My Bridgeport

[Willbird]

Well This is the start of all the fun, been reading here for a few weeks, and orderd some parts. I have 2 bridgeport mills, one dad bought new in 1972 when he had a shop in the garage, I still remeber the soapstone square on the floor where she was gonna set that he drew after he ordered her. She is a step pully 9x42...and she is gonna become a CNC machine. The other machine was bought new in 1986, vari-speed 9x42 and for now she is staying stock.

Coming via USPS and UPS is one 1160 oz/in stepper motor from keling, I got the dual shaft one because if I want to add encoders it gives me a place to do so. Also coming from keling is a 20 amp 72 volt power supply and a gecko G201.

Coming also is a C11A multi-function cnc board from CNC4PC and some timing pulleys and belt, I have the bracketry all drawn up in acad14 for X any Y, going 28-motor 56-screw on the pulleys....keeping the brackets fairly simple, I will post drawings from home later, basically a 1/4" steel plate behind the stock bport mounting, with another plate stacked on top to hold the motor, and some provisions to adjust belt tension.

I drew some long drawn out flight of fancy stuff to put in better thrust bearings than stock...but in thinking about it went simpler to get the machine moving with the acme screws...fun and fancy stuff it can make for itself and earn it's own keep instead of loafing while I turn the handles.

Hiwin ground ball screws are further down the road.

I'm not sure on the Z but leaning towards using the Knee to start anyway, I did some Boyles law work and it looks like (2) 2" bore air cylinders plumbed into a decent sized tank will allow counterbalancing the knee within + - 10 lbs at either end of the 16" stroke....I'm going to go 3:1 to 4:1 on the knee stepper once X and Y are done and use the acme setup at first...then if it looks decent, build a knee ballscrew.

I was taught to never mill with the quill down unless you had to, and dad would thump a boy if he caught him at that business hehe.

Bill

[mxtras]

Sounds like you have a plan!

One suggestion - run the G212s instead of the 201s - the 212s allow micro stepping and they run much smoother than the 201s. I used 201s for start-up of my conversion then switched to the 212s - big difference in low speed performance and smoothness of overall motor operation.

Scott

[Willbird]

Well it is too late because (1) 201 is on the way, I just looked at the Gecko webpage and the only differance I see between the 201 an the 212 is that the 212 can be set for full step, half step, 1/5 step, or 1/10 step but both drives are micro step drives ?? The only differance in the specs I can see between any of the drives are that some have short circuit protection and the 203v has all kinds of neat stuff ??

Bill

[mxtras]

The 212 also has a built in capacitor. From what I gather, there is also another difference, but I honestly can not recall what it is at the moment.....but I know you can buy a chip from Gecko to basically turn a 201 into a 212 and add your own Cap to smooth it out if you so desire. There is a huge difference in performance but it may not be a requirement for you - I don't know.

Perhaps someone else will chime in and either clarify or straighten this info out? Either that or I will do a little digging to refresh my feable memory and post an update.

Scott

[Willbird]

I do remember reading that in the manual for the drive, about upgrading it by pulling something out of a socket and plugging something in there :-) now that you mention it. I only have bought one so far so we can sure change what the others end up being.

I went to post a cad drawing last night and forget all about not being able to save it as .jpg or whatever from autocad....what a PITA :-)...remembered I used to just use a screen capture program to save the file as .jpg.

Bill

[mxtras]

You can 'BMPOUT' of ACAD. It's not that great, but it works.

Scott

[Adobe Machine]

Sounds like a good plan,will you use the present set up to mill the bearing mounts for the ballscrews once you get going ?

Frankley , it is just real nice to have minimal back lash or none for complicated parts..Doing a 12 bolt circle pattern, .001 clearence on each bolt, and the everything fits so good you can start and finger tighten just makes your day !

What software will you use ? Does your CAD program have CAM capability? You can not believe how good it is to CAD it then push a button and all the "G" code is done..now..fast. The only thing I have to do is add 2-3 M codes, add the Feed speed on the 1st G01 and Export to notepad..

I have had some 12,000 line programs that executed flawlessley using the CAM program , and truthfully have some MDI( Manual ) programs that were just horrible, so I draw everything up in CAD 1st,as there are a lot less mistakes, crashes and frustrations.

Most of all, have FUN..

Adobe (old as dirt )

[Willbird]

Yes I plan on making some booty kicking ABEC 7 bearing mounts when it is running and the ballscrews are in.

Yep 0.0000 backlash is the good stuff for sure, circle milling holes of any size beats boring them all hollow :-).

In a past job I used BobCad, some malign it, I never used it as a fully functioned CAM, just to draw difficult 2d toolpaths, cut and past them into subroutines and off we go. A good CAD/CAM will be another learning curve :-)..

Simple stuff I can think in G Code and it flies out of my fingers and onto the screen like magic...CAM can be a crutch to the point that I have seen people never learn to use it rathar than have it use them. Some of the shortcuts you learn from hacking G code by hand are good practice anyway, like using subroutines instead of repeating he same profiles over and over with several tools and thus making a longer program (all opinion on my part and worth what yaal paid for it )

I have ACAD 14 right now, and only work in 2d for the most part...have played in 3d but that isnt acad14's strong point from what I hear

Today the usps and ups truck brought a huge freaking power supply (22lbs worth) an 1160 oz/in stepper motor...a gecko 201(that stuff from Keling) a multi-function CNC board(from CNC4PC)...and some timing pulleys and a belt, I went with the GT2 pitch 15mm wide. And I stepped on my organ ordering the 56 tooth pully so if anybody needs a 50 tooth one with a 1/2" bore and no flanges I can hook you up :-) (A 6A55-050NF1516 is the part # of the extra timing pulley I have from stock drive products) I was jacking around with pulley sizes and got my numbers crossed, or just mis-clicked as it is the one above the one I actually wanted.


Bill

[Willbird]

OK lets try this :-) this drawing is just a rough out to give me some ideas on center distances and pulley sizes, etc.

Looks like it worked :-).

[Adobe Machine]

I would have to confess that I use CAM as a crutch..G code does not " fly off my fingers", in fact , not drawing the piece and using CAM, usually ends up a frustrating mess for me. I have several examples of some of my messes that as soon as I'm out of the wheel chair, they are going on a wall display, to constantley remind me slow down, draw it up 1st. In fact I sometimes print the part on a 1 to 1 basis, cut out the part and fit it up to ascertain that in the real world what I concieved fits and will function.
Couple of questions : What ratio are you using, servo to acme screw ? Can not tell from the drawing, but are you useing tensioner or slide to adjust the belt ? I have found from some past expensive experiments ( read screw ups) that if I did not have at least 50% of the drive sprocket engaged with the belt ( wraped) that it can slip.In fact I use a simple idler and a tensioner to both get good wrap and the correct tension, as opposed to a slide that you pry down..
Keep up the pictures, every one is intrested in your progress !

Adobe (old as dirt)

[RICHARD ZASTROW]

Adobe,
I hate to disagree but, (assuming the drive sprocket is on the motor) I believe you can have 60 degrees of belt engagement, as long as 6 or more teeth are engaged, and transmit the rated horsepower of the belt. At least I hope so or I'm in trouble. I got the above from a Godyear engineering manual.

[Willbird]

Here is what I have roughed in for adj. The plate with the motor on it can be moved 1/4" by the setsrew pushing against a pin or suck on a riser that is attached to the bottom plate.

I did see how you did your lathe Adobe,,,,I'm not an engineer by far, but to me it looks like the considerations the Konstructor must take into account are belt stretch, pulley wrap, and overall length of the belt that is in tension. (the shorter that distance the better for what we are doing with it IMHO) I did leave room there to put in 1 or two tensioners like you used on your lathe....and I intend to build a simple center distance test jig to see how much stretch takes place with my length of belt,

what is in my mind right now is to drill+ream a 1/2" hole in a piece of steel in the mill vise, and put a .500 gauge pin in the hole (.499 if the hole is tight on a .500) then put one pulley on it, and put another gage pin in a .500 collet in the spindle and slip the other pulley on it, and move the mill back in Y with the belt on the pulleys and see what center distance measures like with a decent belt tension...then build the system with the data thus gathered.

I went with 28 teeth on the motor and 56 on the leadscrew, 5mm GT2 pitch belt in 15mm width 80 teeth long....the center distance calculates to 3.6347 with the Stock Drive Componants center distance designer

https://sdp-si.com/Cd/default.htm


Before I had CAD I would get a mental idea and then start making chips....sometimes making paperweights too...........the CAD is a great tool for us, if your like me you play with an idea, and then get taken away to do other things...days, weeks, months, or years later I can open the drawing back up and my work is still there and I can pick up from it and go forward or apply the concept I was exploring to another plan, or finish it even.