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npdion

Setting Zero

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HI - I am a retired CNC machine shop owner and my daughter thought that I needed something to do, so, I received a 3D printer for my birthday last week. I hadn't thought that it was something that I really needed, but the more that I've gotten into it - the more I think that maybe I do!

At this point, I have spent most of my time renewing my CAD modeling skills (it's been a while) and I've printed a few sample open source things that I picked up from OnShape's web site. Here is my problem - on my CNC mills I had a "floating zero", that is, I could set my zero point anywhere on the bed of the machine and program in any of the four quadrants around that zero point. I assume that machine zero on my printer (a new X-one from QIDI) is the front left hand corner of the support plate (designated as the "Home" position) and all commands to it are X+ and Y+. All of that is fine, my question is - how do I offset the start point of the print? Several of the files that I have downloaded are attempting to print beyond the edge of the support plate. All I want to do is move the start point over an inch or so, but I can't find a way to do it in the Cura software. There is, under preferences - Build Plate Adhesion, a check box that reads "Extruder Prime X Position" and a similar one for "Y". I checked those, but I still don't see any place where I can change the start point of the print.

Thank you, in advance, for your help. I'm looking forward to this new adventure!

N Dion

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G92 is your friend.

After cura creates the gcode file you can go in there and edit it (now don't panic - you don't have to do this every single time). Look at the gcodes - somewhere there should be G28 commands to home different axes. Later you can do a G92 to set the position. For example G92 X-20

should tell the printer that print head is currently at position -20. I've never tried negative numbers but it should work.

Alternatively in cura check to see if machine type has the center at 0,0 or if the corner is 0,0. Usually 0,0 is at the home position.

More on gcodes here:

http://reprap.org/wiki/G_code

I'm assuming through all this that your printer uses Marlin or Repetier or some other firmware that is on that above web page.

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Oh. Also you probably want to use Cura 15.X and not the newer Cura 2.X. 2.X is a big rewrite and some features may be lost or hard to find. Cura 15.X supported lots of printers quite well - not sure that Cura 2.X is there yet (soon I hope).

In cura 15.x you can go to machine settings and setup some of this stuff - like how big your build plate is and where the center of the machine is.

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In cura 15.x you can go to machine settings and setup some of this stuff - like how big your build plate is and where the center of the machine is.

 

You can do that in Cura 2.3 as well. Printers -> Manage Printers -> Machine Settings

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All good stuff above, but why not

right click the model in Cura and select "centre model on platform"

if it is still trying to print beyond the edge of the print plate, ie grey in colour, then it is too big and needs to be scaled smaller.

Of course I am assuming that a printer has been defined with the correct x/y/z dimension settings.

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G92 is your friend.

 

Well, kind of...

When it comes to coordinates, the GCode used by the traditional 3d printer firmwares (Marlin, Repetier, ...) is nowhere compared to what CNC are doing.

G92 will (re)set the coordinate system, not create a 'user space offset' like you do with G54,... on a CNC.

Once you change your coordinates with G92, if you are using software endstops (like it is configured on UMO+/UM2 printers), you will crash the head on the borders if you go out of bounds, because the firmware won't see it...

The safest way is to place your part in the slicer.

 

More on gcodes here:

http://reprap.org/wiki/G_code

 

Indeed, very good resource.

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Of course I am assuming that a printer has been defined with the correct x/y/z dimension settings.

 

Lol. well that's the problem. The 0,0 point is in a different spot. So cura puts 0,0 in the corner but his printer probably puts it in the center of the bed. So when he prints in the center of the screen in cura it's printing in the corner on his machine and partly outside the build volume.

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OK I get that but when you define a custom printer in Cura there is an option entitled "machine centre is zero" which I assume compensates for that? A bit outside of my knowledge area as I use Repetier Host to control my printing and that has a separate dialogue for locating the origin on the printer bed.

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