Problem- New Patriot, Few Issues

[Jim_V]

I just got my new patriot setup and running, with full cnc, dro, and ball screws. The first issue is with the charge pump on the Gecko G540. I can only get the cnc to work with the charge pump switch turned off. If I leave it on, the G540 won't come out of fault, and mach3 shows a permanent e-stop condition. I've gone through the Shopmaster manual meticulously, deleted the files it says to and replaced them with the ones on the disc, and still no change. From my reading, the charge pump is for when you boot up the computer while the machine is turned on to keep it from making any unwanted movements. So if this is the case, it shouldn't be a big deal, but I'd still like to know if something is wrong.

My real concern now is when I actually started milling some test pieces. I started out getting a lot of vibrations, especially when I tried milling a slot in a piece of 1/4 inch mild steel. The vibration was so bad when I tried to mill the slot that the machine sounded like a souped up jackhammer. I played around with the gib adjustments, and got it to where I could face mill along the outside of a piece or on top with less vibrations, as long as the width of the cut was less than half that of the cutter. But slot milling was still terrible, as was the finish on the part. I tried using both a half inch end mill and a half inch rougher, both at various speed and feed rates. Vibrations are less when I run the spindle at full speed, but still almost impossible to mill a slot.

After reading several threads on here about movement in the mill head, I decided to reinforce the bridge and 5th column in hopes of solving the problem. I replaced the flat stock bridge with a 6 inch i beam, and made a new 5th column out of some 1/4 inch 2x3 I had laying around. I extended the 5th column so I could bolt it two both the top and bottom of the bench, since the factory one flexed the top edge of the bench like crazy when I moved it back and forth.

The modifications had very little effect on the ability to mill a slot, and face milling stayed about the same. If I try to mill a groove instead of a slot, the sides of the groove have a poor finish whenever the machine started to vibrate, but the bottom of the groove is fairly smooth, meaning side to side movement is the problem. This leads me to believe the problem lies in the table, and not the mill head. I've tightened up the gibs to the point where I just start to feel tension in the handles, and I don't feel any slack in the table when I try to wiggle it with my hands.

When I contacted Shopmaster and asked about the vibrations, he said it's probably due to the wrong spindle speed, and/or feed rate. I've tried all different speed and feed rates, and it's not getting any better. Hopefully somebody on here has some ideas.

[instructor37]

Originally Posted by Jim_V I just got my new patriot setup and running, with full cnc, dro, and ball screws. The first issue is with the charge pump on the Gecko G540. I can only get the cnc to work with the charge pump switch turned off. If I leave it on, the G540 won't come out of fault, and mach3 shows a permanent e-stop condition. I've gone through the Shopmaster manual meticulously, deleted the files it says to and replaced them with the ones on the disc, and still no change. From my reading, the charge pump is for when you boot up the computer while the machine is turned on to keep it from making any unwanted movements. So if this is the case, it shouldn't be a big deal, but I'd still like to know if something is wrong. When I contacted Shopmaster and asked about the vibrations, he said it's probably due to the wrong spindle speed, and/or feed rate. I've tried all different speed and feed rates, and it's not getting any better. Hopefully somebody on here has some ideas.

You need to give more details on your setup before someone can offer some help
Coolant ?
Type and size of end mill?
Material - alloy, thickness
Depth of cut
Spindle RPM
Feed Rate.

[Jim_V]

Originally Posted by instructor37 You need to give more details on your setup before someone can offer some help Coolant ? Type and size of end mill? Material - alloy, thickness Depth of cut Spindle RPM Feed Rate.

Coolant ?-Yes
Type and size of end mill?-Both a 1/2 end mill and a 1/2 inch rougher, both hss
Material, alloy, thickness-Mild steel, I've tried both 1/4 inch and half inch plate.
Depth of cut-Anywhere from 20 thousandths to a full slot. Face milling is OK as long as the width of the cut is less than half that of the cutter diameter.
Spindle RPM-Anywhere from 300 up to 1500 full speed. Full speed works best, anything slower just made things worse.
Feed Rate-If I'm trying to cut a slot the full depth, just about any turning of the crank produces major vibrations unless I instantly back off. This happens when trying to cut a groove in the middle of a piece as well.

[Mkroe]

When I got a hold of my friends Patriot it had the same issues. He wanted it to mill steel molds for castings. After many hours of rework on the mill to stabilize the bridge doing much the same as you Jim as well as the CNC conversion I did. Also bolted the entire mill to the concrete floor. The problem was lessened but not gone. Finally we added a 2in thick aluminum plate to the table so the spindle would be deeper in the head. Now milling steel is much much better. Can cut steel at 4 to 5 IPM with minimal vibrations. Aluminum milling is smooth as glass now and can run 7 to 12 IPM using spindle speeds from 600 to 1100. Just my observations making his mill work for his needs.

Mike

[aisrad]

I had similar issues with the mill. I bolted several test pieces of iron on the table and found flex between the blue table and bed. I also found about that I would get about 7 thousandths of flex in the flat iron on the bridge when I forced the mill.

I went with building a fifth column that is attached to bed and table. I also added angle iron on the bridge.

the main iron is 3 x 5 x 5/16 angle iron and column is 2 1/2 x 3 1/2 to give you perspective.

Photos attached.

[dahui]

First, you want the quill extended as little as possible. You also want to use and end mill that has the largest acceptable diameter and the shortest practical length. Is your endmill a "normal" length or extra length?

Second, it seems like you might be using too much depth of cut. I have an eldorado, but .100 is about the most I like to take if I'm cutting a full width slot...in aluminum, not steel. If you are trying to cut a .5 slot .5 deep in one pass on steel...well that ain't gonna work on the shoptask.

Last, I'm sure you are getting up to speed, but I'm a little confused by your terminology. You are slotting any time you are using the full width of the cutter, regardless of depth. There is a lot of load on the tool when the cutter is fully engaged. This should be avoided on the shoptask whenever possible.

By "face milling" I assume you just mean "facing"...as in making the top of a part flat. You don't say what your depth of cut is when facing so it's hard to say anything helpful. However, like other cuts, you have to trade depth for step over. If you want a 75% step over you might only be able to take .050 DOC...or less.

Lastly, cutting on the side of the endmill is called...well a lot of things Regardless, if you are (let's say) taking a radial cut you will need to balance step over and depth of cut. More step, less depth and vice versa. If you are making a radial cut that is .5 deep...I'm guessing your stepover should be no more than .050...maybe double that with a (coarse) rougher. Cut both of those in half for steel!

As a general rule, the ST likes to cut light and cut fast. Bottom line, if you are getting chatter: step 1, reduce step over or DOC. step 2, reduce RPM or increase feed rate. On other machines you might adjust RPM and feed first, but the ST doesn't have much of either. On bigger machines chatter can be the result of too little chip load, but on the ST it's usually because the tool is overloaded and flexing the machine. Hope something in here is coherent enough to help.

Oh, if that doesn't work, sometimes chatter can be the result of too little bearing preload. Wouldn't mess with that until other options are exhausted though.

This is an image of slotting with a 1/2 end mill (4 flute) on aluminum. You can see a little indent in the foreground. I had to back off the DOC. I think I tired .200 DOC and had to back it off by half.

[Jim_V]

Well I think I found most of the problem, hopefully all of it. I was getting a lot of table rock whenever I moved the work piece against the end mill. So basically, the table was acting like a sideways spring board bouncing back and forth against the end mill while I was trying to mill a slot. This would explain the notches on the side of the work piece when I was using the side of the end mill. The gib strip on the x axis happened to be the culprit, it was only making contact at the ends and a spot a little off center. I stuck a piece of sandpaper on the mill table and kept running the gib strip back and forth until the low spots disappeared, which took a good half hour.

I won't be able to run coolant again until the silicone drys around some table bolts and drain tube, so I had to take it a little easy. I did manage to cut a 1/2 inch slot full depth in some 1/2 inch mild steel plate in one pass, about an inch long until the end mill started to smoke. All I can say is this thing is 100% smoother, no crazy vibrating or anything.

Things are looking good so far, I'll do a lot more testing tonight after I can run coolant again. I'll run the table feeds with the computer so I can get an exact feed rate, and post the results later.