routercnc_MK3

[routercnc]

Didn't you measure the stiffness of this machine a few months ago? If so it would be interesting to compare the readings before and after the upgrade.

Yes, I do plan to measure the stiffness again but it will be at the weekend at the earliest before I can get back in the garage.

Eddy, I've made all the changes together so won't be able to measure individual contributions but my best guess at where any improvements would come from are:

1. Y axis ballscrew plate changed from 18mm plywood to 20mm aluminium (forms part of the 'box' assembly at the top of the Y axis)
> Should improve Y direction stiffness

2. Z axis thin wall aluminium box section and plate arrangement with large offset from gantry changed to 20mm aluminium plate with pockets and lower gantry offset
> Should improve X direction stiffness, plus some Z and some Y due to having much less offset from the gantry

3. Spindle mounting bracket changed from a pair of 20mm thick clamping plates to a converted linear bearing housing
> Probably wasn't a limiting factor in the previous machine, but would in theory improve all 3 directions a bit.

Obviously don't try this at home but whilst I cut out my first part last weekend (from 10mm aluminium) I touched various parts of the machine and felt the vibrations. Not the most scientific method, but found the following, working back from the tool:

Spindle vibration high (not excessive or troubling but high relative to the other points)
Z axis plate vibration high
Z axis rail vibration fairly high
Z axis carraiges (which are on the Y axis) medium /medium low
Y axis assembly medium / low
Gantry low
Gantry sides low

In other words the biggest delta was across the Z axis linear profile bearings, in particular the top one which is the one further from the tool. These are 15mm units. If I was to start again I'd go with 20mm units as they are stiffer, plus they are a bit easier to mount (15mm rails take M3 bolts!), involve less pocketing, plus other general advantages.
But I'm pleased with the progress and if everything is as good as it can be and I've hit the limit of the rail then its not such a bad place to be.