Hot End MK-II


Please note, there is a modified version of this called MK-IIb. It addresses some of the problems with the MK-II build. Problems that are not a problem on a printer like mine, but on a faster printing machine.

The MK-IIb is a “better” version. As I do not have a fast printing machine I can not do real world testing, but manual testing of extruding speed and leakage is looking promising.

I was going to remove this page, but then I thought, no, it can stay. But don’t make the hot-end this way, look at the MK-IIb.

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5/4/2012

Have made few for testing. (It is very time consuming). As my printer is very slow I can’t fail it. But when I go into pronterface and just do manual extruding it seems to be ok at maybe 40 to max 50 over a longer period. But since I do not have a “normal” speed printer I can not recommend building this design yet. I do apologise, but I rather cop the shit now then after many builds have failed.

If you are building a machine like mine, then go for it. It is the best hotend for my machine I have ever had.

BUT DO NOT USE THE BOLT METHOD FOR MOUNTING. It does require a fan for cooling as the bolt does get too hot after aprox 5min into the print.

As my next printer will be a belt driven machine, I will have to find a way of making my own hotend that will cope with the much faster extrusion speeds.

For now I will concentrate on getting parts printed for my new printer.

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3/4/2012

I have done some speed testing and it failed on me at speeds above 30mm/min in pronterface.

Working on the problem.

Will post some more info soon.

Apologies again for any inconveniance.

Regards

Jan

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Working on a smaller hot end with nozzle and no fan. Coming soon if my testing is successful.

Today, 27/03/2012: Passed initial testing. 4hrs continuous printing. No problems so far.

Today, 28/03/2012: Printed several smaller parts. No problems. Have added some photos just to get an idea of the design and size. Will post more details later, as I am going to make another one, just to confirm that I can repeat the process. In the mean time I am just printing anything  to test……fingers crossed.

MK-II Prototype

MK-II Size compared to a ball point pen.

Above pictures shows my new MK-II hot end. It measures about 55mm from top to bottom (nozzle tip). (I think I should be able to make it 45mm total lenght next time). The black screw is a 4mm screw and the pen is a normal sized ball point. The copper pipe used is standard 1/2″ (half inch) water pipe class a. It has approx 10mm inside diameter with 1.07mm walls. (Yes I know, there are some exposed wires on my heater, will cover it up later).

Just finished off printing almost non-stop for approx 5hrs, which is not bad. I am very happy with this design, especially the way the PTFE is secured to the brass with a copper pipe, looks like a winner. 🙂

My extruder is made of wood and therefore does not go soft when it heats up, so there might be a possibility that a fan is required when I attach this hot end to an ABS extruder. Needs to be tested.

The clear liquid looking stuff on the mounting bracket is glue from a glue gun. I had a fan glued to the extruder before. The heat makes it run.

30/03/2012: Made another hot end today. And It was as successful as the first. I think I can say that if you make a hot end this way it will not leak or the ptfe will not come off. (on a printer like mine)  And all you need is a brass rod, some 10mm PTFE and some copper pipe. For heating I use (as you can see on my photos), an aluminium block.

Resistors for heating. 2 x 6.8ohm resistors in parallell gives me 3.4ohm and it heats to 230degrees in approx 3min. I will post exact part numbers etc, later.

My MK-II sketch

30mm long brass rod.

25mm long PTFE 10mm dia.

6 x 20mm long copper pipe 1/2 inch thick (type A, 1.07mm walls and inside dia approx 10.1-10.2)

25mm  30mm copper pipe for middle section. Se photo and you see how it goes together.

Copper pipes are held in place by a wire while being soldered.

I use a small $12 blow torch, purchased from hardware store, for soldering. You can also use a large soldering iron. I use standard solder. It works fine.

Here are some photos of the process making the second one. Please note that I don’t show the heater block in these photos. It is just a alu block with a tapped hole to go onto the nozzle. You also need to drill some holes and make up a way of attaching it to your extruder. (For more details on how I make the parts see this page.)

Cut 30mm brass rod

Start by cutting a piece of 30mm long brass rod.

File and shape to specifications, drill holes.

File and drill brass to shape. One end must be 1mm larger then the hole it is going into. I make it 7mm and the hole in the PTFE I make 6mm for a nice tight fit. (HowToDetails)

3 grooves and rounded end to make easier to press into 6mm hole

Grooves made and rounded end for easy insertion into 6mm hole.

6 x 20mm pipes and 25mm pipe in centre. All half inch water pipe. Hold together with wire when soldering.

Heatsink is made up of small pieces of water pipe. Simple and easy to make.

Nice! Hold together using a wire while soldering.

Heatsink is very easy to make. But you do need a small blowtorch or large soldering iron to solder them together.

Total size under 50mm.

Nice and compact. I will also drill vent holes in the pipe (see photos of the one attached to my printer and in use), to increase airflow. This may not be needed. May test that next time. But the holes are easy to drill.

Finished soldering and pressed onto PTFE. Just need some mounting brackets to suit extruder.

That’s it!

For more details on the process I use to make these parts go to this page: Hot-End with Nozzle . You will there see my first good hot-end. The process I use to make parts is the same.

If any one ends up making this (Jan’s Hotend MK-II), please let me know how it performs. On my printer it works fantastic. What makes it even more exciting right now is that I got some samples from Lybina to try out. Yellow and purple ABS. Just Printed a little easter bunny in yellow, purple is printing as I write. Love it. The colour is nice, quality of the ABS is the best, what can I say, Christmas is already here…(for me).

31/03/2012: Just completed a 5hrs print job. Still no sign of any problems.

Are making a change to the way I will mount the hot end to my extruder. Will tap the middle pipe inside. This way it can be screwed onto a mating part attached to the extruder. Will post updates when I am ready.

01/04/2012: My printer have been printing almost non-stop for the last 20hrs (most of the night and today). The hotend is keeping up very well. No problems.

Please note: This bolt mount MUST have a fan for cooling. It gets too hot.

I have done one modification. The centre pipe has been made longer, 30mm instead of 25mm. This so that I can make a thread inside the pipe to accomadate a bolt for securing the hotend to the extruder. I tapped 7/16″ thread and got a 7/16″ bolt. Drilled a 5mm hole through the bolt for the filament to go through. I don’t have a plastic extruder but this is how I picture the mounting. A 7/16″ hole for the bolt to go through with a hex hed. Use nut and washers to tighten and then screw the hotend onto the bolt.

Centre pipe is now 30mm long instead of 25mm. Inside thread at the top.

Thread at the top. (Make sure to clean it....I have still got to do that.)

Bolt with 5mm hole through.

Hotend with bolt attached.

This new design without the bolt mount, has been working fine on my machine. It has been very reliable, though I have only printed for about 30hrs with it (I just made it a few days ago). Some of the jobs have been 7hrs non stop and then 10min later another similar job has started. Due to the long jobs there has been plenty of time for the heat to reach the top and soften the filament, but that has not happened and it is still going strong, so with ABS this design seems to be very good. I know PLA is a different material and unfortunaltely I do not have any of it to try out. I am working (in my head) on an enclusure for this hotend which will accomodate a small 40mm fan. This will force air through the copper pipes and away from the hotend. This may be what is required if the current design gets too hot for the PLA at the top of the hotend.

Here is a comparison photo of MK-I and MK-II, quite a difference. 🙂

Can you spot the difference? 🙂

When I sat out to make myself a printer, my goal was to be able to make most parts myself, including the hotend. I think I have succeded at that and are quite pleased with this latest hotend design. But this design at present is only good for this kind of printer. Slow speed printing. X and Y axis have threaded rods amd move slowly.

I hope I may have inspired someone else to make it or hopefully a better version still. There is always room for improvement. And I need one for my next printer. One that can extrude fast!

Kind Regards

Jan (IceMan)

PS: I have not had any blockages with the MK-II so far, but I have changed colour several times. Black then yellow then purple and then black again. What I find to be a very easy way to clear out old filament is to let the hotend cool down to around 120 degrees. Then reverse your extruder. As it reverses it will come out like a plugg. It works for me every time. Nothing left of the old filament.

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