Here we go again . . . MK4

[mekanik]

Very nice,
Looking forward to seeing this finished.
Mike

[routercnc]

An update on the next bits on the list - the gantry lower bearing plates. I need to make 2 mirrored parts, here is the first one progressing -

Setting up and cutting some slots. These are to adjust one of a pair of ballnut brackets. I'm going to run 2 ballnuts pre-loaded against each other:


The other holes have been spotted (to finish on the drill press) and the profile cut out. I tried something a little different to try and get the profile size as good as possible. As this sits on the X bearings I want this to be a datum part during the build. The rough profile cut was +1.0mm, then another rough cut at 0.2mm, and finally a finish cut at 0mm. You can see the finish in the photo which is excellent. I'll check with calipers how accurate the overall size came out.


I've yet to drill out the holes on the top, and there are lots of holes required in the sides, but I thought I'd try a quick fit to make sure all was well. No bolts yet just propped together but looks good!


Here is the start of the one for the other end. I had to line this one up using a DTI and get it very accurate to avoid hitting the holes in the donor plate I'm using. I've cut the slotted holes, next up will be spotting and profile:

[routercnc]

Also, I'd made a few design changes a while back but hadn't posted them so here they are.

1. Z axis
-Twin ballscrew instead of single
-Main body machined from solid
-Upgrade from 15mm miniature rails to 20mm Hiwin





2. Y axis
-Double ballnuts, one fixed ballnut housing and one floating housing to allow pre-load to be added
-Simpler bracing pieces


3. X axis
-Double ballnuts, one fixed ballnut housing and one floating housing to allow pre-load to be added

[Davek0974]

Twin ballscrews on the Z - should be able to punch the cutter through the work with the motor turned off !

:)

[routercnc]

Cheers Dave !

It might do that yes, but it is still one stepper motor so it's not any more powerful than before. Reason for doing it is that it should help reduce vibration as both sides of the Z axis are held when machining, not just one side.

[Davek0974]

Following with interest ;)

[routercnc]

The first plate has now been drill and counterbored:


The second one is cut out:


Spotted and ready for drilling:


The DRO I fitted to the pillar drill works really well for CBs. Although the depth is not critical, it looks nice if they are about the same height as each other. These are the CBs for the M6 bolts, drilled to a depth of 10mm as the thread needs to stick out to get good engagement:


All the top holes are now finished. Then onto a light sanding with well used paper, then green scouring pad to remove the scratches and after about a minutes work they look quite nice:


Another dry assembly fit:


Next job is the tapped holes in the sides. I bought one of these precision vices a while back to hold the work on it's side:


Mine is the second from the top - Precision Tool Vice Type 2 - 90mm wide

But I need to make some special clamps to fit into the groove. Here is some 10mm plate roughly marked out. I should get 4 clamps out of this strip. I'll put the usual stepped clamp triangles under the far end of each clamp initially, but may add a packer piece of the right height instead to make setting up quicker.