<p>Basically, your setup is the following:</p>
<p><a href="https://i.sstatic.net/96FEK.png" rel="nofollow noreferrer" title="Y axis schematic"><img src="https://i.sstatic.net/96FEK.png" alt="Y axis schematic" title="Y axis schematic" /></a></p>
<p>The overhang of the bed, assuming the bearings are in the center, equals <code>(300-105)/2 = 97.5 mm</code> on each side. So the distance from the leftmost bearing face (when bed is at <code>y = 0 mm</code>) to the center of the Y rods assembly equals <code>300 - 97.5 = 202.5 mm</code>. Knowing this distance for the other side of the center to the right when <code>y = 300 mm</code> is the same, the minimum length of the rod will therefore be <code>2 x 202.5 = 405 mm</code> which equals the addition of the bed length and the outer bearing distance <code>300 + 105 = 405 mm</code>.</p>
<p>Please note this excludes extra length for e.g. a limit switch, and some extra space around the bed. Basically the extra length of the bed <code>300 - 220 = 80 mm</code> needs to attributed to each side of the bed, so <code>40 mm</code> on each side extra.</p>
<p>For a 220 x 220 mm bed, the minimum length would be <code>2 x (220 - (220 - 105)/2) = 325 mm</code>. When I measure the rods between the acrylic flanges it measures about <code>365 mm</code>, about <code>40 mm</code> extra for clearance around the bed (<code>20 mm</code> on each side).</p>
<p>The overhang for the 300 mm bed is not that much, and a construction under the heated plate will be used to fasten the bed at the corners, as long as that construction is not too flimsy, the current distance will be alright. For other distances you should change the value of 105 in the formulas above. E.g. for an outer flange distance for the bearings of 120 mm, you would require rods of at least 420 mm.</p>

CC BY-SA 4.0
2018-07-12T21:17:30.247Z
2023-01-14T13:06:37.600Z
2023-01-14T13:06:37.600Z
0scar
<p>I have an Anet A8 which I want to convert to an aluminium frame printer like the <a href="https://www.thingiverse.com/thing:2263216" rel="nofollow noreferrer">AM8</a> (rebuild of Anet A8 parts):</p>

<p>&emsp;&emsp;&emsp;&emsp;&emsp;&emsp;<a href="https://i.sstatic.net/gEiyEm.jpg" rel="nofollow noreferrer" title="Anet A8 conversion to 2040 Al profile"><img src="https://i.sstatic.net/gEiyEm.jpg" alt="Anet A8 conversion to 2040 Al profile" title="Anet A8 conversion to 2040 Al profile"></a></p>

<p>This should give a much more stiff frame with respect to the acrylic frame to aid in a better print quality.</p>

<p>Since the bed (220 x 220 mm) has a slight warp, I want to use a larger build platform (200 mm x 300 mm) I have laying around. My plan is to use the 300 mm in the Y direction. </p>

<ul>
<li><p>Knowing the maximum outer distance of the current Y bearings to be 105 mm, is that too short for such a large bed?</p></li>
<li><p>How do I calculate the length of the Y axis rods? (especially if you take another distance than 105 mm)</p></li>
</ul>

<prusa-i3><diy-3d-printer><anet-a8><build-plate><y-axis>
How to calculate linear Y rod length for a larger replacement bed?
0scar
# How to calculate linear Y rod length for a larger replacement bed?

(Asked by: username_0 on 2018-07-12)

I have an Anet A8 which I want to convert to an aluminium frame printer like the [AM8](https://www.thingiverse.com/thing:2263216) (rebuild of Anet A8 parts):

[![Anet A8 conversion to 2040 Al profile](https://i.sstatic.net/gEiyEm.jpg "Anet A8 conversion to 2040 Al profile")](https://i.sstatic.net/gEiyEm.jpg "Anet A8 conversion to 2040 Al profile")

This should give a much more stiff frame with respect to the acrylic frame to aid in a better print quality.

Since the bed (220 x 220 mm) has a slight warp, I want to use a larger build platform (200 mm x 300 mm) I have laying around. My plan is to use the 300 mm in the Y direction.

* Knowing the maximum outer distance of the current Y bearings to be 105 mm, is that too short for such a large bed?
* How do I calculate the length of the Y axis rods? (especially if you take another distance than 105 mm)

**Tags:** prusa-i3, diy-3d-printer, anet-a8, build-plate, y-axis

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## 1 answers

### Answer by username_0 on 2018-07-12. Score: 5 | Accepted answer

Basically, your setup is the following:

[![Y axis schematic](https://i.sstatic.net/96FEK.png "Y axis schematic")](https://i.sstatic.net/96FEK.png "Y axis schematic")

The overhang of the bed, assuming the bearings are in the center, equals `(300-105)/2 = 97.5 mm` on each side. So the distance from the leftmost bearing face (when bed is at `y = 0 mm`) to the center of the Y rods assembly equals `300 - 97.5 = 202.5 mm`. Knowing this distance for the other side of the center to the right when `y = 300 mm` is the same, the minimum length of the rod will therefore be `2 x 202.5 = 405 mm` which equals the addition of the bed length and the outer bearing distance `300 + 105 = 405 mm`.

Please note this excludes extra length for e.g. a limit switch, and some extra space around the bed. Basically the extra length of the bed `300 - 220 = 80 mm` needs to attributed to each side of the bed, so `40 mm` on each side extra.

For a 220 x 220 mm bed, the minimum length would be `2 x (220 - (220 - 105)/2) = 325 mm`. When I measure the rods between the acrylic flanges it measures about `365 mm`, about `40 mm` extra for clearance around the bed (`20 mm` on each side).

The overhang for the 300 mm bed is not that much, and a construction under the heated plate will be used to fasten the bed at the corners, as long as that construction is not too flimsy, the current distance will be alright. For other distances you should change the value of 105 in the formulas above. E.g. for an outer flange distance for the bearings of 120 mm, you would require rods of at least 420 mm.


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