John's Alu Profile build

[Evengravy]

Hi All,

So I'm starting this thread quite a way through the build process. I didn't want to document the entire thing from the start as I knew this was going to take me a long long time.

I built myself a Momus CNC build some years back and got the bug, but that machine is pretty limited as it flexes all over the place (on the Z axis). It's also belt driven which is an absolute pain in the backside as the belt pulleys loosen over time. I initially wanted a machine for wood and after time started machining more and more aluminium, so the new machine I want to be two fold: rigid enough for working aluminium but with a much bigger footprint for working on larger hard wood projects. I also do quite a bit of diamond drag engraving on aluminium which the old machine isn't accurate enough to do.

I basically have been piecing it together bit by bit over the last couple of years, and at the current stage it's moving and wired, but I have some changes to make for sure.

The Gantry is 80 x 160 profile and its running on two 80 x 120 profiles in the Y axis.

Linear rails are all 20mm THK ( the black Y axis rails are Raydent(?) coated). I got all the higher end motion parts used (but they're in great shape).

The Z axis was a real Achilles heel of my old machine, terrible design, so this new Z axis was bought as a full unit from an old machine in Korea (used for IC production I believe) it is made from stainless for the most part and has 15mm THK rails and a THK ground ball-screw for movement and optical limit switches. I milled an aluminium backplate for it and mounted it to the Y axis blocks.

I have a Ground NSK ball-screw on the X axis, positioned on the top of the extrusion. I chose to do that as I wanted to get the Z axis as close to the rails as I could.

The Y axis is driven both sides with ball-screws (Chinese 1605) but I'm really not happy with those so I just ordered some 20mm (2005) ground ballscrews from TBI. I would have liked something better brand wise but I think they should be okay.

Most of this is probably overkill in a aluminium based router I know, but I want to get it as functional as I can really.

You'll notice I haven't got a base/table as yet, the reason being is I'm a bit undecided about that. I've been toying with the idea of mounting it to a wall (and have some blocks ready for doing that, but I'm struggling to decide. I really don't yet know how I could effectively level the wall surface in practice before fixing the machine to it (any advice would be greatly appreciated.)

The spindle looks like the regular cheapo chinese ones but I went with a company Jain Ken for this, it's 1.5Kw ER16 and has ceramic bearings, as far as I can measure it has no runout on it (!). Mind you my dial indicators aren't serious quality, but it's definitely accurate enough for my needs.

For VFD I went with RS510 from RS electronics, it works really well and is essentially a Teco 510 it seems.

I made up the control box from scratch, a linear power supply (70V) was made with a transformer, regulator plus capacitors and I put a soft-start on the incoming AC to smooth out the turn on a little.

The stepper drivers are all AM882 running at 8th micro stepping. I'm really impressed with these drivers, they're very smooth.

I'll figure out how to upload some images shortly, and add them here.

[Evengravy]

Here's a picture of the main machine as it is today.

[Evengravy]

Here's a couple of shots of the spindle and Z axis details.

[Evengravy]

The Z axis came with three optical sensors inside, I kept one in there as upper homing limit switch and reused the other two as home/limits for the Y axis, one each side. For mounting I machined a carrier from Delrin/Acetal. I'll probably replace this with aluminium at some point soon.



The plates which mount between the Y axis bearing blocks and the gantry were modified to fit a piece of aluminium L profile, this moves into the optical switch when homing.



For mounting the Gantry to the ballscrews on the Y, I had a local company weld me up some brackets to my design.



They made a bit of a balls of it to be honest, It's not square and I had to rework it by hand a lot. I can't weld so I didn't have much option, I really should learn to. Since I'm replacing these chinese ball-screws with ground screws from TBI I'm not going to sweat it just yet. Once the parts are here I can redesign this part and the motor coupling for each.

I'm using LinuxCNC 2.8 for this with kins, if anyone wants me to upload my .ini and .hal files let me know. It's working well so far.

[Evengravy]

So, as I said the spindle is from China, but seems to be much better quality than the regular ones, certainly run out and machining quality is amazing. Running at full pelt it is really smooth.

Here's the company if anyone is interested (no affiliation with them at all btw): http://www.jian-ken.com

The VFD is model RS510 from RS Electronics (no affiliation with these either): I'm really happy with the quality of this too. It's actually rated for 2.2Kw but I thought some overhead would be a good idea. Definitely one to add to the list for the other Chinese spindles too.

[Evengravy]

Part of the reason it's taken me so long, apart from sourcing all the parts here and there, is the fact I had to build myself a little workshop to house it in.



I still have a bit to do to finish this place, insulate it in between the stud walls and plywood the internal walls, but it's dry and solid.

At the right hand side outside you can see the six inch blocks. I don't know if these exist in the UK or not but my idea was to build a wall with these on the flat and bolt the entire CNC to it with the Y rails running parallel to the floor. If anyone has an experience I'd appreciate some advice.



I'm really not sure how I would level a wall to the degree necessary to accurately fit this too, but maybe I'm overthinking it.

[Evengravy]

As a test, I knocked up a pencil holder out of some delrin and some drill rod, with a spring for applying pressure and for accounting from deviations in the surface. It worked great, but the chinese ball-screws really aren't great (noise, vibrations etc.)



I actually sourced angular contact bearings for the BK12(?) blocks, so I might now have to sell those too.

[Evengravy]

Here's a snap of the internals of the control box, the main cabinet was sourced from RS electronics and I fitted the rest after bench testing. I probably could have used a smaller case but I have plenty of space so I don't mind the extra space from a cooling perspective.



I went with GX 16 type pins for termination of the wiring both on the motor/sensor side and the case/enclosure side. The wiring is done so that the case side takes the Sheild of each wire to earth.



I think that's all I have for now guys/gals.

[Evengravy]

A couple of questions I have, then, if you don't mind:

+ Playing with the machine as it stands, there's a lot of resonance from the hollow sections of the profile, for the Y profiles I intend to either fill with sand or maybe epoxy/granite. With one end almost closed at the front and the significant vibrations from the less than stellar 1605 ball screws these are resonating like an instrument at the moment. I'm sure this will hurt surface finish as I can clearly feel the transmission through to the spindle by hand, but I expect a sand fill will help since these parts won't need to move.

+ With regards the Gantry, I'd imagine filling that with epoxy/granite will be much too heavy for my motor/screw combo (480oz/in plus double nut 2005 ground ball-screws). Has anyone any experience with filling the voids of profile with expanding foam to dampen vibrations/resonances? I suppose I could test a piece but I don't have any spare material to hand. I wonder if something like silicone fill could work if it could be done cheaply enough.

+ Also would be keen to hear any input from the idea of bolting this entire CNC to a concrete wall, specifically how I might line everything up in practice. I like the idea of gravity pulling away chips and using less floor space but could just go for the traditional setup.

[mekanik]

Hi John
Regarding vertical mounting you will have to build yourself a substantial base, if you make another post asking for ideas for designing a vertical assembly machine Dean(JAZZCNC) might give you some advice regarding this, he has a video of one of his larger builds but i couldn't find it.
Regards
Mike