There is no flyback part cooling fan circuit, the fan is switched directly to ground. There is a resistor used to limit gate current from the MCU to the switching transistor, but is not part of the fan driving circuit…
Here’s the steady state information. I think the nameplate rating must be based on either worst case or more of a dynamic startup current.
I also measured the inductive kick of both fans, since there’s no clamping circuit.
I love it!! I think I might try to modify this to screw in from the side. Between the existing side plate and main body so that the wiring can run directly into the modual and eliminate the need for the tape (using longer m2 screws instead), upgrade to a all metal throat (thank you @Franky) and upgrade the heat block cooling fan. Should all be cheap upgrades with a lot of value added. After that I want to get an ac bed (30 min. To get to 100 is ridiculous!) Then this should be a pretty darn good 3d printer! Eventually I think it would be good to upgrade to a CAN controlled stepper like the ananasStepper preferably with a .9 degree step angle for increased accuracy.
Thanks for sharing!
What I find a bit disappointing: In the Kickstarter video Snapmaker brags quite a bit about improved cooling with a video shown of a modelled air flow… A bit of a downer that print cooling still needs modding.
Agreed - I think their upgraded design is fine except for they used an axial fan, and there’s bends and turns that there just isn’t enough pressure to drive air through. A radial fan may have been better.
After further thinking and discussion, it seems the part cooling fan does double duty - it also pulls cool air over the PCB and toolhead internals.
I am going to splice the internal fan into this new fan with the diode so that it also runs. I previously thought it was optional, I now think it’s required to ensure stable operation of the toolhead.
I am going to do my best to make a XH connector Y-adapter so that I can plug both fans into that, instead of having to splice cables with soldering. One of my goals is that it’s possible to revert to ‘factory’, if for some reason a warranty issue came up, or for troubleshooting purposes.
No, too much metal nearby. I think you have about 3mm of clearance, maybe. Keeping everything electrically insulated would be impossible. I could feel the wires moving and compressing slightly as I reassembled. If you’re willing to sacrifice or change out the fan, you could use a small inline Y via soldering wires directly with heat shrink, or a small crimp connector.
Also, nice print! I’ve noticed the air favors the right side a bit, I moved mine to the left a bit, and I think if I ever reprint this I may shift the air outlet about 5mm to the left. It hasn’t affected print quality or anything, so I don’t think I’ll update the model on Thingiverse.
Please let me know how the threaded holes go for you. I’ve never printed threaded holes in anything except the Z up orientation. If you have a tap set, maybe clean up the threads first with it so there’s not extra pressure that could cause the layers to split?
Yeah I don’t think it printed the threads at all, normally when I do holes like this I either make them with a nut behind, or I size them the same as the screw post and let the threads cut the plastic. It has worked well for me in the past. Still waiting on the fan but I will let you know when it gets here.
As far as shifting the vent, if others are interested in using this mod then I could cut it into pieces so that it would print easier and screw together with adjustment points to get perfect positioning. So to all of you reading, if you want that, let me know.
It’s a JST XH connector. You can buy a kit on Amazon that includes the special crimp tool required for not too much money.
They are a royal pain to crimp so I’ll give some advice I wish I found earlier: Strip 1mm of wire, then get the connector only lodged in the crimp tool by crimping it like 50% of the way, then worry about sticking the prepared wire in. If you try and hold the tool, and the connector, and the wire, you’ll never get it to work.
I’d also recommend checking the resistance of the finished connector because if you crimp it too hard it’ll sever the wires under the insulation and you may not be able to see it. Don’t overcrimp it. Once the insulation piercing pin is set, if the bare wire crimp isn’t set use needle nose pliers to finish the crimp, don’t keep crimping with the tool - then you sever wires.
Many power FETS have internal flyback diodes and don’t need external ones. I always put them anyway because I don’t want to take the chance my product dies because the internal diode was inadequate.
If you really want to be able to crimp those tiny JST pins you need one of these really nice $600 JST crimpers, makes those pins a snap to crimp other than you need good eyes to make sure to get the wire in the proper spot. Feeding the pins in via a strip is just the best. I have the correct Molex crimper for a similar sized pin and I have to place the pins in the crimper with a tweezers so needless to say, I don’t use those pins much.
Hi @Ira, those are some nice looking crimpers. The main issue with mine is the width - the short box crimps will get crushed when the piercing pin is correctly aligned - a smaller set might alleviate that.
You must be referring to the FET internal body diode. Here’s the fan circuit being used, as factory delivered:
In this case the body diode would not function as a flyback, unless the entire power supply is allowed to function as part of the discharge circuit, possibly dangerously over-voltaging other components, or at least stressing any voltage clamping diodes. I would not recommend anyone plans on using the body diode for flyback functionality on these circuits.
For anyone else interested, the addition of a flyback diode in parallel with an inductive load will allow for collapsing magnetic fields to generate current through a designated safe dischage path, here labelled ID:
Obviously They were using it that way because the FET lived, but adding one is probably not a bad idea. Having the proper crimper is really nice. I’ve got 38 or so sets of hand crimpers 6 or 8 of which are somewhat universal, 2 reel fed crimp presses and 15 or so applicators for the pins we use lots of and even with that I come across pins I have trouble getting a proper crimp on. Mostly the issue is with pins with seals, finding a generic crimper for seal crimps seems impossible.
@brent113: How well does your radial fan answer to PWM control? Is it still running when you do a M106 S128 or even a M106 S50 or so? I just replaced the tiny 25x25 mm print cooling fan with a 30x30mm fan (with a small adapter I printed), but despite being the same manufacturer/series (a XYJ24B3010H istead of the stock XYJ24B2510H), even at M106 S225 it was not rotating any more. Will not continue in this direction anyhow - despite the 30x30 having double airflow from the datasheet, it made no real difference. I suppose I’ll follow your example and put on something externally, although it looks - sorry - rather ugly…