After having designed and built Delta printers, the next step was CoreXY.
When you buy the machine
You have to make adaptations and improvement to this printer. It will take you a lot less time to make the modifications at the building phase, and so you have to buy some stuff, So I created a page referencing stuff you shall buy, modification pages, which often propose printed parts. You probably have to wait a few weeks to get your machine, so as you shall already own a printer to buy this one, you can print stuff. For miscellaneous reasons, one of the mains being that I want to enclose the machine, I prefer doing structural stuff in aluminium (only with hand tools) than print part, but you may have another opinion. One possible solution is to use PLA specialised for heat treatment, which is actually the best plastic you can print in term of stiffness and heat resistance, but you have to add a heat treatment phase to your process (in a domestic oven)
No paper manual, just a pdf file, that I printed because I find using a tablet for assembly very unpractical.
Then, questionable design points
The fan box (cannot realistically be called ‘duct’) not only have no ducting or air flow guiding to the hotend heatsink, but in addition, send a big chunk of the air flow directly to the hotend block and the bed. This have two effects:
This fan support weight 77 g, add 9 g for the two fan grids, which is insane. This support have no structural purpose and weight many times the hotend and even more than the carriage plate (which is quite heavy).
The X carriage is in steel (2mm thickness), so it is quite heavy. I replaced it by an aluminium plate of 3mm thickness, reducing its weight by half (so ~38 g gain)
There is a lot of travel lost. when the Y carriage is stopped at the bed side, there is still 40mm remaining between the fan box (which is quite bulky and could be reduced with good design) and the frame. On the X carriage, if the twin wheels were placed on the bottom instead of the top (with the added benefit of better stability), it will give approximately 40mm more travel on each side, so 80mm total.
If the wheels were replaced by ‘Mini’ openbuilds wheel (as is done on deltas or other CoreXY printer like the D-Bot), you can still add some travel. So, a good design may allow to reduce the width of this printer by 100mm and its depth by 40mm, which is quite something. That will be lower cost, stiffen frame and will use a lot less space.
The screw lead is 8mm, so the motion is reversible, which means that when you push the bed, it moves. The problem is that this is a two motors bed, so when it moves, this is never the same amount and the bed is tilted. A unique driver control the two Z steppers, so there is no possibility to adjust each side with another Z switch.
The game is to not push the bed when you remove the part, It is not easy and not quite funny, so you end up having to adjust the bed for almost each print. Using a 2mm lead screw should have costed exactly the same. Sure it makes the Z move quite slow, but adjusting the bed at every print is not nice and you rarely move the entire height.
As explained in first paragraph, when you install the Z shaft, you have to add washers to compensate the space between the top of the rods and the rail beam. A washer is 1mm thick, so the adjustment is not very precise, and you will end up at best, with a bending of 0.5mm, which is a lot when you depose your first layer. If your beam is bent to the bottom of 0.5mm, this is equivalent to a bed bulge of same value. Remember that this machine does not have a sensor for bed height and no automatic calibration. To aggravate the problem,if you tight firmly the rods at the bottom (you shall as this is structural), the rods bury themselves in the profile slot. I did not noticed first and I ended to bend the rail beam by more than 5mm, hopefully it seems to have recovered its original shape. The final space was around 8mm, so I had to add many washers and change the top screws for longer. There was a benefit, anyway, having many washers, I was able to play with different washer thicknesses to make a better adjustment than possible with the original design (3 washers max). This is a bad design and the rods should have been attached by supports screwed sideways to the profile. It shall be noted that such twin lead don’t need 4 rods, only two rods of larger diameters (12mm) installed just aside the screw and properly installed with rod supports. This shall not be more costly than the actual setup and be better. You can find this Z setup by example on Eusthatios, Herculien or other printers. It shall be noted that in term of stiffness, the actual setup is quite stiff and sufficient. When you push the bed on one side, it lower easily rotating both screw without visible tilting (but too much to print properly anyway).
Depending the bed you received, the bed power is 80 to 100W, which is way insufficient to heat up a bed of 33×33cm (~0.085 W/cm2). At best, you can increase the temperature from ambiant by 30°C for some, only by 25°C for others. This needs time and patience and allow you to only print PLA. It is quite marginal to print PETG (while I succeeded to do with caution and slow speed) and it is unthinkable to print ABS. But honestly, I think printing ABS without a filtered enclosure is unreasonable, the odour is unbearable. In addition to its low power, there is no bottom insulation on the bed.
The power supply is 360W, so you can at maximum use 300W, take into account 70 to 80W for the steppers and heater (40W), approximately 220W was available for the bed, which is still a fairly low value (that makes a power density of 0.2W/cm2, while a rule of thumb estimate requirement to 0.37W/cm2 and a comfortable power - fast heating - at 0.5W/cm2), but more usable. however, this is a 12V machine, and the board used is not 24V capable, 220W makes 220/12 = 18.33 A . Board Mosfet did not accept more than 10A, and you shall have an external MOSFET board to handle that, with a safety added benefit, as the onboard MOSFET frequently cause problems.
The vertical position of the screen needs you to be kneeled on ground or be crouched to operate it. It became quickly very boring.
This screen should have been reclined to be usable or installed on the top beam. Installing it on the top needs to raise hands, which may be tiring, but much more practical. In addition, a position on top will shorten significantly the wires and reduce the huge bulk of the wire harness. A nice solution can be the control board near the top for good wiring and a reclined screen on the bottom but the board/LCD screen cables are rather large.
The belts supplied are in shiny material not in rubber and are reinforced with steel chords. This makes them very stiff, which is good for quality printing, but they have difficulties to run over idlers and especially over the motor pulleys (20 teeth). In principle, steel armed belts shall run on pulleys with a minimum of 36 to 40 teeth. People who have experienced this kind of belts tell that when running on too low diameter, the belts tend to disintegrate over time and loosing wires. Using 40 teeth pulley is doable on this board but may need a bit more powerful steppers, which may be 0.9° (400 steps/rotation) to maintain precision.
The frame is not bad in itself, bolting the aluminium profile is a good and strong solution, but a CoreXY do impulse its loads on the top of the frame, which is very demanding for a printer of that size. So the frame tend to vibrate at high speed and acceleration. Rippling remains moderate, but reinforcing the structure, especially in the YZ plane may improve the situation.
Interesting design points
The Z motors are installed in an unusual way, bolted to their bottom on a quite flexible plate. This have an interesting effect, the flexibility creates sort of a ‘virtual articulation’ at the motor bottom, while maintaining its torque stiffness. Combined with the flexible coupler, that reduced significantly the side loads which may be introduced by the Z screw and limit significantly the Z wobbling. Some people displeased by this weak installation have designed and installed reinforced ones, but this is a wrong idea.
My SD card reader lock stopped working after 10 uses,so the reader became unusable. I should have added an extension micro-SD to SD extension from day one, but I did not had one at hand. I will try to glue an extension to repair it.
There is no eccentric on the wheels, so it is quite difficult to adjust them and even if well adjusted, they will became loose with time. The 4 wheels on the Y carriage aggravates the situation. 3 wheels will be better and lighter and if we want to improve rotational stability on X axis, we have room to increase the space (in Y) between the twin wheels of Y carriage.
The plates are in laser cut acrylic. They are too thin and flex a lot, this apply especially to the Y carriage and motor plates. Some retainer shall be installed on the motors because the belt tightening makes them to bend significantly. In addition, the belt is armed with steel wires, which is good for precision, but need quite high tension. It already exist on the market stepper metallic bracket, so it won’t be really more costly to use an appropriate material.
Acrylic is not a bad plastic in itself, but when laser cut, the thermal impact creates micro-cracks, so acrylic parts submitted to high loads (which is the case here) always end up cracking. Acrylic is used because it is the easiest plastic to laser cut but is is known since years to fail at short or medium term.
The wheels are installed cantilevered on plastic spacers, which make them quite flexible in bending. A lot of users are replacing the plastic spacers with washers, which is much better but weights a bit more. Standard installation are aluminium spacer. Though, it may be acceptable to use plastic spacers when wheels are between two plates.
TronXY had already been firmly criticized for the wheels installations on their other printers, some reviewers even telling that makes these printers unusable, but it seems this company do not listen very well.
All electronic is nearly fully exposed and only protected on its sides by acrylic cut plates. This is not very durable and , as already underlined, is dangerous in case of an electronic fire.
This gives an unfinished look to the printer.
Extruder is a traditional MK8 in aluminium, with a gear 10mm diameter and a 40mm stepper. Direct drive extruders are simple and economic, but they need high torque steppers, especially because here we have a gear of 10mm (hobbed bolts have a diameter of ~7.5 mm). The long Bowden (80cm) add loss and increase the force needed from an extruder. This extruder is really weak and will face troubles as soon as there will be difficulties with the nozzle. Hopefully, the hotend is PTFE lined and may requires less pressure than an all metal one. This seriously limit the flow-rate you can have and the possibility to use thick layers to reduce printing time.
What appeal people for a static frame as the one of a CoreXY is the easyness of enclosure.
However, on the X5S, the Z motion system protrudes from the frame and so do the wheels. It should have been quite easy and at least equally stiff to install the vertical beams on the sides of the Y rails, instead of below, and combined with ‘mini’ wheels, you could have bolted directly a panel on the frame enclosing all the motion system.
Yet, you have to add beam spacers on the sides to bolt side panels. This is a missed opportunity (added to the fact that the Z-motion between the beams is a wrong design as underlined above).
Improvable software configuration
The Marlin version used is hopefully recent and have activated thermal runaway safety.
Practically, I found that on this printer, the couplers are easily accessed and when you print your first layer, you can adjust the height by manually rotating the couplers and so, makes manually the ‘baby-stepping’. The steps jump are well noticeable and that is easy to do. 1 step is 8/200 = 0.04 mm, so the adjustment can be relatively precise.
One of the expected quality of a CoreXY is light mobile mass, so possible high acceleration. High acceleration have two benefits:
The default acceleration are set at 1000, which is a value for heavy Cartesian directly driven extruders. Tested values (again, for my modified printer) were the best around 3000 for X and 2500 for Y. This can be modified by setting your own G-code start-up sequence in your slicer or modifing the configuration default if you are connected with USB (I am not, my computer being remote). Please find my G-code at start-up for the X5S using slicer Slic3R (I Ignore if other slicers use variables like the first layer temperature here). However, these larger acceleration, aside making a bit more noise, are quite demanding for the machine structure, which is a bit weak due to its large size and lack of reinforcement brackets. Adding reinforcement or cross-bracing (especially on the Y planes) will help.
Note: The Marlin file configuration could be found in the files supplied by GearBest for this printer. You shall have an account to access these files. You can find a copy of the files I get at the end of November 2017
Note 2: Marlin is using the very last resources of the poor 8 bit processors of this kind of boards and often exceed available memory or computing power, notably when you are using LCD which consumes resources, so it is possible that some options were not activated for lack of processor resources. I am new to Marlin and cannot confirms such details.
The good stuff
Is it a good design
Globally the design is sound but is undermined by abusive cost-saving, poot quality control and absence of tests. Also, the printer shall be much smaller than it is for its usable space.
Was it easy to assemble
Yes, aside the time required by my modifications, while relatively long, this was easy and pleasant to assemble. Cables look messy, but are supplied with the appropriate length and use locked connectors with mechanical coding (and not the infamous and unreliable ‘Dupont’ connectors). There was some spare for screws and other fittings. Some precisions are lacking in the manual, notably for the belt installation.
Does it print well
At least for my modified version, it does print quite well PLA, when you have found a good configuration and modified the default values. One of the reasons is the use of steel core belts, which makes them quite stiff and compensate for the large size of the printer. However, others materials are out of reach with the given configuration.
Is it easy to operate
Yes, aside the quirky behaviour of the knob, it is relatively easy to operate from the LCD screen and SD card (I have not configured supplied computer software because my printers are yet quite far from my computer and are supposed to be accessed by Ethernet or Wi-Fi). There is a curiosity in the operation, the rotating knob is moving ‘the wrong direction’ for parameters adjustment.
The cable chains
Once the Z chain anchor point position is corrected, these chains are neat and work well. The links are not openable, so adding a new cable will not be very easy. I removed 2 links on the X/Y chain (cutting them, as my wiring was already done).
What about the bed
The bed is in aluminium, with a fibreglass plate on top of it and what looks to be a ‘BuildTak’ surface clone. I haven’t glued the surface because I have bad experiences of the BuildTak that are consumables. For a printer that size, changing frequently such surface will be painful (they are not easy to unglue) and costly. So I used hair spray on the fiber plate, with success with PLA. The adhesion of PETG was a bit marginal though, because of the too low temperature. I know from experience that PETG do adhere well on ‘Buildtak’ without heated bed, so using the surface supplied could be a solution for PETG. If sticking to the original Bed heater, bottom insulation is not an option. What I also use for small printed parts is I add a shield atop the bed on areas which are not accessed for the given printing job to have slightly faster heating.
A quick comparison with the Ender-4
Creality sells the printer Ender-4, telling it is a CoreXY, but of a much smaller size than the TronXY X5S. Creality having get a reputation since the huge success of the CR-10, a quick comparison is interesting.
So, the quality of the Ender-4 appear to be better than the X5S, but is not very good either and is far from what is proposed on the CR-10, especially regarding the safety of electronic and wiring.
As all Chinese printers, this one need many adaptations to be safe, reliable and durable. A CoreXY can potentially be a faster machine than other designs, so it is appealing for experienced users which thinks that the X5S can be the base for a good machine. My initial intent was indeed to makes improvements to get a better machine. But at the end, it will need so many modifications that I finally decided to use this machine as a test bed and sell it, to finally design and build the machine I want, using the experience I had with it (and with my former designs).
It shall be noted that while electronic and wiring in Chinese printer is known to cause fires, there is at least a positive in this new generation of machine, which is the hotend support in metal, which cannot melt in case of hotend fan failure. This is a vast improvement against printed hotend supports. Also, the use of locked connectors is safer than the infamous ‘dupont’ connectors we were using just a few years ago.