Why some pegboard does not fit properly in your gondola?
Part I of II
What happened, it won’t fit
A customer phoned recently and said,
- “We ordered panels 46-15/16” wide. The panels you shipped measure 47”.
- “We can’t fit them into our frames!”
In a case such as this we commonly find our sizing of the panels at point of manufacture was correct. The problem is caused by expansion of the panels between manufacture and point of installation.
We manufacture thin (less than 3/8” thick) components for our customers using hardboard (both wet and dry process variety) or HDF (high density fiberboard). All three substrates contain wood fibers.
In fact, they are essentially more “wood” than a tree is. While the details of the actual manufacturing process for each substrate differ somewhat, the finished product consists of wood fibers combined with a minimal amount of resinous binder and then reconstituted in a controlled environment under heat and pressure into sheets of various sizes.
Material Expansion
Any wood product will shrink or swell as it gains or losses moisture. Home-dwellers in seasonal climates recognize this phenomenon, called Hygroexpansion, as the difference in fit of wood doors and windows between winter and summer.
It is impossible to confine a wood based panel so as to restrict its expansion. If a panel is closely confined within a welded metal frame, for example, it will expand exactly the same amount as if it were not confined. The expansion will cause bellying or humping of the panel as it grows and could conceivably even break the frame.
Effect on Store Fixtures
Store fixtures and displays often combine metal, wood based, and occasionally plastic components in a single unit. Designers must consider and allow for the difference in expansion of each material.
Please consider these aspects:
- STEEL –
- Steel will change dimension slightly with change in temperature but within range of its normal exposure it may be considered to hold a fixed dimension.
- ALUMINUM –
- For a given change in temperature aluminum will change dimension more than twice as much as steel. The designer must sometimes give this consideration. For example, if a wood based panel is closely confined within an aluminum frame and if this assembly is then shipped in cold weather the frame could shrink enough in transit to warp the panel or crack the frame.
- PLASTIC –
- Commonly used plastics have great reaction to temperature change, easily up to 4 times as much as aluminum. Within range of temperatures easily experienced in transit and/or use (0 – 90 deg. F) a 48” length will grow or shrink 3/16”.
- WOOD PRODUCTS –
- Wet and dry process hardboard, HDF, particle board, plywood, OSB, etc. show no significant change in dimension with change in temperature. They do, however, change dimension an appreciable amount with change in relative humidity and resultant moisture content.
For the Designer
Engineering Handbooks give the Designer good information on how steel, aluminum, and plastics change dimension with changes in temperature. However, information on how wood based products change dimension with changes in relative humidity is not well known.
We surmise this is because variations in wood density, species, resin type and amount, etc. affect this characteristic and preclude listing a general tabulated value. In fact, we see results for panels from different manufacturers that vary enough to preclude their use in our production facilities.
The recommendations passed along in this article and the numerical data included in the appendix are for panels from manufacturers of substrates that consistently conform to our rigid Hygroexpansion specifications.
In part II of this article we hope to give a basic understanding of how wood based panels behave with changes in the humidity of the environment surrounding them. Midwest Retail Services is providing this information for the benefit of our customers who purchase our wood products.
For more information, call 800-576-7577, or email us atinfo@mw-rs.com. The full article is available upon request.
[msh_feedburner]
