I have several hundred smallish parts to whiz out that measure about 2" x 10" with a bunch of small .101 holes and .125" slots, with a handful of .4" holes. The material is mostly FR4 and G10 / G11 (like printed circuit board material without the copper). Since I hate the thought of plugging up the coolant filters in the VMC's or HMC's I've cobbled together a small flatbed CNC router that can mill the 3' x 4" sheets of material.
The material thickness is going to be .063", .093" and .125" thick. While I have loads of experience in hold downs and machining strategies for our "real" CNC machines, I'm coming to the collective wisdom of the board for a couple suggestions.
For a spindle, I've got a Hitachi router mounted with a 6,000 - 24,000 RPM spindle. I figure no point wearing out a real machine spindle either... The router uses a 1/4" size shank collet holder and has no tool changer which limits my options.
If I were to pick the smallest feature I need to mill, it would be around .094", and since I don't have a tool changer, the fewer tools I can use, the better. For a control I'm using a Mach 3 stepper system that runs open loop. So far it seems to have plenty of speed and accuracy.
The first issue is even holding a cutting bit. I'm guessing (but don't know for sure) that they make reducer bushing to allow a 1/4" collet chuck to hold smaller diameter tools. If so, I need a decent source from someone who has experience.
I'm pretty sure high speed tooling is out, and a carbide endmill is probably mandatory. Any suggestions to a tool in the 1/16" - 1/8" diameter that holds up in FR4? Is it possible to plunge and cut the features in one shot in material up to .125" thick? Any idea of feeds and speeds that you have tried and no work well for the material? do they make, and does it make sense to use diamond coated tooling to reduce the abrasive wear on the tooling?
I plan to add a vacuum with a skirt to suck up most of the crap. My guess is that chips if any will be small, most likely powder, so will this solution work to prevent re-cutting the swarf?
For hold downs, I'm probably going to use a couple well placed screws through the FR4 into my spoil board. I may actually add a tapped insert if it looks like wear is an issue. Anyone have a better idea? I figure I can either tab the parts to keep them in the sheet, or completely cut the parts free slowing the federate for the final severance step.
Ideas and insight are most appreciated.
Thanks,
Stu
The material thickness is going to be .063", .093" and .125" thick. While I have loads of experience in hold downs and machining strategies for our "real" CNC machines, I'm coming to the collective wisdom of the board for a couple suggestions.
For a spindle, I've got a Hitachi router mounted with a 6,000 - 24,000 RPM spindle. I figure no point wearing out a real machine spindle either... The router uses a 1/4" size shank collet holder and has no tool changer which limits my options.
If I were to pick the smallest feature I need to mill, it would be around .094", and since I don't have a tool changer, the fewer tools I can use, the better. For a control I'm using a Mach 3 stepper system that runs open loop. So far it seems to have plenty of speed and accuracy.
The first issue is even holding a cutting bit. I'm guessing (but don't know for sure) that they make reducer bushing to allow a 1/4" collet chuck to hold smaller diameter tools. If so, I need a decent source from someone who has experience.
I'm pretty sure high speed tooling is out, and a carbide endmill is probably mandatory. Any suggestions to a tool in the 1/16" - 1/8" diameter that holds up in FR4? Is it possible to plunge and cut the features in one shot in material up to .125" thick? Any idea of feeds and speeds that you have tried and no work well for the material? do they make, and does it make sense to use diamond coated tooling to reduce the abrasive wear on the tooling?
I plan to add a vacuum with a skirt to suck up most of the crap. My guess is that chips if any will be small, most likely powder, so will this solution work to prevent re-cutting the swarf?
For hold downs, I'm probably going to use a couple well placed screws through the FR4 into my spoil board. I may actually add a tapped insert if it looks like wear is an issue. Anyone have a better idea? I figure I can either tab the parts to keep them in the sheet, or completely cut the parts free slowing the federate for the final severance step.
Ideas and insight are most appreciated.
Thanks,
Stu