Kossel Mini build : Part 3

Recap :

Kossel Mini build : Part 0 – a brief explanation of intent and also sources where I got the parts

Kossel Mini build : Part 1 – building the top triangle frame, as it seemed like the simpler of the 4 main components

Kossel Mini build : Part 2 – built the diagonal rods by leveraging parts used on the bottom triangle base

 

The epoxy was properly hardened when I checked, so I removed them from the extrusions.  The 6 x 240mm extrusions are for the bottom base of the Kossel Mini, so I put that aside as I continued on.

This part, I used the following components

  1. 3 x carriage rails
  2. 9 x M3x25mm screws
  3. 3 x M3x15mm screws
  4. 2 x M3x16mm screws
  5. 2 x M3x20mm screws
  6. 7 x M2.5x12mm screws
  7. 6 x M3 nylon nut
  8. 6 x M3 nut
  9. 1 x effector
  10. 1 x euro connector
  11. 1 x allen wrench(came with nuts and bolts pouch and it meant to be used in autoleveler)
  12. 1 x retractable housing
  13. 1 x j-head hotend
  14. 1 x pressure fitting
  15. 1 x micro switch

In addition, I needed to get the following parts:

  1. 40 mm PC fan
  2. a safety pin
  3. a compression spring
  4. a metric tap and die

 

There appears to be several different revisions of the rail carriage piece – the piece I got does not resemble the ones in Blomker’s site, nor the current one available from the creator’s github page.  This is the reason for using 15mm screws with 25mm screws for this build.

parts to vertical carriage
parts to vertical carriage

 

The effector is an interestingly looking piece and it is the platform that the hotend will be attached to.

I had put about 3 or 4 screws and nylon nuts together when I hit a problem.  The nylon nuts seem to lock onto the screw prematurely.  Normally, a little bit of force would get them going again, but this time the nut started to rotate, chipping away at the plastic.

 

So I went out and bought a metric tap and die kit and spent some time threading the nylon nuts.  It turns out most of the nylon nuts needed to be tapped with an M3 tap.  I also had to rethread the screws.

fixing the nylon nuts?
fixing the nylon nuts?

Well, that was a bit unexpected.

 

Anyway, the opposite end of the rods are screwed into the effector, basically the platform for the nozzle with the heating element.

The effector also has quite a few things going on, so I took a break to work on the effector.

An important feature of the Kossel Mini is the auto level probe.  I have high hopes for this probe as it will hopefully be the end of time and effort spent in trying get the height just right.  This probe uses a hex allen key as a probe and a string and endstop switch to detect the bed.

 

This is when I encountered another issue – the opening on the side of the retractable housing would not allow the allen wrench slide down(shown in green).

Auto level housing
retractable housing

I was able to remedy that with the aid a dremel and a cutting wheel (shown in red).

Next, I found that the J-Head nozzle does not fit the opening on the effector.  Strange, but no longer hesitant to grab the dremel and enlarged the opening to make the J-Head fit.  I just enlarged the hole by shaving the walls of the opening on the effector.

shaved the sides of the hole on the effector to fit the J-Head
shaved the sides of the hole on the effector to fit the J-Head

And for the final test fit:

J-Head in effector with the aid of a dremel
J-Head in effector fits!

I added the bracket with the 40mm fan mount and noticed that the hole on the effector is not deep enough – but I left it as is, since evenly boring a hole is beyond my capabilities.

mind the gap!
mind the gap!

2 x M3x16mm  screws go on the effector and bracket with fan mount, 2 x M3x20mm screws go through the retractable housing, effecotr, and bracket with fan mount

note that the tubing from the J-Head is visible in the center hole!
note that the tubing from the J-Head is visible in the center hole!

 

Now, back to the rods.  Each end of the rods require 1 x M3x25mm screw and 1 x M3 (tapped) nylon screw.

this required a little bit of care
this required a little bit of care
tapped nylon nuts definitely helped
tapped nylon nuts definitely helped
all done!
all done!

Getting back to the auto level – next step requires modifying a safety pin into a spring powered latch to lock the probe.

From saftey pin to probe latch
From saftey pin to probe latch

*note – I bent the wrong leg on the safety pin.  😐

A M2.5x12mm screw goes through the safety pin’s eye and onto the hole half bottom of the auto level housing.

I removed the retractable housing from the effector to install the switch.  A quick photo of the components that make up the auto level switch :

auto level components
auto level components

The compression string is from a hardware store, cut to 24mm.

The auto level switch needs to be wired up on the C and NC prongs.

wires soldered to C and NC
wires soldered to C and NC
shrink wrap after soldering, because... why not.
shrink wrap after soldering, because… why not.

Upon test fitting, I noticed that the legs of the switch needs to be bent(this is probably better illustrated on Blomker’s PDF)

the legs need to be bent
the legs need to be bent
like so!
like so!

Next, I’ll need to trim the lever.

side view, the green area is where I am thinking of cutting the lever
side view, the green area is where I am thinking of cutting the lever
top view
top view

When I cut the lever, it wasn’t a clean cut and a little bit was left bent up.  I think I’ll leave that as is.

removed a part of the lever on the switch
removed a part of the lever on the switch
done?
done?

I reinstalled this back into the effector.  I also added a bit of shrink wrap to the handle of the allen wrench.

shrink wrap on the handle of the wrench
shrink wrap on the handle of the wrench

Back on the retractable housing.

safety pin's leg is holding the wrench in the locked position
safety pin’s leg is holding the wrench in the locked position

I installed the spring and the euro connector this way.  On the locked position(see green on left picture), I fully compress the spring and screwed the euro block facing an angle(see red on left picture).  This is so that when the probe is released(see green on right picture), the euro connector is facing out(see red on right picture)

auto level install complete
auto level install complete

 

Finally, I got the 40mm fan from a “Chipset Thermal Package” kit and installed it using 4 x M3x12mm screws.

this is a neat kit
this is a neat kit
installing fan to mount
installing fan to mount
fan installed
fan installed

I was able to just screw the pressure fitting ontop of the effector without any problems.

pressure fitting on effector
pressure fitting on effector

Whew, finally done for the day… The amount of trouble I had with the nylon screws and overall fitting issues was bit unusual.

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