A different multi-extrusion approach - UM tool / printhead changer

[neotko 1,417]

I see. Well the think its that the way it clamps in and out it's a slide movement, so I think something like C would hit when the head parks when it changes the angle that makes the magnets loss strength so they can get separated from the main magnet changer. I think the use of B rotated should help make the vertical forces disperse to the main changer. Anyhow on my mod for umo I placed 2 millimetters that actually rest on the upper part and the lower part also, so the up/down forces are always transfered to the main area. At least that's my theory

I think there's a point where too much magnet force can be a problem, clearly foehnsturm it's on a sweet spot, his prints videos show real repeatable accuracy. I think that he solved this on a very elegant way.

Edit: Well after changing the clamps I saw why I used also the same kind of clamps, it's because overhangs. You have holes on a side and overhangs on the other, and in my case I think one part I could manage to change so it don't need supports but the main clamp area has holes and that thinks to ajust, so unless you print in two parts and glue, that kind of helpers won't help much, at least not for my early design.

 

[jonnybischof 60]

Dudes, this design is worth millions! Make sure you put a license on it before takerbot does!!

Anyone else thinking electromagnets?

Easy to handle, and maybe the magnets can even be fabbed with good results...

If there's enough space in the printer, one can easily combine 3 - 5 extruders which would open up whole new possibilities that no SLS printer can ever do

[mastory 44]

Yes Jonny. I have been. Something like these may work.

https://www.planetengineers.com/product.asp?pid=3086 They have many to chose from that would be in the force range needed.

There is another magnet technology where permanent magnets are used for holding, and when release is necessary, electromagnets are energized in proximity to cancel the field. I don't know how these could be used, but I throw it out as food for thought. I think its called Electro-Perm

I'm trying to figure out how it could be possible to dock two or more nozzles side by side without causing interferences with the X-Y rods. Side by side so the change time could be minimized and to minimized the lost bed space.

 

[macua85 52]

Guys, Printed my design today and have to say it prints very well and fits the e3d perfectly. I'll fit it tomorrow and post videos. I'm probably going to re-use the original UMO bearings as i'm that confident in this design! Ive just installed 2 of the 6 magnets to start with. They seem to have pretty good holding power now I don't have the skin in front of them (12x6x3mm magnets), but test prints will determine whether this is enough for bowden tube setup.

Will report back soon!

 

[foehnsturm 969]

If there's enough space in the printer, one can easily combine 3 - 5 extruders which would open up whole new possibilities that no SLS printer can ever do

 

That's exactly the point which distinguishes this idea from others. It's scalable.

However, besides electronics, this requires smarter slicers and firmware as well. That's why I'm eagerly waiting for the new Cura. The fun really starts with different nozzle sizes and slicing settings for each extruder.

 

[foehnsturm 969]

I'm trying to figure out how it could be possible to dock two or more nozzles side by side without causing interferences with the X-Y rods. Side by side so the change time could be minimized and to minimized the lost bed space.

 

Well unfortunately, due to the interfering rods the UM geometry is not the easiest setup for that. A H-type gantry would offer two sides where several tool heads could easily be docked without any interference with the rods :???: .

 

[zumfab 3]

So much yes. Forget multiple extruders in one head, this will do many colors and do it better I am impressed this all seems to work so well so soon, after the whole dual extrusion exercise seemed... painful before.

It makes me wonder what more this could do. Instant plotter or laser cutter tool heads?

 

[macua85 52]

The finished print head:

On the Printer:

First Print (as it came off the printer, XT, 0.2 layer height):

I've had a blocked e3d problem, hoping that doesn't continue to happen, as I don't know the cause.

I'm now printing the tool holder for the corners of the machine, fingers crossed it doesn't block half way through!

AS a note, 2 magnets are sufficient to hold the head firmly in place, as seen on the robot, layers are accurately positioned.

 

[macua85 52]

So disappointed....the design works great, but I can't print any more than an hour before the e3d gets blocked...what to do!?maybe try with no retraction.

 

[macua85 52]

This is the last part, and then i'll hopefully have a working system...although I can't print it at the moment due to the e3d blocking continuously and under extruding. Not going to upload it until I have printed it and tweaked it to make sure its right. No glue required, mechanical fixings (normal 3mm ultimaker style screws).

Hope to resolve the blockage thing tomorrow....but if anyone has any suggestions they would be very welcome!

Thanks,

 

[ultiarjan 1,223]

ah well, I just had a little disaster as well.... finished the parts, mounted my last head design, mounted the new and smaller docking station in the front left, all went well. Did some successful pick and put tests. Started to print some parts for the 2th feeder mount and then 1 linear bearing got out of the basemount, causing the the head to detach from the mount and spit the plastic in a big pile .... now I've got some cleaning to do ... and find a better way to fix the bearings... probably print another with slightly smaller holes ...

 

[aviphysics 9]

You could use a temperature controlled soldering iron at a low setting to melt a bit of plastic on at either end, as a sort of retaining ring. The axial forces should be pretty small, so you just need a little bit of something to stop them from slipping.

[jonnybischof 60]

So disappointed....the design works great, but I can't print any more than an hour before the e3d gets blocked...what to do!?maybe try with no retraction.

You have to cool the entire heatsink of the E3D hotend or it will clog. It looks like the bottom part of your E3D heatsink is not cooled by the fan. If the heatsink gets warm, then the hotend doesn't work correctly. Also, the hotend fan must be on (full speed) all of the time, never connect it to the print cooling PWM output.

Fyi, that's what the E3D guys say - I haven't tested the E3D myself yet.

About the "more than two" toolheads thought:

H-Bot is exactly the (only) way to go

I didn't realize the problem with the UM gantry and my idea at first, but that's because I was already planning to use this with an H-Bot...

The problem with an H-bot is that it's very difficult to "hack" one together and get it to work properly. You need a very good quality build in order to get it to move accurately and without distortions.

Technically, you don't even need more than one extruder motor driver - just need to be able to route the driver to different motors. That is as long as you don't need to do anything with the idle extruders (like prime them before they're used).

So yes - new (or adjusted) firmware is needed. This is the part where I'll need some time o.O

 

[macua85 52]

Hi Jonny,

Yea after reading around I've come to the same conclusion. Im guessing the problem won't persist with no retractions. So I'm planning to adjust the holder and hopefully get it to print well enough for the first iteration, and then if successful I should be able to print a good one. I'm also going to up the voltage to the 30mm fan in the meantime, as I've connected it to variable voltage controller.

[aviphysics 9]

You have to cool the entire heatsink of the E3D hotend or it will clog. It looks like the bottom part of your E3D heatsink is not cooled by the fan. If the heatsink gets warm, then the hotend doesn't work correctly. Also, the hotend fan must be on (full speed) all of the time, never connect it to the print cooling PWM output.

Fyi, that's what the E3D guys say - I haven't tested the E3D myself yet.

About the "more than two" toolheads thought:

H-Bot is exactly the (only) way to go

I didn't realize the problem with the UM gantry and my idea at first, but that's because I was already planning to use this with an H-Bot...

The problem with an H-bot is that it's very difficult to "hack" one together and get it to work properly. You need a very good quality build in order to get it to move accurately and without distortions.

Technically, you don't even need more than one extruder motor driver - just need to be able to route the driver to different motors. That is as long as you don't need to do anything with the idle extruders (like prime them before they're used).

So yes - new (or adjusted) firmware is needed. This is the part where I'll need some time o.O

You probably don't want to allow the extruder motors to slip, which pretty much means they would need to remain energized. Thus the necessity multiple drivers.

However, you could still potentially get away with multiplexing several stepper drivers to a single pair of step and direction lines. That would allow you to control 4 drivers with just 4 lines or 8 with 5 lines (and writing some code for merlin to handle that.)

[ultiarjan 1,223]

Jonny > H-Bot is exactly the (only) way to go

On an UM you could also go with a toolhead lift, should not be to complicated but speed would suffer significantly as the head would first need to position in front of the correct tool/extruder before the tool lift can go down...

 

[ultiarjan 1,223]

You could use a temperature controlled soldering iron at a low setting to melt a bit of plastic on at either end, as a sort of retaining ring. The axial forces should be pretty small, so you just need a little bit of something to stop them from slipping.

 

Thanks for the tip! just designed some small bulges at the end of the bearing hole, which I can heat a little and push in front of the bearing. Printing it now...

 

[ultiarjan 1,223]

That's exactly the point which distinguishes this idea from others. It's scalable.

However, besides electronics, this requires smarter slicers and firmware as well. That's why I'm eagerly waiting for the new Cura. The fun really starts with different nozzle sizes and slicing settings for each extruder.

 

After many recommendations I just got myself a copy of Simplify3D, have not done a single print using it, but it seems to be supporting different nozzle sizes on multiple extruders !

 

[neotko 1,417]

I got s3d since 4months ago. It's quite nice on doing some stuff. The only part I hate it's that it don't heals the fast stl as good as cura. But it has some very nice features. I use it for good fine prints. For print and run I go cura

[jonnybischof 60]

You probably don't want to allow the extruder motors to slip, which pretty much means they would need to remain energized. Thus the necessity multiple drivers.

However, you could still potentially get away with multiplexing several stepper drivers to a single pair of step and direction lines. That would allow you to control 4 drivers with just 4 lines or 8 with 5 lines (and writing some code for merlin to handle that.)

 

Ah, true. Didn't think about that

I won't be using Marlin, but adding a few more stepper drivers to an FPGA isn't a problem (except that it's expensive..).

 

[neotko 1,417]

Well finally found a company that could cut my 4mm aluminum. I'll have 4 units 'hopefully' on friday. I have also take the time to improve my design and make it 2cm smaller. Also the distance between hotends will be just 2-3cm (more or less) different from the dual extrusion experimental kit. Also because the head it's 2,5 shorter on a side I think the print area loss will be minimum, and if only one head it's used it should increase it. I think I'll also post a single head solution for the stock hot end. Now I'm trying to find the best solution for the fans, and probably I'll go with 30x30x10 fans x3, one with the main area and one on each hotend.

What's the best glue to stick the neodymium magnets to the pla? I have superglue, glue for plastics, ptfe binary, wood glue (this one sure isn't any good) and a glue gun (that for what I saw googling won't work since the heat can kill the magnet). Should I buy other glue?

Edit: I also have Loctite 638...

 

[jonnybischof 60]

A normal cyanacrilate superglue should work fine. With printed PLA parts I usually take quite a lot of superglue since it can dissipate into the PLA (similar to wood).

Another (better) possibility is to use two-component epoxy glue (for example Araldite). This stuff pretty much glues anything to everything - forever.

 

[ultiarjan 1,223]

I tried "loctite super glue-3, which failed, it may have been rather old ....

Now I'm using bison "seconde lijm" (=cyanacrilate superglue) and this seems to work fine.

 

[jonnybischof 60]

Cyanacrilate glue degrades with time. It can be preserved longer if you store it in the fridge (not deep-freeze, just ~ +5°C). But DO NOT just put it in your fridge as the glue generates toxic (or at least unhealthy) fumes!

Either have a dedicated fridge (that's what the professionals do), or put the glue into an airtight container.

I like the normal UHU superglue that comes in three very little tubes instead of one large tube. This also helps preserve the glue longer.

 

[aviphysics 9]

After opening my CA glue, I keep it in a ziplock bag with as much air as possible squeezed out. This seems to keep it in good shape. The only issue was one instance where the cap wasn't sealed well enough and fumes from the CA caused severe degradation of the bag.