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mattcrichards / modthotend

Building a replacement hot end for the MOD-t 3D printer
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Replication on early batch Mod-t #1

Open serialc opened 2 years ago

serialc commented 2 years ago

Dear Matt,

First of all, a huge thank you. You've made this whole process accessible with your great instructions. This following 'issue' is a description of the issues I ran into - many of which you cover, some perhaps are unique to my Mod-t (?).

I'll describe chronologically as best I can my process, provide images (that you have my full permission to use for any and all purposes and integrate anywhere you see fit).

I'll skip the obvious steps for those who've already disassembled their machines in the past.

My MOD-t

It's the earliest batch possible - I was one of the 100(?) to get a discounted MOD-t ($USD100?) on the crowd-funding site. It's always been a delicate beast. I've disassembled it many times, usually due to the filament grinding or breaking then jamming after the filament feed/gear.

The Molex plug

I was able to reuse the molex plug by removing the crimped metal bits (Molex KK 254 - example 1, example 2).

If I had realized I could find and buy these little guys it would have made things a bit easier, as you had mentioned, but I did as you did and just crimped the existing wires to the Heater Block & Thermistor wires. However, by removing the KK254 bits I was able to slide over the sleeves for the insulation tubes and heat protection.

molex You can remove the bits by pressing down on the catch and lightly pulling on that wire

Removing existing hardware

My stack, plate, and bottom bolt heights were similar to yours: 12.13mm, 1.56mm, and 1.91mm (3.47mm - 1.56mm).

stack_height plate plate_bolt

Rebuilt hot end

I bought some half width M6 nuts. This turned out to be not necessary for me and I will replace them with normal size ones and maybe washers if I need to disassemble it again. I'll explain why in a bit.

new_hot_end Rebuilt hot end

Here's my rebuilt hot end after crimping. crimped

Then after installing the insulation. insulated

Installing the hot end - problems

I had two main problems here:

  1. The plastic feed mechanism could contain the old aluminum tops of the stack but the new M6 threaded teflon throat tubes do not fit in the housing.
  2. The whole feed assembly sits flush with the metal grate to which the hot end is mounted - there's no room for the nut of this size (M6) - the nut thickness is not the issue.

Solution to problem #1

Looking in the image below you can see the previous stack fit in the plastic feed guide, which is below the extruder in the plastic feed assembly (PFA). The new M6 threaded teflon throat cannot fit inside.

The problem The problem

I just cut away the arms that where in the way.

The solution The solution

Solution to problem #2

The M6 nut doesn't fit above the plate. The plastic feed assembly sits flush against the plate and the hole is smaller than the nut's width.

I again cut away the 'excess' plastic. It's a bit chunkier than the last cutting exercise - I also used an X-acto knife to carve the bottom size (in the second image below).

While this seems worrisome in terms of structural support, it is two thin parts of plastic coming together at the hole. So it's fine. You can see however that I've over-tightened the screws in the past and it's stressing the plastic. I put some crazy glue on the cracks to hopefully hold off any problems a little longer.

problem2 The second problem - the plastic feed assembly (PFA)

solution2 The second solution - cut at the red lines

Adjusting the teflon throat height

It turned out that measuring the throat height ahead of time wasn't useful for me.

I simply put the plastic feed assembly (PFA) in place and the pushed up the teflon throat to make contact with the assembly above. Holding it there I wound the outside M6 nuts to the plate, removed the PFA, tightened the inner M6 nut, and then checked that everything is inline and joined properly with the PFA back in place.

Because the plate hole is a bit larger than the teflon throat it took a few minutes of fiddling to get everything inline and tight.

Final adjustment to the hot end

I took a different approach to the merging of the throat and hot end inside the block (after some leakage problems).

I did the following:

I read that the nozzle shouldn't be flush. Also, and more practically, if you didn't tighten your nozzle-throat enough but your nozzle is bottomed, you can't easily tighten the pair anymore (due to plastic inside, connected moltex, etc...). If you have some space between the block and nozzle you can tighten this more if there's any oozing of plastic out the thread.

Conclusion

It's printing a little smoother now than before (with the same Cura profile). I'm now using the Cura profile you provided for less stringiness. Thanks!

I'm happy to answer any questions if I've left something out.

Matt, thanks a bunch. You made it look relatively straight-forward.

I feel like I have a better and more reliable printer on my hands now. So thanks again Matt.

mattcrichards commented 2 years ago

Hi Cyrille,

Sorry for the delay getting back to you. The holidays were crazy. Thank you so much for your detailed report. I no longer have a MOD-t, and thus haven't moved this project forward any more than I outlined. If I get some time I'll factor your feedback into the overall process. I've made a note on the wiki home pointing to this issue, so that anyone who stumbles upon this will be directed to your writeup.

Thanks again!

hipsi commented 3 months ago

Thank you both Matt and Cyrille. I bought a Mod-t here in Australia about a month ago from someone who stopped using it when New Matter closed down. I thought for $50, no a bad way to get into 3d printing. I had a couple of weeks to play with it before the hot end went. That's when I found this. My AliExpress order of parts came in today and I've just finished the mod.

If it wasn't for Cyrille's post here however I would never have completed it, as I had exactly the same obstacles. Thank you both, I've just run a successful test print, which I'm double happy with because at the same time I've switched to a glass print bed. That also seems to be working great.

mattcrichards commented 3 months ago

@hipsi - I'm so glad that the guide, and the follow on work from @serialc, was helpful and that you are up and running. Enjoy!