MPCNC…My series of unfortunate events!

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This topic contains 6 replies, has 2 voices, and was last updated by Profile photo of Bashar Bashar 4 months, 4 weeks ago.

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  • #16320
    Profile photo of Bashar
    Bashar
    Participant

    Well it all started when I decided to start my MPCNC project on the 29th of July and thought I would just order the part off Ryan. Sadly the IE parts (I live in the UK) were out of stock (which were restocked the very next day!) and I was so anxious to start that I ordered a Prusa i3 printer in an impulse frenzy. Two days later the printer arrived, 17 hours in and the whole thing was assembled and ready, only to realised I needed twice that time to learn how to use it and more importantly calibrate it!

    Eventually I started printing the parts which I would have to admit came looking amazing, which only pushed me to be greedy half way through and started printing faster. The quality wasn’t affected much but I’m sure the strength was. Meanwhile I started ordering the rest of the parts, motors, electronics etc. I had few parts not printing properly with the high speed and so I went as far as putting proper glue on the surface before printing just to get it going.

    The conduit I bought (which was listed as 25mm on the website) from Screwfix looked rigid with a nice chrome finish. When I went back home and looked at them I realised it said 25mm (1″) and it was in deed 1″ not 25mm. Having no alternatives and all being 1″ around, I thought I will try it as it is and see how it works. Most parts fitted nicely, except for the corner feet and the lock corners which needed some force and sanding to fit. I had my Prusa i3 disassembled because I was using most of its parts for the MPCNC as they are similar. THE MAJOR problem was the Z motor bracket which was bent as it was warping during the printing which I didn’t notice and therefore when fitted the z motor is not parallel to the surface and doesn’t connect properly with the threaded rod. Anyway I left some leeway inside the coupler to offset for that and upped the current output from the driver to make it overcome the stiffness just enough so I can print a new z motor bracket. Anyway my build was 410mm X 600mm X 300mm, now the prints were looking awful! With most of them warping and extreme under-extrusion making it impossible to print, and the MPCNC was shaking like a bull rider. Having read through the forum I realised Ryan mentioned a great care should be taken to the z axis height, and so I cut the legs shorter down to a 150mm build. Now that made a massive difference the machine was a lot more rigid and I think tightening the belts helped a lot! Now the printer was working ok, managed to print a new z bracket which I fitted, I have to say it didn’t look great but it does the job until I calibrate the machine and can reprint it properly. The machine is way better now, I fitted a heated bed to overcome the warping, with the intention of a z probe too. Now the machine looks quite rigid, prints are alright, but I just can’t understand the reason for under-extrusion still, and I can see the extruder not extruding some lines or having discontinued lines, now I pumped the extruder multiplier which did improve it, but I still don’t understand why do I need to pump it more when it was working fine on the prusa i3?! Perhaps my Simplify3D profile needs fixing, I have been using Ryan’s Simplify3D profile which can be seen when editing the gcode for the test_IE_part. Could it be the speeds of printing? or axis movement speed? or the pumped up current to the z axis?

    Anyway I thought I would share my crazy (perhaps stupid?) experience, and yes I will be sharing images later on!
    Needless to say, Thanks you so much Ryan for a well designed project (which I think I was deliberately trying to sabotage lol).

    Cheers,
    Bash

    #16321
    Profile photo of vicious1
    vicious1
    Keymaster

    Same control board, extruder, filament, power supply, drivers, ect?

    If all that is the same check your filament path and make sure it is an easy pull, or turn up the extruder driver.

    #16323
    Profile photo of Bashar
    Bashar
    Participant

    The control board is a ramps 1.4 which came with the prusa, same mk8 extruder, the power supply that came eith the prusa ws 24v/5a so i upgraded to a 12v/30A. The filament is the same, the drivers were A4988 and i changed them to DRV8825 with the extruder’s driver having a Vref of 0.4v meaning 0.8A for the extruder motor, does it need more?. Now the filament roll im using is at its end and they get quite spirally at the end and hard to pull so i might try a new roll. Do you think i should up the extruder driver current snd to ehat current should i bring it. Thanks a lot. I might test the old A4988 and see if it makes a difference and perhaps check the current its outputing and apply it ot the DRV8825. What do you think?

    #16325
    Profile photo of vicious1
    vicious1
    Keymaster

    If it is the same as the ones I sell, start at .6V.

    #16329
    Profile photo of Bashar
    Bashar
    Participant

    I upped the voltage on the extruder motor to 0.6V, and I think it definitely made a difference. But the printed key chains you see in the pictures have missing infill near the hole where the ring goes, as if its some sort of under extrusion. There is slight misalignment between the layers, and over extrusion near corners.

    #16341
    Profile photo of vicious1
    vicious1
    Keymaster

    That missing part is a slicing issue try less perimeters or more, have a look at the preview. it is a thin section and it just isn’t trying to print there. The misalignment is from the nozzle hitting the warped part and skipping a step.

    #16497
    Profile photo of Bashar
    Bashar
    Participant

    Sorry for the late reply but i was away in holiday for a few days. Anyway, i managed to tweak the points you mentioned and installed an inductive probe which I had to design the holder for http://www.thingiverse.com/thing:1732225. Now the prints are simply PERFECT! I fixed the printing profile as it wasn’t suiting the MPCNC and I’ve printed the holder for my router (Makita knock-off) and I will start milling quite soon, I just need to understand more about the process. Btw how do I go about making the MPCNC drill the holding holes in the table?

    Thanks again you’ve been amazing!

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