New Machine Build Large Epoxy Granite Vertical CNC Mill - Page 22

# Thread: Large Epoxy Granite Vertical CNC Mill

1. ## Re: Large Epoxy Granite Vertical CNC Mill

Is there need to go to such length ensuring squareness of axis on CNC machine? Can't it be compensated in software, leaving only task to buld bind-free and slop-free linear motion?
No, you can make up for some elements such as play in axial (along the ballscrew) with software but if the machine is not square, you will always have issues.

2. ## Re: Large Epoxy Granite Vertical CNC Mill

Originally Posted by Chazaxl
... but if the machine is not square, you will always have issues.
Can you elaborate, what kind of issues?
If machine is out of square in XY plane for example, when you command movement in X direction software can add small movement in Y direction and vice versa.

3. ## Re: Large Epoxy Granite Vertical CNC Mill

Can you elaborate, what kind of issues?
If machine is out of square in XY plane for example, when you command movement in X direction software can add small movement in Y direction and vice versa.
Suppose it could be done but I dont see the value of taking the risk.

As it is, good machines struggle to do 'perfect' circles. This will add another dimension of issues and tuning. I think its difficult enough to make a good machine work well and reliably if it is square (think of high speed machining), I cant see the value in taking something not square and then somehow mathematically trying to fix it.

Plus, not all errors are linear. If the X 'snakes' a few micron left and right, how would you compensate? You would need a massive calculation to know, your time is better spent just getting the mill square in the first place. Within reason, its not that difficult if you have the correct tools.

My own mill will probably have 0.05mm error only as I have a limitation on what tools / ability I have to do at home. But for me, that's fine.

4. ## Re: Large Epoxy Granite Vertical CNC Mill

Mostly, yes. But, most machines aren't great at moving near zero velocity, due to friction and backlash. So, lets say you are moving back and forth in the Y direction. The X will have to make very small moves with changing velocity direction, causing motion problems. These will be very small problems, but will likely show up as strange surface finish issues. If tiny surface finish issues are ok, then compensation will likely work for you.

nice

6. ## Re: Large Epoxy Granite Vertical CNC Mill

Yeah, I did not post for a long time, did I? I've been very busy lately with... moving to a new place.

The column mold is completely finished now with all bells and whistles required (well, it was actually completed before the move). Here's a picture of the bottom side of the mold being glued together.

The holes in the bottom (there are six of them) are where the bolts mounting the column to the base will go. You can see I'm trying hard to make all angles be 90 degrees! And here's the mold almost finished.

You can see the shiny tubes that are going to create the column to base mounting holes. I also added thick metal plates on the top side to distribute the pressure so the EG does not crack while tightening. Here's another view of that.

There are two rebar assemblies that will be embedded in the column and the rebars also hold the bolts to which the Z-axis linear rails will be mounted to as you can see from this picture.

I will post on the detail of the rebar and the mold in later posts. I hope this quenches you curiosity for the time being...

Been over a year... Didn't see an update from this pour. Not nice to leave us hanging man...

7. ## Re: Large Epoxy Granite Vertical CNC Mill

Originally Posted by nateman_doo
Not nice to leave us hanging man...

8. ## Re: Large Epoxy Granite Vertical CNC Mill

nagging? its been a year, and I asked once. How is that nagging?

9. ## Re: Large Epoxy Granite Vertical CNC Mill

Any progress?

10. ## Re: Large Epoxy Granite Vertical CNC Mill

see? and people thought I nagged :P
going on 2 years now.

11. ## Re: Large Epoxy Granite Vertical CNC Mill

If you left click on the person's name, then select 'view profile', you can see their last activity date. June of 2017 in this case.

12. ## Re: Large Epoxy Granite Vertical CNC Mill

Originally Posted by ger21
Epoxy does not dissolve styrofoam. Polyester resin does.
This is true. However it might make sense to use Polyester instead of Epoxy to make granite. It's hella' cheaper! Can live without styrofoam. Replace it with fibreboard structure or PUR foam (which can handle polyester, unlike styrofoam)... I am thinking about making milling machine using Polyester granite. Wonder why everybody uses expensive epoxy. Polyester might be little harder, which makes it kinda brittle. But i guess this can hardly affect thick pieces that are casted for milling machines. Such machines are commonly made using relatively fragile cast iron. They even use plain old concrete to cast such machines!

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