[RCaffin]

Of course it matters which way around you mount them. They only work in one direction.
Um .... let me think about that again ....
:violin:

Cheers
Roger

[handlewanker]

Rog....gasp...you mean it won't work in the other direction????…..Ishi will have a purple fit if he has to revise the whole of the drive trains.
Ian.

[jkkmobile]

Here is the redesigned horizontal carriage mounted on the machine's frame.

You should round or facet all inner corners.. any sharp inner corner is easy cracking point.

[ishi]

You should round or facet all inner corners.. any sharp inner corner is easy cracking point.

I believe this is what I am doing. If you see any in need of rounding or faceting, please let me know.

[ishi]

Rog....gasp...you mean it won't work in the other direction????…..Ishi will have a purple fit if he has to revise the whole of the drive trains.
Ian.

Ian,

Changing this would take about 5 minutes per drivetrain. I'm not sure why you get so amped up about it all. The reason why I have not done it yet is because I do not fully understand the reason for doing so, and I saw NSK doing it the way I did.

[ishi]

Here is a redesigned Z-axis carriage. It's a lot more rigid than the previous one. This was made possible by moving the linear scale out of the way (we'll put it outside of the column's canal), which in turned allowed us to add a lot of material on the back of the carriage, espousing the shape of the sliders and rail support beams (see last pictures). But with some aggressive material relief, weight is just 137kg, which is half of the spindle head's weight.

As mentioned earlier, we're still waiting for the spindle head's CAD model, but we can still design quite a few things without it.

[ishi]

During our last review session with RAMPF (our supplier for mineral castings), they suggested that we could use mineral castings for our carriages as well. Clearly, the process would be a lot easier than cast iron, but I'm not entirely sure about possible drawbacks. Vibration dampening would be improved, but I am concerned about stiffness. Obviously, all the castings would have to be redesigned if we were to go down that route. Any thoughts?

[ishi]

The hydraulic counterbalance has been redesigned in order to ensure that the cylinders' stroke (32") is significantly greater than the Z-axis' travel (25"), just in case. Mounting screws have also been added.

[ishi]

Here is how we are planning to mount our linear scale for the Z-axis, right in between the rail shoulder plate and the nut mount, on the left side of the Z-axis carriage.

[RCaffin]

Changing this would take about 5 minutes per drivetrain. I'm not sure why you get so amped up about it all.
Both Ian and I were joking.
You can blame the Australian sense of humour.

Cheers
Roger

[RCaffin]

use mineral castings for our carriages as well.
This could be problematic as the carriages will have to deal with localised point forces - T-slot bolts etc. I am not sure that epoxy resin is good enough for this: localised distortion could be possible.

Cheers

[ishi]

Changing this would take about 5 minutes per drivetrain. I'm not sure why you get so amped up about it all.
Both Ian and I were joking.
You can blame the Australian sense of humour.

Cheers
Roger

Give me more of it then!

- - - Updated - - -

use mineral castings for our carriages as well.
This could be problematic as the carriages will have to deal with localised point forces - T-slot bolts etc. I am not sure that epoxy resin is good enough for this: localised distortion could be possible.

Cheers

I'd be afraid of that as well. Let's stick with proven solutions...

[ishi]

Blocks for all three linear scales have been mounted again. Each linear axis requires a slightly different mounting scheme:

- The X-axis block uses a simple plate mounted on the carriage.
- The Y-axis block uses a more elaborate plate mounted on the rotary table's torque motor.
- The Z-axis block mounts directly on the left nut mount.

[ishi]

I am checking travels on all axes, making sure that linear scales are long enough. The X-axis is good to go...

[Goemon]

During our last review session with RAMPF (our supplier for mineral castings), they suggested that we could use mineral castings for our carriages as well. Clearly, the process would be a lot easier than cast iron, but I'm not entirely sure about possible drawbacks. Vibration dampening would be improved, but I am concerned about stiffness. Obviously, all the castings would have to be redesigned if we were to go down that route. Any thoughts?

As a general point, you can compensate for reduced stiffness by increasing thickness. E.g. If you want an aluminum plate to be as stiff as a 1/4" steel one then make it 1/2" thick instead.

what is more likely to be an issue than stiffness is that epoxy granite does not hold screws particularly well. If you try bolting parts to EG carriages, it won't take a particularly large force to rip them out sooner or later. The back and forth linear motion could also widen the bolt holes over time until it causes some sort of disaster for someone. To solve this issue, you will want metal plates embedded in the castings to hold the screw threads.... or using a clamping mechanism instead of screws to attach stuff.

For my gantry (which is partially epoxy granite), I embedded tool steel plates in the casting (to prevent hole widening). To mount the gantry actuator, I have a tooling plate attached to surface with 12" bolts that go all the way through (passing through the tool steel) to a second tooling plate at the back (with threads). This creates a clamping mechanism and it was the best method I found for mating metal parts with epoxy granite so far.

[ishi]

As a general point, you can compensate for reduced stiffness by increasing thickness. E.g. If you want an aluminum plate to be as stiff as a 1/4" steel one then make it 1/2" thick instead.

what is more likely to be an issue than stiffness is that epoxy granite does not hold screws particularly well. If you try bolting parts to EG carriages, it won't take a particularly large force to rip them out sooner or later. The back and forth linear motion could also widen the bolt holes over time until it causes some sort of disaster for someone. To solve this issue, you will want metal plates embedded in the castings to hold the screw threads.... or using a clamping mechanism instead of screws to attach stuff.

For my gantry (which is partially epoxy granite), I embedded tool steel plates in the casting (to prevent hole widening). To mount the gantry actuator, I have a tooling plate attached to surface with 12" bolts that go all the way through (passing through the tool steel) to a second tooling plate at the back (with threads). This creates a clamping mechanism and it was the best method I found for mating metal parts with epoxy granite so far.

Goemon,

That makes a lot of sense. Thanks a lot for your help. Another problem I can foresee is that mineral castings do not support the addition of threaded holes down the road. Therefore, the design has to be perfect from day one. Metal castings are a lot more forgiving in that respect.

We'll go for iron castings, as originally planned.

[ishi]

The machine's enclosure will be made of a frame assembled from aluminum profiles and bolted to the base using six of these brackets:

https://us.misumi-ec.com/vona2/detai...wysiwyg_area_0

UPDATE: Two additional pictures added, showing the fasteners to be used. M10 for bolting the bracket to the base and M8 for bolting a rail to the bracket, using this t-slot nut:

https://product.item24.de/en/product...ainless-38849/

Not entirely sure whether the washers are useful or overkill. For info, all fasteners use stainless steel and the brackets are made of cast iron.

Thoughts?

PS: If you've never worked with Item, you should consider them. They're a bit more expensive than alternative suppliers, for their service is second to none.

[Goemon]

Goemon,

That makes a lot of sense. Thanks a lot for your help. Another problem I can foresee is that mineral castings do not support the addition of threaded holes down the road. Therefore, the design has to be perfect from day one. Metal castings are a lot more forgiving in that respect.

We'll go for iron castings, as originally planned.

You can't put screw threads in epoxy or epoxy granite but you can put them in epoxy granite parts if you cast them around a metal frame (to hold the screws).

Looking at your design, you will come up against the same issue when attaching rails to your column and base. It is easily solved though with a metal surface plate on your mounting surfaces.

Take a look at this guy's design. I found it fairly helpful for my own with the way he attaches surface mounting plate to his metal skeleton frame before casting the epoxy granite around it:

https://www.adambender.info/single-p...e-Frame-How-To

[ishi]

You can't put screw threads in epoxy or epoxy granite but you can put them in epoxy granite parts if you cast them around a metal frame (to hold the screws).

Looking at your design, you will come up against the same issue when attaching rails to your column and base. It is easily solved though with a metal surface plate on your mounting surfaces.

Take a look at this guy's design. I found it fairly helpful for my own with the way he attaches surface mounting plate to his metal skeleton frame before casting the epoxy granite around it:

https://www.adambender.info/single-p...e-Frame-How-To

Goemon,

Thanks for sharing this. This is a great project indeed.

I am quite familiar with what you are describing, and this is one of the reasons why our rails for X and Z are mounted on a steel beam that will either be incorporated into the cast or bolted onto it, using threaded inserts incorporated into the cast.

In order to familiarize ourselves with the process and design requirements, we are using this outstanding presentation from RAMPF:

https://drive.google.com/file/d/1t5g...ew?usp=sharing

Best regards
Ismael

[ishi]

A notch has been added on the front of the base in order to add a mounting bracket for the enclosure's frame on the front of the machine. This will make the frame a lot more rigid, especially when the operator is leaning against it when trying to move a part or adjust a fixturing.

This is a perfect example of why a mineral cast is far more suitable than granite stone for a machine base: making this kind of notch on granite would be really difficult and expensive...