Monday, 11 January 2016

There must be 50 ways to mount a fan

Time to adjust the tension, see if that helps. The extrusion from yesterday got a little too high, so I'm turning back to 50/30. Then I'm turning the tension screws all the way out until the screw don't jut out. That's pretty damn loose, for sure. From there, I tighten 3 full rotations on each and do a test cube, fully expecting it to not grip well. And I was right, total underextrusion.

Increasing by two full rotations on each, and doing an Atomic to get rid of any gunk and undo any stripping. BTW, the video of the Atomic method from Ultimaker shows a pretty horrible design: Temperature adjustment via a dial that has to be dialed many times to turn temperature from 260 to 90.

Looks pretty nice on the sides, corners still upturned a bit, and the top is still not fully connected. Another two turns of each.

Still upturned corners, a bit, even nicer walls, still a bit gap on the top. Two final turns, and it's almost as far turned as the springs allow. The result is really nice, though, much more even on the top.

I want my fan on, but the nicely designed fan piece that guides the airflow beautifully in to the hot end bends the heater and thermistor wires. For now, I'll make a smaller holder that puts the fan higher and at an angle. Less effective for sure, but also less in the way.

So, dive into the scad files for the Mendel90 itself! It's rather complex, with a lot of included files holding functions and definitions - and some of those files depending on other files having been included first. The definition for the fan mount is curiously in the same file as all the other X carriage parts, defined in a single module, inherently translated to an off-center position. That's rather odd. I'm impressed that nophead is able to make parts that good with code that messy.

But I manage, and create a version of the fan holder where the fan side is rotate 45 degrees, so it can be flipped and aim inwards. First print comes out ok, but the holes are too small. I also notice that there's hardly any place for the carriage mount screws to go in.

In the second print, I have fudged the hole diameters and lowered the plate, so there's more room for the screws. It fits onto the carriage screws now, but hits the belt tensioner.

Offsetting the screw slots a bit to factor that in.

I'm making good use of the # operator in OpenSCAD to figure out which part of the code I'm looking at. Too bad I can't just put my cursor somewhere and then it highlights it immediately, that'd be nifty.

It's fun to print parts for the printer itself. Once I have the fan mounted, I can re-print this part in higher quality because it is doing what I wanted it to. Then I can replace it with the higher-quality version. It's like building compilers, just with physical things.

It still hits the tensioner a bit. I can add 3 mm more before hitting the other side, but I'll wait for the working model before doing that.

Mounted it now, rather fiddly mount really, and the carriage mount came off a bit while mounting the fan, so I had to re-tighten that through the fan blades. But it sits there, just a bit above the bed, and works! Here's a test cube done with it:

There's corner lift on the far side where the fan doesn't reach as well, but the layers on the front and top are absolutely beautiful, and the top is a lot better, too.

Reprinting the fan holder, though not moving the holes since during the mounting proces I found there was just the right amount of space on either side of the nuts.

The problem of using my SLR to take nice pictures of the prints is that I need to set some time aside to do that and process them, so I end up doing other stuff first, and it accumulates. Hence the long posts.

I printed the bit I designed the other day. One side is perfect, flat hex sides, nicely rounded top, the other is weirdly rounded and the top leaning towards the good side. Proof enough that I need to do the proper all-round fan.

Changing the design of the fan duct is hard. Easier to change the fan holder part a little.

The first print of the elongated fan holder has one side of the vertical part being really crappy and the other being fine. I suspect it's a retraction issue - the bad side is the one being printed right after the middle, so there's a much smaller retraction time.

Maybe if I increase the retraction? Trying double retraction, didn't make a noticable difference. The holes look funny here because I sanded them a bit to get the screws in.

Ended up doing two extra prints because I didn't realize I was saving into the wrong directory. Since I had the modified holder ready, I took off the kludged fan, and only then realized I had used the wrong size settings, dibond instead of sturdy. So I printed again with correct settings, but no fan - and it came out nicer! Not perfect, but not as bad either. Here it is, mounted on the fan.

Unfortunately, while trying out the new fan, the two screws mounting it to the X carriage came out, and in turn the nyloc nuts they go into fell out, into the underside of the carriage. That's going to be a pain to get back in - either I do some really clever fudging, or I take the entire X carriage off. Might have been a better design to drop those nuts in from above.

That's probably a sign I should stop here for the weekend.


  1. Hey Lars this is really great! Where did you get the printer?

    1. This comment has been removed by the author.

    2. I ordered it from nophead in the UK. I made the mistake of ordering a partial kit rather than the full kit. Didn't save much money, but took a lot of extra time.

      Unfortunately, nophead no longer sells kits:

      Other places do some parts of the kits, just search for Mendel90 kit. Using the dibond version makes it easier to follow the excellent manual, but variations in items from different suppliers may require some tweaking.