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    Default Starting Charter Oaks Mill build #2

    Here we go again, another Charter Oaks CNC build. The first build turned out really good and a neighbor purchased it so now I'm going to build up the other one I have sitting here. Going back to the RF 31 to make the parts for the new one really seems archaic. What a difference in machines, gotta love the 12" Y on the Charter Oaks. I'll try not to bore anyone as this build will be pretty close to the last one except I have a new Y axis direct drive design that I'm going to implement on this one. Saves a lot of parts and the motor mounts flush on to the back of the machine. I am also going to see if I can take advantage of the way the manufacturers put there handles on with the 3 cog system. Since I always build my machines dual purpose, CNC/manual I would like to make the Y axis handle pull back from the cog while in CNC mode so it does not spin, that way it's a bit safer. Although I do take the stock handles and cut them down to nubs on my machines so your less likely to get hit in the gonadiums. I also think I came up with a nifty way to install the Z axis ball nut without having to machine a big piece of aluminum to replace the stock one. Just use the stock steel one and cleanly bolt a 1/4" plate under it to mount the ball nut to upside down. 6 bolts a 1/4" deep will hold the ball nut just fine and don't forget the 300 lbs resting on it. It has the same effect as mounting the ball nut inside the mount with the flange underneath as both are pretty much pulling up on the same surface whether the ball nut is inside or underneath. I don't really see any binding happening since it's all held straight by the dovetails. There's plenty of room under the steel block so there won't be any bottoming out either. On the Charter oaks they also put 2 pins in the Z axis steel block. Those will be drilled and tapped so I'll have the large center bolt and two 1/4" back up bolts for a very secure mount. Got a lot of parts built today and I'll take some pics tomorrow for everyone. I almost forgot, I have a 3 HP, 3 ph, 3450 rpm Baldor motor, VFD, and pulse width to analog relay board coming also. Of course I bought 2 just in case I have to upgrade the other one I sold since the variable speed will be awesome. This one will have quick change tools and a ATC system too. Maybe I won't bore anyone but it seems everything has been done before.

    Anybody got a good source for the Tormach style ATC tool holders?

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    Default Re: Starting Charter Oaks Mill build #2

    Tormach style holders are on ebay very reasonable. The seller has the ones with the groove and tapered shank for a ATC also but they cost slightly more.

    Glad to see a new build in the RF45 section, its been a while.



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    Default Re: Starting Charter Oaks Mill build #2

    Sparky, Thank you that will help.



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    Default Re: Starting Charter Oaks Mill build #2

    Pretty much got the X axis ball screw and nuts done today. It has a double ball nut setup, although it still needs the spring washers installed, and hidden fixed and floating ball screw bearing mounts. The RF 31 kicked butt today for me. Yesterday it was a CNC for cutting out the Nema 34 counter sunk mounts and today a manual mill for doing a lot of quick drilling and milling. Here's some pics of the things I have moving along. The third photo is the milling of the ball screw flange, It's just the nature of the beast on the Charter Oak mill. You have to take about sixty or seventy thousands off one side. Just make sure you take precautions as not to induce chips into the ball nut. I taped my ends up then vacuumed the chips off, I avoided compressed air so I wouldn't blow any micro chips into the nuts. I really like the hidden fixed and floating bearings hiding under the x axis, makes the mill a bit more compact. I don't know about you guys but it seems my dream CNC mill for me would be a 12" Y by a 16" X work area. and a say 16" Z. Small and compact for the home shop. Although I love the I.H. Charter oaks machines the X is way more than I need, the Y is perfect. Maybe I should cut 6" off the X in a big band saw. Hmmmm. OK, maybe next time. Tomorrow I'll tackle the Y axis, should be a quicky since I'm going to couple and direct drive it off the back of the machine, this should save a ton of space. I'm making the back mount bolt to the base of the mill with 3 bolts across the bottom so it can move forward and backwards a couple thousandths of an inch for expansion or contraction of the Y shaft due to temperature. I live in California by the beach so the temp range is only about 30 or so degrees fluctuation year round so the expansion should be pretty small. Parts, other than the Motors and drivers which I got from Ebay and rest of my CNC parts came from Automation technologies, various other parts where Mcmaster Carr (timing belt, nuts, bolts, etc.) and SDP/SI for timing sprockets. So that ends todays update. I'm hoping 2 weeks to chips.

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    Default Re: Starting Charter Oaks Mill build #2

    looks good. I don't know about you, but machining those ballnuts is not something I'd like to do again...haha.

    Did you make sure your X axis motor will clear the mill base at the extreme travel? I started out having my motor facing the mill as well, but switch it over when I swapped out different motors and lost my clearance...oops..



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    Default Re: Starting Charter Oaks Mill build #2

    Any progres

    Sent from my XT1080 using Tapatalk



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    Default Re: Starting Charter Oaks Mill build #2

    Hi, Yes actually a bit of progress. Went on vacation for a week and then had to straighten out a friends mini CNC for him. I got the Z axis mounted, new 3 phase 3 HP 3450 RPM Baldor Super E motor installed on the gear head and will be using a VFD to control it manually and remotely through Mach 3. All the parts have arrived as far as the DROs and the like. The computer case with 3 fans for the power supplies and a 450 watt power supply for the 5 volt and 12 volts BoBs. I really like using the computer cases for the power supplies and break out boards because they look hi tech and they are cheap to buy. This one has red lights that glow when turned on which I think is pretty cool. Gives it more of a hi tech look then a metal electrical box. The X axis is done and now tomorrow I'm going to whip out the Y axis. I also have the 1.5" x 3" x 1/8" wall rectangle steel tubing and 5 inch diameter 700 lb casters to start building the table. The 3 foot x 3 foot coolant pan with 2" lips made it here too. Hopefully some pics in the next couple days.

    Jack



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    Default Re: Starting Charter Oaks Mill build #2

    Todays report on Charteroaks #2 build. Finished the Y axis and got a few other odds and ends done. I took some pics, they won't be in order. I took a couple liberties on a couple things like cutting the internal cross bar that they cut in half about 1" wide and the factory. I opened it up so my Y axis ball screw could have clearance to travel in there if needed. The double ball screw in biased against each other with bevel washers and of course blue thread locker for safe keeping. Here's some pics. On my last build I put the Z axis all inside and it was really clean and time consuming to do it that way, this one I did the 4 leg stand so I could remove the motor if I needed to to move it through a 7 foot door opening with it on the stand. The Y axis motor is out the back now, figure I'd try this way as It's pretty clean and saves 2 pulleys and a belt drive setup. I found out a fun fact for everyone too. We also float the one end of the ball screw, The bigger precision CNC machine guys pre tension their ball screws, the question was how much? Well they just put in a 5 axis CNC at my day job which is at Robinson Helicopter company, I'm a test Pilot and work in R & D. I talked to one of the guys who was setting it up and he told .001" stretch on the ball screw. He said tighten the main fixed end and put a dial indicator on the floating end and then tighten it up until it stretches .001". Of course this means that you have to have another fixed end bearing setup on the float side. Good to know next time. He said as we know it helps eliminate the expansion issues of the ball screw.

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    Default Re: Starting Charter Oaks Mill build #2

    Looking good! Are you concerned about removing the cross brace? It looks like the column would act as a brace when bolted up but not sure what else supports the Y axis diversions from bowing under load.

    Sent from my XT1080 using Tapatalk



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    Default Re: Starting Charter Oaks Mill build #2

    Actually I did not cut the brace out, the Charteroaks brace is already cut out. It has about an inch opening stock, I just opened it farther as it was already useless since it was cut. The first Charteroaks I did was the same way.

    Last edited by Roadstercycle; 08-17-2015 at 01:19 AM.


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    Default Re: Starting Charter Oaks Mill build #2

    I got a little more finished today. X-Y-Z are done now and put on my X axis DRO scale. I had to do this to be able to finish the X axis motor install, but all is done. The Sinpro DRO is pretty nice and now they even give end caps for the covers. Really make it look clean. The red strap you see is because I live in Los Angeles and sometimes I get spooked about earthquakes and don't want it to hit the floor. It's funny, because when I put a car on the lift I strap it down too. Could you imagine your car falling off your lift in your garage? That would ruin my day.

    Attached Thumbnails Attached Thumbnails Starting Charter Oaks Mill build #2-img_1990-jpg   Starting Charter Oaks Mill build #2-img_1989-jpg  


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    Default Re: Starting Charter Oaks Mill build #2

    Well, I finally got this one finished. I also set up a 4th axis but I am waiting for the power supply to run it. The mill turned out pretty nice and seems to work well. I used a Huanyang VFD for the 3 phase, 3 hp motor. Well this drove me crazy. Tried to wire it like cnc4pc and Automation technologies websites but neither way worked. It worked great manually but would not work through Mach 3 even though it showed turning on and rpm but the spindle never turned on. So if anyone has any insight as to why give me a shout as I would like to know the answer even though I made it work through a usb to serial setup I found on the web. That turns it on and off and adjust speed through Mach3. Like I said I'd love to know why Mach 3 can't control it using a C41 board through CNC4PC. So any way back to the mill. I bought one of those sweet spindle lights off Ebay that works awesome. I can't believe I never saw that before, Love it!!! The mill is set up for manual and CNC so I can do a quicky without turning on Mach 3 and having to program something that is done faster than turning on the program. I have not cut anything yet but just ran a couple programs to check speed and movement. Here's a few pics if anyone is interested. Couple of side notes, I use a signal generator for the Z axis so when the computer is off, It runs the Z axis up and down to be able to do quick tool changes in manual mode. Also in one picture you'll see the control box with a red light in it. That's a computer box that I use to hold the power supplies and BOB and the ethernet board from warp9. I like using the computer as a control box as all computer power supplies give me 5 volts and 12 volts to run everything I need. They also are light and really inexpensive and 3 fans already build in. It's a pretty win, win, win situation. I also run a fro and the mach screens side by side for comparison. After I finish a job I have mach go to zero and my separate DRO better read zero too or something happened during the run. Kind of a double check of the system plus it's great for manual mode.

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    Default Re: Starting Charter Oaks Mill build #2

    Quote: I talked to one of the guys who was setting it up and he told .001" stretch on the ball screw. He said tighten the main fixed end and put a dial indicator on the floating end and then tighten it up until it stretches .001". Of course this means that you have to have another fixed end bearing setup on the float side. Good to know next time. He said as we know it helps eliminate the expansion issues of the ball screw.


    Hi Roadstercycle, Interesting information on the ball screw. Would this means that you only need one angular contact bearing on each end with stretch of 0.001"??



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    Default Re: Starting Charter Oaks Mill build #2

    [QUOTE=GtG001;1863924]Quote: I talked to one of the guys who was setting it up and he told .001" stretch on the ball screw. He said tighten the main fixed end and put a dial indicator on the floating end and then tighten it up until it stretches .001". Of course this means that you have to have another fixed end bearing setup on the float side. Good to know next time. He said as we know it helps eliminate the expansion issues of the ball screw.


    Hi Roadstercycle, Interesting information on the ball screw. Would this means that you only need one angular contact bearing on each end with stretch of 0.001"??


    Yes you would, that would be the only way to get a stretch of .001 and still have a smooth running ball screw shaft. You would eventually eat up a conventional bearing with a side load like that.



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    Default Re: Starting Charter Oaks Mill build #2

    One of things that I have wondered about was the different expansion rate of aluminium in the bearing supports of the ball screws, particularly in regards to the angular contact bearing and keeping the bearing preload accurate. I am going to use steel for my bearing support plates and bearing housings for this reason ....

    On another matter, does some one sell the spindle adaptor/sleeve for a the belt pulley?

    regards,
    Allan.



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    Default Re: Starting Charter Oaks Mill build #2

    Stretching the ballscrew is a great idea - it does away with the issue of cheap unmatched angular contacts and trying to get their preload right using shims etc. I think the 1 thou the big boys use is based on the load it places on the bearing. Need to do some math but say its a big ballscrew on a big machine - 1 thou stretch may be a few hundred or thousand pounds acting on the ballscrew bearing. For machines our size we should figure out the desired preload on the bearing and then work out the stretch required. Who knows, maybe it will be more than a thou, maybe less. I'll do it someday just for kicks and let you all know what I come up with.
    Mike



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    Default Re: Starting Charter Oaks Mill build #2

    Hi Mike,
    I think you might be right with the relationship to stretch; it is proportional to force and diameter of the ball screw. Sometimes, the obvious is not so obvious until someone points it out. Thanks Roadstercycle and Mike.

    On another matter, Roadstercycle said that the 1605 ballscrew was the largest he could use on the X and Y axis, could you give more information on this matter please?

    Thanks, Allan.



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    Default Re: Starting Charter Oaks Mill build #2

    On Y there is plenty of room for a large diameter ballscrew and nut. On X - not so much. Have a look up at post #4 by Roadstercycle and look at the mounting of the X ballnut to the saddle. Its not the screw diameter that is the limit but rather the ballnut, go bigger and you need to sink it into the saddle and / or clearance under the table. Also, though its been quite a few years since my conversion, I recall doing the math and the 1605 was more than sufficient for the loads the X-Y will see.
    Mike



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    Default Re: Starting Charter Oaks Mill build #2

    Thanks Mike - good information
    I really appreciate the good information on this site and I have started my RU-45 conversion with pretty much copying what others like Roadstercycle, Arizonia and Steve (Jumps4) from hobby-machinist have done. I will be adding my little bit of my own too but these guys have paved a good platform to start from - thanks guys To say that CNC is addictive is an understatement and maybe that there should a warning on this site with a Skull and Cross-bones icon, enter at your own peril (lol)



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Starting Charter Oaks Mill build #2

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