Bridgeport Clone Mill CNC Retrofit Project

[Paraprop]

Hi to all experienced forum members here.

I have made up my decision to go ahead with bying a Taiwanese Knee Mill clone. The ARGO 3H with a 3 hp Spindle motor.

The Table is 50" x 10" (1270 x 254 mm)

and the travel is 35" x 15" x 16" (890 x 384 x 407 mm)

The spindle travel is 5" (127 mm)
and it's Taper is NT30

you can see it at.
http://www.argo.com.tw/e-pro1-1.htm

I will buy it without the power feed option.

Here in Thailand they want the equivalent of $ 4,540.- for it including a 6" precision vise, the coolant system and a tool box.


Is this a good basis for my project ?


If yes, my next step will be to find the correct ball screws to replace the lead screws.

checked HiWin site and they have several length sizes for X & Y axis. all are 32mm diameter and 5TPI.

I am not sure with which one I should go length wise in my case.

For the X axis they do have:

32", 36", 42", 48" and 50"

For ex. the 36" model has a threaded length of only 28" and a total length of 46 "

The 42" is 34"/52"
The 48" is 40"/ 58"
The 50" is 61"/71"
My guess is that the model 48" should be OK as the thread is more than my X table movement of 35". However will then the overall length be OK in my case ? If not, what to do ?


Same issue for Y axis where they do have:

9" 14"/20"
12" 17"/23"
16" 21"/27"

as my axis seems to be 15", I have even less of a clue ofwhat is right.


Any experience on this issue ?


Else, I will have to wait until I got my mill and dismantle the lead screws to get a better picture.

They also do sell a replacement Yoke housing to accomodate the ball nuts of the X & Y axis. Is this required or can one simply bolt the ball screws against the existing housing of the lead screws ? My understanding is that on a CNC Masters kit, the X ball screw is fixed on the right hand of the existing yoke but I am not sure.


Finally, the 200 $ reward question.

Size of steppers or servo motors ?

I would like to Bolt the motor directly to the shaft without reduction so as to avoid any additional accuracy issues. The only one I could find doing this, was again CNC Masters using 1500 oz.in micro stepper motors for X & Z (ball screw lead is also 5TPI) and 1200 oz.in for Z (Quill)

Can this also be done with servo motors ? if yes, what would be the required size ?

From my searches, with a 1:2 reduction, the kits using servo motors are around 464 to 640 oz.in (rated torque) would this mean that for direct drive, I would have to double the servo motor rating to 930 - 1280 oz.in ? If this is the case, it would make the solution very costly and explain why most stick with a reduction.

But as a matter of fact, what is really the adequate motor rating needed with or without a given reduction pulley/belt system considering the 5TPI ball screw of 32 mm diameter and the maximum workpiece weight mentioned by the mill manufacturer which is 660 lbs (300kg) ?

For this same setup in addition to the recomended motor size torque wise, what should be the max table speed one should look for with:

1. Stepper motors. (Master CNC mentions 40 IPM max and 0.5 IPM min.)
2. Servo motors.

Once this recomended data is known, it will help me to select the motors.

For servo motors, given that on the market, their nominal RPM at the rated torque can be had as 1000 RPM, 2000RPM of 3000 RPM.

(In the case of CNC Master's steppers, looks like they turn at max 250 RPM.)

I guess a servo would allow for higher table speeds may be 100 or 200 IPM ?

in this case the servo max speed in direct drive configuration would be 500 or 1000 RPM max in direct and 1000 resp. 2000 RPM with a 1:2 reduction in between.

So Is my first guess right that I should aim for 1000 or 2000 RPM Nominal rating motors (for servo)

Personnally, I would of course like to go for a servo motor system if the budget allows it. But first I need to settle on the motor rating.
Once I am settled with the motor specs. I can also look for the drives.

Thanks in advance

Daniel

[Paraprop]

I go 1 step back.

for a Bridgeport mill.

What would be the machining forces one has to reckon with for the X, Y, and Z axis ? (in Lbs or N)

What normal and max speed seem appropriate for such a mill and metalworking (aluminum and stell) ? (in IPM or m/s)

Thanks i advance

Daniel.

Paraprop
Thailand

[Paraprop]

I am amazed that so many do read my thread but not one single reply.

Am I doing something wrong ?

May be I should have gone trough all the Bridgeport threads talking about retrofit. Well I did tis in the meantime and have to admit that the answer to some of my questions where there already but not all.

Is this mill a good starter for this project ?

There are no Bridgeport Boss mills around here only old Taiwanese and Japanese clones. They are may be half the price of the new one but in a terrible state. No reputable machine re-builders too...

I was thinking of getting a mill second hand from my home country Switzerland but the transportation cost and parts availability issues for those mills don't do it worthwhile. THe bridgeport clones are the most comon here.

May be some suggestions of a Knee mill source in Taiwan which already got ball screws or even a quill drive ?


The Hiwin dealer here in Thailand has also not bothered to reply me till now .



At least I am going to stick with their standard or the 5mm pitch equivalent.


Stepper or motors ?

i am still not sure about which force I have to requon with when milling a steel part at a decent speed.

However based on my surfing in the different threads and Kits offered,

I guess 1500 ox.in stepper directly coupled to ballscrew shaft and Gecko drives

or

460 to 640 oz.in rated servos with 2:1 ??? reduction (3000 or 4000 RPM rated motor).

still not made up my mind.

would have loved someone to tell me what max speeds are realistic on such a machine so I can settle on there reduction ratio. This would allow to optimize the servo size based on his rated RPM.

Thanks

Daniel,

[racecomp]

Hi Daniel,

I'm in the same boat; I've got a big made in Taiwan mill that I'm about to retro fit a cnc kit to. I find this site is really informative with a wealth of knowledge with some very clever and helpful members. I'm sure help will be forthcoming once your post is read.

I’m looking at going with the www.lowcostcncretrofits.com recommendations including the 4th axis, VER:3 Jog Remote upgrade and NEMA 23 stepper motor for the indexing table. 3/ NEMA 34 / 1200oz.in HYBRID Stepper Motors including 2 meter pre-wired leads
4 Axis 7amp stepper Motion controller with (4 internal opto relays and NEW!! translation board) plus all the bits and bobs that go with it. There is a bit to do with the belt drives but Steve at low cost gave me the heads up on what to do.

[Paraprop]

Racecomp,

Thanks for your kind words.

I hope all works out for you like you wish.

I am now considering a Rutex drive (200 V / 40 A) / Magmotor C40-E-500 servo combination for about $ 2200.- for 3 drives
(the Gecko G320 drive seems to be too small (80V / 20 A) for those motors)

Gecko G203V with stepper 1800 oz.in KL34H2160-62-4A ½” Dual shaft (www.kelinginc.net) about $ 1000.- for 3 drives

An Oriental Motor closed loop stepper and drive package (only wondering about price right now) the AS98AC-N5 Price ??? (list price on their web is $ 2310 per package !!!)

Siemens stepper (1FL3061-) and their FM Stepdrive. price ???


I hope I can get the price for those next week.

I would like to find a suitable 500 to 600 oz.in servo to match the G320 drive as those are quiet affordable.
May be I have to check out the C40-C-400 with a 3:1 reduction or the
C40-C-300 with a 2.5:1 reduction

No clue which combination is the best match.


Daniel.