[InventIt]

Anyone know how to figure this out?????

I am trying to determine the force required to compress the draw bar on the BT30 spindle I'm working on for the mill. I used a gear puller with a "acme style" screw, 10 threads per inch, about .42" dia and it required 140 inch pounds to completely compress the draw bar.

So, anyone know how to figure this out? I am trying to determine how large an air cylinder I will need based on a supply of 90-120 psi air.

Any help is appreciated, Thanks

[alex_ku]

force(N) = 2*PI*torque(N/m)/pitch(m)

Just convert your units into "normal"

[InventIt]

OK, So it looks like i need to generate somewhere around 2800 lbs of force to compress the draw bar. I'll add a few hundred lbs so I have enouigh force to break a stuck holder from the spindle. I did not realize it would take that much force! Guess I won't be using an air cylinder.

Using 90psi at the cyl, I would need a 6.25" dia piston to generate about 3000lbs force. Looks like i'll have to do a air over hydaulic setup.

[InventIt]

This will be the housing for the BT30 spindle cartridge. I sure hope the Z axis will get off the ground! The weight of this thing is adding up VERY quickly!

Plan on using one of the hydraulic cylinders shown, it's 1.25", very compact. It will actuate the draw bar for a tool release.

Feels like the housing is about 80-90 lbs so far, including the cartridge, still need to add the motor and the hydraulic draw bar mechanism

[InventIt]

Spindle progress!!!

Managed to get the spindle housing finished (besides paint). Then I mounted the spindle cartridge into the housing and mounted the unit to the z axis to see if the Z axis could handle the weight. Surprisingly the Z axis had no problem lifting it! I was even able to put all my weight on the Z with the spindle still mounted and it still had no problem lifting the z axis up.

Anyway, the housing turned out well. I'll order a belt tonight and hopefully be able to get this thing spinning later next week! I'm so psyched!

So, the motor is 3400 rpm and on a vfd should have a range of about 1000 to 7000 rpm. I'm thinking of running the belt 1:1. Does that seem like a good range? Or should I reduce or increase the ratio? The spindle is capable of at least 10000 rpm. I don't think i want to loose all my lower rpm though, in case I want to do tapping or boring. Just a few of my thoughts.

[lukewarm]

Impressive work! Can't wait to see the results you get with your new spindle, keep us posted!

[toranacar]

Absolutely impressive i must agree.
Ive been looking around this forum and there is alot of impressive work here.
Is there a reason you chose gantry style, is it more rigid?
Ive seen people retro fitting mills but i never thought of actually making the frame/chassis from scratch, just awesome.
So InventIt, are you working off plans you bought or did you design the plans your self?
Ive been looking at retro fitting a big old mill or even retro fitting a new mill but im curious if the CNC mill you're building would be more cost affective than retro fitting. Because retro fitting requires a good base mill to start with obviously and adapting the motors etc where you are making the mill as you intend from go.
If you bought the plans can you tell me where to get them?
Keep up the great work mate
Bart

[InventIt]

Absolutely impressive i must agree.
Ive been looking around this forum and there is alot of impressive work here.
Is there a reason you chose gantry style, is it more rigid?
Ive seen people retro fitting mills but i never thought of actually making the frame/chassis from scratch, just awesome.
So InventIt, are you working off plans you bought or did you design the plans your self?
Ive been looking at retro fitting a big old mill or even retro fitting a new mill but im curious if the CNC mill you're building would be more cost affective than retro fitting. Because retro fitting requires a good base mill to start with obviously and adapting the motors etc where you are making the mill as you intend from go.
If you bought the plans can you tell me where to get them?
Keep up the great work mate
Bart

Thanks Bart. Plans? No, I designed the machine completely from scratch. I originally had intended to make a conventional column style machine. After thinking about it I decided on building a gantry style machine because I thought it would be more rigid and allow a larger work area for the floor space taken up. Gantry style also allows me to cut 4ft wide sheet material, so I could cut a 4x8 sheet of plywood in the machine. Of course I am limited on Y axis so I would have to index the sheet into sections.

[toranacar]

Thanks Bart. Plans? No, I designed the machine completely from scratch. I originally had intended to make a conventional column style machine. After thinking about it I decided on building a gantry style machine because I thought it would be more rigid and allow a larger work area for the floor space taken up. Gantry style also allows me to cut 4ft wide sheet material, so I could cut a 4x8 sheet of plywood in the machine. Of course I am limited on Y axis so I would have to index the sheet into sections.

Thanks for sharing
Are you planing on cutting aluminum and steel block or just sheet.
Will be great to see this in action.

[InventIt]

Thanks for sharing
Are you planing on cutting aluminum and steel block or just sheet.
Will be great to see this in action.

Mostly aluminum block and some steel if it will cut steel without too much fuss. Occasionally I have a need to cut plywood sheet. The idea was that I could setup a vise off to one side and have a large area for a table/tool plate. That way I will not have to remove the vise much. I like to make things versatile. Ironically though, most parts I make are small 2-6"


Hopefully I'll get some time this week to test the spindle.

[toranacar]

Mostly aluminum block and some steel if it will cut steel without too much fuss. Occasionally I have a need to cut plywood sheet. The idea was that I could setup a vise off to one side and have a large area for a table/tool plate. That way I will not have to remove the vise much. I like to make things versatile. Ironically though, most parts I make are small 2-6"


Hopefully I'll get some time this week to test the spindle.

Im all eyes and ears
I was hoping to build or retro fit a mill to be able to cut Aluminum and steel with ability to cut to the size of a custom wheel (Face of the wheel)
Maybe you can set up a 4th axis where you set up your vise?
Any how it will be great to see your beast in action, and learn more from you.
Very interesting

[InventIt]

After making a pulley for the motor to fit the 5M-5 section Polyflex belt and a mount to attach the 3hp motor to the Z axis plate, I got a chance to test the spindle under power. Spindle runs incredibly smooth! The air oiler setup for the spindle bearing lubrication works perfect! So now I know the spindle is ok, I can move forward. I will mount two 50lb gas springs to take some of the weight off the ball screw. Then the next big project will be making a air over hydraulic tool release mechanism.

Testing Spindle:
[nomedia="http://www.youtube.com/watch?v=vOGRY2k5i1M"]YouTube - 100 0720[/nomedia]

[InventIt]

Update,

I finished the spindle housing for the Kitamura BT30 spindle cartridge and got it mounted onto the Z axis along with the motor. Mounted two 75 lbs gas springs to alleviate about 80% of the weight of the Z axis. Also made a mount for the spindle oiler, ran the lines through the cable chain and hooked up a mist coolant nozzle. Still need to make a release mechanism for the draw bar and get a cover over that belt before I loose a finger

I have been playing around with a 1/2" EM cutting mild steel. I'm impressed with the results so far. Did a test cut today at .050 DOC and 15 IPM and the machine handled it well. I know those feed rates are VERY low for a REAL cnc mill, still though for a DIY mill I'm happy with the results



[nomedia="http://www.youtube.com/watch?v=nM_-8V3tHgE"]YouTube - ‪Test Cut, milling slot in mild steel‬‏[/nomedia]

I'll try to get a few pics up soon.

[thewho]

where are the pics?
Interesting project btw

[InventIt]

where are the pics?
Interesting project btw

Should have an update soon, been working the the drawbar release.

[InventIt]

Got my springs, that finished up the draw bar release WOW! It's so easy to change a tool and I am not stuck with only being able to mount a 1/4" or 1/2" tool as before when I was using the PC router. Maybe I can start using offsets now The hardest part of getting the release mechanism working was getting all the air out of the hydraulic side of the system. Being such a small area with limited fluid movement, it was imperative to get all the air out before it would work properly.

Also mounted the 4'x2'x1" thick aluminum table to the mill and skimmed about .010 off the top. looks like it turned out good. Used a Glacern 2.5" 45* face mill. It left a very smooth finish as you can see in the photos. I'll have to recheck the tram, seems like it may have been slightly out judging from the tracs the face mill left. Skimming only about .010 off the table produced a huge pile of chips!


[nomedia="http://www.youtube.com/watch?v=bw0DnPsmi8o"]YouTube - ‪mill update and release mechanism‬‏[/nomedia]

pictures:
1-reflection in table
2-overall view
3-hydraulic intensifier mounted to gantry
4-hyd cly on spindle
5-chips from skimming .010 from table

[InventIt]

Anyone have any reccomendations for workholding? I can't mill T slots into the alum table because it will most likely warp it. So, I was planning on tapping a bunch of holes into the table like a tool plate. Maybe add a few dowel pins for easy alignment of vises and fixures??? Also considered milling a grid into the table, about .250 wide x .050 deep, maybe I could use that for alignment of vises and fixtures.

So,what would be the easiest, most acurate way to set up the table?

Any suggestions?

[AFAIK]

What about buying a used T-slot table from ebay etc?
Or maybe fixing some aluminium T-Slot extrusion to your existing plate? Might be a bit too weak though.

[InventIt]

What about buying a used T-slot table from ebay etc?
Or maybe fixing some aluminium T-Slot extrusion to your existing plate? Might be a bit too weak though.

I do occasionally scan ebay for fixture plates with t slots. May buy one if I can find one the right size locally. Until then I will use the alum table.

[InventIt]

Decided to drill and tap the table using a grid pattern of 1.5" left to right and a row spacing of 4" front to back. 186 holes total. Also bought a 3/8 clamp set. Got a few dowel pins for aligning fixtures and setups. Watching the machine tap the holes was awsome I kept thinking about all the time I spent hand tapping one or two holes that ussualy came out crooked cross threaded! (chair)

Quick vids of the machine drilling and tapping. Drilling took about 1hr10min and tapping only took about a 1/2hr

[nomedia="http://www.youtube.com/watch?v=HzDQ6OBKR6U"]YouTube - ‪Drilling CNC Table‬‏[/nomedia]

[nomedia="http://www.youtube.com/watch?v=7m0suvqVHs4"]YouTube - ‪Tapping CNC Table‬‏[/nomedia]