Standardized test shapes

[chrisb]

Increasing accuracy is very intelligent. It doesn't introduce additional tesselation, so you can very well try it before exporting the GCode. To have the high precision as default needs quite some computing power or time.

[freman]

OK here is the result of the 3mm step version, with geom set at 2um and GRBL arc approximation set to use trig fn instead of their nifty small angle approximations.

The top mill face could be a little sharper if I could use spiral cut, that works better on wood. Sadly that is currently broken when not in an x or y direction.

There is still a central nipple on one of the segments where I used spiral cut too. Strange only one of the four nominally identical segments gets this problem.

The cylinder is the only part where I'm cutting either side of line. I may make another test piece which only does this and on a full circle.

In any case this shape has already proved useful in testing both FreeCAD paths and the hardware.

[sliptonic]

In any case this shape has already proved useful in testing both FreeCAD paths and the hardware.

Indeed it has. I'll add it to the repo.

I think you're pushing Path more thoroughly and systematically than it has been for a while. I really appreciate it!
Somebody get this guy a mantis account!

[roerich_64]

@freman,

can you make a step by step tutorial how we could become the precision?
It helps a lot for the grlb users

BR
Walter

[freman]

Indeed it has. I'll add it to the repo.

OK, I'm glad you consider it useful.
I should add a final cut which goes to zero in the stock, leaving a few connecting tabs to stop the piece moving and snagging the tool. Then you' be able to snip it out and start measuring it in all directions with the verniers or a mike and an engineer's square.

I need to lower the table first, I have very little Z movement in this position. That involves some time levelling it afterwards. Then I can set the machine vice and try cutting metal. I'm still setting this machine up.

[freman]

Here is another test piece, which I've called the wall of death.

It mills either side of a circle and should, theoretically, leave no material. In a similar way to the last pattern, my machine does leave some traces in wood.

This seems to come from about a thou of play in the chinese ball screw on the gantry. I already had to change the ball bearings since it had about 2.5 thou new. It seems the Chinese make these cheap parts with lesser precision then some poor guy has the job of trying different ball sizes until it's about right. In this case I must have got someone who was ready to jump out of a window and didn't really care any more. Luckily, I have a selection of balls: 3.15, 3.16, 3.17 ..... Hopefully the next size will not be too tight.

Looks like another strip down.

Anyway the pattern may be a useful diagnostic, focussing on what I saw in the previous , without the multiple passes of the other shapes possibly destroying part of the evidence. When cutting a harder material like ali, this will quickly show up problems due to lack of rigidity.

[freman]

I think you're pushing Path more thoroughly and systematically than it has been for a while. I really appreciate it!

Being thorough and systematic is one of my character defects, it's a hard cross to bear but it has some uses.

If I can open a few bugs maybe some of these issues will get fixed. I suspect most of them are pretty trivial to fix for someone who is familiar with the code base. In particular it would be good to see spiral path fixed. Some of the alternatives make very complex, jerky paths to clear the same area and are not consistent for different directions. There are always traces of the cutting path left on the work-piece but this can be attractive if it is a regular pattern. Piecemeal to-ing and fro-ing tends to look untidy.

I see a wide choice of tool types in Tool Manager but not all are currently supported by Path. Does it handle ball-end mills or only straight end mills? Once I'm done with the simple geometric tests, I have jobs which need round ended tool .

[sliptonic]

I see a wide choice of tool types in Tool Manager but not all are currently supported by Path. Does it handle ball-end mills or only straight end mills? Once I'm done with the simple geometric tests, I have jobs which need round ended tool .

It depends. Most of the operations only use the diameter property. They don't even care what type of tool you select.
Opencamlib operations can theoretically use several different shapes and the other properties and types are intended to support that but its not fully implemented yet.
The vcarve operation I've been working on will use an engraver type tool but it's waiting on some openvoronoi improvements.

[freman]

Would vcarve be able to do something simply like this part at the moment. If not, is there a way I can trick FreeCAD into producing paths to do this by specifying a flat endmill but really using a 45deg mill?

Maybe if I used specified a 0.5mm end mill and overlap to 1000% and then used a 5mm V-shaped tool?

Thanks.

[herbk]

Hi freman,
yes you can do that. The Engraving OP works along only a line. It can also be just a (helper) line made witch sketcher to extend the path to leave no material at the end.

Deburr may be also works, but i havn't used it