You can not use the mega power port. The green plug has to be powered. I have more details at the bottom of the assembly page.
Ah ha! So I’ll snip and clip to adapter into there then. What does the cross over do?
It powers the mosfet for the heated bed. You don’t need it, but it’s easy enough to connect it.
I think the history is that you could get use a power supply with two 12V supplies so you could balance the load.
Really appreciate the help.
Looking at the different ways to wire the board. I wont be using end stops, so is is better overall to wire the steppers in series or individually? It makes a little sense to wire them in series so that you get consistent travel on the axis, but I don’t know the pros/cons. If they were individual, would they each need to be calibrated separately? I read a little but I’m sure there’s more.
Does series just use the three drivers then, and I wont use all 5? I guess that would free me up to add a 4th axis someday…
There are pros and cons to each. What is the firware you have set up for (or are you planning on flashing yourself)?
Either way will work, so don’t stress too much about it.
The steppers will move in lock step in either configuration.
I would say if you like wiring, do the series. If you like flashing software, choose separate drivers. You can also switch later. I’ll probably answer a lot of your questions that way. 
Getting the wiring cleaned up but hit a snag… grrr
Last night I plugged the ramps USB into my laptop and looked like I fried it all. The laptop and the ramps power supply were both plugged into the same outlet, and maybe the USB completed a circuit or something? I was really worried I broke my laptop, wouldn’t turn on, or charge, or make any sign of life. After opening it up, I unplugged all the internal batteries and ram and everything I could grab, and after putting it all back together it fired right up. I think its probably the power supply to the Ramps, but could also be the mega. After work today I’ll take another look and see what I did wrong.
Has anyone else ever experience this? Seems like I shorted the USB port, but I didn’t think that would be possible on my new thinkpad T570. Thankfully its working now, but really stressed out to know you can lose it all so quick.
Ill try to get it all fixed up and hooked up right tonight. I really want to carve up some sweet files I’ve found.
Making a ground loop can sometimes cause noise, but it wouldn’t take down your computer. The other sides (120VAC, 12VDC, Laptop DC, USB 5VDC) Are all isolated enough to not make any difference. So I dont think it’s any loop issue, but you can try it again with just the battery. If it works though, it could have been something else and then you’d have this suoerstition for the rest of the time
I would just look everything over again carefully and make sure all your power is going in the right place. If you have a multimeter, then check the voltage at a few key places. Like 5V on the USB and 12V on the green jack. And the two grounds should be the same.
Well looks like it was the Mega that fried. Replaced that with a spare I had and reloaded Marlin. Got the whole thing running just fine now. cut a calibration cube and now going to plan on my first real cut with it.
I’m always going to be suspicious now of that usb. Everything seems to be set right, and all the voltages seem to be where they should be. I guess ill keep everything as insulated from each other as possible and keep an eye out.
On a technical note, a couple questions:
The only way I found to zero the machine in Repetier Host was to use
G92 X0 Y0 Z0@isathome
Otherwise turning it off and on does that. Is there better way that you can think of?
Also, my steppers don’t engage when the machine is first turned on, they don’t lockup until they are used the first time. Is this normal? Trying to keep this thing calibrated is going to be tough. One side drops under its own weight when not locked down. Is there a way to lock upon startup, a command or setting?
That Is how I do it.
Yes, that is normal. What is the difference of locking on boot and just locking when you hit start on your Gcode? I believe I have my use in the instructions. Start it against the Y blocks (this is square), all The way down (this is level Z), power it on, use the controls to lift it above the material, drive to the start spot in Y, move X by hand to the start spot, drive Z to the surface and hit go. The first line of G code is G92 x0 y0 z0. Faster than the dual endstop offsetting on the Mpcnc.
G92 is a good way to do it. The @isathome isn’t for Marlin, it’s consumed by repetier host.
I thought Ryan’s low rider Marlin configuration included the magic config for keeping the motors on all the time.
I don’t use Marlin (I have been meaning to switch, but just haven’t found time). I always pull the machine up against some brackets I have to square it up as I power it on. I also twist the Z axis screws a little, just so the couplers don’t have any tension on them when I start it up. Then I always move it using controls, and I do the equivalent of the G92 to reset zero (again, I’m not using Marlin, so it’s a different command on my firmware). Out of an excess of paranoia, I also always start it with the carriage all the way to the same side. I’ve been able to recover from a job by powering off, pushing everything back to start, and then navigating exactly the same amount before doing another G92. It’s not really part of the “prescribed” method, but it did save a little plywood.
Another alternative is just to use a tape measure to make sure each side is close. Since the gantry is 5’ long, a few fractions of a mm is plenty square enough. Just make sure whatever you’re measuring from is also square to the direction of the wheels. For me, the table is the reference, so I always measure from the front edge of the table, and the wheels are forced to travel along it’s edge.
Both Z sides should fall when you disconnect power (and that’s why it’s so important to have Marlin configured to leave them on). If they aren’t then there might be something sticking that shouldn’t.
That sucks. Trust is pretty valuable, really. For some reason, I thought you had a rambo. The import megas have a crappy 5V regulator, and if that gets toasted, it can do funny things. I’m guessing your laptop was (successfully) protecting itself, so that’s good.
There are probably USB isolation cables that don’t connect the 5V. Might be worth looking into.
For 6 minutes after the gcode ends.
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Ah. Mine are on when I start the machine (and they stay on). I like that, although I’m sure I’ve never waited 6 minutes after a move.
Thanks, that all really helps. Stumbling through the dark but I see the light ahead.
Programmed tonight’s cut on lunch, going to take the plunge after work later. I found a cool whale lamp that I was able to fit onto 3 2x4 sheets of ply.
Thank you SO MUCH to this community, I am so insanely excited to get this going.
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That looks great. I hope you post pics, and ask for help if you get any problems. That looks like a fun project.
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Maybe we can scale it up and make it into a lounger!
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Rolling smooth from here. Did two 2 hour long cuts last night and they were both perfect. At one point I got my x axis unplugged but quick acting saved me from anything ruining it all and I was able to restart it just fine.
I definitely need to set up my dust and vacuum set up. standing there with the vac really got old after a while.
This is a really solid design. I’m so impressed with the quality so far, all of the cuts are consistent and there’s no movement or skew to the cuts at all. It’s very easy to use so far. Looking forward to making some 3d signs maybe soon. I think the belts are just tight enough, and i figure as long as i keep an eye of them, it shouldn’t change much if at all.
Going to cut a new 611 plate with the dust port. Using the version on thingiverse, hopefully that does what I need, seems like it will. I have read the concerns about suction though, so I might make a few tweaks.
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If you add some channels between the dust port and the 611 circle, that would fix the suction. I’ve been meaning to do that to my plate.
Just 2-3 1/2" wide channels, doesn’t even have to be very deep.
I can’t wait to see it done. the cuts look interesting already. Glad to hear it is all going well and making sense.
Well, I have a couple projects under my belt with this model, time to upgrade to the V2. Ill be cutting out the sides and the new 611 plate tonight, and start the printing maybe on lunch. I have plenty of black filament, but wish I had a more interesting color.
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