Fusion and an 808 D

I’m new to CNCing. I have a 2 axis lathe with an 808D controller. I have had a couple of days training and the guy who trained me is giving phone and email support but I’m struggling with the ‘repeat’ command.

I’m using Fusion and I’m making parts, that all working great. I find the Fusion posts need some editing in particular the tool change position needs to be further away from the chuck and some of the feed rates are missing. Could this be a post processor problem?

I’m getting caught up on the commands that repeat particular parts of the program. For example I want to machine the OD to Z-27mm and then part off 5/6 times before resetting the stock to Z0. What are the commands for repeating the parting off section of the program?

Do you have a license for Fusion?
If you're only using the hobbyist version, then you don't get rapid feeds.

Tool change position for a lathe is normally done in the code, as for a lathe you want to minimise dead travel, so you rarely have a fixed tool change position.

I'll admit I do 90% of my lathe coding by hand, so can't comment on how Fusion handles lathe tool change positions. Generally you do need to edit the post processor to suit your own specific requirements.


Repeating code can be done two ways.
Easiest way is to simply hard code the routines. Not the most elegant, but is the simplest in terms of writing code.
The next option is to make use of either a sub-routine, that you call multiple times, or a repeating loop.
Within whatever loop/sub-routine you use, you either need to use temporary offsets, calculate positions, or use relative moves.

I'd suggest you find the controller manual, and start reading the relevant sections on sub-routines.

Yes I have the Fusion licence. My programs are so small that it would be very quick to change the coding to G00 had I not upgraded.

I have been trying to use a G91 ti move the work offset. You think I should use G54, 55, 56, 57, 58 and 59? What happens if I need more work offsets?

Hard code? Would that be to copy and paste the code and edit movements to suit?

If you need more work offsets, then you need to keep track of them, and change them as needed, but some controllers let you set offsets via code.
Offsets depends on the control. I know my current control, I can use G50 to set a workpiece coordinate, but the two previous options I've used, have used different methods.


Yes, by hard code I mean copy/paste and edit.
Not elegant, but sometimes the KISS approach is easiest.

I settled down tonight and wrote a short program for cutoff using the repeat command and it worked great. I used G91 to move down the bar and G90 to return to G54 true zero. I find the simulator on the machine unhelpful because I can’t see exactly what it’s doing, air machining is much more helpful.

What is unhelpful is swiping the end off my cutoff tool last night! I can see my error and I’ll correct it when the new tool arrives. Fortunately cutoff tools are fairly inexpensive so I’ll put this one down to experience and add the mangled remains to the pile!

Now I’m starting to understand more about how it works the manual is becoming more useful so I’ll refer to it more frequently in the future.

Thanks for your help. I agree Aluminium Warehouse is shocking.