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Quick change hotend

Posted by Andy1989 
Quick change hotend
December 02, 2020 01:40PM
I'm looking for a quick change hot end so I can quickly switch between a standard and volcano V6 extruded.
I'm using a Bowden setup.

Anyone know if there is anything out there already before I embark on designing my own?

I plan on pairing it with some sort of hotend probe similar to that on the lulzbot machines so the different hot end length can be automatically updated after a swap.
Re: Quick change hotend
December 02, 2020 02:19PM
Are you asking for an auto-change hotend or one than can be quickly manually changed?

Re: Quick change hotend
December 02, 2020 04:31PM
Just one that can be quickly changed manually. I just stumbled across this which l think could do part of the job.

Re: Quick change hotend
December 02, 2020 07:26PM
That's interesting.

What I do nowadays is to use 2 4-pin connectors for the hotend... one for thermistor and heater, the other for fans. This is more to make it easy to unclog or otherwise work with the hot-end than anything else. I have opposite gender connectors on each connector so I can't accidentally plug the fans into the heater/thermistor. The fans could probably be serviced by a 3-pin connector with a common ground to both fans, but 4 pins keeps it simple.

Make sure your heater connector is good for the current. e.g. for a 24V 20W heater I use these that are good for 2A continuous: [www.aliexpress.com]
Re: Quick change hotend
December 03, 2020 06:05AM
I have not heard of or tried anything in the way of a quick change hotend of the sort you describe, but if I could offer a couple of thoughts:

For electrical connections you could use Pogo pins [en.wikipedia.org] example at [uk.farnell.com] has a 9 amp rating. Smaller ones are available for thermistors, fans etc..

A possible way of attaching the hotend to the carriage to allow a very quick change is to hold it on with a magnet or pair of magnets. In order to get a good repeatable location you could use something like a Maxwell kinematic mount - three balls and three grooves [en.wikipedia.org]

If the intention is to be able to change rapidly to a new hotend at the end of one job and beginning of the next, it may be advantageous to have the filament already installed on the hotend to be fitted and also have the hotend at temperature. In this case my earlier suggestion on pogo pins would not help and standard connectors such as Molex Micro-fit or JST XH connectors would be better.

Hotends will be variable in length even after careful adjustment, they and will also change under heating, often by different distances even if they appear to be made of the same materials. Because of this variability it is probably better to use a nozzle contact sensor for setting the Z position.

Re: Quick change hotend
December 04, 2020 11:26AM
The pogo pin connections look perfect!
It's a 24v machine, so the heater will draw 1.7A max, so even the tiny little connectors like this have plenty of spare capacity. Could even use them in parallel if I want more capacity.


I'm going to knock up a design where the hot end and fans are attached to a removable bracket, and all the electrical connection is dealt with using pogo pins. The Bowden tube will be fixed to the X carriage, and simply align with the hot end. I will align the two parts using a couple of bosses or pins, alignment isn't too critical, just needs to be close enough so the filament can pass through the junction in the Bowden tube.

My PowerPoint engineer drawing shows my intentions.
open | download - 2020-12-04 16_21_53-Presentation1 - PowerPoint.png (38.3 KB)
Re: Quick change hotend
December 04, 2020 01:03PM
a possible buzz kill here.
this is my own opinion, but i dont think pogo pins are a solution for a moving extruder.

i think press fit connectors are a better solution, especially for something that moves around so much. any misalignment or jolt can cause arcing and do a lot of stress on electronics from micro disconnects or alignment shorts to other pins.
unfortunately i do not have a perfect alternative, just recommend several wires nickel plated to prevent oxides connecting heater ground and Positive. probably a ribbon cable is best. maybe even a 10 pin connector that is press fit and secured by a zip tie.
prob best to use as many pins that go to wires as possible to spread out current over the wires. again thicker wires can break, or cause extreme fatigue on solder joints. but if enough engineering is done about anything can be possible, just not practical.
Re: Quick change hotend
December 04, 2020 01:41PM
I have used pogo pins on test gear that experiences high levels of vibration and acceleration and don't think that will be a problem. Each pin has a built in spring and this will allow continuity to be maintained.

There is one problem that I had not thought of mentioning though. There needs to be a mating contact for the pin to make contact with. I typically used a part of a PCB with a 20um gold plating - these were fabricated for the test gear under construction. A possible solution is to find a PCB with an old style edge connector that can be salvaged for the purpose - some of the older computer memory modules may be good donors for this purpose.

Re: Quick change hotend
December 20, 2020 06:18PM
Printermods have just released a kickstarter for a quick change tool head that does exactly what I'm looking for!

I'm not convinced about the alignment system tho. Looks like it uses 4 tapered pins that will need very careful alignment to work properly. Misalignment of one will prevent it from connecting correctly. I'd rather see an e3d style kinamatic coupling that uses 3 points, rather than tapered pins.

Re: Quick change hotend
December 20, 2020 10:11PM
Printermods have just released a kickstarter for a quick change tool head that does exactly what I'm looking for!

Yeah, but you can buy an entire 3D printer for the price of one of their quick-change heads.
Re: Quick change hotend
December 22, 2020 09:55AM
I hope your Pogo pin insulation can take the heat conducted through the wires.

Ideally you will also have to input different PID values for the different hot ends via gcode. I don't think all firmware lets you do that on the fly... Although some might let you input values via the controller instead.

Others appear to just do a calibration each time and store those values. Which adds time to your "quick" change.

Edited 1 time(s). Last edit at 12/22/2020 09:56AM by DragonFire.
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