I’d like to get a sense of the capabilities of the Longmill for cutting 3/4" Baltic Birch, which is often used for shop projects, jigs and furniture making.
There are some Sienci published feeds and speeds available for wood here as a general starting reference: https://sienci.com/docs/longmill-benchtop-cnc/common-materials/wood/
General plywood is listed at 1200mm/min (~47 ipm), with a 250mm/min (~9.5 ipm) plunge rate, and a 3mm step down. These seem quite conservative to me (which makes sense), but are they?
The loaded cutting speed I can’t really comment on as I haven’t used the machine yet, but I am hopeful it can go to at least twice that speed? 47 is on the slow side for sure. I saw the reference to the lead screws being a drag on overall speed due to the reduction factor they have, but I’m hopeful there is more juice available?
There are some interesting tid-bits in this older Wired article: https://www.wired.com/2012/10/you-suck-at-using-a-cnc-router/ But like all information on CNC feeds and speeds, I detect some comments that I’ve already experienced are incorrect. 80 ipm for Plywood can be far too slow on larger machines. I turn up my recent cut to 180 ipm before the chip load and sound was ideal. I have a feeling 80 might be more in line with what the Longmill could do and more appropriate for it’s design, but given that it’s almost double the listed speed (acknowledged as a conservative place to start), I’m curious if 80 ipm (2032mm/min) is possible on the Longmill?
The step down of 1/8" seems too shallow to me. I’m hopeful 3/8" would be feasible, and of course it have a dramatic affect on overall cut time. Why such a shallow step down? If doing carving or detailed 3D work I can see it, but for profile and pocketing or larger items it seems very shallow?
The plunge rate also seems a bit too conservative to me. That’s only .15 inches/second, which is far slower than I believe I plunge by hand without any issues. That’s just slightly more than 1/8"/second. Does that seem right given the rigidity of the Z-axis on the Longmill? Is it an issue of avoiding any flex and deflection?