Pm45m Cnc Conversion With 7800 Rpm Belt Drive 3 Hp Upgrade, Bt30 Spindle, Power Draw Bar + Enclosure

Thanks for the clarification. Your head extension is an interesting modification and simple to do. Have you experienced any rigidity issues?

I agree on the overhang being no more than a third of the saddle front to back length. Mine is about 3-3/16" which is a third of my saddle.

Again, thanks for the info. I've been around the machining business my entire career, now retired, but I'm still learning.

Tom S
 
Thanks for the clarification. Your head extension is an interesting modification and simple to do. Have you experienced any rigidity issues?

I agree on the overhang being no more than a third of the saddle front to back length. Mine is about 3-3/16" which is a third of my saddle.

Again, thanks for the info. I've been around the machining business my entire career, now retired, but I'm still learning.

Tom S

I have had no rigidity issues with the head and this mod.
 
I had someone pm me about the cad files for the mounts for the conversion. Unfortunately, there are material differences in dimensions between these mills, even the same model between batches. You would have to use the exact ballscrews I used( you can do better) cut to the identical measurements also. I had to tear apart and re assemble the mill every time I made a part- I also know these mills inside and out now.

Here is a list of links I drew from to do the conversion:

Start here: http://www.cnczone.com/forums/benchtop-machines/122462-cnc-cad.html

Next go and read g.d. marshes awesome thread- got me started and was inspiration for using 2 ballnuts and bellvilles, vfd with poly v belt and pulleys + repurposing of the spindle tube and so much more:

http://www.cnczone.com/forums/bencht...onversion.html

Ekkeke for lubrication, over building the z axis and misc:

http://www.cnczone.com/forums/bencht...f45_clone.html

mattbesquare for wiring and servo mounting:

http://www.cnczone.com/forums/bencht..._thread_-.html

Bob Warfield and CNC Cookbook- awesome resource I am still reading:

CNC Machinists Cookbook: Software and Information

I think Jid2 and g.d marshes threads really made things accessible made me inspired to hack up a perfectly good mill:

http://www.cnczone.com/forums/bencht...sion_rf45.html

Graetech site for tearing into the head:

Graetech RF45 milling machine CNC conversion - RF45 gearbox photos

I hope this helps,
 
Part II:

BT30 conversion with pnuematic drawbar

Here is a business end shot between stock R8 spindle and and the BT30:
bt2.jpg

Industrial Hobbies said they have over a 100 30 taper spindles and I can confirm they fit the PM45m mill.

To convert the manual draw bar to pneumatic you have to work within the stock spindle measurements . The drawbar hole diameter is .684" with the top of the cone at .703 for a short bit. That is because it is NMTB 30. My plan is to cut a relief above the cone where the stud would sit so my gripper can release when the drawbar is pushed forward and put a triple valve spring on top of the the drawbar in place of bellevilles. Because my motor is so large, the air cylinder will be mounted upside down in front of the head and push up on a pivot arm to push down on the drawbar to release.

I took the IH NMTB 30 spindle and bored the straight section deeper by an inch while keeping the diameter to 0.72". This allows me to fit a ball type gripper where the straight section would be. Next I cut groove a 0.25" wide and a depth of 0.95". When the grippers balls are aligned with the groove, the larger diameter allows the pull stud to be released. I made an aluminum version of the spindle and it released properly. The trick is measuring everything right.

I will post some more detail later but here are some pics of the new drawbar. It is O1 steel, properly hardened and tempered to around 55 rc. (PID kiln)

Gripper Close up:
gripper.JPG
Gripper on drawbar with bt30 toolholder:
gripper2.JPG

Gripper parts:
gripperparts.JPG

There is no room for springs inside the IH nmtb spindle, I am putting the spring on the top of the pulley with a top hat and fabco 2 stage 4" cylinder- 1500 lbs of spindle clamping force.

Meanwhile, took 8"x 3" thick diameter round of 7075. This is inspiring me to make a new head assembly with an extension. I already cut the top plate by the y axis to the vertical wall of the base and that freed up a lot of travel. Adding an extension

Having a head extension allows up to 12" y axis travel on the RF45 type mills.
head%20extension1.jpg


Finished part bored for (4) 5/8" bolts:
head%20extension2.jpg

Back to the spindle, I took the plunge literally and cut the inside of the spindle to make way for the pull stud gripper. This entailed slightly boring past where the taper terminates and then cutting an internal groove for the balls in the gripper to drop into. I test fit and with the balls in place, tool holders are held and then if you allow the drawbar to move down approximately 1/2", the tool is released.


I spent some time further test fitting the spindle. I found I was .0006 too narrow when the gripper was retracted with all 4 balls in. During my initial test fitting, I only put 2 balls in. With all 4 in and the gripper assembly retracted, the tool holder wouldn't retract all the way into the spindle. As a result, I had to slightly enlarge the bore in the spindle. After that, the gripper works smoothly.

Here are a few pics:

Inside the spindle:
gripper%20balls.jpg


Tail end:

tail%20end.jpg

Basically you need to machine the part in the oval, make a gripper and draw bar.

spindle%20cutaway.jpg

After finishing the plate for the 2 stage air cylinder, I took some cuts. I put a tool in, fully inserted it using the gripper with the balls and then manually tightened the bolt on top of belville washers with a wrench. No problem taking .2" cut with a glacern 4" face mill- it holds just fine.

The power draw bar works. I am really happy because bt30 tooling is plentiful and cheap smile.gif

Video below:

I cleaned up everything with the enclosure and things are starting to come together. A few pics of the mill in it's current state with a power drawbar, one shot oiler, enclosure and diy fog buster with pressurized coolant:

Shot of the mill head with the bt30 power drawbar installed:
millhead.jpg

Belleville springs:

bellevilles.jpg

Overview shot showing the enclosure. You can also kind of see the 3.5" head extension. I am getting a full 12.75" of Y travel now. I will need to make a fixture plate to take full advantage. Considering these mills have 8" of y travel, this is really awesome:

millenclosure.jpg


Power drawbar switch. I ended up using a foot pedal momentary pneumatic switch. Seems more robust than the toggle type and the price is right:

footpedal.jpg


Diy fog buster built out of scrap 1/8" npt plumbing parts I had around and a mig nozzle tip. I forgot to snap a pic of the pressurized coolant tank but it is a whole house water filter housing modified with a pick up tube. compressed air goes in and forces the coolant out through the pick up tube connected to the top. The needle valves allow for both pressure and fluid level adjustments. Works really well:

fog%20buster.jpg


Sample part being machined:


Thanks for looking...

Hey great job, what size and material are the ball bearings in your gripper, what is it's dimensions? Thanks.
 
The ball bearings were .250" and there are 4. I will have to look to see the final dimensions but basically I took the recessed part of the gripper + 2 times the bearing diameter + a small allowance for clearance. FYI, the gripper works great but the 30 taper spindle does deform some over time from the bearings because the steel doesn't appear to be fully hardened. I bought a petal style gripper to retrofit to that and will get around to it someday. It can stick at times with the bearing style. The TTS style using your existing r8 spindle may be easier.
 
gt40, could you share your Mach3 spindle settings? I have everything working on my belt drive conversion except I cannot set the speed with an "S" command. It always goes to 100% spindle speed. I can slow the spindle with the manual override but the "S" commands do nothing. I'm guessing it is a setting somewhere.

Thanks
Jay
 
gt40,

I was able to figure it out. Turned out to be a VFD setting.

Jay
 
You did an excellent job on this mill. We have a Charter Oak 12Z that we have already converted mostly. We are using air over hydraulic power drawbar. How much would you charge us to make the same BT30 drawbar?
 
Darkzero pointed me to this Forum. Looking forward to looking around. This thread is great! Almost exactly what has been done on my ZX 45 mill. except the VFD drive. I am sure this will come later. I need to actually read the whole thread rather than look at pictures real fast.. LOL. Need to go drop my Boy off at School and head to the day job! This place looks promising!
-Eric
 
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