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General Mach Discussion / increased speed equals bad corners

« on: March 14, 2007, 03:13:51 PM »

I have been asking around about feed rates and the info I have seen pretty much says to cut at the highest feed rate possible before breaking the router bit. Well I have been increasing my feed rates little by little.  I am making guitar bodies.  Shaping like tummy cuts and carve tops can probably get away with a little inaccuracy but neck pockets and cavity covers need to fit exactly.  I have cut many guitar bodies now at feed rates around 50 to 75 IPM.  These have been cutting properly, no problems.  But as I have increased feed rates up to 100 and 150 IPM,  I am now getting sloppy corners. 

Example:  In a square neck pocket with a .5" bit.  The first corner where the bit plunges in looks exactly as it should with a .25" radius corner.  The other corners that the bit travels through look more like .3" to .35" radius corner.

What I am wondering about is under Motor tuning - Acceleration.  I had this set at 8.  If I bump it up to 20, it seems that I get less deceleration going into a corner.  I am thinking that with the lower acceleration one axis is starting its move before the other axis is reaching its full position. 

I am going to run some tests on this but any thoughts on acceleration or anything else that may be affecting this? And are there any drawbacks to using too high of an acceleration?  I will say that the movement seems a lot more jerky and maybe could be harder on the motors and parts?...

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General Mach Discussion / What is a good feed rate?

« on: October 22, 2006, 05:46:52 AM »

Hello everyone.  I need some expert advice on feed rates.  I have a K2 CNC and I build guitars with it.  I have been re-vamping my files to reduce the time spent on the CNC.  I have been able to shave 45 minutes off the total time just by tweaking my feed rates and order that things are done.  Used to take 2 hours and now at 1:15.  Most of the time I am cutting alder wood with a .1/2" bit at 50 IPM and .25" depth of cut.  This works very well on the alder wood but on the occasion that I cut something like Bubinga, it does bog down the router.  So here are my questions...  How fast of an IPM can I run my motors at without burning them out (Nema Steppers) even with no load.  I have the max velocity set at 100 and am afraid to go any higher then that.  Can I jog at 200, 300, 400 safely?  -  Anyone else cutting a similar wood to alder or other types,  what feed rate do you cut at?  -  I've just been afraid to push the machine too hard for fear of damaging it.  And because I am relatively new to this,  I don't know what is appropriate as far as what are the maximum capabilities.

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General Mach Discussion / Can I load multiple G codes?

« on: August 25, 2006, 04:22:39 AM »

Hello everyone.  I have a question that I want to know if it is possible to do.  I use my CNC to build guitars and I have broken apart all of my files so that I can load up specific pickups - tremolo bridges - neck pockets - etc..... from different files and mix and match whatever I want on a specific guitar body.  This is easier then creating a complete file for every combination of guitar body.  But I'd like to run all of the cuts that I can with a particular bit all at once instead of having to load another file at the end or each operation.  So my question is:  Is there a way to load up several G-code files to run in succession?