Thoughts and feedback as I progress pls

[Mogal]

Hi Guys!

I'm finally back for round 2 and looking for a little feedback as I progress through this build.
I'm pretty happy with how this is turning out so far, but another set of eyes to catch what I miss, or could do better would be great!
My main reason for this is wood, but also wanting to do non ferrous as well. But really, 95% wood projects.
I have a 2.2kw water cooled spindle to mount on this as well.

I've already committed to materials so just looking to make the best with what I have available.
I am using heavy 4080 for the frame and gantry and have some heavy 4040 for extra frame supports. (not made yet)
Should I put in some 45 degree bracing in the frame? or not necessary?

I have a RF-45 mill and a 10k Southbend for making parts. The old cnc is dismantled and not available. (using for parts)

Still working out the details of the Z axis, but getting close I think.
I'm using 3/4" aluminum at 6.5" wide and approx 13" tall for Z backer plate.
Rails will be attached to this plate with moving bearings.
I need to pocket this plate to allow spacing for the ballscrews/nuts (1610)
I'll post more images and thoughts as I progress.

(Don't mind the Z axis pictured here, I just did that mashup to see approx spindle placement when mounted - It's not how it's going to be)

Thoughts so far?
Thanks!

P.S. Last pic is my old cnc I built 12 years ago now.

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[Mogal]

Well, being as I got no comments, good or bad, I figured it was fair and kept going! LOL

I've slowly been plugging along with this and very happy with how it is going so far.
So much more rigid then the old machine!

X axis is complete and Y is 1/2 done.

Still so much to do!

[adam_m]

I'm no designer but I would think that this section is going to be very weak with all of the downward force being applied at the bit.



Maybe bolting the unit together would add some rigidity??



Just an opinion...

Adam,

[Mogal]

Hi, I'm no designer either.

Pic 1: That little dip got added as a stress relief to help prevent cracking in the corner.
I'm only doing wood and non ferrous materials. I don't think there would be enough forces applied to be of concern?

Pic 2: Everything will be bolted together, The lower extrusion is bolted to the lower plate, the upper extrusion is bolted to the vertical plate,
and the two extrusions will be bolted together with either 4040 corner brackets, or a length of 1x2x0.25 steel angle in the back.
Also has the two end plates that keep the extrusions tied together. The steel angle is the way I'd like to go, extending the length of the gantry.

I actually have the luxury to change things up if needed. I have lots of spare material I got free (or really cheap)
I have 1/4, 1/2 and 3/4 inch plate and a variety of bar and angle (All aluminum) So if needed, I can remake/redesign parts if needed.

[peteeng]

Hi Mogal - The lack of comment should give you confidence. Poor design gets jumped on quite quickly here! You have made some very nice billeted parts so I suggest for your next machine not to use construction extrusion. That is now the poor area of the design. If you use structural aluminium sections it will be locally and globally stiffer then the extrusions and will be cheaper. Construction extrusions also have lots of free edges that can vibrate.

Or assemble the gantry out of plate then you can tailor the size and its details. Use this one to make the next parts! Keep Making.

Those stress reliefs, not needed. That won't crack.... Peter

[Mogal]

Hi Mogal - The lack of comment should give you confidence. Poor design gets jumped on quite quickly here! You have made some very nice billeted parts so I suggest for your next machine not to use construction extrusion. That is now the poor area of the design. If you use structural aluminium sections it will be locally and globally stiffer then the extrusions and will be cheaper. Construction extrusions also have lots of free edges that can vibrate.

Or assemble the gantry out of plate then you can tailor the size and its details. Use this one to make the next parts! Keep Making.

Those stress reliefs, not needed. That won't crack.... Peter

Thank you, one of the reasons I posted this here. The knowledge here is amazingly impressive.
And yes, the lack of response was a little reassuring

I don't have enough plate large enough to take it to that next level, hence the extrusions.

I know this machine still has it's weak spots, but overall, it's 100x better then my old one.
and I will get some really good use out of it.

Thanks for the reassurance. I'll post a little more as I progress.

Eventually I'm wanting to incorporate a laser (maybe one of the newer 20watt LED lasers?) and have it referenced with the spindle.
I'm also thinking of making a partly removeable bed. The way the bed is currently laid out, I could build a removeable panel
that opens up the bed and I could drop my little 4th axis into the recess to give more clearance for working in and around the 4th axis.

[luke peter]

Any updates on this build Mogal? I am keen to see how the machine performs.

[Mogal]

Hello,

I do have a bit more progress made.
With the exception of sensors, both the X and Y axis are done.
(at least all in place, nothing is set or calibrated yet)

I'm still working out the design for the Z axis.
I really want to have stationary bearings, and have the rails move. It's kinda tricky to mount things this way.
I'm seriously considering putting in only 3 bolts to hold the bearings in place, that way, I can cross overlap the bearing to save space,
but not sure how detrimental that could be to the life of the bearings?

[luke peter]

I had a similar design issue with my z axis. My solution pictured below:

assembly order is as follows:

Mount yellow plate onto y bearings

Mount z bearings onto adapter plate

Mount adapter plate onto yellow plate


this will allow all bolt holes to be filled, and the z to slide onto the bearing assembly afterwards.

Edit: I really like the look of your machine. Billet ali parts bolted together look so sleek.

[Mogal]

Hey! Thanks for that!!

I was trying to avoid the second plate to reduce the spindle sticking out so far.

I was going to use 3/4" but I guess I'll double up 1/2" and mimic your design.

I think it will work out okay... I'll try CADing it up.

[luke peter]

Hey! Thanks for that!!

I was trying to avoid the second plate to reduce the spindle sticking out so far.

I was going to use 3/4" but I guess I'll double up 1/2" and mimic your design.

I think it will work out okay... I'll try CADing it up.

I used 10mm on mine, to allow for the countersinks. It meant I had to add a 3mm shim on top of the ball nut housing, but 6mm plate wouldn't have allowed the cap screws to get flush.

Because the bearing spacing matches the y bearings as closely as I could, the plates are not actually loaded other than in compression (there is small bending possibilities, but moment arms are very short on the adapter plates). Thickness is thus not very important (structurally), at least as far as I understood the force transfer.

Good luck.

[Mogal]

I know my CAD is lacking and needs some work, but this is enough to get chips going again.

This has the Y axis plate at 8.5" wide and approx height of 13.5"
- This allows for about 5.5" of travel
- This will allow the Z axis to drop to about 1/2" above the table (Roughly 6" clearance under gantry)

[luke peter]

Your CAD is fine. It does exactly what you need it to.

Have you confirmed ball screw height etc? and is there sufficient space for cap screw heads on your mount plate (looks like it would be ok for M6's, but without dimensions I can't really tell). Half of my design was figuring out where to put screws, and ensuring I could actually assemble the thing once part are made

[Mogal]

Yes, there is clearance for the ball screw, the blue spacer plates are 3/4"
And I'll have to trim them down to get the proper clearances and fit. (about 1/16")
- and if I get that right, no shimming.
- but I do need to verify a couple of things before I start cutting.

Most of the cnc is m5 with a couple 1/4/-20 thrown in.
I'll be counter sinking everything.

I wont be starting these till next week so I have some time to think about it over the weekend.

Thanks Luke.

[luke peter]

Looking forward to seeing it run. Your build is so very clean...

w.r.t. screw sizes... I really hate how strong most screws actually are - maths will indicate that 5xM5 cap screws will be good for a bolted connection, with a hefty safety factor, they will ultimately look so out of place on my builds though, that I end up doing M8's or M10's

[Mogal]

So I think I've found my final design.

But I'm debating how I want to mount the stepper to drive the ball screw.
I can either direct couple with the stepper standing on top of the ball screw, or I have some 5m drive pullies
(Stepper: 20 tooth - Screw: 60 tooth) and I can place the stepper behind the Z Plate and drive the screw with a 3:1 reduction.

Stepper is: 23HS45-3504S (425oz/in)
Leadscrew: SFS1610
Spindle is 2.2kw water cooled
System runs at 36v

Thoughts?

[luke peter]

Can you drive them at higher voltage? they are 5mH motors, 71v is a good voltage to drive them at, they will perform sub optimally at 36. (I have higher voltage drivers on the way to replace the 36v tb6600's I have)

Z design looks good.

[Mogal]

Yeah... sigh, this is the old kit I originally put together 12 years ago... it still runs well so...
Max power the drivers can handle is 36v.

If I do have issues with the power/speed, I will make the leap to a new system, but for now, this one works.

Thoughts on the stepper placement? Up or in the back?

[luke peter]

Yeah... sigh, this is the old kit I originally put together 12 years ago... it still runs well so...
Max power the drivers can handle is 36v.

If I do have issues with the power/speed, I will make the leap to a new system, but for now, this one works.

Thoughts on the stepper placement? Up or in the back?

With 10mm z pitch, I reckon behind with the reduction it will give you addition real resolution (which microstepping can't actually do properly), it also will bring the mass centre back towards the gantry a little (not that it matters all that much)

[Mogal]

Thanks for that, yes I would prefer a little more resolution.
I can't remember why I picked the 10 over the 5...
So I ordered a new 1605 leadscrew, should be here in a week or two.
I also realized that my pulleys are 20:40, not 20:60 like I thought.
The belts I have wont fit, so ordered some of those too.

Made some good progress otherwise.
I need to trim down the 'bearing riser blocks' so it slips right in parallel with the rails.