I was quite excited about my new prototype. Interested in my findings?
Im offering since months the improved rapman-like hot-end (still need to write an article about it),
but I wanted to try out a new design. I made this:
Other then the above mentioned features, it contains the following improvements:
- three holes at the top, so the wires are going in an S-form, so harder to broke one of them
- simplified nozzle tip
- flared the hole with reamer
Seeking for the right fire cement
This was not easy. I have tried out more then 9 different brands, and finally prusajr sent me the right one.
The fire cement is black, can withstand 1200C, and dries the outher surface really quick.
If you bake the cement too soon(without waiting to dry it), it is prone to develope cracks:
Although this cement dries really fast, but takes ages to dry it completely. It is best to heat
up slowly the hot-end to fasten the drying process.
(Also disconnect the thermistor until the fire cement is not completely dried!)
It is really painfull process. It is extremely hard to assemble the hot-end, so I started to hate by heart the
fire-cement thing. I dropped fire cement completely, my next design will not contain it for sure.
Comparison with my Rapman-like hot-end kit
I dont know how many people know this, but Im offering Rapman-like hot-end kits for sale since ages.
I will write an extended article about it.
It is rapman-like hot-end because contains the following improvements:
- machined PTFE tube
- simplified nozzle tip, also flared out
So I could compare my new prototype with this design easily.
Its clearly shows that my design is shorter about 20mm.
Experiences and mistakes
1. First and foremost this big melting chamber didnt work out.
At first it is really easy to push the plastic, (and some comes out of the nozzle's tip), but it is harder and harder to
push it, as the melting chamber is filling up.
So this big melting chamber does not improve the hot-end, but makes things worse.
2. First layer of firecement is 1mm width in my design, while in rapman's its about 0.3mm.
It makes a huge differences. At the end my hot-end can be heated up (using standard rapman's electronics) up to 205C after 2 hours. While the stock one can be heated up until 250C for sure, and I use it at 244C when printing.
Also having a bigger melting chamber does require more power to heat up to the target temperature, maybe this influenced too the too cold final temperature.
Making prototypes is a slow process. But I dont give up, Im still searching for the best design, and I already made the next version, and should be manufactured in two weeks. So please keep an eye on this blog.
I finish this article with some more photos for eyecandy. Enjoy!