Anyone know how to get Sfact to home xy after printing a set amount of layers?

As the title really.... Anyone know how to get Sfact to home xy after printing a set amount of layers?
-the home button seems to be missing. I dont want it to do it every layer (if poss...)

Thanks

You don't want to home during a print. Home before the print starts or in the start file.

If you're missing steps, you need to fix the reason for the missed steps.

Is there a good reason to home the x and y periodically?

Well, i had some problems with my gen 6 missing steps, so i added a heatsink and fan, turned the stepper trimpot up to 2.8v but still missed steps. Didnt realise steppers miss if they get hot too. Voltage back to 2 volt. located problem as a dodgy y axis pulley. Changed that, but i was still a little concerned. I ran a gerber sabre 408 for several years and that would home/ restart perfectly; saw a homing button in skeinforge, thought i'd try it, but no button in sfact, although there is still a homing
.gmc (sfact gcode) in the alteration folder.
doesnt anyone use it?

Homing only makes sense at the beginning of the print, so the machine can figure out its position. I home using commands in start.gcode, but in principle I think putting them in homing.gmc and enabling that would have the same effect.

I read that the original reprap host software homed before every layer... so why is this so bad?

I ran a 224 minute print - and went out. when I got back, I had prints as shown in the attached pics.
I can see that it is a stepper skipping problem, but I dont know why.
I have a heatsink and fan on the gen6, and the x and y motors were (reasonably) cool.
The extruder motor was hot.
If the extruder stepper overheats, will it affect the x and y motors?? This is the only thing I can put the missing steps down to.
Do I need a fan to cool the extruder stepper? (its an Adrian's) - I'm guessing I do?



these were run at 30mm/s
I have tried 184 degrees through to 205
Replaced my (rubbish) steel z studding for stainless (helped on the strata layers - a lot)
belts tight
Pulleys on firmly - flats on shafts
I've just changed back from sfact to skeinforge with Mendelparts settings for 3mm pla (slow) so I'm hoping to see an improvement.

Any advice on how to get my prints looking generally better would be appreciated too.. - bit lumpy... its weird - when I make a thin wall box test, the walls look lovely. I think its the infill that is ruining it.

Quote
Lucastar
I read that the original reprap host software homed before every layer... so why is this so bad?

It's not so much BAD as unnecessary.
I don't know about other RepRappers but I always build objects in the center of the build plate.
Since I now use a heated bed this helps to keep the object in warm air.
A home operation requires that he move to the lower left hand corner to reset 0, 0 and then go back to 100, 100.
This takes some time and can cause the plastic to drip (especially if the gcode doesn't back up the filament).

There are only two problems that the homing every layer fixes:

1. Steppers are losing steps
2. Hot end caught on plastic shifting position

BOTH of these things should NEVER occur and if it does then you should FIX THE PROBLEM.
I believe that Adrian and nophead (Chris) had some discussions on this topic.
Skeinforge can also home each layer and/or print a wiper but most Skeinforge users do not do this as it is unnecessary and just uses time (and plastic if the wiper is aktivated).

It's like the story of someone with a big hole in his driveway that he keeps falling into and hurting himself.
He says, "It's dark, I didn't see the hole" or "I was blinded by the lights", or "...".
THAT is NOT the PROBLEM - FILL IN THE DAMN HOLE!

I see the homing in the same light, it is a workaround for a couple of problems.
Don't use a workaround - FIX THE PROBLEM!

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

Ok, point made...

I ran a 113minute print, and after 25 mins, the extruder was hot. so (as it was running) I stuck a fan to it. The extruder stepper cooled down.

Although the print run was shorter than last time, there was definitely no missing steps.

Quality looks terrible though - it was my first run with skeinforge 41 from mendelparts, running Camiel's 3mm PLA Slow setting.

What you might not see on the photo however, is that the print quality is almost perfect from about 9mm to about 11 mm, then it all goes bad again.
I've adjusted the layer height to 0.32 - - with a W/T of 1.6 (Camiel's original was 0.4 and 1.6)
Trying again...

I've been using Sfact up until now...Am I better off with skeinforge, or Sfact?

I am using Skeinforge 44, SFACT is supposed to be easier to get good prints with quicker.
I haven't been able to get SFACT to work on my system (yet).
Are you sure your E_STEPS_PER_MM is set properly for your extruder?

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

E steps are set - although I did it with the hot end attached... not sure if this makes a difference - shouldn't think it would


I changed the layer height to 0.3125 from 0.4 - that keeps at W/T 1.6 - for a 0.5mm extrusion width.
Infill perimeter overlap=0.1,
Infill W/T=1.6
I've never got a print as good as that with Sfact (yet...) but I have been working on a W/T of 1.56 and 1.7
I (almost) cant believe what I am seeing! I can even get an M4 screw through the hole without drilling!!!!!

(ok - I know that I'm not exactly a pioneer here, but it really is a major breakthrough for me!)

I didn't realise how important it was to keep the steppers cold as well as the driver chips though. Oddly enough the Y motor doesn't get hot when running, but the X still gets quite toasty. I might attach a fan to that too...


I do find that if I run with 'extra shells on base layer' switched on (fill tab), the second time it traces the perimeter, it pulls the first layer off.

Now I only switch 'extra shell on sparse layer' to 1, all the others I switched off.

I would really like to get the first layer to stick a little more reliably - as you can see, the base is a bit ragged on the edge.
I might switch the raft back on, with layer as 0, and run it at 15mm/s (slows print-head without actually making a raft)

I also don't know how to stop the weird l random lines in the top surface of the print.... any ideas???


Incidentally, Sfact is pretty easy to get running - just rename the skeinforge folder in your printrun folder (or wherever you have it) to skeinforge-old and dump the Sfact folder in printrun folder and rename as Skeinforge, and it seems to do the trick. You don't have to mess with your old skeinforge settings - it runs them independently.
To change back, I just rename the folders again. (although I'm sure there is an easier way) Sfact will pretty much print (something) out-of-the-box.

It isn't important to keep stepper motors cool, other than preventing them from melting the brackets. They are rated to run up to 100C. When I run mine in a heated chamber they are too hot to touch, probably about 60-70C, but they don't miss steps. The resistance goes up, but with a constant current drive it should compensate and keep the torque constant.

The random lines on the top could be ooze while the head moves across it, or if the flow rate is a little high furrows from the nozzle ploughing though it during moves.

Edited 1 time(s). Last edit at 11/10/2011 10:32AM by nophead.

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[www.hydraraptor.blogspot.com]

So, what you are saying is that I haven't solved my skipping stepper problem with the fan - I just got lucky?

Sometimes the nozzle gently touches the plastic that has already been deposited as it moves so the flow rate might be a fraction high I think, Chris..- although I did measure 100mm of filament. when working out my E-STEPS. I guess that the stepper might slip if the nozzle bumps though...

Should I turn that down in the firmware? or in Skeinforge?

I could imagine temperature affecting the motors if they are high voltage, i.e. close to the supply voltage. It doesn't seem to bother the 2.8V motors which are normally used.

The easiest way to tweak the flow is to adjust the Filament Packing Density in SF.

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[www.hydraraptor.blogspot.com]

I've tweaked mine from 2.1v through to 2.8v and back down to 2.1 - The heat-sink didn't seem to make a lot of difference.

I'll try the Filament Packing Density adjustment in the morning - I've tweaked it to 95% but I've got a small house, and the Mrs is getting irate at the noise, so it will have to be printed in the morning. I'll post up my results here.

The blocks shown in the attached pic show what happens when I turned the Infill width/Thickness from 1.6 to 1.5 - shame I did a 198minute print of these!

Changing W?T should not make a lot of difference. SF calculates the necessary volume and extrudes the amount of plastic with the nozzle height and line spacing to match the T and W demanded. I.e. if there is too much or too little plastic you can't fix it by changing layer height or W/T. You have to fix E_STEPS_PER_MM or tweak the Filament Packing Density.

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[www.hydraraptor.blogspot.com]

I think first there probably is a lot of play in all the x y and maybe even z axis, and probably belts too loose. Backlash kinda, but i'd say looks more than that. This kinda makes your layers not sit perfectly one on top of another. Imo, recheck everything, tighten belts at least.

Also i think your hot end might have some issue, from pictures i think its "squirt" is not consistent. It does not look like making a nice even and consistent deposition. Maybe the extruder temperature swings too much and gets too low in lower area, or temp is generally too low, or its hole has some obstruction, or leaks, or something like that. Try do a print with all speeds not bigger than 16 mm/s, even maybe lower than that, and temperature like 10-15-20C higher. That could ease things for extruder, and if there is an improvement then thats your cause. If looks the same, then you are in the hole.

Seems kinda weird and unhelpful the way i putted it, because fixing x y z and then the extruder is basically everything there is, but i couldnt think of any better specifics.

Edited 3 time(s). Last edit at 11/11/2011 10:13AM by NoobMan.

I also suspect the extruder or hot end. It's also possible that the drive gear or hobbed bolt is slipping on the feed.