# Dimensional Shrinkage of the Maslow Frame

**URL:** <https://forums.maslowcnc.com/t/dimensional-shrinkage-of-the-maslow-frame/1990>\
**Category:** Hardware\
**Created:** [January 20, 2018, 1:44pm UTC](https://forums.maslowcnc.com/t/dimensional-shrinkage-of-the-maslow-frame/1990 "2018-01-20T13:44:31Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![MeticulousMaynard](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.maslowcnc.com/meticulousmaynard/32/2744_2.png) [@MeticulousMaynard](https://forums.maslowcnc.com/u/MeticulousMaynard)\
**Post date:** [January 20, 2018, 2:10pm UTC](https://forums.maslowcnc.com/t/dimensional-shrinkage-of-the-maslow-frame/1990/2 "2018-01-20T14:10:22Z")

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> [@Joshua](#):
>
> one thing I thought of is the tendency of wood to shrink and expand with changing humidity.

This was one of my concerns when I was thinking about building my frame. @Bar had updated the frame a little while ago to use more solid lumber for that stability along it’s length. Originally, the frame had been made mostly from plywood and there were reports of the ply bowing and twisting in high humidity.

> [@Joshua](#):
>
> This could be accomplished in many ways. First, solid lumber could be placed directly between the motors, which leverages the most dimensionally stable wood selection (vs. plywood).

This is a top-beam frame, which we have seen the greatest successes with. @Dlang has suggested the best material for the job is LVL, which is a special type of composite structural lumber that has incredible dimensional stability. I have worked with the stuff building houses and they are great! They’re available at most lumber yards and the big home improvement places usually at 10 ft lengths.

Solid wood might be a good option as well, but it still could twist or bow and that would significantly affect your distance between motors.

> [@Joshua](#):
>
> Another option is to use a steel channel placed directly between the motors.

YES! and this is the route I’ve taken. Compared to wood, steel has much better dimensional stability. It does flex more but as long as you get a good structural section like channel, pipe, tube, or unistrut, that won’t be a problem at the forces we’re dealing with here. I welded a steel tube frame myself, and the machine is very stable.

The easier steel frame to build is the [Unistrut frame](https://forums.maslowcnc.com/t/unistrut-frame-designs/1267), and you may want to look into it. It’s a little more expensive than a wood frame. The thread goes into pretty good detail about it.

> [@Joshua](#):
>
> A third option is to use a steel cable stretched between the two motor arms; if the distance shrinks, the cable will sag and it will be visible.

I like this idea, and think it could be used well with a wooden top beam frame. I think having a visual indicator that something’s off is a great idea.

If you haven’t already found it, [Musings on frame design](https://forums.maslowcnc.com/t/musings-on-frame-design/165) and [Frame design options](https://forums.maslowcnc.com/t/frame-design-options/322) are good discussions on frame construction.

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