Tensioning the gear against the rack works reasonably well for plasma
cutters as they are lightly loaded. One problem is that gears generate a
force that is trying to push them apart. If I remember correctly the
generated force is about a third of the linear thrust. You end up having
to use a lot of tension otherwise they lose accuracy or jump teeth.
A router sees relatively high cutting forces so I wouldn't recommend
tensioning. Assuming you are using fairly accurate rails, such as
profile rails I would hard mount the pinion and adjust it so you can
just feel a tiny amount of backlash. Check it over the whole travel.
This will give long life while retaining reasonable accuracy. I have
worked on plenty of commercial routers using this setup and they run all
day for years with very few problems. You can use various preload
techniques such as anti-backlash gears or two gears slightly out of
phase but to be honest for a router I think they just increase wear with
no noticeable improvement in part accuracy.
Les
On 31/07/2017 12:13, Tomaz T. wrote:
For my future project (cnc router) I will have to use helical rack and pinion
system on two longer axis (2 and 3.5m). There are some designs where pinion is
forced against rack with spring tensioner, on the other side, if I follow
Atlanta's installation manual for their system, they forbid tensioning pinion
against rack as it would cause wear and tear or rupture of teeth (they suggest
pre-load pinion shaft).
In my case this will be used for woodworking cnc router, so I'm not looking for
very high precision, but anyway if there is anyone heaving experience with this
would be nice to hear.
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