Hobby project

[tonyfoale]

Everybody needs a hobby project. One with no deadline, one that fits in between your real projects. Here is my hobby project - it will be a multi-machine-tool built from the ground up. It started life just to be a surface grinder but grew into a vertical mill and then also a shaper. I do not usually make models first but this time I have partially made a wooden mockup. This will also become a working model before the real thing gets built.

Here is the Statement of Intent video

[DIYSwede]

Thanks, Tony for sharing your thoughts on your project and the tip to the interesting mechatronics site.

FWIW: Given that an epoxy-granite filled gantry will be more rigid than a single vertical support of any design,
one remaining problem will be the gantry-to-spindle overhang distance (for the given precision of the linear rails).
Humble tip: You could mount the vertical rails on the outside of the gantry, to:
1) utilize the rail's inherent rigidity from their greater width (rather than their height, and perhaps even wider distance between the top and bottom bearing) and
2) thus improving overall rigidity by reducing the spindle overhang with app 30 mm.

In Leibnitz' perfect world - one could perhaps imagine a rigid, high rectangular box around the gantry,
with the horizontal rails inside and spindle centre at the centre of the gantry's footprint?
Unwieldy, heavy and cumbersome of course, but optimized rigidity given the components involved.

Just my two cents...
ATB and good luck!
Johan

[tonyfoale]

Thanks, Tony for sharing your thoughts on your project and the tip to the interesting mechatronics site.

FWIW: Given that an epoxy-granite filled gantry will be more rigid than a single vertical support of any design,
one remaining problem will be the gantry-to-spindle overhang distance (for the given precision of the linear rails).
Humble tip: You could mount the vertical rails on the outside of the gantry, to:
1) utilize the rail's inherent rigidity from their greater width (rather than their height, and perhaps even wider distance between the top and bottom bearing) and
2) thus improving overall rigidity by reducing the spindle overhang with app 30 mm.
Just my two cents...
ATB and good luck!
Johan

I did consider putting the vertical rails as you suggest but having decided to use plain granite slabs for the slides, and my lifelong membership of KISS, it was what the youth call a no-brainer to put the rails on the face.
However, I do plan on counterweighting the assembly, see these videos for hints on how I might do that.

and

[tonyfoale]

Here is a very short video showing the preparation of the bottom granite slide. Even with the wooden working model all the slides will be the final granite versions.

[albertq]

Hi Tony, I'll watch you build this machine with great interest having gone through similar planning stages when building my surface & cylindrical grinder.
I note you haven't mentioned grinding dust protection for the rails and ball screws. Are you relying on the built in dust seals of the linear bearings as its only occasional light duty use? Dressing the grinding wheel will cover all those precision parts.
Have you considered using coolant when grinding and drainage of same?
The vertical control movement should be as fine as possible for grinding. I used a motor for rapid up down, then switched to hand feed to the ground surface with a very fine adjustment. There will be some conflict of priority between the mill/shaper and surface grinding feed needs.
Lovely challenge!

[tonyfoale]

Hi Tony, I'll watch you build this machine with great interest having gone through similar planning stages when building my surface & cylindrical grinder.
I note you haven't mentioned grinding dust protection for the rails and ball screws. Are you relying on the built in dust seals of the linear bearings as its only occasional light duty use? Dressing the grinding wheel will cover all those precision parts.
Have you considered using coolant when grinding and drainage of same?

All of your concerns will be addressed.

The vertical control movement should be as fine as possible for grinding. I used a motor for rapid up down, then switched to hand feed to the ground surface with a very fine adjustment. There will be some conflict of priority between the mill/shaper and surface grinding feed needs.
Lovely challenge!

Fully motorised with a commanded resolution of 1 um. I can't match that by hand. There will be no conflict of priority. The motor will put the head where it is told without concern for whether it is a mill or grinder.

Watch this space. Maybe you will like this horizontal version

[tonyfoale]

Hi Tony, I'll watch you build this machine with great interest having gone through similar planning stages when building my surface & cylindrical grinder.

I had another look at your grinder to refresh my memory. You did a great job of that. I see that I made a few comments which I had forgotten. To bring those comments up to date.

1. I mentioned planning a surface grinder, well that is the focus of my current post. There has been a long gap but as I mentioned in the recent video I was not happy with any design until I recently thought about using the gantry construction.

2. I also mentioned a CNC cam grinder. Well that has been built and works up to expectations or hopes. It is based on a lathe but only to get a solid base, the X axis runs on ball rails and is driven by a ball screw, and is what controls the infeed. Rather than use the lathe head stock I fit an electronically controlled rotary table as the workhead which has a resolution of 0.01 deg.
When not doing duty as a cam grinder it becomes a CNC cylindrical grinder. Being CNC means than I can grind tapers from software, no mechanical alignment setup needed. So no need for test cuts.

Now that yours is a couple of years old is there anything that you would do differently if you were doing it again?

I will make a progress update post in the next day or two.

[albertq]

I think you have all the main bases covered Tony, enjoy the project. If I understand your design correctly, for surface grinding you will be using a vertically mounted cup-grinding wheel.
So far happy with both cylindrical and surface operation and no regrets using it as designed.

[tonyfoale]

I think you have all the main bases covered Tony, enjoy the project. If I understand your design correctly, for surface grinding you will be using a vertically mounted cup-grinding wheel.

No, you do not understand the design correctly. The grinding wheel will be mounted in the normal, non-Blanchard, surface grinding orientation. See how I am holding the grinding head in the video.

Although I have used a cupped wheel in the mill for some surface grinding operations. With a CBN grit that can produce very nice finishes but cooling is very important because these wheels are usually built on an aluminium cup and if allowed to get warm they will expand and increase the depth of cut and then produce more heat, expansion and increase the depth of cut and then produce more heat, expansion and depth of cut.....until very bad news.

[albertq]

[QUOTE=tonyfoale;255171]No, you do not understand the design correctly. The grinding wheel will be mounted in the normal, non-Blanchard, surface grinding orientation. See how I am holding the grinding head in the video.

Ok now I think understand, the grinding spindle will hang horizontally below the cross plate so as to clear grinding wheel.