Re: [CAD_CAM_EDM_DRO] 18 ft. router

On Monday 02 February 2004 13:26, Douglas Pollard wrote:

> I am in the process of building a large router out of oak as I already have
> the material. Some on this list felt that expansion and contraction would
> be a problem and I agree. I am thinking that I could put a rotary encoder
> on each axis with a piano wire running the length of the axis with a couple
> of turns around the encoder. This would measure the expansion and
> contraction of the machine and I could enter this factor into my cam
> program to compensate.
> I plane to use rack and pinion drivers with the rack attached at one
> end only to the machine. I am expecting that in this way the rack will not
> expand with the machine.
> The Y axis will only be 6ft so expansion will be much less than the
> 18ft. axis. Watcha all think.

Sell the oak .. Buy some steel. You will then have: a better machine and
money in your pocket. Building it out of Oak would be a waste of good Oak
in an unsuitable application.

It will expand and contract with humidity, it will bend and buckle any steel
rails attached to it .. it is plain and simply unsuitable. Get some sice
1/8th wall 4 inch box section steel and get welding ... better resultsfor
less money. Sometimes 'because I already have it' is not a good reason at
all.

Oak is very acid and over time will attack any steel fitting placed in it,
theres another good reason ..

> Doug Pollard
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