unit I received. I’m excited to get started printing at gMax scale.

- Bob
This post was the exact opposite of FBI Directors Comeys press conference about Hillary Clintons emails.

Scathing remarks throughout followed by high praise of the machine vs (no prosecutor would press charges) haha.

Anyway... I had some of the same issues with my printer, loose screws etc... I didnt have nearly the firmware etc issues that you dealt with, and I also dont actually do ANY profiles from other users.
I find that each filament, etc is so different that I need to just start from scratch and make my own profiles.

With regard to the bed leveling, can you elaborate a bit? Im confused by your statements about it not being an automatic leveling system?
No the bed doesnt change heights, but the nozzle compensates accurately for the different in heights where they may lie.
For example, I am about .15mm different right to left, and when my nozzle moves, I can see my lead screws turning slightly to compensate for it.

thanks for the post
Yeah, it's complicated.

I'm of two minds about the printer gCreate shipped me. I can appreciate how much more challenging it is to design, build and operate a machine with a bed the size of an aircraft carrier relative to today's mainstream gear. But it *seems* that the gMax design is up to the task. And then there's the "fully assembled" machine that gCreate shipped me. I pulled it out of the box, set it up, turned it on, and -- naively -- just started printing. Everything went well except for the printing part. But at that point I didn't stop and triple check everything for assembly missteps. I just kept debugging one problem after another, each time thinking I'd resolved the last nuanced assembly quirk. Then I'd start another job, which would fail for some other nuanced assembly quirk. And so it goes.

I came in this morning to find the job I'd started yesterday afternoon had failed with a MINTEMP error. So now I'm working my way back through the wiring path from the thermistor to the motherboard. Yeah, this is what I'd be doing if I built this unit myself, but... Maybe I should have.

Here's the problem, taken right from the source. Kyle's response to my asking for help on this latest error included this telling missive...

[table][tr][td]The biggest design challenge with a huge fully assembled printer is getting them to survive shipping. I am willing to bet that your machine was subject to some intense vibrations or abuse in transit.[/td][/tr][/table]
Yet the box, which still sits in the middle of my lab because I still don't know if I'm going to need to use it soon, doesn't have so much as a scuff on it. These screws didn't vibrate loose during shipment. If they did then the design is fundamentally flawed, because the amount of vibration during printing hour after hour after hour is orders of magnitude more significant than that experienced during shipping.

The gCreate team needs to get religion about designing and assembling "defensively" if they're to have any hope of shipping a reliable product. They need to take the experiences being reported by their customers as the golden nuggets that they are, instead of making excuses and continuing with the status quo. For example, if the screws are vibrating loose, then they need to replace them with nylon nuts, which I'm off to get from Bowlin Screws right now.

Yeah, it's been trying. But the allure of printing at this scale is exciting. Right? That's why we're all here. And when I look beyond gCreate"s low build quality standards, I see a machine that can pull it off. We'll see if that's actually true.

- Bob
I experienced similar shipping issues.. My box was in good condition, and i had some screws out.
That said, after I dialed everything in, this printer is my favorite ive ever owned (this is my 9th printer).
I havent printed ANYTHING big yet either. The quality that this large format printer can churn out is stunning. THe only printer that matches it is my old Flashforge creator pro , which is widely considered one of the best printers ever made, especially for the quality parts it turns out.

I did swap the hotend for an E3D which was super easy, allows me to print Polycarbonate etc.

While my experience wasnt perfect, my satisfaction with the printer trumps all that.. stick with it, hope it works out.
It sounds like you and I came to gMax with a similar provenance. The bulk of my printing has been on Flashforges as well, though I also have/had units made by Makerbot, Lulzbot, Printrbot, Leapfrog and MendelMax. The Flashforges, of which I still run 2, have been great machines for K-12 3D modeling classes. But now I need to scale up or my art is going to die.

Just to play this question out... The fact that yours, mine and maybe everybody else's gCreate printers are arriving with loose screws COULD be an indication of poor handling during shipping. But I gave greater weight to the possibility that the screws just aren't being properly tightened during construction. But that's almost a mute point. Whatever the cause, the fact that this condition is so common screams for a solution, like using lock nuts. That said, my guy at Bowlin Screws said that lock nuts don't exist for sizes smaller than M3. I/he thinks the the screws securing the X belt to the gantry are M2.5's. He gave me some M2.5 lock washers, which I'll try out once the printer is idle again. But I wonder whether the long term solution involves changing the design to accommodate M3's.

I need a large format printer like the gMax. But this has not been an auspicious introduction.

- Bob


New Member
I ordered the gMax 1.5 3 weeks ago.

I have to say after reading the above I am thinking about to canceling my order.
It is hard to believe that for almost $3000 you have to play around with having to look for screws that are lose and have to spend so much time in double and triple checking before you can print.

I was looking for a printer with self-leveling but after reading now I am to understand that the gMax is not really self-leveling…WOW

Is the problem quality control or is it the product itself. The main reason I ordered the gMax is because the (3D Printing Nerd) had a great review and show it out of the box to print without any problems.

I don’t know what to do about the order, I was looking for quality and easy of setup.
With any printer its not going to be open box, hit button.. that simply doesnt exist.
YES i had a couple loose screw too, but its not that big of a deal. Put them back in and you are set.

From the second I unboxed the printer, within an hour i was printing. High quality stuff.
the quality of the prints is insane...

I dont know what you, or the other poster mean by the bed doesnt auto level. If its off a touch left to right, you will see the stepper motors adjusting to compensate for that.
bobr said:
I ordered the gMax 1.5 3 weeks ago.

I have to say after reading the above I am thinking about to canceling my order.
It is hard to believe that for almost $3000 you have to play around with having to look for screws that are lose and have to spend so much time in double and triple checking before you can print.

I was looking for a printer with self-leveling but after reading now I am to understand that the gMax is not really self-leveling…WOW

Is the problem quality control or is it the product itself. The main reason I ordered the gMax is because the (3D Printing Nerd) had a great review and show it out of the box to print without any problems.

I don’t know what to do about the order, I was looking for quality and easy of setup.
There's no such thing as a 3D printer that "just works", so get that idea out of your head.
So many people who have no business buying one go and buy one and then complain that it doesn't just work.
It never will.
I've said it many times, with 3D printing, the people are gonna have to learn enough to be able to functionally operate it. After all, it is a CNC and al the problems that come with them. Even more because of the additive "machining" of a printer versus the subtractive machining of a CNC mill or similar.
I have 4 CNC's in my house, including the printer, and none of them just work every time. Always need something done to maintain proper function. Hell, I have a friend with a waterjet and he doesn't even put the caser together anymore, says he spends more time in the guts of the machine than using it!

As for loose screws, blue locktite and you're done.
bobr wrote:
I ordered the gMax 1.5 3 weeks ago.

I have to say after reading the above I am thinking about to canceling my order.
It is hard to believe that for almost $3000 you have to play around with having to look for screws that are lose and have to spend so much time in double and triple checking before you can print.

I was looking for a printer with self-leveling but after reading now I am to understand that the gMax is not really self-leveling…WOW

Is the problem quality control or is it the product itself. The main reason I ordered the gMax is because the (3D Printing Nerd) had a great review and show it out of the box to print without any problems.

I don’t know what to do about the order, I was looking for quality and easy of setup.
The gMax does auto level. It does this by Z compensation. The bed itself does not move, the z axis automatically adjusts to compensate. This has the exact same effect as adjusting the bed. Most if not all auto leveling 3D printers work this way.

neobobkrause's machine did have some errors. The X-axis belt was loose,a few bolts which secure the extruder were loose and the BL touch probe was not adequately powered. Once the problems were identified we shipped him the necessary parts and instructed him on how to fix them. Moving forward, all gMax printers power the BL touch directly from the power supply making them more reliable. neobobkrause also ordered a dual extruder which requires more precision and a thorough understanding of the gMax to use. Combined with loose hardware, it was no wonder his first few days did not go smoothly. That is what I am here for, I walked him through fixing the machine via email to the best of my ability. We continually work hard to build, calibrate, test, ship, and support a high quality 3D printer.

If you have any questions feel free to email us.
It's complicated.

Some will say that "works out of the box" is a myth. It's not. I've probably bought 20 Flashforges over the course of the last 4 years. Read the section titled "Low Reliability" in this blog post from a few years back for a little snapshot of the condition their printers would arrive in. But I took delivery of 2 Flashforge Creator Pro's in the last 6 months. And I can say without reservation that they've really worked the bugs out of that product line. I never thought I'd compliment FF for their build quality, but they are damn fine machines for the price.

@bobr: I'm a big fan of the gMax+ design. I've printed 100's of kilos using mini to standard format printers. But printing at gMax scale really raises the bar. As I tried to convey in my opening post -- the gMax design is very good for it's day. That said, the gCreate assembly team needs to get religion and stop saying that it's just not possible to produce to a higher quality standard. They can, they must, and I believe that they will.

I also need to correct a misstatement I made in my original post: the gMax does have bed leveling built in to the hardware and software. I hope to see future design improvements that enable me to use a hand screw to adjust the probe, rather than having to use a jewelers screwdriver adjust 2 screws under the gantry hood. I also hope that the probe vendor improves the reliability of the probing mechanism so that it doesn't fail as often as it does. But the gMax's bed probing solution fits my requirements in a production environment.

- Bob
This photo shows my gMax most of the way through laying down a very large first layer of a PLA print sliced using my updated Simplify3D factory file (Krause gMax 16.08.21.factory). (This factory includes new PLA Vase Mode processes. All other processes are unchanged from the earlier version.) The print shown is being laid down on a sheet of 3mm double strength glass with 3M Scotch-Blue painters tape on top. I still have the stock 0.6 extruder nozzle installed. The glass being as flat as it is allows the printer to lay down an initial layer at only 150% the standard layer height, thus preserving the design intent of the model's bottom. The layer height of this print is the "standard" 0.20mm, but I've printed almost the same job with the gMax's highest resolution layer setting of 0.08mm with equal success. I print PLA with the heated bed at 50C, but my lab partner doesn't use the heater while still getting equally good results.

- Bob
I can say there assembly practices have not improved! Unboxed my printer today and there was loose hardware in the bottom of the box! :shock:
Did the box look like it had had a rough trip? These problems with newly arrived gaar being in pieces are avoidable. I've received large-format printers of equal complexity from Leakfrog, Lulzbot without these kinds of design and assembly problems. The gCreate team needs to turn their attentions toward higher build standards. I like the results I'm getting from my unit now that I've resolved the build errors. I'd consider buying another unit -- but only once I hear that these kinds of issues have been resolved.

- Bob
The box actually looked immaculate. The packaging was phenomenal, the printer was secure and not able to move around. I was utterly shocked when I saw the hardware on the bottom, but from the review of yours I was kind of expecting that to happen, just a little disappointing.
Right? I think you can now appreciate the complexity of my initial gMax review. It's a very functional printer that the gCreate assembly team needs to take the quality level up a notch or two.

Enjoy your new printer. Can't wait to see what you come up with.

- Bob
I have never had a 3D printer and have never used Simplify3D.
I received my printer yesterday... the packing was great and I did not see any damage to the box or printer.

However I did have a problem with the printer.
The problems was the printer right bed rail was off my 3/4 of an inch in the back, this made the bed not move all the way to the back... and made a grinding noise.
After finding the problem and re-adjusting the rail I had no problems.
I'm also using Simplify3D for the first time and had no problem with plugin it into the gMAX.

To the guy who say it's not plug-and play... for me it was and I'm very happy that I chose gMax 1.5 XT as my 3D printer.
That's great. Glad to hear you haven't had any problems yet.

I got a note from the gCreate crew about 3 weeks ago along the lines of they're being optimistic about the opportunities their new space provides as far as improving their build quality. I suggested that Gordon blogging about specific changes would help reassure people and set expectations. But I haven't heard any news from them on that front yet. Let's all keep our ears to the ground.

- Bob