3D Printer problems - Monoprice/Wanhao D6

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ddmckee54

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I'm posting this on several forums, so for some of you this might be a repeat.

I've got a Monoprice printer that is actually a re-badged Wanhao D6. I managed to kill my printer last week, I static ZAPPED it - but that's not the only problem. As I was plugging in the SD card to load a new G-code file I felt a shock through my finger tips and the LCD screen went dark at the same time. I remember I said "Oh Fudge", or something like that because those two events occurring at the same time are NEVER a good thing. I tried cycling the power to the printer but that made no difference. I tried the turn it off for a few seconds and then turn it back on trick, still no screen. I tried turning it off for over a minute and then turning it back on but still no joy. By this time it was past my bed-time and I'd run out of the expletives that I've learned in the past 65 years, so I planned on trying it one more time in the morning before I left for work. The next morning, this was Friday, when I turned on the printer the screen came to life. I said Praise Jesus, turned off the printer, and went to work.

After I got home from work that evening I tried to actually do something with the printer and discovered that I had no cursor on the screen and apparently no way to control the printer. At this point I opened up the printer to see if I could find any part numbers to order replacements. The D6 uses two proprietary PC boards, through my research into these boards I found that they call them the control board and the motherboard. I think the control board is the one that I ZAPPED. It has the SD card hardware, the LCD hardware, and the control knob/button hardware and would have been the first in line when the static charge hit.

BUT, and it's a big BUT, I also found reference to a relay problem on the motherboard. It seems that Wanhao cloned the motherboard from another of their printers and didn't quite do their due diligence in the design. They used a relay with contacts rated for 10 amps maximum at 30VDC, this is a problem when just the heater load is 12.5 amps. Having designed industrial control systems for over 30 years, I can assure you that relay is going to fail. It's not a matter of IF it's going to fail, it's a matter of when. One of the messages the failure of this relay will generate is a Heater Error message, which I had been getting on rare occasions for several months.

So my motherboard relay was failing, along with a dead control board. I try to avoid the long shipping delays by buying from suppliers on this side of the pond - no such luck. The only place that I could find that had the control board in stock was Aliexpress. Even with UPS Expedited shipping I won't see my parts until the end of the month at the earliest.

I'm pretty sure that the only thing wrong with my motherboard is the relay. I have not been able to find a relay that meets the power requirements, both coil and contact. I'm leaning towards using a remote mounted something, either a relay or a DC rated SSR, there's plenty of room available in the base of the printer. The problem I've got is that I think the existing relay has both a NO (Normally Open) contact, and a NC (Normally Closed) contact. I'm not sure if Wanhao is using the NC to do anything. Anybody know if somebody has already gone to the work of figuring out the schematics of the motherboard? I could eventually get it figured out, but if somebody's already done it, why re-invent the wheel?

Don
 

ddmckee54

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It was static, I was the one that did the ZAPPING.

Recently I had been getting shocks when I touched the metal frame of the printer, or the water faucet for that matter, so that's how I knew it was static. I'd been trying to be sure and ground myself to the frame before I touched the SD card. But it was getting late, and I must have forgotten to ground myself before I inserted the SD card. Felt the ZAP through my fingers holding the SD card.

Maybe I need to look into investing in a grounding mat, we'll see how much one costs.

Don
 

awake

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Don, if I understand correctly you've already purchased a replacement motherboard ... but if not, or if you run into trouble with that one, you might consider changing over to the "old reliable" RAMPS 1.4 setup. It is a long way from the latest and greatest - only 8-bit, not 32-bit - but it has been running my home-built machine and thousands (hundreds of thousands?) of others, both home-built and commercial units, for a long time now. As a result, it is cheap, it is something of an industry standard, and there is tons of info on the internet on how to set it up.
 

ddmckee54

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Oh I totally agree, for most machines an 8 bit processor is quite satisfactory. I don't do any type of printing where a 32 bit processor is required.

Yes, I have purchased a replacement motherboard. I got verification from Aliexpress yesterday that they had shipped, now I just have to wait for the slow boat to get here from China. I'd like to keep the input/output setup that the original control board provides, with the LCD, the SD card slot and the control button all on the front of the printer. I haven't seen anybody else that offers this, but I haven't really been looking either. I've seen a version of Marlin on GitHub that's specifically for the Wanhao D6 printer. So maybe a RAMPS board at 24V can be made to work with Wanhao control board?

The Wanhao motherboard is, according to Wiki, based on the ATMega2560. It's primarily a 24V circuit with a few 5V pins. I had considered replacing it, but that relay is really the only issue I've got with the motherboard - other than it's replacement cost. A supplier in Texas has recommended a replacement relay that at first glance looks good - still thinking about that part. If I can fix the relay problem then I'll have two working motherboards. I should be set for a few years.

Don
 

awake

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RAMPS board working with Wanhao control board - could be. One of the common options for the RAMPS setup is a ribbon cable connection to a board with an LCD screen plus rotary controller and SD card slot - screen can be 20x4 or a larger graphical display. I don't know if that sounds anything like the Wanhao control/interface.

Only issue on running the RAMPS from 24v is that you need to separate the supply to the Arduino board - it can handle 12V just fine, but I don't think it is able to handle 24v. Basically you would need to supply a separate 5V to it.

On the RAMPS board, the heated bed is switched by a MOSFET rather than by a relay. Arguably this MOSFET is operating at the upper end of its range, but it has functioned perfectly for me. However, it is also easy to use the signal from MOSFET to switch an SSR.
 

ddmckee54

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That's the advantage of a 24V board over a 12V board, you're halving the amperage. So those MOSFET's that were at the upper end of their range are now operating at an more comfortable level, at least as long as THEY are rated for 24V.

The Wanhao control board has got the LCD drivers, the SD card slot and the rotary controller. It appears to have the same features as any other LCD with smart controller, just in a different physical layout. The Wanhao has the SD card slot rotated 90° when compared to most LCD smart controller cards. The Wanhao control board uses 2 flat ribbon cables that APPEAR to be the same as any other 3D printer using the RAMPS boards. I'm just not sure what the pinouts are, they could be a direct match. Marlin being able to tell the ATMega 2560 to drive the control board gives me hope that this would work.

But even better news..... I think I've found a drop in replacement relay that's got contacts rated at 20A. Well actually it was recommended to me by the supplier, but that's just semantics. I'm still waiting to hear back from the supplier about ordering in small quantities, and whether or not I need to sign away my first-born to get them.
 

ddmckee54

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RM-MN:

I had considered just replacing everything with a standard RAMPS setup. But in addition to having to replace/reconfigure everything if I did that, the Wanhao board is a 24V board and most combo offers like what you listed are 12V boards.

I ordered several replacement relays this morning and I should have them by next week. They'll allow me to directly replace the under-rated 10A Songle relay with a 20A relay. It'll either fix the problem, or show me the next weak link in the 24V chain on the motherboard.

If the Wanhao motherboard fails after the relay replacement, I'll probably wind up replacing the motherboard with a 24V RAMPS board. I'd like to keep the Wanhao control board, just because I like the way they've got the SD card slot, the LCD, and the control button arranged.

I'm not totally without a printer now, I've still got the older Prusa I3 clone. It is usable, it's just when compared to the Wanhao printer it's a little slower, noisier, and has a little worse surface finish.

Don
 

ddmckee54

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It's been a while, but I have actually accomplished something. I have received the replacement boards that I ordered from Aliexpress, and I received the replacement relays that I ordered from Omni-Pro Electronics. I was only going to order 3 of the relays, but the way Omni-Pro had their quantity/price-breaks arranged it only cost me $3 more to order 5 relays as opposed to the 3 that I was going to order. I've probably got a life-time supply of spare relays now - I hope. Over the weekend I installed the replacement input board and I'm happy to report that my Monoprice printer is now functional again. It's still got the original motherboard and 10A relay in it though, I wanted to see if the original motherboard also got static zapped when I fried the original input board. Since I successfully completed a 20mm cube test print I'm gonna say that the motherboard is good to go.

I will replace the 10A relay on the new motherboard that I ordered from Aliexpress, and install that motherboard in the printer. I will then replace the 10A relay on my original motherboard and turn that board over to the Storeroom for inventory. (I'm gonna stash it in the 3D printer toolbox with all the other 3D printer spare parts.)

Now that I have 2 working motherboards I think I'm going to try loading the version of Marlin onto the printer that was developed for the Wanhao D6 printer. That way if I totally dork up the download I've still got a working motherboard that I can plug in.

The original Wanhao controls never did impress me. And their main info screen leaves a LOT to be desired, like ANY usable status info on the printer. I got spoiled by Marlin on my Prusa I3 clone. The Monoprice main screen doesn't tell you JACK. No temperatures, no feed-rates, no Z location, no NUFFIN!!! They don't even give you any reliable information about where you are at in the print, just a very vague count down clock. It counts down the estimated time remaining in hours left to print completion. When the estimated time goes under an hour it counts down the minutes left, and that's about all that screen is good for. Any other information that you want you have to dig out from the various sub-menus.

Don
 

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