12" I3V Build

[Dustin B]

So the bearings in the delrin wheel measure 11mm. The bearings by themselves measure 10mm. The washer they came with is 0.8mm. Add a 0.2mm clutch bell shim, tighten down nice and firm and it turns completely smooth, no binding at all. Two teflon washer from the slash are a little thicker than 1mm and seem to compress. There was no binding but not as smooth as the metal clutch bell shim. The precision 1mm washers recommended above are highly recommended. Colin should be sending these kits out with those. I'm not going to wait for them as I can get enough 0.2mm shims from a local hobby shop that's minutes from my house.

[Dustin B]

So didn't work out that 0.2mm shims worked every time, but with enough playing around with combinations of shims I got all the wheels turning completely smooth after being really torqued down tight with no side to side play. I highly recommend picking up some shims, the extra effort is well worth it (5x7x0.1 : 5x7x0.2 : assorted set) Should finish up most of the mechanical assembly this afternoon and later tonight, then it's on to assembling the extruder/hotend and wiring it.

The relay had solder on both sides of the board and I was unable to get it cleanly removed. Ended up cutting it off and then getting the pins left behind out. Little work with a reamer and a 14 gauge sold copper wire just fit in the hole. Got that soldered up and continuity still checks out.

[Dustin B]

Didn't get as much time as I would have liked yesterday but made some progress. Got a 3/4" mdf base cut for it and made 2 braces to prevent any flex around the y-axis belt attachment points. Paid close attention to the diagonal measurement of the y rails making sure they were perfectly square before screwing the front brace down. Also cut two small blocks and screwed them down to force the two parts of the frame to be square to each other. Also pushing down on the z motor mounts before screwing the fame into these blocks pulled the rest of the frame flat to the MDF pulling the z-axis rails into being perpendicular to the MDF. Without being pulled down flat they were leaning a bit towards the back of the printer. Once I'm up and running I might print some nicer braces to replace these crude plywood ones.

Tensioned the y belt with it off the base which flexed the frame in a bit, then putting it back over these braces added that extra little bit of tension to the y belt making it nice and tight. Belt doesn't track well on the y idler though so I'll definitely be printing a new idler that has a lip to keep it in place. After it was tensioned I also cut a small block that wedges in between the back of the y motor and frame so the mount doesn't have to take all the torsional force from the belt being tensioned.

IMG_20160220_245737042.jpg

[printbus]

The 11A input will also need 12V going to it in order for the heat bed output to have any voltage to drive the SSR. You won't need much current. It's fine to run some light gauge jumpers from the other 12V input over to the 11A input.

EDIT: The power input for the heat bed is kept separate in order to support those people who run a different voltage heat bed, like 24V.

[printbus]

There are a lot of resources on the web that can help guide through calibration and efforts involved in bringing a new printer up. Here's just one that touches on some of your current questions - http://reprap.org/wiki/Calibration

Your list of early efforts seems pretty complete. I'd maybe add that on early prints, scrutinize how the bottom layer turns out. Good prints will rarely result if the bottom layer has issues.

One crude way to gauge heatsink or component temperature is to simply feel the amount of heat. Anything that feels uncomfortably warm to touch is something that should be looked into. The stepper drivers will automatically stop driving their motor if they get too hot, which would be very noticeable. Other than that, just touch the heatsinks every now and then on some of your longer initial prints and see how they feel.

On the stepper motor driver adjustments, there's arguably two main camps of opinion. One is to adjust them to for the current spec of the motors, assuming you know what that is. This approach is argued as providing the highest degree of precision to each of the movement steps. The other camp feels this is overkill, and that you can successfully print with the stepper drivers adjusted significantly lower. Higher currents lead to the printer making a lot of harsh noise as the motors are rotated. Adjusting to lower currents can lead to the printer running far quieter. In my case, I noticed that running at lower drive currents also helped eliminate some flutter observed on the X-belt and Y-belt during long moves, as well as eliminated resonances that would come and go as movements were accelerated and decelerated. EDIT: Beerdart later describes how to adjust for the lower current drive level.

[printbus]

Congrats on the first prints and a fairly painless startup.

On the clicking, one suggestion is to use a short length of garden hose or similar tubing as a listening aid to help locate the source. I know I had a very annoying click that seemed to be coming from the area of the guidler bearing and hobbed bolt area. I was never really able to pinpoint it, but eventual replacement of every component involved seemed to solve it. A couple of others have reported a similar clicking from that area. I've even wondered if it was simply the sound of the hobbed bolt cutting or creasing into the filament.

Another possibility is the extruder motor is skipping when attempting to do retractions. Assuming your gcode includes retractions, they're not happening based on the rotation of the large gear in your video. Looking through the gcode file in a viewer like gcode.ws will help you understand what the printer is being told to do, including whether or not retractions should be occurring when the nozzle makes a non-printing move from one location to another, as it likely would on infill. Colin's firmware baseline used to set the extruder maximum feedrate (the fourth term in configuration.h DEFAULT_MAX_FEEDRATE) to 22mm/sec. At least two of us determined the extruder motor can't be driven that fast, and that something in the range of 10mm/sec to 15mm/sec is more appropriate. If the extruder motor is driven too fast on a retraction, it'll just twitch a bit without movement each time a retraction is attempted.

The steps per unit for X, Y and Z are fixed by the hardware design and the microstepping selections for the stepper motor driver boards. You can work through an understanding of how the settings are determined through something like Prusa's on-line calculators. Changing the settings based on a fixed size test print will likely create a printer that can only print that dimension correctly, with all other dimensions off by some scaled error. What was the LCD displaying as a print height on the last layer? What does a viewer like gcode.ws show as the height of the last layer?

Jumping into early prints with 100% infill is gutsy. If the extruder steps per mm aren't right, 100% infill won't turn out very well. For example, if there's a bit of over-extrusion, the excess filament has no-where to go and you'll be left with ratty walls and a bad top of the print. The sticky on calibration might be a place to start. Simply listed as another source, Triffid Hunter has a calibration guide that touches on extruder calibration and the countless other things involved in bringing up a printer from scratch.

[Dustin B]

Here's my solution to the x belt connections until I have it working and can make printbus's replacement. Just a small piece of roof flashing cut to act as a washer that spans the two screws. Replaced the 16mm m3 screws with 20mm m3 screws I had from my RC stuff to.
IMG_20160221_141604099.jpg

I ordered two of these z-couplers from Colin. Drilled and tapped them to have 3mm set screws as well as the pinch screws they came with. So I filed some flat spots on the bottom of my threaded rod. No worries about the tubing letting go now.

IMG_20160221_164142314.jpg

Only issue is the way I have them connected to the lead screws right now the lead screws are tall enough they'll interfere with the spool holder. So I either have to adjust them or cut them down a bit. Not sure if it's better to have them nearly touching inside these couplers or to cut them down. Guess I could also just leave them as the spool hold doesn't have to turn and I'll likely make a different lower profile one relatively soon.

[Dustin B]

So ya, read the instructions more carefully when assembling the Greg's extruder. When I was tightening the second locking nut wasn't thinking and put a wrench on the bolt head instead of holding the spur gear (end result I turned the nut inside the capture in the spur). Nothing some epoxy couldn't fix though :P I also had to clean a bunch of globs out of the teeth in the spur as they were causing it to bind. Sure hope after I'm done tweaking and tuning my I3V 12 prints better than the supplied extruder was printed.

[printbus]

Hopefully someone with an SSR and heatsink used with a 12-inch heat bed will chime in. How hot the SSR gets depends on the current rating and the quality of the MOSFET inside it. IIRC some have reported their SSR getting pretty warm. If the MOSFET is only rated for around the 40-amp limit on the SSR, there could be enough on-resistance that it'll dissipate noticeable heat with a 12-inch bed hanging off it. Some that have built their own MOSFET board have used up to like a 200-amp MOSFET in order to ensure a very low on-resistance. Those would dissipate very little heat. There's also so much counterfeit and knock-off stuff out there that you don't know what you're really getting these days, especially from sources like eBay and Amazon.

You could always try it without the heatsink grease and see how warm it gets.

[Dustin B]

Ya I'm leaving the rods alone for now as I tightened the spool holder down so it won't turn easily. I'll replace it eventually.

I'd read about the ball bearing thing between the motor and lead screw, thought that was just for the tubing. I'll pick a couple up and add them into mine.