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|
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!