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

[foehnsturm 969]

I had a quick look at misumi already but found the options a bit overwelming

 

Very true. TBH, I didn't do any calculations, to some extent it's a shot in the dark. Just went for the long blocks for less play. An axis with two parallel rails should always be fine. With the one rail axis, I'll have to see. And for the other options: I tried to choose the cheapest ...

[foehnsturm 969]

1000m/s ... And it didn't move the table? That alone it's impressive. Really promising.

 

:-) Just found the typo ... those units ...

Well, 1000 m/s would be close to Mach 3 and I should have heard a supersonic bang ;-)

[neotko 1,417]

Lol XD indeed

[aviphysics 9]

 

I had a quick look at misumi already but found the options a bit overwelming

 

Very true. TBH, I didn't do any calculations, to some extent it's a shot in the dark.  Just went for the long blocks for less play. An axis with two parallel rails should always be fine. With the one rail axis, I'll have to see.  And for the other options: I tried to choose the cheapest ...

 

When I looked at rail systems for my CNC many years ago, my impression was that one really needs a pair to avoid any significant wiggle. It just doesn't take much angular freedom at the rail to cause problems, when the tool extends out several cm. Perhaps designing the tool holder to keep the hot end as close to the axis as possible would help, but than your center of mass (and/or Bowden) will be way off axis and able to apply a substantial torque.

A lightweight second rail could be added opposite the tool changer to help reduce the degrees of freedom. This would be like the very small bearing used at end of the non-load bearing side of a rotating shaft, in order to offset the load. In thise case, the rail could be oriented to maximize its vertical rigidity.

[foehnsturm 969]

When I looked at rail systems for my CNC many years ago, my impression was that one really needs a pair to avoid any significant wiggle. It just doesn't take much angular freedom at the rail to cause problems, when the tool extends out several cm. Perhaps designing the tool holder to keep the hot end as close to the axis as possible would help, but than your center of mass (and/or Bowden) will be way off axis and able to apply a substantial torque.

A lightweight second rail could be added opposite the tool changer to help reduce the degrees of freedom. This would be like the very small bearing used at end of the non-load bearing side of a rotating shaft, in order to offset the load. In thise case, the rail could be oriented to maximize its vertical rigidity.

 

I think you're right. There is a tiny play which at least causes a "mechanically" unpleasant sound when the printhead changes direction. I'm not sure if there would be visible inaccuracies in the prints but I don*t want to hear that. I ordered a pre-tensioned second rail and will figure out how to modify the setup.

[ultiarjan 1,223]

Maybe the actual impact is not that big... bcn's 'sigma' prints nicely with the head on 1 rail (at least I think it's 1 rail... not 100% sure. Only have pics from the front)

[foehnsturm 969]

I sorted out the main issue. The part of the belt tensioner which isn't bolted to the print head was vibrating.

[neotko 1,417]

Going back to the subject (please keep posting your progress on that printer)

The road so far...

I got this, hammer it with an anvil like I posted pages ago. But finally found a safe and steady hold for it. The problem it's that the fans... The fans suck big time. They are 30x30x10 Fans 24V (0.08amps each) from E3D shop. This fans you can't PWM them, they go full power at 240'ish or nothing at all at 239 or less... So I had to rething all, again... for the 25th time XD

So let's cut to the chase, literally..

Got my hammer, my mini 2kilos anvil out of the box and one of my metal chisels and slashed the 'fan' area to leave just the core, so I can properly insulate the head from the air and also make a heat barrier for the pla.

Also got the chance to hammer it again to make more clean angles.

And this it's the final state (but the fan holders are the beta, I'm printing new ones right now).

Edit: Important if you plan to do this mod ever. I changed the order of the wood laser cut so now the upper head has better heat cut. Also changed the springs for propper 4mm springs and they work fantastic. I have a 12dia spring being delivered that I'll add to the isolator coupler (a'la um2 style) and that should left this part totally undercontrol. Anyway this should and (imo) must be printed on at least abs. As soon I have time I'll print everything in carbon filament and update the desings because I did some minor updates to increase the precision).

Edited July 27, 2015 by Guest

[ultiarjan 1,223]

Ahhhhh. I also have some e3d fans but did not notice the pwm thing as I use them on a old manual controlled adjustable power supply....

[neotko 1,417]

Yeah a shame to just have to put on the bag the x4 fans. Also a lot of time wasted because I didn't even think that there where fans that could not allow pwm on the umo board. Also the other 30x30x10 fans I got from ebay when they arrived they surprised me with a 0.13amps so no way I plug that x4 amps on the fragile transistor of the board. I wonder if anyone knows how to know if a fan can be pwm by umo+/um2 boards. It's there any spec to check to know in advance?

[foehnsturm 969]

Well, the Darlington is good for a few (at least more than one) amps. I know, because I managed to fry it when I was testing the polisher tool head. Stall current of a motor is multitude of its rated current ;(

[Anders Olsson 136]

It is probably not much of a help, but I use SEPA MFB30G12 fans on my UM2 and they work fine with PWM: https://www1.elfa.se/elfa3~fi_sv/elfa/init.do?item=54-216-61&toc=20906

The data sheet says 120 mA starting current and 70 mA operating current for these.

[neotko 1,417]

That ones are 12v. The hard thing to find are 24v ones. The problem by using 12v on umo+/um2 board it's that it needs to go serial and x4 fans it's a bit risky. Even ultiarjan had to use the 2 fans of the second head using an external pwm. I will keep using my 40x40x10 fans.

Anyway thanks a lot!

Edit. Also since I had to rethink this the mod it's nicer since now I'll be able to swap fans (holder or the fans) very easily and without disassembling the head. Actually it's one of the thinks I'm most proud since with this head you can change heater/block/sensor without the big throuble of the original design. Well everything except the peek but that's just an impossibility of the original design since the peek must get some kind of dissipation from the aluminium. Also since the fans ain't steel/alu I added two extra ventilation holes that will blow a bit over the peek to make the ptfe isolator/peek last longer and avoid clogs. It's the little stuff that makes this mod cool.

I'm also making the v3 of this rethinking the clamp method and size of everything (except the laser cut alu since its on an area that can grow without hitting almost anything) but will take time. My goal it's to actually have the same printing area (hopefully) of the original dual design.

Edited July 28, 2015 by Guest

[amedee 349]

Actually, @Amedee is online in the new forum. Maybe he'll respond to the tag

 

Yes I always respond to tags...

... just need to be patient, it's not a secret I don't like this new community thing so I don't pass here very often. That combined with vacation time

But I'll have a look to add this feature in my builder...

[aviphysics 9]

For smaller fans, an RC low pass filter works pretty well. I used a 5 ohm resistor and picked a ceramic capacitor to filter down to 3kHz.

It kills some of your top end voltage though and it doesn't work as well with the electronics in my non-PWM crossflow fan.

Edited July 29, 2015 by Guest

[macua85 52]

Great thanks for that amedee. Its not such a pressing issue for me now though. I've put my printer back to oem due to constant problems with the e3d v6 jamming, despite all of my best efforts to rectify it. It seems to me that the area that isn't being cooled by the heat sink (the heat break between the block and the heat sink), is the cause in my case. The filament is swelling and jamming there.

Its a shame, I really like the design, maybe i'll go for the same hotend as foehnsturm. Can anyone advise where to buy from, that would ship to China? What max temp are they good for?

Edited July 29, 2015 by Guest

[foehnsturm 969]

Perhaps www.aliexpress.com or www.reprapdiscount.com. Might be the same vendor.

They're good for 250 °C. The PTFE inliner won't last forever.

[macua85 52]

Hmmm, I print at over 250 for XT with my oem hot end. Think it would last printing to 260?

[foehnsturm 969]

Well it should do 260°C. But for sure the PTFE will degrade faster.

[neotko 1,417]

You can always add a fan to the peek/ptfe.

Hopefully the last version. Went for a simple spring. The head upper never goes higher than 45C. After a 2h print this was the heat

It makes noise. But Since now the design only uses 1 spring if the fan deforms it's so easy to replace it.

I will check after a month of prints but so far perfect with this 30x30x10 24v fans connects to the 19-24v output of the umo+ 2.1.1 board

Another photo of the heat over 65C (yellow)

Edit: This it's now the configuration for the head. Much simpler and cleaner. The metal part arround the isolator coupler it's an m10 2mm used on springs, I placed it on my Vice and counter-twist it to make it flat, this focuses all the preassure on the specific point that needs to be hold and the upper wood helps with the heat as originally was designed. This with the fans 'so far' works like a charm. It took me a lot of goings but I'm so happy now.

Btw I forgot to publish this image from the 1month and ahalf status of my previus fan cap and this explains why I went for all the trouble of cutting the heat from crawling up:

Edit 2: One unexpected improvement also. The head dripping it's amazing low. It was low but now it just almost nothing. This will need more tests ofc. Also I'm going to really forget about z adjusting by screws. The way to go it's z change by software and since I already have 1-2 (almost 3) mm of range on the dock I will just meassure the difference from one to the other with a feller and make it by soft. That also will remove the chances of lossing alignment between the heads because z alignment. Less factors and less work.

Edited July 30, 2015 by Guest

[gr5 2,172]

foehnstrum is giving a talk in my home town about his tool changer! Check it out:

http://www.fab11.org/workshops/ops304/

Maybe I'll crash it and ask some difficult questions?!

[neotko 1,417]

I think a hard question could be how tonsolve the misalignment of the heads when replacing nozzles or adjusting z (well z should be pure z soft I think).

On my v3 I plan to focus on that (and size) by separating the upper nozzle from the adjustment area. Making the stock nozzle on a tight clamp with screws and adding a different set of screws that would attach to the upper block. This way the movment of the heater block/nozzle should be reduced to a minimum.

Can anyone record that sesion? I would love to see that...

[aviphysics 9]

foehnstrum is giving a talk in my home town about his tool changer!  Check it out:

http://www.fab11.org/workshops/ops304/

Maybe I'll crash it and ask some difficult questions?!  

 

So far :(. @foehnstrum, you are always welcome on the west coast too.

Edited July 30, 2015 by Guest

[foehnsturm 969]

foehnstrum is giving a talk in my home town about his tool changer!  Check it out:

http://www.fab11.org/workshops/ops304/

Maybe I'll crash it and ask some difficult questions?!  

 

So there is at least one person who can help me out if questions go over my head

[jonnybischof 60]

About PWM fan control:

The ideal thing would be an actual PWM control built into the fan. That's the ones with 4 wires, mostly used in computer CPU coolers.

I didn't find any 40x40x15 mm fans with PWM control. Only some 40x40x20mm which are very powerful, but also weigh a bit more than the thinner ones. And they only come in 12V versions + PWM control...

-> Sanyo Denki SAN ACE 9GA0412P6F001. www.mouser.com has it.

There is a more powerful (higher rpm) version, but I doubt that would make much sense.

You could easily power them using a 24V to 12V DC/DC converter like the Mean Well PSD-30B-12 (Mouser.com). *

The electronics switch the fan in the GND side, so as long as you connect the 12V's GND to the main GND (just put a wire from the input GND "DC-" of the converter to the output GND "-V" from the converter), you can even use the mainboard's PWM output.

The problem with small fans is that they have a relatively high detent torque. Usually, they're made to work just at the given voltage and speed, and you can only lower the voltage like 20 - 30% until they stop rotating.

PWM regulation behaviour can sometimes be improved by changing the PWM frequency (which would be difficult with Marlin).

* If you buy that converter, don't forget to also buy some mating connectors! I always forget these and have to unsolder the connectors and solder the wires directly into the PCB. Which is not so nice.

Edited July 31, 2015 by Guest