***Update - Eitri 3D has made a series of videos on this mod upgrade. It's another option for those thinking about doing this mod, especially if you are more of a visual learner. The first video is available here:

https://www.youtube.com/watch?v=ybTcS1KZIGg&ab_channel=Eitri3D

Thanks Eitri 3D!

***Update - Added a Fan_Duct_5mm_Back.stl as an alternative to the OG fan duct piece. This moves the blower fan vents back 5mm towards the back of the printer. In testing, it seems to have better cooling performance.

***Update - Shaun Farmer from the Qidi 3D FB group was kind enough to create an assembly PDF complete with pictures, so I've uploaded it to the files section. Thanks Shaun!

*** Update - I've made two remix versions of this mod for printing in resin. For FDM printers I'd recommend the files on this page with the heat-set inserts. The remixes are available here:

https://www.thingiverse.com/thing:4546836 - Nut version

https://www.thingiverse.com/thing:4563185 - Threaded version

First of all, this is a remix of “qidi x max - bmg & and v6 upgrade” by jhenrikb. Too many modifications to mention them all. Thanks to the original poster. :)

This is a new carriage and hot/cold end mod for the Qidi X-Plus and X-Max printers. This was originally published back in November of 2019, and a massive overhaul was done and posted July 4th, 2020. All the original files have been removed and replaced with the new version. Thanks to Bob Martin from the Qidi 3D Facebook group for his help with testing prototypes and giving measurements and feedback to get the X-Max version to fit properly as I own an X-Plus. The bottom fan duct and belt clip pieces are universal, but there are separate carriage and top frame pieces for X-Plus and X-Max. If you have printed/used the first version, this one has the following improvements:

1. Better printer bed/inside frame clearance. The printer nozzle in this version will line up slightly different than the previous version, but maxes out the bed's print space.
2. Extruder PCB board no longer has to be removed/rotated to remove extruder.
3. Extruder PCB cable easier to remove.
4. Ability to use a 35mm extruder fan (can always use normal 30mm fan also).
5. Ability to mount an optional 30mm output fan on the right in a pull position, this also prevents the belt clip from falling off, and provides a spot for heater cartridge and thermocouple wire management, preventing them from blocking airflow through the carriage, along with the fan helping the carriage breathe better. Optional fan can either be spliced in with the regular extruder fan or put on a y-cable with the extruder fan or can be connected to the empty 3-pin port on the extruder PCB. If spliced with the extruder fan, it will come on and off at 50C like normal. If wired to the 3-pin port it will be always on. The optional 30mm fan has recessed nut holes for easy tightening. (like the PCB mount).
6. Some plastic (in an arc shape) removed from the carriage piece to help the heater block clear better. This is partially due to the position being changed along with giving it better clearance/breathability.
7. Some other minor improvements/changes. The fan duct had to be moved over to accommodate the new position of the nozzle. I removed some plastic on the top frame and carriage to allow for the stepper motor to be orientated with the wire connector in a down position, which is preferable as it helps clear the top and left/right of the machine's frame. Probably some other stuff I forgot. :)

Note for X-Max users. You will need to also print out the following Thingi, which is a shortened handle for the BMG extruder. The original handle is too tall. You will also need to use a M3x20mm bolt with the spring and washer instead of the turn-screw because the top of the turn-screw knob will hit the frame. Bob also said with his original BMG, the metal filament clip hits the frame, but on a clone, the plastic filament clip on the top of the extruder clears, so either use a BMG clone, or replace the metal clip with a shorter plastic one. But with the X-Max carriage and top frame, with the shorter extruder handle, everything clears the top frame of the X-Max and the entire build plate is usable. This is an improvement over my original mod as the blower fan was hitting the rear stepper motor requiring people to shim it, the blower fan has been moved in with this version. Here is the link for the shorter handle:

https://www.thingiverse.com/thing:4522420

For people who own an X-Max and X-Plus, you could use the X-Max version on both machines. The right limit-switch is the same, but the PCB frame, strain relief towers are shorter with the X-Max version. They are also moved towards the front of the carriage, as is the blower fan with the X-Max version, but they will work on both machines. If you only own an X-Plus, I would stick with the X-Plus version as it's a little easier to get at cables.

Also note I'm currently using this with a Trianglelab Dragon hotend, but it also works with a V6 hotend, they are the same size. I will link where you can download a Dragon and V6 35mm fan shroud if you go that route.

Why upgrade? Qidi’s OG single-drive extruder is pretty terrible. If the nozzle is close to the bed, it likes to click (skip), and it has a lot of problems with PETG in my experience. It also has a really hard time with .2mm nozzles at any decent speed. Other irritations of mine with Qidi’s design is the cooling is very bad, with 4 really small slits that get blocked by socks pretty easily and without a complete carriage mod such as this, it’s near impossible to mod the stock cooling. Also, Qidi uses really tiny impossible to find flat thermocouples that go inside a heater block that I also cannot source. Switching over to a standard heater block with a normal 3mm K-type thermocouple gives fit issues with the limited space in the Qidi carriage cradle. The X-Plus/X-Max come with two extruder assemblies, the low-temp one that they say is good for around 230C and the higher temp one, which they claim 300C. The higher temp one is not all-metal, and uses a lined throat which will degrade, warp and clog over time. Qidi will tell you it cannot be replaced and you need to swap out your entire hot-end. It’s not technically true, you can replace parts once you pry the apart, but it’s not an ideal setup. The high temp extruder also does not have a blower fan stock (not hard to add one, but irritating) and uses the same weak extruder the lower temp one does. Frequent plugging and un-plugging of the ribbon cable having to switch between these setups wears out the connector, requiring you to buy a new extruder PCB and/or cable at some point, and the cable is a complete pain to replace. You have to take almost the entire machine apart the way it’s weaved through.

When done, you will have replaced the weak single-drive extruder with a strong, tension adjustable dual-drive 3:1 gear ratio part, along with changing out the hot-end with the V6 or Dragon. The Dragon comes in two versions - standard and high flow, either will work. The advantage of the Dragon is out of the box it's ready for high-temp materials and has an anti-torque nozzle change design. The downsides are replacement parts are still relatively expensive compared to the V6 and you are limited to an all-metal heat break, which is generally not as good as a PTFE lined heat break for soft materials such as PLA and TPU. The V6 is probably the most popular hotend available, with multiple clones and cheap, readily available components. You can either use a PTFE lined heat break or an all-metal variety, such as their standard, titanium or new bi-metal version. The downside with the V6 over the Dragon is unless you use the titanium or bi-metal heat break and their high-temp block, you are more limited with max printing temps than the Dragon, but it can be upgraded. It also is not anti-torque like the Dragon, so when changing nozzles is more of a pain since you have to deal with the seal between the heat sink, heat break, heater block and nozzle, compared to the Dragon where the heat sink, heat break and heater block are all connected, and all you have to do is screw the nozzle in or out.

Since the extruder has a different gear ratio, the e-steps in the firmware will need to be changed, along with the X motor direction because this mod grabs the rubber belt underneath instead of on top. The extruder motor direction also needs to be reversed. These are simple changes and persistent on the printer even through reboots. The original settings can be gone back to at any time if desired.

Here are the lines of code in the firmware file you’ll need to print:

;x-plus or x-max
M8002 I0;Reverse X motor direction
M8005 I1;Reverse stepper motor direction
M8011 S0.002388919;E-steps
M8500;Save changes

The E-steps were calculated with the hob gear circumference / 3200 /3 which gave a value of 0.002388919 e-steps. (Note, that value is for a 1.8 degree motor, like the OG Qidi one. For a .9 degree motor, that value will need to be changed to 0.00119446). I've also provided excel spreadsheets for 1.8 and .9 degree extruder stepper motors for calculating e-steps if you want to fine-tune calibration.

The original calculator was found at:

https://docs.google.com/spreadsheets/d/1VOz1dg8I2bXwsOWCdKM_GWCrxGOX-A2hQ6pdoTR2gPw/edit?usp=sharing

But it’s not for this printer or extruder gear ratio, so I modified it and put it in the files section.

Instructions:

Print out the four parts (Carriage, Top Frame, Fan Duct and Belt Clip). Clean up any rough areas and remove any supports. There is a picture that has all of the parts on one build plate, that is correct orientation. Make sure there are no supports inside the fan duct or you’ll never get them out. If you set support angle to 85, it generally does it right. Otherwise, use a support blocker in Cura or manually remove them in S3D using the cross section view to make sure supports are not printed inside the fan duct. The way it's designed it doesn't need any supports internally and prints fine, but slicers do what they want sometimes. Use your slicer's layer-by-layer preview feature to just double-check there are no support printed internally.

Pre-assembly. Using a soldering gun, insert the 8 inserts for the carriage and the 1 for the blower fan. If you haven't pressed inserts in before, follow this guide, specifically the plate-press technique:

https://hackaday.com/2019/02/28/threading-3d-printed-parts-how-to-use-heat-set-inserts/

After inserts are in, assemble the carriage to make sure everything fits before installing, if any of the screws in the top frame/bottom fan duct aren't screwing in exactly square, widen the hole the bolt goes in slightly (in the top frame piece or fan duct piece) to give it a little wiggle room. If the parts don't warp when printing at all, and the threaded heat inserts are put in square, they line up perfectly.

Turn printer off, move carriage to middle of platform. Remove the top cover, then take out the two screws holding the hot/cold end assembly in and remove. Take out the two screws holding the belt clip on and remove it. Now carefully, trying to put equal downward pressure on the back rail, pull up on the rear of the carriage to pop it off of the bearings. Do the same for the front of the carriage, then remove it. Once all four bearings are popped out, move them to the side to make it easier to get it out.

Now would be a good time to check if your rails are parallel with the bed. Mine have moved in the past, from a big jam-up, jumping a tooth, etc. If you need/want to re-align the rails with the bed, the belt on either the right or left side can be pulled out from the clip holding it in, and then re-positioned after re-aligning the rails. Some people also just grab the rails and force them square by jumping teeth, up to you.

Now, install the new carriage piece on the rail bearings by snapping it into place. The part in the middle with the teeth that hold onto the belt should be towards the back of the machine. Move the top and bottom belts around the carriage belt fastener, then use the belt clip you printed out to secure the bottom belt to the carriage. Make sure you align the teeth from the bottom belt into the grooves on the carriage. Slide it back and forth to make sure everything is working right, the bottom belt should be attached to the carriage, and the top belt should slide over it.

Assemble extruder and hot-end (look online for guides if you don't know how). Then put inside the middle carriage piece and screw it into the stepper motor. Initially, I would leave the heater cartridge, hot-end clip/fan and thermocouple out of the heater block until after its secured in to make things easier. Don't over-tighten the screws holding the extruder to the frame and stepper motor. Turn the exposed gear on the stepper motor manually to check how tight it is, it should turn without being super tight. Also check that the gears are turning properly to begin with without catching on anything or any random clicking. When turning the gears, you should be able to feel the individual steps in the stepper motor without any other mechanical feel. If things seem overly tight, try moving the hob gear on the stepper motor in slightly.

Make sure the hotend fan is orientated to blow into the hot-end, and if using the optional 30mm exit fan that is also blowing out of the frame. All the airflow should be going from left->right.

Attach the heater cartridge, stepper motor cable, hot-end fan, blower fan (and possibly optional 30mm fan), and thermocouple ends to the Qidi extruder PCB, and attack the PCB to the top frame.

Insert the thermocouple and heater cartridge into the heater block and tighten down. Mount the blower fan and secure with a screw. Try to organize the cables so they are out of the way to allow the hotend fans to push air through the carriage, put a silicone sock over the heater block if desired and attach top frame to carriage. Insert the ribbon cable into the PCB and loop the cable between the strain relief pillars.

Attach the fan duct to the bottom of the carriage if you are going to print with a blower fan. For hot materials that don't require it, you can leave it off.

Load one of the new firmware files (which one depends on what degree stepper motor you have) onto a usb drive and print it. It commits instantly and you don’t need to reboot the printer. Re-home the printer now to get the carriage in the home position. Check the manual jogs to make sure everything is moving in the right direction, and without filament loaded, jog the extruder to make sure the gears are turning the right way. If you printed the firmware file, they should work properly. If you want to check x/y position in relation to the bed, you can use Qidi Control Panel or Octoprint or another terminal sort of program, or manually jog the carriage to x0 y0 position and see if the nozzle is where it should be. You can adjust the firmware x/y max stroke if it’s off a little bit with the following commands:

;X-Plus max stroke
M8024 I270;X Maximum stroke
M8025 I200;Y Maximum stroke

;X-max max stroke
M8024 I300;X Maximum stroke
M8025 I250;Y Maximum stroke

If you create a blank notepad file with a .gcode extension and then print it, you can change individual firmware settings. For example, if you wanted the change the X-Max's max X stroke to 302 and Y to 252, you could put this in a file and print it:

M8024 I302;X Maximum stroke
M8025 I252;Y Maximum stroke
M8500

Bed leveling. If you try to level the bed at this point the nozzle is going to jam into it because it’s lower. Take off the bottom fan duct piece and loosen the top frame from the middle carriage so it’s sitting loose so when the bed raises to level it just gently pushes it up. Then do a quick level to get the overall z-height down. I’d also screw in your 3 bed leveling knobs pretty tight to maximize your Z-axis since this nozzle is lower. I screwed mine all the way in, then backed them out 1 full turn. Then did a full level and everything was fine and I could print the entire Z-axis.

The cooling of this mod, especially with the 35mm fan installed is massive compared to the old one, and if you upgrade to a 50w heater cartridge (recommended) over the 40w, you will want to do a PID tune to re-calibrate your heating. If you don't your temps will bounce more than you will probably like, maybe between 5-10C. Once a PID tune is ran and committed to firmware, it will be +/- 1C. You will need to be hooked up to Ocotprint and use it's terminal to PID tune, then run the command:

M303 E0 S230 C5

That will heat up the heater block 5 times, measure the drift and then output the new PID values in the Octoprint terminal window, which you can then commit to the printer. The default PID values for X-Plus/X-Max are:

M301 P18.0000 I1.0800 D98.0000;Temperature PID parameters

I will upload a file that you can print with my PID values that I use with the Dragon hotend, 50w heater cartridge and 35mm GDSTime fan. Some fans are also much better than others. For instance, the 30mm fans Trianglelab ships with the V6 hotend push out less than 2 CFM. The 35mm GDSTime fans I will link below push out over 3X that amount of air. I was not able to find CFM specs on Winsinn 35mm fans, but in direct testing head to head with the GDSTime fans, they were significantly weaker. So if you use the exact same hotend, fan and a 50w heater cartridge as I do, your PID values will be close, but I still recommend doing a PID tune yourself, especially if you see hotend temp drift.

Materials needed:

Right non-mirrored BMG extruder or clone. I highly recommend Trianglelab brand, they make very high quality parts, even their nozzles are great. You just have to wait on a slow boat from China. Make sure you don’t buy the mirror version or it won’t fit right, they also call the mirror one left on some sites.

https://www.aliexpress.com/item/32917029058.html?spm=2114.12010612.8148356.2.27bc55b4JUwCLN

E3D V6 24v hotend or clone (can use PTFE or all metal heat break). I recommend using a lined heat break initially and then move to all-metal if needed or desired. All-metal throats have more issues especially with PLA if you are inexperienced with them. I bought the 1.75 24V PTFE lined version, and a bunch of extra lined and all-metal heat break throats. The Bi-metal heat break is the best, followed by titanium, followed by their standard stainless version. You can use the heater cartridge in this kit or upgrade to a 50w, but you cannot use the thermistor, you need a thermocouple, which I will link below.

https://www.aliexpress.com/item/32844028127.html?spm=2114.12010612.8148356.2.7ddd2686zxa5St

If you decide to go with the Dragon hotend instead of the V6, you will need this (either standard or high-flow).

https://www.aliexpress.com/item/4000404170721.html?spm=2114.12057483.0.0.49a35780aoPYrA

Nema 17 34mm max length stepper motor. You can use the OG Qidi one, which is 1.8 degrees. I am currently using a .9 degree angle stepper motor from Trianglelab. Pretty much any Nema 17 34mm stepper motor would work, just check your degrees for the e-steps. You may also need to switch some wires for the motor to turn in the right direction. Some are wired backwards than others, it's easy to check, if you plug it in and when hitting the feed filament button, it spins backwards, then your wires are wrong. Otherwise, you could also change the motor direction in the firmware.

https://www.aliexpress.com/item/32870078897.html?spm=2114.12010615.8148356.5.699e5b75R0TaXa

Extruder PCB Board. You can either use one you have or buy a new one from Qidi on ebay.

https://www.ebay.com/itm/An-extruder-adapter-board-for-QIDI-TECH-X-Plus-X-Max-3D-Printer/333296511767?hash=item4d9a052b17:g:oysAAOSwwRVdU6eC

24v 40 or 50 watt heater cartridge. I went with these, just make sure they are 24v. You can use your OG Qidi one if you want also as long as the cable reaches.

https://www.aliexpress.com/item/32960167491.html?spm=a2g0s.9042311.0.0.4b274c4dCf8xbB

3mm thermocouple. I’d get a high quality one like these, especially if upgrading to a 50 watt heater cartridge.

https://www.aliexpress.com/item/4000832125465.html?spm=2114.12010615.8148356.1.5beb1788eYtHcY

https://www.aliexpress.com/item/32835036293.html?spm=a2g0s.9042311.0.0.4b274c4dCf8xbB
(3x15 version)

5015 24v blower fan. Pretty much any 5015 blower fan will work as long as it’s 24v.

https://www.aliexpress.com/item/4000011565156.html?spm=2114.12010615.8148356.2.13024b97MJ8K7y

A variety of M3 socket head screws.

https://www.amazon.com/gp/product/B07VRC5RJ8/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B072F5WF4T/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

M3 threaded inserts: These can be a pain to find sometimes, the ones I used are Inteq 3mm M3-0.5 Brass Threaded Metal Heat Set Screw Inserts with an overall length of 3.85mm, top outer diameter of 5.6mm and bottom outer diameter of 5.12mm. The holes they go in in the prints are tapered exactly for these inserts. I will link the last place I bought them, but if they are out of stock there, just check the specs I listed to find the right ones.

https://www.ebay.com/itm/Qty-50-M3-3mm-M3-0-5-Brass-Threaded-Metal-Heat-Set-Screw-Inserts-for-3D-Printing/292174792941?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Also, I HIGHLY recommend a JST crimper and some JST-XHP connectors. You’ll need to cut the ends off of the thermocouples and every blower fan I’ve ever bought has been wired backwards. This will also let you cut down your hot-end/thermocouple/blower fans to short lengths and put proper ends on them. If you stick a very small flat head screwdriver into your current connectors, you can push down the locking pin, then pull them out, lift the pin back up and re-insert to swap, but it doesn’t help with shortening. You will also need to put a 3-pin end on the optional 30mm fan if you want to plug it into the empty PCB spot, or maybe you want to splice the extruder/optional fan together into one plug, or make a Y-cable.

https://www.amazon.com/gp/product/B00YGLKBSK/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B0774TF39N/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

As a side note, if for some reason you would need a new stepper motor cable, or it’s wired wrong, you’ll need these smaller connectors. If you just pull out the pins in whatever stepper motor cable you have and re-organize them if wrong, that will work, but if you need to make a complete new cable, you will need this kit for the stepper motor end plug.

https://www.amazon.com/WAM-Direct-Connector-Housing-Terminal/dp/B07DCL9J8K/ref=sr_1_5?keywords=jst+ph+6&qid=1574472640&s=electronics&sr=1-5

I recommend these GDSTime 35mm fans if you are going that route over the stock 30mm extruder fan:

https://www.aliexpress.com/item/32806688975.html

I haven't been able to find any V6/Dragon hotend 35mm fan shrouds. I can't even find a purchasable 30mm Dragon fan shroud that fits properly, the V6 one is too big. I've had to 3D print 30/35mm Dragon fan shrouds and 35mm V6 shrouds, here are links where you can download STLs to print them yourself:

30mm Dragon Hotend Fan Shroud:

https://www.thingiverse.com/thing:4186451

35mm Dragon Hotend Fan Shroud:

https://www.thingiverse.com/thing:4510126

35mm V6 Hotend Fan Shroud:

https://www.thingiverse.com/thing:4510136

I’d also recommend having some Bowden tubing on hand, and if you are doing an order from Aliexpress from Trianglelab, order some extra nozzles, heatbreaks, heater blocks, silicone socks, maybe an additional extruder gear set, etc. It takes about 3 weeks usually for me to get stuff from China (pre-COVID), so I like to have extra parts on hand. I'd also recommend printing in polycarbonate carbon fiber for strength/temp resistance.

Step files have also been provided for people to make their own modifications. Qidi changes model designs from time to time, so tweaks may be needed for machines I don't personally own, the step files will allow you to do this.