Hello all!
I'm looking for machinist friends local and otherwise. Also looking for parts for my machine. I have a 1992 Shoptask 1720 XMTC CNC "with plenty of mods" running Mach3. I'll try to get a photo posted.
I have quite a bit of experience with the CNC lathe side of my machine but due to a chipped mill spindle pulley from day 1, I've never really used the mill much. What brought me to this site is that I'm interested in building stirling engines, and that is going to require getting my mill straightened out. I really like the vacuum engines but downloaded a set of plans for a simpler air driven motor to start with. I've found a very decent local source for brass and AL drops (prices are below scrap dependent on beer, best picked up on Fridays).
So I'm in the process of trying to get the mill functioning properly, with heavy focus on rigidity and getting the Z axis spindle to stop vibrating... The top edge of the stepped pulley got broken off creating a horrible, unusable vibration/shake. This week I contacted the manufacturer and am trying to source a new pulley. In the meantime, I decided to turn off the damaged area of the original pulley in the lathe. Vibration improved somewhat but I'm still getting a vibration above 1000RPM. When I mill a sample of brass (see below for testing parameters) there are close .008" regular marks in the material (chatter or maybe table slop?) as well as wider spaced .600" pattern from what I assume is a cyclic, harmonic vibration. I can also hear this secondary vibration building up and ramping down in the machine and table. Some other Z axis repairs are new bearings all around, disassemble and polish all contact surfaces, eliminate slop where ever possible and lubing everything with quality synthetics. I upgraded the 3/4HP capacitor start motor to a 1HP in the same 1720 RPM range. I may replace the two v belts as I think they may be older and taken on an oval shape possibly causing some of my vibrations.
For testing purposes, I'm using a block of 360 Brass and 6061 AL. HSS, 4 flute .375" endmill, no coating, .020" depth of cut, 1450RPM, running a CNC slotting program for consistency. When I slow the spindle down to 500RPM, the vibration goes away and at a feedrate of 6in/min I get a decent cut.
I do have a few questions... When you have a damaged pulley or have spindle vibration issues do you send the assembly out to be balanced? Any tips and tricks for getting the vibration out or reducing it? None of the pulleys have any drill marks from being balanced ever.
I'm looking for machinist friends local and otherwise. Also looking for parts for my machine. I have a 1992 Shoptask 1720 XMTC CNC "with plenty of mods" running Mach3. I'll try to get a photo posted.
I have quite a bit of experience with the CNC lathe side of my machine but due to a chipped mill spindle pulley from day 1, I've never really used the mill much. What brought me to this site is that I'm interested in building stirling engines, and that is going to require getting my mill straightened out. I really like the vacuum engines but downloaded a set of plans for a simpler air driven motor to start with. I've found a very decent local source for brass and AL drops (prices are below scrap dependent on beer, best picked up on Fridays).
So I'm in the process of trying to get the mill functioning properly, with heavy focus on rigidity and getting the Z axis spindle to stop vibrating... The top edge of the stepped pulley got broken off creating a horrible, unusable vibration/shake. This week I contacted the manufacturer and am trying to source a new pulley. In the meantime, I decided to turn off the damaged area of the original pulley in the lathe. Vibration improved somewhat but I'm still getting a vibration above 1000RPM. When I mill a sample of brass (see below for testing parameters) there are close .008" regular marks in the material (chatter or maybe table slop?) as well as wider spaced .600" pattern from what I assume is a cyclic, harmonic vibration. I can also hear this secondary vibration building up and ramping down in the machine and table. Some other Z axis repairs are new bearings all around, disassemble and polish all contact surfaces, eliminate slop where ever possible and lubing everything with quality synthetics. I upgraded the 3/4HP capacitor start motor to a 1HP in the same 1720 RPM range. I may replace the two v belts as I think they may be older and taken on an oval shape possibly causing some of my vibrations.
For testing purposes, I'm using a block of 360 Brass and 6061 AL. HSS, 4 flute .375" endmill, no coating, .020" depth of cut, 1450RPM, running a CNC slotting program for consistency. When I slow the spindle down to 500RPM, the vibration goes away and at a feedrate of 6in/min I get a decent cut.
I do have a few questions... When you have a damaged pulley or have spindle vibration issues do you send the assembly out to be balanced? Any tips and tricks for getting the vibration out or reducing it? None of the pulleys have any drill marks from being balanced ever.
