is opToolDiameter a sensible default

[freman]

Hi,

what is the basis of the default cut depth of being equal to the tool width.

This is a pretty heavy cut and while commercial machines in a production environment will do this, is it really the best "default" value.

Today I had to recreate a path that I had previously configured and somewhere along the way I forget to set the the stepdown value. I had an 8mm tool and so it used 8mm depth by default. Luckily I only had 5mm to take off so I got a 5mm deep cut. It was a profile using spiral so the first cut is basically an 8mm slot which runs around the finished edge.

now 8mm slot 5mm deep is a lot of metal, it did not break anything ( to my relief ) but it howled a lot and gave a pretty rough finish.

I wonder if this is really a sensible default. A default should work by default, it is not a production optimised cut. Would a more conservative value be better for "default", in the sense that default works without danger in the "fault" of not having a specified valued.

[openBrain]

This looks to me highly dependent on which material you're machining. Polystyrene isn't 100C6 steel. So hard to define what is a good value.
Also notice that Path issues are better handled in the Part subforum.

[freman]

thanks OB, I realise there are a lot of factors, but polystyrene is not very good default material.

IMO a default should be a safe all round value which the user can then tweak according to knowledge of the material and machine in question. Tool o/d as cut depth looks like a pretty hardcore option for most materials.

Also notice that Path issues are better handled in the Part subforum.

did you mean the Path subforum there. I posted here first since maybe I was missing something and did not want to get shouted at for posting a dumb question in a dev forum.

[openBrain]

Yep. Path (as FEM and Techdraw) discussions are better placed in its own dev subforum.

[chrisb]

Moved to Path forum.

I think mlampert has already recommended this to you: You can use your own templates for job generation. Nevertheless I too think that the default could be a bot more conservative.

[geant]

Nevertheless I too think that the default could be a bit more conservative.

Totally agree!

Machinery is dangerous: FAIL-SAFE, and error on the side of conservancy!
Everyone does not use, or want to use job templates; especially for one-off machining.
I would rather start in safe condition JUST in case.

3mm or 1/8 inch is more realistic as a starting default. Then from there, do all the damage you please!

Yet this subject still lingers and continues to be questioned; ever wonder why?

BTW, what chuck capabilities are these defaults based on, 8mm key-less, collet, morse taper, etc,, etc.

[mlampert]

3mm or 1/8 inch is more realistic as a starting default. Then from there, do all the damage you please!

3mm would break every bit I have on any operation I perform unless I start working in foam which would be pointless to me. The fact is there is not a single safe value unless we use 0 (which doesn't work for other reasons).

The reason it is the tool diameter is because all chip load charts are keyed by the tool diameter.

[freman]

yes, clearly this is correctly related to tool diameter but 100% is not a safe starting point.

I tend to use 25% when I don't forget what I'm doing but I asked for those with more trade experience to chip in ( no pun ).

In practice this is something you will almost always need to set for the job , so using default probably means you forgot. Maybe 10% would be a safer starting point for those senior moments.

[chrisb]

Of course this has to be depending on the diameter. Nobody will mill with a depth of 3mm with a 1mm mill and with a 30mm mill it well can be more. When I said to be more conservative I was thinking about 1/3 or 1/4, but even these values are rather deliberate. I thought about asking to put them directly in the preferences, but for which material? So I think it is a good solution to have templates, e.g. for different materials and different mills.

And if common charts use 1/2 or 1/1 we should use it too. If a newbie downloads FreeCAD, creates some model, generates a path, loads it on the machine, and starts milling right away without ever having checked - e.g. by milling in plain air - I would say he is not courageous, he is an idiot.

[herbk]

Some tima ago sliptonic explaned why this default tool is there and why other default settings are not 0: Its a need for the calculation of the path, because if no tool is there and/or it's default is 0, it runs in an "division by zerro" error somewhere.

I'm not a friend of this default settings, because they are at 99.xx% of the cases wrong. I'm with you, if you say "if it's a need for it, set it to a save value". - But what's a save value? One say 25% of diameter, one 10%... But what if we have a usecase which comes not in our mind atm.?

I think we should accept, that the milling parameters are not save and we have to check it each time we create a path.
Partial savety is more dangerus as no savety in this case. If there are no save settings, the user is carefull for all things. If there a some things save, others not, it comes to mistakes like "oh, i thought this setting is safe"...