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UM2 does Not meet its build volume specs

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UM2 is stated by Ultimaker to have a Build Volume of 225x230x205.

Apparently this is a case of marketing gone wild - the entire size of the glass plate is not available for printing.

I created a rectangle with 2mm wide lines, and removed the corners to avoid the clips. I incremented the X and Y size until Cura 14.04RC1 would no longer allow saving the gcode.

The actual maximum build plate size object Cura will accept for a printer defined as a UM2 is 228x208, not 230x225.

You don't get to print in the area between the clips - those bands are excluded by Cura the full width of the printbed. You also don't get to print in the 9mm at left, or the 23mm at the right side without a second extruder. When you are printing at the X228 position, the black boxes at the ends of the rods are up against the pulleys and squealing, so you actually don't even get that last mm of the 228.

If you used a different slicer that doesn't know about the clips you could get another few mm in the + and - Y direction between the clips, but I'd be very skeptical about getting 225mm on the Y axis.

Here's my maximum-size test print.

http://umforum.ultimaker.com/index.php?/gallery/image/5220-biggest-um2-object/

 

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Actually, in my testing, the printable area is pretty close to the reported value, maybe even larger, depending on how you measure it.

I homed the head, and then used pronterface to see how far I could move the head without hitting anything.

In X, I hit a 'soft endstop' in the firmware that stopped me moving more than 230mm, although I actually had an extra couple of mm I could have moved without hitting the frame. If you add the extra area that the second extruder head will be able to reach, then the printable area is greater than 230mm in x.

In Y, I had a total of 229mm of travel although actually only 223mm seemed to be over the glass plate (when homed in Y, the head is behind the glass plate slightly. So maybe 225 is slightly an exaggeration, but you could always use a bigger glass plate. (Also, my frame is slightly bent, so that might cost me a mm or two in Y).

In Z, there was a total movement of 206mm from the home position to where the head was just touching the bed.

I will admit that the clips complicate things a bit. It's true that you can't print right up against the clips or over the clips for the first few mm. And Cura is a bit over-zealous in avoiding the clips, but in theory you could totally fill the dimensions I quoted, other than for the first few mm in z. The print volume - in terms of the total bounding box in which you can print stuff is indeed close to what UM quotes, and in fact, in total volume terms, is slightly larger.

Also, in terms of Cura's behavior there was a bit of a bug for a while regarding scaling and clip avoidance. I think it's better now, but probably still not perfect. It does seem that if you tell Cura that the bed is 330 x 225, it won't let you scale objects to more than 228 in X or 223 in Y (losing 1mm all around) - even without having any skirt or brim set. And you can't scale to both maximum at the same time, because then you would hit all the clips. But it will let you scale a single object to (almost) the full width in X, if you stay inside the clips in Y, and vice-versa. And with multiple objects on the plate, you can certainly fill up the volume if you avoid the clips. Cura could potentially be smarter about allowing things to impinge on the clip area, provided that they only enter the area starting a few mm off the platform. Another slicer that has no knowledge of the clips could certainly generate gcode that includes that area (above about z=5) and get full use of pretty much the entire build volume claimed by UM.

 

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My main concerns with this are twofold:

- A maximum width piece created by Cura runs the head into the right side of the mechanism - an unexpected hard stop. (Yeah, I know, just don't Do that.) This should be addressed in Marlin setup.

- The Cura limitation that the entire area between the clips is forbidden territory is not allowing me to use the maximum width (minus 1mm for X- clearance) on a hexagonal piece I've been working on. I can scale about 3% larger using Kisslicer, but it causes other issues.

 

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The head shouldn't hit the right side while printing something 228mm wide. As I noted above, and in your other thread on this, I can move my print head more than 230mm in x from its home position. So printing 228mm wide shouldn't be a problem. You might want to look at where your head is homing on the left, and see if the switch can be adjusted to the left a bit to get some extra width?

The area between the clips isn't totally off limits in Cura - but you can't fill the maximum x and max y dimensions at the same time. I think Cura just uses a bounding box approach to determine scalability, rather than looking at the contents of the file to see if the clip area is actually covered with printed stuff. Hopefully that can be improved before too long.

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Is there room to bend the fans downwards so that they are tighter against the side of the print head? Some printers shipped with the fans flared away from the print head by a few mm. I doubt your printer is 5mm narrower than mine, so something must be different.

As I mentioned, there is already a soft limit in the firmware at 230mm, and mine has room to move beyond that.

Regarding the hexagonal piece, I would imagine that you can probably sidestep the clip area limitations by defining your print bed area in Cura to be larger. By default it will then position the print in the middle of the new larger bed, but manually adding some gcodes to the start of the file could adjust the origin to put the print back in the correct place. Then you just need to watch it carefully, to be sure it's not going to catch the clips on the first few layers.

 

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I am ever ridden on the left front clip, because settings in Cura allowed this and is generally Ultimaker2 selected as a machine. Damn, I think such a thing must not happen. At the rear right clip my head hung after dismantling and subsequent slightly incorrect mounting of the fan plates. :???:

 

But anyway, that is past:

I think you could remove the front clip completely, since the rear clips hold the glass plate already very strong, so I feel that in any case.

What do you think?

If this possibility unthinkable?

What other problems would be to Expect?

Markus

 

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I had problems with this too. Nowhere near the advertised size. Turns out... it was the skirt. Cura was limiting the object area so that the skirt would fit. To disable it, set Line Count to 0 in Expert Settings. That will buy you more space.

Thought it might help others who get here via Google - as I did!

Edited by Guest
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