Here we go again . . . MK4

[Clive S]

Very nice build log I follow it very carefully its a credit to you. You could also call it tips and tricks

[routercnc]

Well, thank you all for the kind words of support. Means a lot, especially coming from the seasoned machinists on here.

I've re-read some of my latest posts and have realised that they paint a glowing picture where everything I do is perfect and works first time. This is misleading for the novices out there so I've decided to include things that went wrong for posts where there is something of interest. Readers have just as much to learn from things that work for me, as well as what not to do!

So here are some things that did not go so well / areas for improvement.

1. When making the bearing holder I'd broken my last good 6mm carbide the day before and a new one had not arrived. So I was stuck with an old blunt one. To give it a fighting chance at the pocket I chain cnc drilled out some of the material using a 3mm drill bit:


But the carbide bit made a nasty noise and was not happy. I switched over to a 3mm carbide and carefully cut it out. You can see the evidence of the 6mm blunt carbide on the top surface:


I had another look through my draws and found a single flute 6mm carbide which I've used for plastic. I cut the outer profile out with that one, plus all of the second part.

2. The 'second part' in the photo was actually the third part:

The real second part went on the scrap pile. On the drawing I'd called for a 36mm bore to take the bearing. After the roughing cut (~1.0mm under) I offered up the bearing and it almost fitted. Scratched my head and measured the bearing and it was actually 35mm. Using Vectric 2D you cannot leave stock etc so the quickest fix was to frig the tool diameter (e.g. telling the software that dia is '8mm' whereas it is actually 6mm gives you 1.0mm stock). Rather than re-draw the part, CAM, etc. I did a quick calc and frigged the tool. Bearing dropped in the new bore with 0.5mm clearance all round. Useless! Thought about making a sleeve, but 1.5 hours later had a replacement made with the proper size bore.

3. The radius on some of the corners is exactly 3mm. This is bad practice with a 6mm bit as there is suddenly a large tool engagement which leaves a witness mark. Better to go with 3.1 or 3.2 if radius is cosmetic. Look at the bottom right inner radius to see the slight chatter. Not a big deal, but one to be aware of.


4. Vectric cut 2D does not have lead in/out. This means there is a tool witness mark at the start / end of the finishing cut. You can help with a ramp in, but the exit goes straight up past the side of the work leaving a groove/scratch. Look at the wall near the top left screw:


Let me know if the bad stuff is as interesting as the good stuff and I'll include that too . . .

[paulus.v]

Very nice build and documentation of the process. Thanks!

4. Vectric cut 2D does not have lead in/out. This means there is a tool witness mark at the start / end of the finishing cut. You can help with a ramp in, but the exit goes straight up past the side of the work leaving a groove/scratch. Look at the wall near the top left screw:

You could split the finishing contour line and add radii in CAD if you are a perfectionist

[routercnc]

Very nice build and documentation of the process. Thanks!



You could split the finishing contour line and add radii in CAD if you are a perfectionist

Interesting thought Paulus. I see where you are coming from but would I end up with an open contour? I'll check it out but I think Cut2D only accepts closed contours. Longer term I'm transitioning to Fusion 360 where these more advanced options are standard practice.

[AndyGuid]

Thanks routercnc for that stock-squaring video https://www.youtube.com/watch?v=tW8HNAlUXxU

How serendipitous that I found your link to the video almost totally by chance. Enjoyed the presenter's humour also.

[routercnc]

Some overdue updates . . .

To finish off the machining of the ballnut blocks. Chamfered 2 of the edges:


I swapped the 3 jaw over to the 4 jaw chuck and dialled it in using the bore I'd machined out on the CNC. Got it to within 0.05 mm, so pleased with that.


Drilled it out using a range of twist drills up to 25 mm, then bored it out to size


Three more to go:


Then used the CNC to spot out the 6 ballnut holes, then drilled and tapped then on the drill press:


Then onto the mounting holes on the underside. Again CNC spotting the holes, and then drilling and tapping the M8 holes on the drill press:


Checked it with a spare ballscrew - fits OK:

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Then onto the side support plates - spotting out all the holes:




Drilled out, counter bored, and tapped:

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Next parts are the tram plates. These connect the Y axis box structure (which contains the Z axis), to the Y axis bearing plates and allow the Z axis to be aligned in multiple planes to tram in the spindle. The adjustment will be made with M10 cup end grub screws before the main bolts are then tightened. I'll put a screenshot of the updated design in the future post.
Cutting them out:


Spotted, drilled, counter bored and tapped:


Here they are trial fitted to the side support plates (which then sit on the bearing blocks).

________

Then onto parts of the Y axis box structure. Started with some eco-cast from aluminium warehouse. Nice and flat and in good condition:



Marking out the holes with a 3mm drill bit:


Then machined out the pockets which will take the 4off Z axis profile rails. I did a very fine finish pass with large overlap on the bottom of the pockets to get them as flat as possible. There is some adjustment when everything goes together but best to get it close as possible:


Quick check:


Cutout, drilled, counter bored, and tapped:

[routercnc]

Next parts were the triangular supports. No photos of these being machined as I wasn't happy with first one. As the design was just a simple triangle I used tabs to hold it in place. But these left the usual witness marks on one edge which didn't look very nice. I tried to sand them out but wasn't happy.
So I started again and added some internal cutouts to add a bit of style, but more importantly allowed me to hold the part in the middle while I machined all the perimeter away:


Still needs holes drilled and tapped in the sides, but decided to do a trial fit. It connects the tram plates to the side support plates:

[Davek0974]

A work of art, very nice :)

It's very satisfying when you have made a pile of bits and they just all fit together perfectly :)