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I've been through the dimension saga myself, it takes weeks of careful measurement, adjustment, hypothesising, noticing that the error is still there, trying something else, having a sleep, and general problem solving to get to the bottom of it. Things I would look at: * Take careful measurements of...

Your frame is probably not square.

You can either square it up with a set square, wire, calipers, and a lot of patience, or you can use this calculator to adjust your parameters:

http://escher3d.com/pages/wizards/wizarddelta.php" onclick="window.open(this.href);return false;

Have you tried tuning the bridge flow parameter, as well as changing the cooling on those overhangs?

Got a pic of the problem area?

You might have introduced frame twist, that causes weird Z behavior between towers. Check with a large square, ensure that all towers are parallel and not twisted.

I recommended casting because I also have first had experience molding complex parts via molding and it has way fewer challenges. Shrinkage is almost non-existent with many of today's resins. There are some incredible resins that have properties remarkably similar to ABS. I know several people who ...

Thanks Xenocrates, that's very helpful. The 3D printed parts are accurate to within about 0.01mm I think. It's hard to measure. All I have to go on is that I can change the extrusion multiplier, and there is a range of about 2% where the parts fit nicely (on a 0.4mm extrusion width). Any more and th...

RE: rotational casting. There really isn't any way that rotational casting would have the pressure needed to make accurate lego pieces, unless I'm missing something. It needs reasonably high pressure I think? Sure rotational casting might work for something like a rubber duck, but I'm talking about ...

Bridging: Set your bridge flow ratio to 0.5 - 0.75. This will extrude less material when bridging, which stretches it between points rather than letting it sag down. Overhangs: Lower your temperature by 5 degrees, or set your layer fan to run slowly. Yes, even for ABS. First layer: Your extruder is ...

Thank you all. By "hollow" I think I really mean "thin walled". A lot of this terminology is pretty new to me :oops: I've tried plastic casting before using Alumilite resins, and RTV silicone moulds. I found it messy, unreliable, expensive, and generally not a viable option. At l...

The max size of a "Lego" piece is 100mm x 15 x 15, and it's mostly hollow so volume would be only, say, 5ml. I thought that the mill would have to be able to face the entire mould though, hence my 200mm figure.

123D Design works on a mac, I use it all the time. Seems to do the job.

I've seen some posts from some people on here that seem to know about milling and injection moulding, so was hoping for some advice. Basically I've got a product that is broadly similar to lego, in that it interlocks like Lego does. The pieces are for a game that has been in development for many yea...

The most common way of doing this that I've found is: * Calibrate endstops so that nozzle is at 0 when brushing a piece of paper near all three towers * See how far off the nozzle is when at the centre * Adjust delta radius * Go to step 1. The problem with this is that you have to calibrate the end ...

Bob64, I do things exactly the way you describe, it's the fastest way to get the delta radius that I've found. I can normally get it within 0.1mm in 5 minutes or so.

Would it be able to produce injection moulds for something like normal Lego pieces, out of aluminium?

I'm actually looking for a CNC machine that would do this.

Perhaps try increasing your ABS temperature as well. I print ABS at 255 / 240 most of the time for small parts.

Looks like your parts need more cooling. Increase your part cooling fan percentage.

There's some elephants foot happening here as well, lower your bed temperature by 5 degrees.

A cooling fan WILL help with this part. Here's one printed in ABS at 0.1mm layer height, I think around 230-240 degrees, with a weak cooling fan aimed squarely at his face. Make sure it's weak, you don't want much. My fan was a good 50 cm from the edge of the build plate. Note that the keyring part ...

13mm seems way too high. You might be seeing air bubbles due to severe overretraction, which would fit with the popping noises you're hearing. I would set retraction to 5mm or so, and see what happens.

Another option is to use a flying extruder. Here's one that I designed and have been running on my Kossel mini for a month or so: http://www.thingiverse.com/thing:1259941" onclick="window.open(this.href);return false; [img]http://thingiverse-production-new.s3.amazonaws.com/renders/f6/9b/ed...

Would it be possible to add hall effect sensors to the output shaft? Then you wouldn't be limited to sensored motors. No idea if that's possible, just spitballing an idea.

http://mitrocketscience.blogspot.com.au ... t-for.html

What voltage are you thinking of running on your motor? Also what is the max RPM you need it to go? This will determine your KV (rpm per volt). I can't help you much about the hall effect sensors, sorry, never dealt with them before.

Keep up the great work here, I'm really enjoying reading about this. Learning a lot from your documentation. One day I'd like to have a DIY CNC mill. Does anyone have experience with hobby RC motors, like large outrunners? I'm planning on using a 2-3 kW outrunner with a hall sensor to drive this spi...

Fair enough Miglo. Just thought I'd mention it as this has bitten me before and I spent an inordinate amount of time trying to figure it out.

Can you watch your print next time (the hollow one is fine) and see if it's swapping from clockwise to anti-clockwise where the bands start/stop?

Is your slicer set to do some solid layers every now and again when printing infill? If so then there's your problem, I can guarantee that the solid layers correspond to your bands. Also related is using a bowden cable, and pushing more filament out per second when doing solid infill compared to doi...