Profiles for my stepper extruder at 40mm/second

I recently picked up a MakerGear stepper extruder for my MakerBot Cupcake.. This thing is really cool but now I’ve got to go back and redo all my skeinforge profiles. This post, which I hope to update fairly frequently over the next couple weeks, is a collection of different combinations that seem to work pretty well..

Because the plastruder design I’ve got now is a big change from the standard MK4/MK5 plastruders, I’ve got to rethink my calibration routine.

With the DC motor on MK4/MK5 plastruders, you’re limited to pulling filament into the extruder between rates of about 1.5 and 2.0 RPMs. Since this value, the flow rate, doesn’t have a lot of room to tweak, it’s not something that I usually mess with unless I need to. Also, since this flow rate is directly related to build time, it’s something most people try to keep as high as possible.

With the new stepper motor, I can extrude at 0.25 RPM if I want. Or 3 RPMs. Or 4 RPMs. I can probably go even higher than that. Or lower. The point is that I’ve now got way, WAY more room to move around in this area, which means I get to (have to!) think about things from a different angle.

Instead of picking then layer height & w/t, pegging the flow rate at 2 RPM (255 PWM) then poking at the feed rate to get the profile right, I’m going to pick the fastest feed rate my machine can do without having problems then poke at the flow rate until the profile is right.

For my machine, a feed rate of about 40mm/second is what I have to stay under to keep things like echos & waves from showing up in my prints. So.. All these profiles have the feed rate set to 40. These are all for 3mm black ABS (which measures 2.8mm), a 0.35mm nozzle and a MK5-style drive gear. If you’re using a different filament drive gear, Beak90 has a note in the comments below on how to convert my numbers to ones you can use.

If you want to print at a faster feed rate, you can start with the values below then bump the flow rate a bit. How much you should bump it depends on how much faster you want to move.. Same thing with slower feed rates – go ahead but you’ll need to drop the flow rate some.

Since I plan to update this semi-frequently until I get a nice set of profiles done up, I’m putting an Index column in here too, to make it easier to see what’s new. Each time I make an update (which will hopefully include at least 3-4 new lines to the table) I’ll bump this Index up by 1. So, today is index 1, next update will be index 2, etc. I’m also including a Thread Width column, which is just the Layer Height * Width/Thickness value.

I’m only printing 4-5 20mm cubes for each one of these so they’re “not at all bad but could maybe use a little tweaking.” They’re good places to start and may work just fine on your machine. Or you might want to give them a little poke, just to get things perfect.

Index Layer Height Width / Thickness Thread Width Feed Rate Flow Rate
1 0.30 2.4 0.72 40.0 3.0
1 0.30 2.2 0.66 40.0 2.7
1 0.30 2.0 0.60 40.0 2.4
1 0.30 1.8 0.54 40.0 2.1
1 0.30 1.6 0.48 40.0 1.8

Notes…

Index 1: Wow.. Definitely seeing a predictable pattern in w/t vs flow rate here: the flow rate RPM consistantly changes by 1.5 for every 0.1 change in w/t.

I think that’s it for tonight.. For the next round, I think I’ll just do a few different w/t’s for each layer height and see how that goes. This might take a lot less time than I expected!

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13 Responses to Profiles for my stepper extruder at 40mm/second

  1. tmophoto says:

    cool!! my steppers just shipped today, i cant wait to get them and get started with this.

    t

  2. Rob Giseburt says:

    Are these RPM values actual, or the 2x RPM from my (still) broken firmware? 🙂

  3. beak90 says:

    The problem with just saying plain RPM values is that one person may be using a MK5 gear while someone else is using a home hobbed bolt while someone else is using some random timing pulley.
    A much better way of going about this would be publishing the mm/min of extrusion using any filament gear and giving a formula for finding the RPM based on the diameter of your specific gear. For example if someone has a gear with a diameter of about 11mm (the approximate diameter of a MK5 gear) and your table said to set the flow to a hypothetical value of 100mm/min then you would use the formula RPM = flow/(pi*d) to get the RPM needed. So for this example it would be 100/(pi*11) = 2.89 RPM. And for finding the flow in mm/min from RPM just use the formula flow = RPM*pi*d. I suspect that this is basically what 5D is doing behind the scenes, but until the firmware is updated to support this then I believe this is the way we should share this information.
    And the diameter you are measuring should be the diameter from the bottom of a tooth on one side to the bottom of a tooth on the other side. If it is hobbed then the outside diameter should be close enough, but if it is a timing pulley that has thick teeth then measuring somewhere between the top and the bottom of the teeth depending on pinch wheel pressure would work better.

  4. tmo says:

    is there any info on what firmware to use, how it works and what i need to do to get everything up and running for a stepper extruder? i cant seem to find any websites, etc that have any instructions on what to do to get it all to work.

    thanks for all the help/ instructions so far, it has been such a help.

    happy holidays!
    t

  5. Dave Durant says:

    There are some instructions at http://groups.google.com/group/makergear/browse_thread/thread/5616dadfb2a635d8# . I added some bits about machine xml and which firmware I’m using and some other, random stuff to the comments there..

    I know Rick’s pretty pro on the 5D stuff and is working on getting a collection of files and such together. Stay tuned – 5D should be good. (it’s all still just magic to me but I hear it’s really good magic)

    > happy holidays!

    Back at ya! 🙂

  6. Woofpickle says:

    Until I can get my own Stepper extruder from MakerGear …What is the slowest you’ve been able to get your feedrate/flowrate down to? I realize at some point ooze is going to outrun the motor after a certain point, but at the same time… I can’t possibly be the only person wanting to do ultra low speed prints for the sake of my eardrums! 😀

  7. Dave Durant says:

    For a DC extruder, mine started giving up when I got down to a flow rate of 180 or 190 PWM or so.. You can test this out in the repg control panel by plugging in different numbers and seeing if you can get plastic out of the nozzle. Start at 255 then drop by 10-15 or so to see how it does. Once you get to the lowest value it still works at, you probably want to add 10-20 to the number you end up with since extruding into the air is easier (less load on the DC motor) than extruding on a print.

    For feed rate, I never really tried to drop that too, too much – I think mid-20s is about as low as I ever went..

    To help with the noise, make sure you’ve put a little oil on your X & Y rods. Also, make sure you can’t turn the rods by hand; if you can, they’re too loose – pull them out and put a tiny bit of wadded up paper towel or something into the far holes they sit in to add some tension.

    Also, check out these Things, which upgrade your bot to use bearings instead of bushings on X & Y, which will rattle a lot less:
    – X stage: http://www.thingiverse.com/thing:4239
    – Y stage: http://www.thingiverse.com/thing:3697
    – both: http://www.thingiverse.com/thing:4213 (623 bearings) and http://www.thingiverse.com/thing:4430 (624 bearings)

    And you can upgrade your stepper drivers, which (I’m told) will make them a lot quieter. I’ve got one of these waiting to be soldered up: http://www.thingiverse.com/thing:4526.

  8. Woofpickle says:

    Well, that wasn’t quite what I meant…I meant had you tried slowing down your MakerGear Brutstruder. Living Vicariously though other peoples robots!

    True, I _COULD_ do that, and I’ve got all the bearings on hand to do either one of the lowrider mods…buuuuuuut I kind of started printing off bits for an Imperial Prusa, and I hate having two projects going at the same time, never seem to finish if I do that.

  9. Dave Durant says:

    Ohh… I think I’ve gotten it down to about 0.5 RPM or so. Certainly under 1 RPM.

    For feed rates, you seem to start losing the ability to do bridges & overhangs if you go too slowly so I usually try to keep that at around 30-40mm/s.

    The x-axis outriggers don’t look too hard to make – you might be able to do them AND another project. 🙂 What would be reeeally convenient would be makerbot upgrades that you could move to a mendel later..

    Unless you’ve already got the electronics, you can probably use the upgraded steppers on the cupcake now then transfer them over to the Prusa, once you get it all built. Rob Giseburt – see link in comments above – would be able to say for sure. He also hangs out over in #makergear on freenode pretty frequently..

  10. Woofpickle says:

    Naaaaah, where’s the fun in that? I like the idea of having more than one printer going at a time, especially if I can figure out some form of conveyor belt for the Prusa! Multiple single sheet runs of Mendel parts, anyone? ^.^

  11. tmophoto says:

    do you have any recommended settings for the high resolution at 55mm/s .35 nozzle and around .2 layer height that i could try out? the filament that i am using is an average of 2.8mm.

    i don’t have a pc so i haven’t been able to use any of the new calculators that have popped up on thingiverse.

    thanks
    t

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