On Sat, 11 May 2013 21:40:55 -0700 (PDT), you wrote: > Re: Correct use of subroutines > >My old school answer is that most subs should be written in (G91) Incremental >mode. > >My more modern method can be either G90 or G91 depending on the application >but I use variables for D, F, Z and loop to run Z level roughing and finishing >often using several tools. > >RE: G84 > >BTW it is the programmers job to lie to the machine - the machine should NEVER >lie to the operator. > >The value you use for your F should be exactly what the machine feeds at. No >IF's ands or buts... 100% F >This is also a key safety point - The operator needs to be able to read the >G-code and KNOW exactly what the machine will do when it tries to execute that >code.
Which is the reason that many commercial shops never use subs now. >Now if you are using a using a specific tool which needs to run at a reduced >feed then you as the programmer should alter the programed feed rate. In this >case if you wanted to use a Osub to do your tapping and you wanted it to feed >at 95% thats fine - its all man readable in the Osub - Fixed cycles don't >display the inner workings so others would not know of your 95% mod. > >While I started out on a Bandit CNC way back and subs were critical with >controls that could only handle like 99 command lines. These days unlimited code length is the norm and subs are frowned upon commercially in my experience. The operator can't easily alter the code, if required, on the fly. Some of the subs I've seen here and elsewhere are so complex that they could only be written to show how clever the author is, not for ease of machine control. A typical op has no chance of understanding them. If you are hand coding they can save some typing and cut 'n' paste but in the CAD/CAM world they are pretty worthless. One of the big shops I work with don't even use canned cycles unless they really have to! They run a prize scheme where if an operator saves time or tooling cost on code they are rewarded. One operation they do is a deep drilling op in a nasty cast steel. They use a through coolant drill but it still clogs up with chips. It was soon realised that it was pointless withdrawing the drill until it had reached a certain depth to clear it. The deeper it gets, the more it needs clearing etc. The drilling operation is done with G1 and G0 moves, easy to adjust to get the optimum without unnecessary machine moves. It's ended up as hybrid drill, peck, deep hole operation and saves several seconds. That saved time is more profit. Steve Blackmore -- ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. This 200-page book is written by three acclaimed leaders in the field. The early access version is available now. Download your free book today! http://p.sf.net/sfu/neotech_d2d_may _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
