Quote Originally Posted by John McNamara View Post
G'Day Kitwin

Happy New Year

The Men's shed machine was built on a Budget, The rails and belts remain untouched to this day.
The only changes made are the spindle updates, and recently it is mounted on a new stand.

The machine was designed for woodworking and plastics, and light metals. 99% of the work is wood. Fully supported round rails are fine for this sort of application. The forces created by wood routing are fairly light. If I were designing a metal focused machine I would consider profile, Hiwin type, rails and ball screws.

The local Council has supported the men's shed with work, making chunky road signs out of timber sleepers. The machine was used to cut the deep lettering moving the wood along in stages as the signs are very long.

It was also used to cut deep pockets in about 2 metres long 100x100mm recycled plastic posts, there were hundreds of them! This was to make a kind of post and rail fence.

Then there is all the members projects.

If you study the video the long axis timing belt's (Steel stiffened) and Joined to be in tandem by a cross shaft (Note the torsion tube). are fully supported on the bed to avoid vibrating if suspended, rising up only at the drive point on the carriage. The belts are stationary. note the tensioner arrangements. These belts were were properly tensioned at build time, so far they have not required re tensioning.
The Z axis uses a 16mm ball screw.

It should be noted that all rotating parts were supported by Flange or snap ring type ball bearings clamped by laser cut retainers into the laser cut frame. Study the images. This was a big contributor to the overall accuracy. Also note the timing pulleys were carefully bored.

All in all a low cost design that works. It met and excelled the design criteria.

Regards
John
Nice to hear from you John, a very happy new year to you and yours.

It's good to have feedback about the performance of such a budget machine over several years of use, it has obviously proved well worth the investment of both time and money. Maybe not fast enough for time-critical commercial use but that's not what most newcomers to this forum are looking for. You have clearly managed the balance between cost and performance by producing an excellent design. My signature used to be a quote from the duke of Wellington: "An engineer can do for ten shillings what any fool can do for a pound".

Re the belts: I think this has come up before on the forum but one option to help avoid stretching of long belts is to glue a piece of pre-tentioned belt onto the frame so that the teeth of it and the driven belt are engaged. This locks most of the belt in place and only the length rising to the pulley can stretch. There is a name fro this idea, but I can't recall it at present.

I asked about wear on the linear bearings as I had to replace a couple of bearings on my machine after not that much use, though I suspect this may have been due to excessive strain from poor alignment.

Regards
Kit