add part cooling fan

log/gluegun-log.md

@@ -146,4 +146,20 @@ OK, it's 10pm and I'm spent but I think this is done.
 
 ![done](2021-09-01_gg-newagain.png) 
 
-I have to order that alu spacer, but otherwise I'm ready to print and test this. Will probably get the -fxy together and moving again before I fab this... back here in a week or less, let's hope. 
\ No newline at end of file
+I have to order that alu spacer, but otherwise I'm ready to print and test this. Will probably get the -fxy together and moving again before I fab this... back here in a week or less, let's hope. 
+
+## 2021 09 22 
+
+For NIST, I want to print little tiny things - so we want a part cooling fan (PCF). This is actually a totally not-ignorable aspect of hotend design, turns out.
+
+My first shot obstructed the hotend cooling fan (HCF)... this was it:
+
+![pcf](2021-09-22_first-pcf.png) 
+
+So I think I will try to move the HCF up, to get the PCF below it; both should have unobstructed flow into the fan. 
+
+Well I can just barely make this work all flush-like:
+
+![pcf](2021-09-22_pcf-almost.png)
+
+Though to really do it, I need about 5mm more stack on Z, I figure I move the nozzle down by about as much, or the motor up, but either (done well) has me re-printing the main plate, which is an overnight job.