Hi there,
Pretty new in the CNC world I just finished building my first CNC router and made some test cuts.
My machine is kinda similar to Grunblau's Platform CNC except is has rack&pinion on the X axis and it's bit larger (82" x 24" machining area). I use an Hitachi M12VC router on it.
Here's my questioning : I'm the middle of a small project that involves cutting MDF sheets (5/8" & 3/4"), I bought a 1/4" MDF bit from Amana (#46170) but I'm really not sure it's the best choice for my setup. Let me explain.
My machine is only driven by NEMA 23 low inductance 320 Oz-in steppers, I rapid at 300in/min on X (dual R&P) and 200in/min on Y and Z (ACME screws). Since my first cuts I only feel comfortable cutting at feed rates around 60in/min even though I successfully made some cuts at 100in/min and could probably go a bit faster on straight cuts. My concern is the rigidity of the machine, with faster feed rates I'm worried the machine will "deform" when changing direction... but I have no proof to support that gut feeling.
For the first batch of MDF parts I cut, my setup was : Hitachi router at position 5, DOC 0.1", feed rate 60in/min (tried the last cut boosting the feed rate to almost 100in/min, no problem but it was a straight cut)... lots of passes, lots of time but quality was good. Dust collection was also pretty damn good and the parts once cut where clean and almost ready to use.
Yesterday, wanted to speed thing up a bit for the 2nd set of part, setup was : Router at position 5+, DOC .25", feedrate 60in/min, same AMANA 1/4" MDF router bit. The cut felt very "rough" and one thing that changed was the cut stayed full of MDF dust + my dust collection system was having a hard time keeping dust under control, I had quite some MDF dust airborne in the shop... also the edges of the cut were not as clean as the other parts. Dimensionally the parts looked OK though (still need to clean the edges and check...)
So here are my questions :
The bit I use is suggested to run @20000 RPM, which is close to what my router speed should be at position 5. Problem is at that speed, to get an acceptable clip load I should be feeding waaaays faster than what I'm able to do.
Are there any bits (MDF specific or not) that would be more suitable for slow feed rates ?
Am I asking too much to my machine when cutting .25" per pass with a 1/4" tool ? Maybe I should just go with higher feed rate but keep shallow passes..
Is the fact that the cut stays full of dust/chips an indication of something ?
For sure I'd prefer cutting slow in 1 pass (less cutting marks on the edges) but I guess the bits won't allow that and will just burn...
Any suggestion /advice / anything will be much appreciated !
I Hope I made myself clear with those explanations, English is not my first language...
Thanks !
Ben