Drawer guide axes was Re: It is easier to edit than create! was PCB Mill

Hello,

The drawer guides and mdf approach will work fine for a light duty
machine. One trick with drawer guides is to "pre-load" them. Also
remember that a drawer guide is made to be VERY flexible in one
direction, while being reasonably stiff in the other. This is so that
the width of the opening (for the drawer) does not have to be exact.

Knowing this, you can use blocks to eliminate the unwanted direction
of motion; or use additional drawer guides at 90° to the first 2 so
that each is eliminating the others' weakness.

Said another way, the drawer guide will move along the axis(towards
and away from you) fine. It will also be fine in the up-down
direction (if you mount it same as the drawer usage), BUT... It will
NOT be fine left to right, as this is the "width of opening"
direction. Adding a third (maybe a 4th) drawer guide lying flat will
resist this sideways motion and make for a better machine. If you
don't use the additional dr. guides, then fasten blocks of uhmw or
nylon, or ball bearings running along the table edge, to prevent this
side to side movement. Same thing applies if the dr. guides are
used "flat". Add additional guide(s) or blocks/bearings to prevent
the up down movement.

Pre-loading just means to put the guides a "little too close"
together, so that they "fight" each other a little. This will make a
stiffer setup.

Finally, DON'T try to use ALL the dr. guide travel, if you want the
best results. You will have much better success using PART of a long
guide, than trying to use all of a shorter guide. The unused part
can "stick out". Center the roller cage under your axis travel (with
the axis centered). As a guideline, I suggest using about half
the "available" travel; i.e., 12 inch guide = 6 inch axis travel.

Stick with a bridge design, as a gantry is a less stiff design to
begin with; and you want to have as much stiffness as possible if you
are going to be successful with pcb work.

Hope this helps.

Ballendo

P.S. Dan Mauch had a design for a pcb DRILL published in Nuts and
Volts magazine several years back. Back issues are available.

A company called GENERAL makes heavy duty drawer guides for sliding
pantries and rack cabinets. some have said they are better to use in
this application.

--- In CAD_CAM_EDM_DRO@y..., torquemada40223@y... wrote:
> Ballendo & Woody--
<snip>
> if the ball-bearing drawer slides and MDF approach are too chintzy
> to be adequate for a PCB mill, I'd like to know that BEFORE the
> fact, so I can decide whether I want to invest in more accurate
> (and costly) components to build with...
>
> Having seen the sample PCB the other guy (I forgot his name) created
> with the same sort of setup I was contemplating, I'm going to go
> forward. The PCB, while not perfect, was fine for my needs.