OneUp V2 Build Log.

[mr_intensity]

Extruder Sub-Assembly Part II - The Print Head

Mistakes afford an...opportunity...to learn.

So, the hardware store does not have M3x15mm hex cap screws.  They only had 16mm and 12mm.  Since I wasn't sure, I bought two of each.

Useless fact:  I bought a set of metric screws/bolts a while back, for general use, but the smallest pieces were M4, so I couldn't use them.  :-(

Anyway, the 900 pound elephant in the room is:  Why do I need these screws?

Well, it appears I actually got a OneUp V1.75 kit, or a OneUp V2.5 kit, as some of the instructions did not match the parts.

Apparently, at one time, the entire back end (where the filament comes in) of the extruder inserted into a hole in EBASE just barely big enough to hold it, and two M3x25 screws screwed into the assembly, perpendicular to the print head, on either side of the print head, through a groove in the print head, in order to secure the print head.

The parts I got do not match these instructions.

My EBASE has a "double hole" in it.  The "just big enough" hole is now offset,and connects to a smaller "groove sized" hole.  You insert the back end of the extruder through the bigger hole, line up the groove with the thickness of EBASE, and slide the groove into the groove-sized hole.  The head snaps into place, and is held rather firmly.

In my honest opinion.  I believe this new way of mounting the print head is an improvement over the old way.  And yes, as kits progress from V1 to V2 to V3, sometimes the documentation lags behind.  I have so many other reasons to bad mouth Q3D, I don't have to complain about this lag in the documentation.  I was able to figure it out.

   

While this new mount is an improvement, there are a couple of drawbacks.  First, the EIFRAME pieces of the stack interfere with inserting the back end into EBASE.

Tip: Once the stack is bolted together, EBASE has no bolts running through it.  It is just a press-fit.  It can be removed to accomodate installation of the print head.  Once the print head is installed on EBASE, you can plug EBASE back on to the stack.

Secondly, with the machined groove no longer clearing all the way in to the stack, the M3x25 screws now have nowhere to go (they used to go through the groove).

   

   

Now, one could argue that the screws are no longer needed.  However, there are two reasons why I think they should be there:

1) The screw heads are recessed into EBLOCK2, which is currently held on with only one one screw, and wants to flop around.  The two print head screws hold EBLOCK2 in place.

2) One of the screws forms a barrier preventing the print head from "snapping out" of the smaller section of the double-hole.  Also, screws that are snug enough against the head will also prevent the print head from twisting in the hole.

The solution, of course, is shorter screws.  My measurements had me shortening the screws by about a cm (10mm) to 15mm.  As already mentioned, the hardware store did not have that size.

My first attempt was to use the 16mm screws, and those worked just fine.  The one drawback to any screws is that they really do not have a hole to go through.  There are these little semicircular holes in the edge of EHFRAME, and the screws kind of act as a wedge to pry EBASE off the stack.

Either way, the screws are now in place.

XBELTMOUNT (OR EBELTMOUNT, whatever you want to call it) is now Super Glued in place.  I got the Krazy Glue™ brand, in the pen dispenser, so I could get accurate control.

I tried to leave the M4 "adjustment nut" in place, with the screw, and sort of "tack weld" around the nut with Super Glue.  Initially, this appeared to be successful, but it came off the following day.  So, I removed the M4 screw, laid down a good pool of super glue around the hole, and laid the M4 nut in it.  I waited about half an hour to an hour for it to dry before adding the adjustment screw back on.  No dice.  The screw would not screw into the nut.  If I flipped it around, and screwd it in from the wrong side, it worked perfectly.  Apparently, the hole through EBASE and the tensioner sub-sub-assembly somehow hold the bolt crooked/crossthreaded so it does not go in clean.  Once I broke the nut free of the stack, it would screw on to the bolt properly.

I may have to 3D print a wraparound "nut trap" to hold the nut in place, so I may adjust from the screw head end.  Or maybe replace the nut entirely with something 3D Printed.

Speaking of the adjustment screw, the M4 washer that the hardware store sold me is slightly smaller than the one that came in the kit.  No matter.  I put the new washer on the screw head side of ESPRING.  The entire assembly just feels more solid, now, with that washer in place.

While that adjustment screw was out, I was playing with the tensioner sub-sub assembly, and found that its bearing was not spinning freely.  See my tip in the previous post on this subject.

With the super gluing done, and the new screws in, it is time to snap the cooling fan/shroud into place on the print head, and declare victory.