Next up is actually creating a new profile.. I’m using Skeinforge 33 for this, dated 10.11.10, but any version close to that should work pretty well.
I know 2 ways to dial in a new skeinforge profile. One, the one this post is not about, involves picking layer height & feed rate then printing a thin-walled object and measuring the wall width. You do a little bit of math to figure out the width over thickness (“w/t”) then plug that into skeinforge.
There’s nothing ‘wrong’ with this method – lots of people use it – but I don’t like it. I’d rather pick layer height and w/t then tweak the feed rate until it comes out right, which is the other way. The way this blog post is going to talk about…
The reason for my preference here is that layer height has a lot to do with resolution – how ‘fine’ the object is printed. Similar, the w/t values say a lot about the strength of the object. Basically, layer height and w/t are characteristics of the finished object.
Feed rate and flow rate, on the other hand, don’t really tell you anything about an finished object – they’re more about the process of how the object was printed than about how the object ends up.
Because of this, layer height and w/t are values that I want to choose. Within reason, I’m not too concerned about where the feed and flow rates end up – I’m more interested in the resulting object.
All that said, on with making up a new profile. I think the basic process has 2 big parts: The Setup and The Test & Tweak. This post is about The Setup, the next one will be on Test & Tweak.
The plan goes something like this:
- Decide on your target layer thickness and w/t values
- Clone an existing profile and give the new one a descriptive name
- Plug your target values into the new profile
- Take a guess at what the feed rate should be for the new profile
- Make gcode and feed it to your ‘bot
- Examine the result, tweak the feed rate
- Back to step 5
1: The first step is to pick some reasonable values for layer height and w/t. By reasonable, I mostly mean something your hardware is actually capable of printing; probably a layer height in the 0.20 to 0.50 range with w/t values of 1.2 to 2.0.
If you’re shooting for a profile that’s a lot different than one of your existing ones, I strongly recommend doing a series of profiles and working your way towards your goal. This may seem like a lot of extra work but once you do it a couple times, you’ll find that it goes pretty quick. Similar, if you’re changing both layer height and w/t, it’s probably easier to concentrate on just one of those parameters until it’s pretty good then go back and do the other one.
If you don’t actually have a decent profile to start from, don’t worry – below are some combinations I’ve used before. Some of these are better than others but all should at least be in the right ballpark. If you haven’t done a lot of printing before and are picking one of these combos below, you probably want to start with one that’s got a feed rate under 45 or so. Moving faster is certainly possible but takes a bit more work & care – start slower, work up to it.
|Layer Height||Width/Thickness||Feed Rate||Flow Rate|
(yeah, my HTML table-fu stinks.. 😦 )
2: Clone an existing profile and give the new one a descriptive name.
Next up is creating a new profile. Fire up skeinforge and, near the top, click the Profile button then click the Extrusion button below that. At the bottom, there will be buttons for Add Profile and Delete Profile with a list of your existing profiles above that.
You should give your new profile a descriptive name. I usually use names like “0.5mm, 0.32mm, 1.6, 3.0mm” which means it’s for a 0.5mm nozzle, 0.32mm layer height, 1.6 w/t and 3.0mm filament. Use whatever you want but if you call it something like “asdf” or “test”, you’re probably not going to remember what that means, a couple months down the line.
In the list above the add/delete buttons, single-click the profile you want to clone, type the name of your new profile in the area to the right of the Add Profile button then click the Add Profile button. That’s it – your new profile is started.
At least for me, I need to exit and restart skeinforge at this point. If I don’t, it gets a little bit weird and doesn’t let me use my new profile. No big deal – just close skeinforge then start it back up.
Near the top of the skeinforge window, make sure the Profile Type is set to “Extrusion” and the Profile Selection is set to your new profile then click the Craft button, just below those.
3: Plug your target values into the new profile.
Unless you’ve done this a few times before, now would be a good time to wander through all the pages in skeinforge Craft and compare them to my previous post. You don’t need lots of things enabled at this point; you’re really not going to be looking for the perfect print here – you’re just looking for the right combination of the Big 4 (or 5) Settings.
In addition to plugging in the Big 4 (or 5) Settings, there are a couple other things you should set while you’re in there. Here’s my checklist for when I’m printing 20mm calibration cubes:
- Carve\Layers From = 0
- Carve\Layers To = 10000 (or any really big number)
- Carve\Layer Thickness = your target layer thickness
- Carve\Perimeter Width over Thickness = your target w/t
- Fill\Diaphram Thickness = 0
- Fill\Infill Width over Thickness = your target w/t
- Fill\Infill Solidity = 1.0 (yes, really.. set this to 1.0 for calibrating)
- Fill\Infill Perimeter Overlap = some value under 0.25
- Temperature\All Settings = 210 (or whatever value you extrude at.. usually 210 or 220)
- Speed\Flow Rate = 255
- Speed\Travel Feed Rate = 50
- Speed\Feed Rate = your best guess.. 🙂
Since you’re starting with values you chose for layer height and w/t, and since I said to just peg the flow rate at 255 (full speed on the extruder), the only one of the Big Settings left is feed rate. For that, you really do just have to take your best guess.
That said, you can make it a fairly educated guess by looking at various combinations of settings that should work and comparing them to the combination you’re trying to make work – the correct feed rate should go up or down based on if you’re raising or lowering the layer height and if you’re raising or lowering the w/t. In general:
- Lower layer height or lower w/t = higher feed rate
- Higher layer height or higher w/t = lower feed rate
- Change feed rate by 3-4 for each 0.01mm change in layer height
- Change feed rate by ~5 for each 0.1 change in w/t
So, if you’re going from 0.32mm layer height to 0.30mm layer height, you probably want to start by adding 8 to the feed rate. If you’re going from a 1.4 w/t to a 1.6 w/t, you should subtract about 10 from the feed rate.
Forget about fractions here – just use whole numbers – and when in doubt, aim a bit high with the feed rate.
If you’re stressing over get this wrong, don’t worry about it – unless you guess really, really low on what the feed rate show be, nothing bad will happen. If that doesn’t decrease your stress level, just do your best on getting it about right then add 5 to it. Don’t worry.
The Setup is almost complete.. The only prep left to do is to head over to Thingiverse and grab the 20mmbox.stl file from Spacexula’s Makerbot Calibration Set. The other pieces he’s done are also good but I’m just going to be using the 20mmbox object.
That’s it! Next up will be printing the 20mmbox and dialing in your profile.