I know how that goes!I got the x and y sorted out and then other things came along that are preventing me from finishing it.
Ok, time for a very long overdue update on the RF45 mill conversion.
Since my last progress update I have acquired and completely restored a 1977 Bridgeport knee mill. Even though it is a manual machine, I have been using it for most milling jobs
so the RF45 has been more or less sitting except for a couple of occasions when I really needed CNC.
Also for the past year or so my free time (and money) has been dedicated to restoring a '64 Corvair and '59 Austin Healey Sprite ...
But even with all these little diversions, the main reason I haven't used the RF45 more is because I never got it to the point where it was convenient to use. It does not have home switches, spindle is not controlled by the controller, etc. but I have slowly been gathering parts and planning how I am going to finish it.
Here are some of the things I have acquired but have yet to install.
Pneumatic draw-bar kit and TTS type tool holders.
This was generously donated by Small Shop Concepts (AKA Lcvette on the zone), I can't thank him enough!
Marathon Y522 inverter duty spindle motor.
These motors are great, 2-60Hz constant torque, 60-120Hz constant power and rated to 5400RPM!!
On order is a dual touch 22in elo touchscreen, and a 3HP Huan Yang VFD. I've always used the Automation Direct GS series drives in the past, and I really like them,
but the the price on the HY drives is right and I'm curious to see how they compare.
As of this evening I got limit switches and homing working on X and Y, I will write a more detailed post on that in the next day or so when I get a chance.
Kurt
I know how that goes!I got the x and y sorted out and then other things came along that are preventing me from finishing it.
Oops. Double post
Just for kicks, last night I mounted a 6" seco facemill to an R8 adapter and took took some cuts to see how the mill would handle it. This is with the new 1.5 HP inverter duty motor running off a 1HP VFD, so don't have much power at the spindle. Still I'm impressed with how well the mill did and the surface finish is great.
Kurt
Kurt,
Your build thread is quite inspirational! Nice work!
Often I delay and delay when I'm unsure about how to go about a certain step, or I'm wrestling with several competing designs in my head. Case in point counterbalancing. I like your idea of the internal gas shocks. I had thought about that a long time ago but somehow I couldn't really visualize it working easily.. I now see from your thread that it will work rather straightforward. And I thank you! It appears to me that you attached a plate with a round hole to the base on which the ends of the shocks sit, is that correct? Because the stock mill has a square opening in the base where column attaches not a round hole.
One important question: when it comes time to replace the gas shocks, do you plan on going from underneath you mill bench to remove the old shocks and put in new ones ? Or do you plan on doing it from the opening in the back of your column? Reason I ask is my RF clone does not have an opening in the back of the column. I cannot see a way to install new ones unless one goes from the underside of the mill. Thanks!
Also do you have any pictures of your oiling system? I see you have cut the oil grooves, but I did not see any pictures of the rest of the oil delivery system. Did you use metering valves ?
Thanks, John
PS - my RF45-clone CNC conversion, I'm waiting on DMM Technolgy 750W servos XYZ & 1800W spindle servo (will drive the spindle 1:1 through a belt drive - ripped out the gears and stuff from inside the head and discarded) The 1800W servo doesn't care whether you run it at 60 rpm or 3000 rpm, the curves are flat throughout the range. An additional small benefit to this is the spindle drive system, pulleys and all, weighs a lot less than old configuration of the head with the real heavy motor and gears, and the overall height for the servo, pulleys, and mounting is about 1/2 of the old great big motor.
Centroid Acorn 4 axis controller.
Last edited by Cabbagestack; 03-17-2019 at 12:44 PM. Reason: Added question about gas shock replacement
John, I see we both suffer from the same malady, paralysis by analysis
The base of my column has a round opening and enough of a ledge for the gas struts to rest on. They are not retained in any way. My original plan was to add a plate with holes in it to retain the ends of the struts like you mentioned, but it has not been needed.
If you don't have enough of a ledge you could maybe add a bracket to the webs in the base casting for the ends of the struts to rest on.
I have a milti-shot oiling system, it consists of an oil can lol. Eventually I plan on adding a full single-shot system, but I have not got around to it yet. The Millers have some great oiling system ideas in the GRIZ build thread.
Those are nice servos! I just put a 1.5 HP VFD spindle on my machine, but I am still running the gears. I am trying to decide on a fixed 1:1.25 ratio belt drive, or a Fadal style two speed drive. I really want to do the Fadal drive, but its probably more effort than it is worth.
Let me know how you like the Acorn, I've heard very mixed opinions of it.
Cheers,
Kurt
Kurt,
How will you go about replacing the shock ? Going from underneath the mill? I cannot see a way to install new ones unless one goes from the underside of the mill. Thanks!
(dang system wont let me post pictures!)
As far as Acorn I'll let you know but it may be sometime yet maybe end of summer.. But really I'm not investing all that much in the Acorn so if it doesn't work to my liking I can go with something else. All the serious money is really in the Servos & assoc. drives and the ballscrews and assoc components. The Acorn is only 300$.
Edit: Oh yeah, forgot the limit switches are 100$ apeice so are the home switches, that's about $600---- .0005" positional repeatability for the switches themselves, give or take. They ain't cheap!
So the Acorn is maybe 10% of the total mod cost.
Last edited by Cabbagestack; 03-17-2019 at 03:25 PM.
There are a couple of ways to get the struts into the column. I have a hole in the stand the mill sits on to access to the Y-axis screw and nut, so I am able to slide the strut in the opening at the back of the column and down far enough to be able to get the top of the strut to clear the opening, and then just slide it up into place. If you don't have a hole in the table (the hole only needs to be .75" dia, could probably get away with .5") you can lock or block up the z-axis and take the bearing block off the top the the column and lower the strut down that way.
An untested yet possible third way to get them in is thru the slot in the front of the column. It looks like with the Z all the way down there would be room to thread them in. Maybe I'll make a mock strut out of some 3/4" copper pipe and see how feasible that is.
I see what you mean looking at your picture gallery! Since I don't have a opening in the back of the column I'd need to go from underneath, which may turn out to be a MAJOR PITA. So I'm going to give thought to creating a hand hole in the back of the column much like yours. Cast iron (this cast iron in particular) cuts veryyyyy easily ! At my age (64 and at retirement) I dont want to crawl underneath anything if I can help it ! <chuckle> !! A little forethought now will save a PITA later. See there IS sometimes an advantage to delaying when you don't know the way forward or the way is foggy and somewhat uncertain. I had originally designed an EXTERNAL gas shock system. Glad I didn't go with it, It was way bulky and not as clean as your design. Thanks!
Edit: Went down to basement to have a look --- have to create the ledges you spoke of because my column doesn't have any place for the strut ends to sit on - shouldn't be to much of a problem though, and well worth it as I mentioned above - might actually make a couple of shallow "dimples" in the ledges for strut ends to sit in if I determine its not too troublesome. Actually the hand hole in the column is very well worth it, the more I think about it ! Matter of fact I've added these to the "must do" list! As though there's not a lot of "must dos" already - and my wife has 100 more to do around the house! <chuckle> !!
Last edited by Cabbagestack; 03-17-2019 at 02:39 PM. Reason: added these to the "must do" list
here's what I have in mind for the spindle drive end of things, for those interested:
The aluminum brackets (3/4 thick), elliptical plate (3/4), and new mill top are done (1-1/4 thick), just not assembled yet. Pulleys not done yet (all major parts are 6061 Alum). Picture shows a step pulley for 2:1 drive ratio. No longer necessary, (that was for the big heavy 240V cap-start,cap-run 3 hp Baldor (with a VFD that I never ended up buying went this route instead). The pulleys now are 4" and 1:1. The 1800W servo shown doesn't care whether you run it at 40 rpm or 3000 rpm - the curves are flat through the range, same power. The whole thing weighs about 55 lbs and is half the height of the big Baldor setup. Plus being servo controlled and having a integral shaft encoder, stops on a dime, starts on a dime, reverses on a dime; can do rigid tapping,
Kurt, you now have CNC now so you could knock out something like this real quick to use with a belt drive with a VFD. Don't know if it will work for the Fadal two speed since I've never seen one. Note, what a lot of people did is rip out all the gearing and cut the gear off the spline shaft that the spindle draw bar slides through, and reusing it. That's what I did. Also look into getting Trantorque to fasten pulleys onto the shafts. If you are patient you can get them from Ebay fairly cheap; and it solves the hassle of cutting keyways & such; or pondering how to fasten pulleys onto shafts.
Last edited by Cabbagestack; 03-17-2019 at 11:03 PM.
I'd keep the 2 speed setup. You need a lot more torque to drive low speed tools. Remember that power is torque times rpm. So if you have the same torque but 1/10th the rpm (i.e. 300 rpm versus 3000) then you'll also only have 1/10th the power making your servo output only ~180W.
According to what I have found so far DMM Technologis AC servos have a flat speed vs. torque curve:
.
this is for a DMM 750w (that I will use on X Y & Z axes) --- but the same characteristic applies to the DMM 1.8kW - i.e flat speed/torque curve.
Even so, I think I will keep it at 1:1 ratio and will give thought to 2:1 -- Although I can't imagine why I need 2:1 when the curves are flat.
Last edited by Cabbagestack; 06-15-2019 at 02:51 PM.
So I did some checking and the short story is you'll probably be ok with a 1:1 drive and your servo, see below for examples.
Take a 1/2" drill as an example of a tool you may be likely to use on the mill into plain old low carbon steel (1020).
Using GWizard calculator the drill should be operated at 688 rpm, and needs 0.877 KW when doing so.
The 1.8KW servo is rated that at 1500rpm and has as you say a flat torque curve as your speed drops so its power is proportional to the rpm between 0 and 1500 rpm.
688/1500= 45.8 percent of the power
45.8% x 1800 = 0.825 KW
So on the surface your servo won't make enough power by just a bit. However it is rated for intermitent duty at almost 2.5 times more torque so would probably be just fine in this example.
Any large and then your going to be into running in the intermitent range far too frequently and you'll overheat your servo or drive.
i.e. going up to a 9/16" drill - makes things worse - rpm goes down and power required goes up.
611 rpm and 1.096 KW
611/1500= 0.733 KW available in normal operation.
So on inspection you're probably ok from a power perspective, for most normal operations and you'll just need to watch out for large tools.
BTW large face mills are also close on power, depending on depth of cut, diameter and material being cut.
The other reason for a 2 speed setup is to be able to run higher rpm than the 3000 your servo wiil top out at. That will be a limiting factor for many small tools. so you would run 1:2 to get up to 6000 rpm - though depending on the spindle you may want or need to limit the max rpm so as to not blow up the bearings.
I think I have seen that belt drive before.
How about a good word?
youtube videos of the G0704 under the name arizonavideo99
Just saw this build and I have to say excellent work! I have a fully converted G0704 which I got my Freshman year of college. Looking back I wish I had gotten a bigger machine Congrats
I was ready to buy a g704, maybe even the one that's on sale here in the for sale section, and just happened to find this guy on Facebook market for $850. I've always wanted one, just never thought I'd find a used one that was close while I was in the market. I'm stoked.
Last edited by Halfnutz; 11-30-2019 at 06:11 PM.
Hey Kurt, would u happen to have part number for the gas struts used in your build?
Thanks
Shown in 3rd pictur Post# 2:
STRUTS 100# 16.14" stroke
McMaster Part# 9416K23
I'm doing the same build, essentially
Although I chose 75# struts, because I want the struts to assist a little bit but I also want to lessen the counteracting force the struts does when moving in the opposite direction. Hence 75# as opposed to 100#. Not only that, but my Z axis servo is 1.0 HP (750W) so I don't think a large lift assist is necessary (heck, I'm aware of a few machines like this have been running for years with NO ASSIST)
Your avatar is a "cracked picture" icon (for lack of better description) might want to check out what went wrong.