X2 Mill Cnc Conversion

[shooter123456]

A 6" vise is overkill for a RF45 style mill. A 4" is more appropiate for that size mill & IMO 5" max. I have a 5" GMT vise on my PM45 & it's slightly too big. Not enough Y axis travel to make use of the 5" full capacity. Better to save your money rather than getting something too big & most importantly the weight. I take my vise of the table quite often, a 6" is still light enough for me to be carried by hand but I'm glad I have a 5". I also have a 4" vise as well. I prefer the 5" though.

But those GMT 6" Premium vises are pretty nice. I'd love to have one but don't need one on my current mill. But if you plan on upgrading to a full size knee mill in the future than the 6" will be perfect.


Here's what the 5" looks like on my mill.



I couldn't even complete this cut without my bellows & DRO scale getting in the way. Not enough Y travel & the 5" vise is not even maxed out.



Here's what a 6" vise looks like on another PM45 (gt40's)
View attachment 253544

 

[shooter123456]

Here are the videos I mentioned. There is a bit of chatter in some places that I hope will be eliminated when I get that Y axis squared away. The first time I hit the start button, the Z axis shot up to its home position and I panicked and hit the E stop. Then I turned the rapids down to 1% and started it again, and it was just going there because the program started with a tool change. I think I just about had a heart attack then.

 

[shooter123456]

I made brass gibs for the mill and oh my what a difference. With the old ones, there was visible and measurable rock in the table, even when they were tight enough to cause binding. I ran some cuts with the new gibs, and I wasn't able to make it chatter with a 3/8 rougher in aluminum before the spindle motor started to struggle. When I try to rock the table, it feels rock solid now. No noticable movement and it has smooth motion from end to end.

I made some D bits with O1 tool steel to make them, and used a piece of 1/4x3/4 brass bar. It made as much of a difference in rigidity as my column brace did. I don't even want to think about how poorly it must have worked without the brace and new gibs.

Here is the new Y gib with the old one and the 2 tools I used to make it.

The contact with the dovetails still isn't great but it is much better. In this picture, the darker areas of the brass gib is where it contacts the dovetails. I guestimate 35% contact there. The old one was only contacting a 1mm wide strip at the very top.

After I put the X and Y gibs in place, I was cutting the Z gib, and the fly cut had a perfect cross hatch and the cut was quieter than the motor running and there was zero discernable vibration.

I am still working on the tool holders for the pnuematic tool changer. Here is what I have now:

I ordered a facemill for $20 with 10 inserts thats on the slow boat from China. I wanted to give a facemill a try but didn't want to try an expensive one and find my mill cant handle it. I figure the worst case scenario, I can use just 1 insert and use it as a fly cutter and I won't have to wonder if those cheap facemills are any good.

I am going to replace the spindle bearings soon as well. If it has as much of an impact as the new gibs, the mill is going to be in seriously good shape.

 

[shooter123456]

I have decided to do a major round of upgrades after roughly 3 months of having it CNCd. The biggest issues I run into constantly are with the dovetails and spindle motor. The machine needs to be seriously babied and monitored because it loves to run just fine for an hour and a half, then stall one of the motors and rapid into the workpiece. The spindle motor also has a tendency to stall and shut off even with cuts I know it can handle. Now, even with the new gibs and lots of lube, I can't get decent travel along its whole range. In order for it to be tight enough to cut well in the middle, I risk stalling on the outside edges. If I loosen enough that it gets to both ends of travel, the middle will be very loose and chatter even with light cuts.

So I am getting rid of the dovetails and using linear rails instead. I scoured ebay to do it affordably and I ended up with:

2 22" Thomson Accuglide 25mm rails with 4 bearings for $150
2 19" IKO MLFG24mm rails with 4 bearings for $67
1 20" THK HSR20mm rail with 2 bearings for $80
The scrap aluminum I am using was about $60
This puts me at $357 for roughly triple the machining area and hopefully, much smoother motion and rigidity.

I plan to use the accuglides on the X axis, the IKO rails on the Z, and the THK rail will be cut in half and used for the Y.

Here is the model of the machine with the new rails. I need to change the Z axis to the IKO rails and bearings. Almost all of the new parts will be made using 3/4" aluminum. I found several large plates at a scrap yard that appear to be ground. I found a few high spots on the piece I am using for the table, but it cleaned up easily. The new table will be 8.5"x22" and the new travels will be about 15.5"x7.1"x8" (XYZ) and there will be roughly 5 extra inches in the Z that will extend past the top of the column which will be useful for very light cutting and drilling. The fusion 360 simulator says the weight of the head will cause the assembly to tip about .0003" and with a 100lb cutting force at the worst locations, the table will twist about .002" at the farthest and most will be under .001". With the head lower on the column and the table centered, which is closer to where 95% of my machining is, with the 100lb force, the table twisted .0007".

The second big upgrade is a new spindle motor. I have a 1.3HP treadmill motor that I will mount up. It isn't all that much bigger than the stock X2 motor, but it should have significantly more torque and I can gear up the spindle speed to 7200 RPM and still have more torque than the stock motor at its max speed of 4300 RPM. The treadmill cost me $25 which got me the motor, the controller, a big flywheel, a bunch of wires and bolts, and some steel.

Last, I got some encoders to add to the steppers to detect a stall and halt the program before anything breaks. The encoders can run at 2400 pulses per revolution and were $10 each. I read somewhere you can program linux cnc to use assist motors with the encoders to get faster rapids. That sounded like a fun possibility as well.

Here is the table having the ends machined. I squared it up against one of the edges and I may clean up the rest of the sides once it is finished. The top surface will also be flattened once the rails are finished and mounted on the machine.

If anyone has suggestions or questions, I am all ears.