My first MPCNC

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This topic contains 31 replies, has 7 voices, and was last updated by  Matthew Kress 2 weeks, 6 days ago.

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  • #42057

    Matthew Kress
    Participant

    So I got my tortion box table done for my mpcnc. It is 4′ by 3′. I am going to build some drawers for the base later. It is made of cheap 3/4 particle board with the ribs 3″ thick all pocket screwed together. It is HEAVY. Using my starett straight edge in the center(24″) I can’t get my 1.5/1000″ feeler guage under it 🙂 Gonna get on putting it together now! Everythings already printed.

    IMG_1260

    IMG_1261

    #42062

    Ryan
    Keymaster

    So much nicer than my tables…

    #42067

    Matthew Kress
    Participant

    For those who have used wire loom for cable management I am using 24/4 wire for my extentions, should I get the 1/4 inch or 3/8? I saw it recommended on the forums here over a cable chain and I have never used the PET stuff before. I was looking at this https://www.amazon.com/Wang-Data-Black-Braided-Cable-Sleeve/dp/B01M3SG5P7 

    #42086

    Ryan
    Keymaster

    I sell 3/8″ in the shop, It will expand up really far. As is I think it would fit 2 of those wires and not look like a Python that swallowed a small goat.

    1 user thanked author for this post.
    #42091

    David Walling
    Participant

    That looks really nice!

    I built a torsion box for mine too. They definitely make the machines real heavy really fast. I’m hoping to get a stand built for mine this weekend. I was just leaving mine sit on an old table saw when I first set it up. I sold the table saw, so now it’s just sitting on some saw horses.

    My wife is getting tired of helping me lift it, so I need to get it back on wheels 🙂

    #42101

    Matthew Kress
    Participant

    Oh yeah, my top is about a sheet and a half of particle board. With the machine on top it would be a beast to move.

    #42126

    Barry
    Participant
    Oh yeah, my top is about a sheet and a half of particle board. With the machine on top it would be a beast to move.

    Heh, you should try moving a 5 foot by 9 foot torsion box!

    #42141

    Matthew Kress
    Participant
    Heh, you should try moving a 5 foot by 9 foot torsion box!

    Ugg, I think I got a hernia just thinking about it.

    In other news just so I can complain I finished up wiring my mpcnc (took forever, I now hate crimping dupont connectors!) I coudn’t get any steppers to work. Hmmmm….perhaps I should have check which coil wires were pairs. I stupidly just assumed that the side by side ones were pairs on the stepper motor. NOPE! Not so. Here I go undertaking a rewiring. (I should have just bought the wiring from the store, but I already had a crimper and connectors, how hard could it be…. oh, series, I can do that….. I HATE YOU WIRING!!!)

    #42146

    Jeffeb3
    Participant

    You can rewire the DuPont’s without crimping on new ends. I’ve found that the wire makes a big difference.

    Maybe we can share some tips. My process is this:
    – I cut and strip the wire.
    – I hold the connector in some pliers and place the wire in it.
    – I use the pliers to close the connector enough to get it to stay, but not completely clamped down
    – I carefully put the in the crimpers.
    – CRIMP
    – I use the pliers to close the insulation crimp a little more because it never closes it enough to go into the plastic part.

    Is that what you do?

    #42149

    Barry
    Participant

    I wedge the connector into the crimper, then stick the wire in.

    #42150

    Matthew Kress
    Participant
    – I cut and strip the wire. – I hold the connector in some pliers and place the wire in it. – I use the pliers to close the connector enough to get it to stay, but not completely clamped down – I carefully put the in the crimpers. – CRIMP – I use the pliers to close the insulation crimp a little more because it never closes it enough to go into the plastic part.

    Yep that is pretty much exactly what I have to do.  I see why I have seen people using the cat5 cables in their build. Those seem so simple (although I do remember getting super frustrated at those years ago when I crimped my first one, so perhaps it is a skill thing)

    Sad to say it looks like I burned out my arduino mega. I disconnected everything from my ramps board, and then hooked up just the z axis so I could test it out. It still wasn’t moving which I thought was weird so I plugged in my laptop to the arduino while the ramps was plugged into 12 volts. The usb in my laptop went out and my computer said that there was a power surge on the USB and it was trying to draw to much power.

    That seemed weird to me so then to the ramps I took out the jumpsers from the 11 amp to the 5 amp side and only plugged it into the 5 amp side, and then reflashed the arduino with the latest t8 firmware that doesn’t have the extruder and heated bed. Then I went back outside and tried it again, only off the 12 volt and still couldn’t get the z axis to move. I again plugged in my laptop to the arduino and I got the same USB message, and then it started smoking so I quickly unplugged it. Now when I plug in the ramps to 12 volt the screen slowly pulses dim and bright. I tired another ramps board and it does the same thing. This makes me think it isn’t the ramps and is the arduino. I just ordered another one off amazon. Two days is tooooo long.

    This is all my own electronics that I already had, I didn’t buy any from the store.

    #42152

    David Walling
    Participant
    You can rewire the DuPont’s without crimping on new ends. I’ve found that the wire makes a big difference. Maybe we can share some tips. My process is this: – I cut and strip the wire. – I hold the connector in some pliers and place the wire in it. – I use the pliers to close the connector enough to get it to stay, but not completely clamped down – I carefully put the in the crimpers. – CRIMP – I use the pliers to close the insulation crimp a little more because it never closes it enough to go into the plastic part. Is that what you do?

    Close to how I do mine.

    • put connector into crimper. Close crimper just enough to hold connector
    • pick wire up
    • realize I forgot to strip wire.
    • put crimper down and connector falls out… squeeze crimper all the way to reopen the jaws
    • strip wire
    • redo step one
    • cram wire into connector
    • squeeze crimper all the way
    • go to put connector into housing and find out something didn’t crimp far enough. Use flat blade screwdriver to cram connector into housing rest of the way.
    1 user thanked author for this post.
    #42155

    Matthew Kress
    Participant
    Close to how I do mine.
    • put connector into crimper. Close crimper just enough to hold connector
    • pick wire up
    • realize I forgot to strip wire.
    • put crimper down and connector falls out… squeeze crimper all the way to reopen the jaws
    • strip wire
    • redo step one
    • cram wire into connector
    • squeeze crimper all the way
    • go to put connector into housing and find out something didn’t crimp far enough. Use flat blade screwdriver to cram connector into housing rest of the way.

    lol

    that sounds more like my experience now

    #42156

    Matthew Kress
    Participant

    Ok, I wan’t to do a sanity check with you guys that I am wiring this correctly. Here are the wires from my stepper motor. The colors are black, red, green, blue (in that order). When I use my ohm meter I get resistance between black and green, and red and blue. I assume those are the coil pairs.

    stepper

    Into the ramps board I have listed 2B 2A 1A 1B. I have plugged in Black to 2B and Green to 2A assuming that the number 2 corresponds to a coil. And then Blue to 1A and Red to 1B.

    matthewsramps

    Does this seem right? I am only doing the Z axis right now. Will deal with fixing the series wiring after I can get Z right.

     

    PS Also, here is the mechanical parts all set up. I probably should have stuck to only 1 or 2 colors 😉 But I was printing other stuff in between MPCNC part and was too lazy to change filament.

    mpcnc

     

     

     

    #42163

    Ryan
    Keymaster

    Sounds/looks right. If you wire it wrong you should not be able to fry your board. if it doesn’t move just stop and try again. Make sure to set your driver voltage before you try and move it as it is more than 2x’s to high from the factory.

    1 user thanked author for this post.
    #42164

    Jeffeb3
    Participant

    +1 for looking right.

    The coils should have some resistance, but not completely open. I like to test by just shorting the red/blue, the motor should be harder to turn if you got a coil.

    You should be able to see if your arduino has a problem without the motors though. If you have an LCD, then it should be displaying stuff. If you’re using repetier or something from a laptop, then it has some hand shaking, and it should say connected. If you send it an “M119” through the console, it should respond with the status of the endstops (even if you don’t have them enabled, AFAIK).

    1 user thanked author for this post.
    #42165

    Matthew Kress
    Participant

    Thanks, I turned the pots down to vref of .41 volts. My steppers are only .9 Amps. I was helping another guy with this steppers a while ago and we just plugged them into the drivers. When we figured out they were to high I checked on and its vref was at 2.4! They were also .9 amp steppers. Needless to say we had to replace that stepper.

    #42166

    Matthew Kress
    Participant
    The coils should have some resistance, but not completely open. I like to test by just shorting the red/blue, the motor should be harder to turn if you got a coil.

    I tried that as well as checking the ohms and jumping green to black, and then trying red to blue, both gave more resistance as I tried to turn them by hand. Thanks!

    #42336

    Matthew Kress
    Participant

    Finally got is running!!! It turned out I had a bad ramps and a bad arduino. Well, that is all sorted and I now have an extra arduino and 1 extra ramps left. I had some major issues with the wiring. Ended up that one of my crimps was bad, but it broke after I had tested that axis while I was putting the sleeving on. That took me a good 2 hours to diagnose. Anyways…here is my first test!

    I decided to “draw” something other than the crown for my first thing since I wanted something that my friends would think was cool (yeah, I am vain like that, and yeah, I’m geeky like that).

    Here is the finished table (I don’t have the spoil board properly in there yet, I am thinking of t track)

    IMG_1293

    And then last this is how I have it wired up temporarily.

    IMG_1294

    #42613

    Matthew Kress
    Participant

    So my MPCNC is pretty jittery and while I was able to use it to draw it didn’t really do that great of a job. Here is a close up of part of the picture that I printed. Each line was supposed to be drawn over itself, and you can see that I am getting a double line where the cnc slipped. Also it seems really jagged.

    FullSizeRender

    The center rails didn’t really stay square with the outer rails, so I checked the outer rails for square and it was about 5mm out of square. I decided to take it apart and reput it together as square as I could. I used a turnbuckle that I printed from thingiverse, it worked pretty good, after a couple of prints.   https://www.thingiverse.com/make:376442

    squaringup

     

    I got it now square withing 1/2 mm. Now tomorrow I am going to redo the center portion really making sure that it is square. I probably should have done this all much more carefully from the beginning.

    #42618

    Kevin Lopez
    Participant

    Maybe soon your axis can become hella square automatically. :O The power of endstops!

    #42620

    Jeffeb3
    Participant

    Just to be clear, you’re saying you ran the same gcode twice, with the same origin and the lines are supposed to be smooth?

    That doesn’t look like a square problem. Square problems draw parallelograms where there should be squares, and if it’s a Z squareness issue, that leads to cutting more than you can chew, which leads to other seemingly unrelated phenomenon.

    The jittering is probably something too loose. Poke around at things. See which bearings are touching. Check that your belts make a noise when you pluck them. Don’t over tighten anything, though. Look for dragging/binding cables. Looks for cracks that might cause some slop. And of course, are you sure your pen is attached well.

    The other common problem is skipping steps. The steppers don’t know where they are, so if you skipped steps everything after the skip would be wrong. This doesn’t look like that because they skip, then return to normal and even cross back over. The edge of the truck that doubled might be skipped steps. Skipped steps can have a few sources. Either something is binding, or the drivers aren’t configured right (Ryan configures them in the shop, and he sells the wiring harness in series, so if you bought from him, that’s unlikely).

    The last worry is that you machine is too big. You should be able to draw well, but be aware that any tugs in the center assembly will mean more give in a bigger machine like this.

    After you fix your drawings, try foam before you try something harder.

    #42621

    Matthew Kress
    Participant
    Just to be clear, you’re saying you ran the same gcode twice, with the same origin and the lines are supposed to be smooth? That doesn’t look like a square problem.  

    Sorry that want clear. I didn’t run the gcode twice it is that when the g code was generated lines at those parts of the tree were supposed to be drawn over twice, right on top of each other, and the drawing is smith. If you look at the vertical part of the pillar the two lines are pretty much on top of each other, but when the print goes horizontal it gets jagged and offset from when it gets printed the next time.

    I will go back through and check everything. I am pretty sure the pen was tight but perhaps I was drawing with the z too low which caused it to be jittery.

    When the machine was turned off and I would move it by hand it felt jumpy which is why I was thinking it was a square issue, but it does kind of look like the motor skipped steps like you mentioned. I carefully checked the vref on the steppers at right around .4 for my .9amp motors. They are not from the shop, but from my own stock. Could be I am skipping steps because my motors are underpowered.

    #42622

    Jeffeb3
    Participant

    I forgot you had different motors. Regular operations sound smooth, with the pitch changing. Skipping steps sounds like crunching or grinding. The tensions builds up, then releases, then builds up again, a few dozen times per second. Without a router going, it should be pretty obvious.

    If you skipped steps (and that was the only problem) you’d see smooth lines, with lines after the skip offset by a perfect amount. It wouldn’t be perfect if it skipped more than once…

    Even with the other smaller motors, you should be able to draw without skipping steps. I suppose if it was out of square, it could be binding more, which might make it worse. An MPCNC that size should be able to tolerate a few mm of out of square though.

    Look at the pen. Take a closer look for something loose. Listen for skipped steps, and maybe make a simpler pattern, something like a bunch of rectangles. That will help you see where it’s failing, which will help with why.

    #42623

    Ryan
    Keymaster

    There is something odd about that. Unlike anything common that happens. Looks like you  just drew on a rough surface with a loose pen.

    If that isn’t it the odd part is when only one axis is moving it looks okay, when both move you are gets staircasing.

    Power supply maybe?

    #42624

    Ryan
    Keymaster

    This might sound crazy but check to make sure your power supply is switched to the right voltage. If it is switched  to 220 and running on 120 is is super weak but puts out almost 12v. It would probably result in something like this is it ran.

    • This reply was modified 3 weeks ago by  Ryan.
    #42626

    Ryan
    Keymaster

    Hmmm, sorry for all the reply  but this is pretty different.

    Perhaps you have 6 wire steppers and didn’t get the coils right? You can run 6 wire steppers at half power and they would jump between steps, so they would always be a few steps within the right spot and would stair step pretty bad, along with being super weak.

    #42628

    BT
    Participant

    I had a similar issue when I built my MPCNC.  I ended up taking the Z-axis apart and reassembling it, making sure that I didn’t make everything too tight.  I got a little wrench happy the first time and made sure all the bolts and pieces were quite snug.  So, you can try to loosen the z-axis assembly and wiggle the parts before re-inserting the x and y conduits.

    #42718

    Matthew Kress
    Participant

    Ok so it seems to be working much better now. I double checked that I was on 110 volts (which I was, but actually when I did my anet a8 printer I ran it set to 220 volts for about 3 weeks, boy did it work nicely once I switched it)

     

    I also took apart the middle assembly and loosed all the bearings so that they spun super freely. Then I tried to put it back together carefully and square. This I couldn’t do. I can’t get the middle rods square. When I hold up my 2 foot square (same one as in the instructions) at the end of the 2 feet it is probably a quarter inch out. I tried tightening A and B and I just can’t get it square. Perhaps my prints didn’t come out right. Anyways, I decided to try putting it back together anyways. I printed the crown picture and it was a lot better, but the middle assembly was still a little jerky. Then I tightened up the belts A LOT and that seemed to help. The middle is still jerky when it moves quickly, but not bad while drawing. Here is the crown

    WIN_20170829_21_14_13_Pro
    WIN_20170829_21_14_52_Pro

    thanks for everyone’s help. Do you have any suggestions on squaring the middle up? Should I reprint it? Does the quality of the drawing look good enough? I am not sure what to be looking for.

     

    Thanks!!!

    #42723

    Ryan
    Keymaster

    Much better!

    Don’t worry about the squaring right now there is a lot to learn. you can square it before every cut, if needed, and there is a firmware/hardware solution in the works.

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