1 Topic by Otatiaro

  • Otatiaro
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Topic: Speed improvement ?

Hello,

I'll probably get my Solidoodle end of january ... ordered about 1 week ago.

BUT ... I'm already looking at possible mods. I'll be using the printer for pro usage and need my parts fast and clean. Most of these mods are just ideas at the moment, and of course I'll wait for the printer to arrive and play a bit with it before modding it.

First question is if the printer would benefit from higher speed on X and Y axes ?
I could replace the X and Y drivers by CNC stepper controllers + 48V 8A power supply, that would probably speed up the X and Y axes by a few hundreds of percent.
But then the second question is what is the maximum pulse frequency of the sanguinololu electronics ?
Can it handles at least a few tens of KHz ?

Would the extruder axis need a speed boost too ?

Then about the heating bed, it seems it is very slow to get to the temperature + it seems glass bed is a lot better and quite cheap. I'm thinking about a heating PCB the right size sticked on a thin glass bed (2 or 3mm ?) and glass wool on the other side to keep heat from spreading everywhere. The 12V power supply would be replaced by a beefier one (480W ?). I would probably drive this heating bed with external electronics (bigger/multiple MOSFETs, I'm in the electronics).
Am I right ?

Finally, it seems adding a fan is a great improvement for small parts, bridges and overhangs. Is there some output available on the electronics to drive it ? And can the various software be setup to control it during extrusion ?

Also I have an hot air blower for electronics soldering, on which I can control temperature (from 50 to 480°C) and air flow ... I was thinking about bringing this warm air instead of the fan ... to get the part a bit warm for better sticking between layers and keep the plastic cooling faster, temperature would be around 100°C I think.
Would this be a good idea ?

Thomas.

2 Reply by IanJohnson

  • IanJohnson
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Re: Speed improvement ?

Nothing needs to change with the motors to make them go faster.  The acceleration functions in the firmware smooth out the motion enough that they can go quite fast.  The limiting factors are how fast it can extrude the plastic to keep up with those high speeds, and overshoot.

The options for speeding up extrusion are a larger nozzle (.5mm) to reduce the amount of pressure in the hot end, and higher temperature so the plastic melts faster.  I tried a larger nozzle, but it didn't seem to make much difference.  There is a limit to how hot the Solidoodle can go, because it is possible to melt the black insulator barrel.  You can either get another all metal hot end like the Arcol and make a mount for it, or  use PLA.

PLA melts at lower temperatures, and is more runny so it is more likely to flow fast enough to keep up.  However if you need to make prints that are highly finished and don't look like they were from a printer, you will need to fill and sand by hand.  You won't have the option of using solvent vapor as with ABS, unless you work with some chemicals that are far nastier than acetone.

The other problem is overshoot.  There is enough flex in the system to allow the nozzle to go a little too high when changing direction at high speed.  You can see an example of it in the bunk bed, where the corners are pushed out where the cross beams meet the front supports-

http://solidoodletips.files.wordpress.com/2012/11/img_2251.jpg

The way you avoid overshoot is reduce the mass of the extruder.  The best option is a Bowden tube, like the Ultimaker uses.  The motor and gear are mounted on the back of the frame, and push the filament through a PTFE tube to the hot end.  Since the nozzle is the only thing on the X carriage, it is much lighter and can run at higher speeds before running into overshoot.

You can minimize overshoot by avoiding high speeds where it will be evident.  Run the outer perimeters slow, then use high speed for the inner loops and fill.  You might need to reduce the setting for the amount the fill overlaps the perimeters, and let the overshoot make up the difference.

You can set up a fan to be controlled through gcode.  See my blog post here - http://solidoodletips.wordpress.com/201 … ruder-fan/

3 Reply by Otatiaro (edited by Otatiaro 2012-11-09 18:01:33)

  • Otatiaro
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Re: Speed improvement ?

Hello,

Thanks for the info ... I guess it's the same trap as for CNCs ... want faster, need more strength, but strength is adding weight, so need more power, then need more strength ... and you end up with a 300k€ Mori Seiki CNC big_smile

PLA is probably a good options for some of the parts, but I'll need some "warm/low heat" resistant parts also.

I'll do the fan mode described in your blog post, very nice.

What about the bed ? The picture you posted shows significant warping at the bottom, would a better heated bed help ?

I have to check the Sanguinololu heated bed output MOSFET if it can handle it (changing the power supply) but I can design a PCB 15x15 cm with a 1ohm trace at 150°C (about 5m length by 3mm width), that means 12A at 12V for a power of 144W. With the correct power stage and PID regulation it would probabl be a lot faster to achieve temperature, no ? I just checked, I can have 10 PCBs made for about 120€, that's 12€ per heater.

Thomas.

[EDIT] Are the RX/TX pins on the Sanguinololu header free and can they be used to send/receive (at least send) serial byte ? I could use this to interface an external temperature regulator for the bed, I highly doubt the Sanguinololu would accept 12A on the 12V line.

4 Reply by elmoret (edited by elmoret 2012-11-09 18:08:03)

  • elmoret
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Re: Speed improvement ?

You'll burn the heated bed traces at 12A for sure. I think the MOSFET will handle it, though. I also think there's at least one serial pair open as long as you don't used the LCD/SD card mod.

Why not use a SSR off the existing Sanguinololu header? They're about $10 for the size you want.

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5 Reply by Otatiaro

  • Otatiaro
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Re: Speed improvement ?

Hello,

Yes 12A straight on would probably burn the traces ... this is why it would need PWM control and PID regulation.

Don't know SSRs very much, can they be fast enough for a few tens of KHz PWM ?
PWM frequency has to be quite high to not burn the traces (at start, a few seconds at 12V would obviously destry them).

Thomas.