I am importing a MoI model into my cad package. If I make a 5 inch Sphere in MoI it has a size of 5.0020 in the Cad side.

Is there a setting in MoI that is controlling the level of precision?

If not, My next question would be the same to the Cad people.

Thanks,
Burr

Hi Burr,
I don't know if this is related to precision but there is a 'decimal display' dropdown in the options dialog you can try.

(MoI 2.0 beta Aug-4-2008)


I tried the same thing over here with only 2 decimal display, exported a 5 inch sphere as .iges, imported it to another cad package and got the analysis below.

'Surface Type (Non-Parametric) Spherical

Center XC = 0.000000000 X = 0.000000000
YC = 0.000000000 Y = 0.000000000
ZC = 0.000000000 Z = 0.000000000

Radius = 2.500000000'

So I don't what's happening there, dude, is there an import precision option in your other cad package ?

-

Hi Burr, can you describe the process of how you are making it 5 units?

I mean are you moving the mouse around and watching the readout until it says 5, or did you type in 5?

It's not a good idea to do the first method (just wave the mouse around until the readout says 5) unless you have grid snap or something on, because like Danny mentioned, the readout is rounded to the nearest 0.01 unit by default, so for example if you are at 5.002 units the readout will read 5 since 5.00 is closer than 5.01 .

If you need more precision with the readout, you can increase that display precision, but instead of that I would recommend entering a precise value directly when you want a particular result.

Like for example when you want a radius of 5, then type in 5 <enter> (you don't actually have to click first, just type 5 and it will appear in the radius edit box).

That kind of direct entry should eliminate any kind of rounding problem.

- Michael

Hi Danny, and just to clarify that "Decimal display" just purely controls values that are displayed in the UI, like the radius value that is updated when you drag the mouse around, point coordinates that update to give feedback while you move the mouse, etc...

It just controls what is displayed in the UI for those numeric controls and does not actually have any effect on entering values or snapped points.

- Michael

Hi Michael,
> just to clarify that "Decimal display" just purely controls values that are displayed in the UI....

Yeah, I thought this was the case, but it would show you if you were precise when displaying 4 decimal places and you did the drag method....wouldn't it ?

Anyway, I like the way you slip in these small dropdown niceties in V2 beta, quietly :)

-

Thanks for the replies. I am typing "2.5" for a 5 inch ball. It could be a setting in the software Danny though it could just be the software. I'm importing it into BobCAD. I'm going to ask over there to see if there is somthing controlling a tolerence or the likes. Just needed to be sure there was no accuracy setting with MoI.

Danny, Have you had any experience with OneCNC or heard anything about them. I may need to look at something in the future.

Thanks again,
Burr

HI Burr,

> Have you had any experience with OneCNC or heard anything about them.
> I may need to look at something in the future.

No I haven't, all the companies I worked for had lots of money and went for the mainstream stuff, there was never enough time in these companies to do proper evaluations on CNC software from the smaller vendors, managements mentality was, 'They're only a small company, it wouldn't be that good, what about support, what if they went under......blah, blah'. I gave up in the end, it wasn't my money they were spending ;)

I haven't programmed for years, so I'd be a bit rusty on the CNC trends, there's a guy here at work who built a CNC router at home and uses Mach3 software for his PC machine controller, and I think he uses VisualMill.

Cheers

Hi Danny,

> Yeah, I thought this was the case, but it would show you if
> you were precise when displaying 4 decimal places and you
> did the drag method....wouldn't it ?

Well, I mean it would show you that you were precise within 4 decimal places.

But if you got a value with your mouse of say 5.00002 , then that would still display as 5.

It just makes the amount of rounding for the display smaller but does not eliminate it.

It isn't very feasible to not have any rounding in the display at all because you would be seeing huge numbers like 5.000012502502301250120510 all the time when you moved the mouse around, there just isn't room to fit a huge number of digits like that in the UI.


> Anyway, I like the way you slip in these small dropdown niceties
> in V2 beta, quietly :)

Oops, yeah I forgot to mention that.

Actually there was the same function in v1, but it was labeled "Decimal places to display:", and took in a number value. When I added feet & inches units, I needed a similar kind of rounding value for fractions, and that works best with a dropdown instead of a number of digits entry. It seemed like the dropdown was also nicer for the decimal number of digits as well (just illustrates its function better), so I switched that over as well.

- Michael

Hi Burr,

> Just needed to be sure there was no accuracy setting with MoI.

No, there is not any setting for that.

There is a value used for certain operations that need to be approximated, like when the intersection between 2 surfaces is calculated, that intersection is calculated to an accuracy of 0.001 units.

But that "fitting tolerance" value will not come into play at all when drawing a sphere, that should be precise to a much greater amount than just 3 digits, more like 13 digits or around there.


Do you happen to be creating the ball a large distance away from the 0,0 origin spot?


Other than that, I'm not sure what is happening in BobCAD. Can you do a test of trying to export a 5 inch ball created in BobCAD and see if it comes back into BobCAD as 5 inches or if it also gets reported as a different size?

- Michael

It most likely is something with BobCAD. It's 3dm export and import read its own 5 inch sphere fine.

Here are 2 files. the one from MoI so you can see how I create it, and one from BobCAD. The Bob File imported into MoI produces a huge sphere far away from the origin.???

Somehow they are not compatable.

They are using "OpenNURBS toolkit version 200609070 (compiled on Oct 19 2006)" Is this far outdated or reasonable?

Mostly I can create things that dont require tolerances though for stuff that needs to be tight, I have to figure out what may be up.

Thanks for your time,
Burr

Hi Burr,

> The Bob File imported into MoI produces a huge
> sphere far away from the origin.???

It looks like the Bob file has its units set to millimeters, that's why it is larger in unit size, since 5 in = 127 mm .

The other thing is that the Bob one has a diameter of 5 inches, but the MoI one has a radius of 5 inches instead.

- Michael

Here may inlie the problem. The diameter or radius isnt quite the issue, this was me just making something fast. It's the .002 thing.

My bobcad interface is set to inches. Is the MM thing an internal file format or are you under the impression that my interface is set to mm?

If it is an internal export function, this could be my cause to take to Bobcad. What told you it was in mm?


[EDIT] Could there be a version issue with open nurbs. MoI is on version 3 and bobcad using 4? (Am I mistaken? I am getting this from the toolkit)[EDIT]
Burr

Hi Burr,

> Is the MM thing an internal file format or are you under the
> impression that my interface is set to mm?

It's what was set as the unit system in the .3dm file - the .3dm format has a place in it to mark what unit system is being used, in the bobcad file that is set to mm. (and coordinate values have been scaled so that they are in mm units instead of inches).

If you open that file up in MoI, then go to Options, you'll see Unit system: Millimeters, also same thing if you open it in Rhino.


> Could there be a version issue with open nurbs. MoI is on
> version 3 and bobcad using 4? (Am I mistaken? I am
> getting this from the toolkit)

It's true that MoI is using v3 of the OpenNURBS toolkit, but files written by OpenNURBS v3 are able to be read in by OpenNURBS v4 without any problem... I can't think of anything that would introduce error in coordinate values for example.


Maybe Bobcad does not like to get files with Inches as the units in the file?


I guess another test you could do would be to start a new file in MoI, set units to mm, then create a sphere of radius 127 mm - then import this into BobCAD - does this then show a value of exactly 5 inches in Bobcad? If so then maybe there is a possibility that BobCAD has a bug when importing files with inches as the unit system and converting it to mm...

- Michael

>guess another test you could do would be to start a new file in MoI, set units to mm, then create a sphere of radius 127 mm - then import this into BobCAD - does this then show a value of exactly 5 inches in Bobcad?>

This is exactly the case Michael.

If you could respond one last time with what I could approach the BobCad people with, that would help to set me in the right direction.

Thanks again for the support,
Burr

Hi Burr, well that does seem to point to a problem in Bobcad where it seems to work internally in mm and has some kind of error when importing a file with units in inches instead.

I guess what I would recommend would be to tell the BobCad people that you're having a problem with importing .3dm model data when the units in the file are set to inches.

Give them 2 .3dm files - one file with the sphere with 5 inches and explain this seems to give the incorrect value of 5.002 units when imported into BobCad, but if the units are set to mm and you have 127 mm (5 inches = 127 mm), that seems to work fine.

Please let me know if you find anything out from them.


It looks like for the time being a workaround for you would be to convert your units to mm before you do your export into BobCad. MoI will handle the scaling for you, so for example when you switch your units to mm your sphere will be converted from 5 inches into 127 mm.

- Michael

Thank you.

I'll post back any results.

Burr

You're welcome Burr! It's kind of a strange problem, I hope they will be able to give some more information on it.

- Michael

I just posted on their beta side. We'll see what comes of it.

:)

I suppose I could also learn to convert and work with mm. (Seems again I shouldnt have been so stubborn when they wanted me to learn it in school :o)

Thats what I get!
Burr

Still waiting. Will post back.