UCCNC scaling issue

Check your units - you've probably drawn in inches, cut in millimeters (25.4 : 1).

Thanks for the response. Correct, I have drawn in inches. Can't seem to find anything units-wise in UCCNC. Is there an option somewhere to cut in inches/mm?

UCCNC defines operations in terms of units - without actually defining what units are in use. Standard Stepcraft profiles use mm as the basic unit, hence everything else is scaled to suit (e.g 133.3 steps per unit and so on). If you wished to use inches then this would become 133.33 x 25.4 (3,386.6582 steps per inch). Approximately!!

All the other configuration control parameters would have to be adjusted similarly - either multiplying or dividing by 25.4 - quite a daunting task. Might be easier to use mm in Vcarve from the start - your choice obviously.

Peter

You can use mm or inches when drawing in the VCarve, just be sure to use the correct post processor that is suitable for the stepcraft, and for the default setup it is the Mach2/3 Arcs (mm) (*.txt).

Do NOT use the "Mach2/3 Arcs (inch) (*.txt)" post processor, that one is not for stepcraft.

Internally Vcarve uses whatever unit it uses, and then shows them to you either as inches or mm depending on your job setup. You can even change the units in the middle while working in the VCarve, just in case you have some parts which you need to type in inches while rest are in millimeters or vice versa. When you change the units all objects are scaled accordingly, but the toolpaths are not automatically fixed, you need to recalculate them all after you have changed units.

So when you have your design in inches, and calculated toolpaths with those settings, and then go to save the g-code the post processor you select will scale the internal VCarve units to something that is suitable for your machine.

I.e. if you have 1 inch == 25.4mm line in toolpath the post processor will scale it matching the units in the machine you are using. When you are using the correct "(mm)" version of the post processor it will always generate 25.4 units for the final G-code regardless whether VCarve used inches or millimeters for display units for your job.

Then the UCCNC takes that X25.4 and converts it to steps it is sending to the machine, and for that it uses the steps per unit conversion in UCCNC config. By default this is 133.3 i.e. that X25.4 will result 3386 steps to be sent to the stepcraft. UCCNC will then use the acceleration, feed speed, and max speed settings in the configuration to slowly accelerate the speed it is sending steps until it reaches the lower of max speed and feed speed. If your feed speed is for example 500mm/min = 8.33 mm/sec = 1111 steps / sec, thus it will take bit over 3 seconds to do that move with that feed rate, when not taking in to account the acceleration.

So UCCNC does not really care anymore about inches or millimeters, it just takes the raw numbers in the g-code and assume they are in the units configured in the UCCNC.

Hope this helps a bit to understand how all these things work.

Thank you very much. This is exactly what I needed to know. It does seem slightly backwards to export my file as metric to get it to cut cut right in imperial. Anyways, thank you for making some sense out of it.

I have this same problem -- thanks for verifying that it is a units conversion problem.

I am concerned that the list of post-processors in VCarve Desktop doesn't seem to include anything relating to Stepcraft or UCCNC. I used just "G Code" as the post processor selection. Is there anything better to use with VCarve and UCCNC?
Thanks.

Mach2/3 arcs mm .txt is what you need.

Hi everyone,

I seem to have a similar issue with my Vcarve Pro 11 to UCCNC. In VCarve I set up my material for say 12”x 24” x .14” corresponding to the physical dimensions of my work piece. After creating the tool paths and saving to different post processors, the G-code seems to return in a reduced size in uccnc, about half. The only solution I found has been to double my work piece size in vectric and then the g code come out about the size I need but I know there’s something wrong and that’s not the way to do it. Any thoughts or help is greatly appreciated.