Tag: z axis

3D Printing Questions – Z Offset for First Layer Nozzle Height

Everyone knows that getting your first layer right is 90% of the battle to getting a successful 3D print. Even if your temperatures and everything else are correct, if your nozzle height is off you will get bad adhesion on the first layer.

Setting it up is actually pretty simple, but it can be confusing. In this video I explain, in very deep detail, what all the parameters and settings do that control nozzle height on your first layer so that you can get perfect first layers. In this video I am using a Cartesian style machine, a Prusa i3 MK2, and Marlin as the firmware – but the principles will remain constant for most printing systems.

Reprap / Prusa 3D Printer – Complete Initial Setup & Configuration – Step by Step

Bit of a monster video, for me, at nearly an hour. It is compacted as much as possible but there is a lot to fit in!

You can use these links to jump to specific steps in the video:-

Step 1 – Limit Switches
Step 2 – Motor Direction
Step 3 – Homing & XYZ Zeroing
Step 4 – Maximum Endstops
Step 5 – Bed Levelling
Step 6 – Z Probe/Bed Sensor
Step 7 – Extruder Calibration

I power on the printer for the first time and set up the Limit Switches, Axis Movement, End Stops, Bed Extents, Bed Levelling, Z Probe/Bed Sensor and do the Extruder Calibration!

I spent quite some time going through the Marlin documentation to see what each possible configuration instruction could do. I had already done a very basic run through of the Configuration.h file in this video/post but now it was time to get it spot on.

One side benefit of the exercise is that I can see I will need to change the way I mount the heated bed. Most importantly the nyloc nuts sitting on top reduce the Y axis extents by nearly 25%!!!!. But secondly the ply wood under the bed allows the nuts to squash the edges down too much, resulting in the opposite bed bend to that I had before! Still, good enough for a first print 😉

How to Build a Cheap Prusa I3 MK2 3D Printer – Building Z Axis & Extruder

Aside of being careful to keep everything lined up, parallel & square the build of the Z Axis, mounting the Y Axis and putting all the extruder and hotend parts on was pretty simple and in line with the official Prusa Manual.

Really the only thing I had to find a solution for was mounting my lead screw nuts. Toms version uses 5mm threaded rod and he provides STLs for parts to hold a M5 nut for that. The original MK2 looks like they use their own lead screw nuts. The ones that came with my lead screws had their mounting holes too close together and there was no way to centralise the nut in the Z carriers. I customised Toms Z nut holdahs to do the job – which it seems to do fine.

I will say this though, after building it all I examined the extruder to “sanity check” it and it turns out that it was very tricky to feed filament through the extruder and into the telfon tube running to the hotend. I will do an extra post discussing that as I think it is a mis-match between the extruder body design and the commonly available MK8 hobbed gear. I think if this was left unchanged, apart from having to use tools to get it to feed in, it would put a lot of load on the extruder stepper just to overcome this tightness.

I would also recommend that if you can squeeze an extra £20/$30 to get a Z axis frame laser cut – do that. It will save you a lot of time and insecurities about the Z axis being parallel and square. My wood will probably work fine, but it’s just a lot harder to make sure it is correct.

A Better Prusa i3 Frame Template?

I decided to get on and cut the frame out first – made from two identical pieces of 12mm plywood glued and screwed together to maximise rigidity. ( I used 2x12mm as I had a sheet of 12mm lying around)

As I discuss in this video – I found the PDF template found on Thomas Sanladerer’s site a little bit tricky. It might be that its just lost quality due to scanning or something but the exact cut lines are hard to figure out as there is a double line around the edge and the hole marks are also slightly vague. On top of that I found it quite awkward to line up when printing on multiple sheets of A4.

So I made my own! Hopefully it helps out someone in the future looking to cut their own Prusa i3 frame.

Download it here.

As you can see, it is designed to be printed onto 6 A4 sheets – then each sheet should be cut along the green dotted lines. The edges these leave should be butted up against the red lines (not to be cut!!). Tape it all together and there you have it.

You will notice that this is slightly different to Tom’s – not in dimensions but in corner treatment. I have changed all internal corners into 5mm radius arcs. The idea being that you drill all these points with a 10mm drill before cutting out. This is much easier to do that trying to make accurate tight angles like the original.

One thing to note; I have only included the centre marks for the Z Axis top and bottom mounts. The rest are either for tie wrapping wires to or mounting the power supply/control boards. As none of that is critical, I left them out.

The other thing I might suggest is to only drill the two Z axis mount holes at the very bottom, then drill the rest using the actual 3D printed parts as a template. The reason being is that, with all the best will in the world, it is unlikely you will drill them all accurately from the template. As Tom found out.

My method was to drill the two bottom holes, use those to bolt in place the bottom Z axis mounts, then attach the smooth rods and top mounts and align everything up with a square. Mark the position of the rest of the holes through the 3D printed parts and then drill them.

© 2017 Jules Gilson

 

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