[Ahab345009]

Well, here I go with my new build thread. I’ve learned a lot from this forum and I thought I’d document my experiences here to help out others and get some advice. I intended to start it awhile back before I ordered parts but haven’t gotten around to it until now. I’ve already ordered the basics for the conversion which I will detail below. I like photos so I intend to post a bunch as I go. I will also try to give details of the various parts along with my experiences with different vendors since these are things I value in reading in others’ posts. This is going to be a long one to start with to go over what I’ve done so far.

I converted a Harbor Freight mini-mill to CNC several years ago. I really love machining with it and CNC in general. I have actually built or converted 4 CNC machines already so far: 2 x hotwires, the mini-mill, and a router. I love my mini-mill but it has some big limitations that I’m always running into. The table and travels are too small and the Roton ballscrews have too much backlash. I even loaded oversized balls and went from .012ish to about .005ish which is ok for a lot of things but it makes it difficult to make really nice cuts and all my interpolated circles have little bumps in each quadrant. I thought a lot about upgrading to a bigger table from LMS and getting new screws, etc. but finally decided that the money would be better spent on a whole new machine. I wanted a much bigger machine with some real capabilities. I ruled out a Bridgeport as I am active duty military so I move to a new state about every 2-4 years. This limited me to something I could move without a forklift. I thought about a G0704 but the y axis still seemed fairly small and I was skeptical that its 350ish lbs would be enough for a good base mill. I’ll probably be regretting I didn’t go with a G0704 when I do move again. Anyway, an RF-45 type machine seemed to be about the max I would be able to deal with but most of them don’t have much more travel than the G0704. Then I found the IH model which has a really nice sized envelope and seemed ideal. They seemed pretty pricey, however, until fairly recently when Charter Oak put them on sale for $300-$400 off.

IH has changed hands several times in recent years and I’ve seen some bad reviews about them in the past. I can only document my experience with them and I’m happy to say the most recent owners, Charter Oak, were easy to deal with and I had no significant issues. I bought my manual IH mill back in Jan. They shipped it within a day or 2 of making my order and they worked out the shipping to where I could send it to the nearest terminal in El Paso and then pick it up there which saved me a couple hundred $. They actually shipped it a day earlier than they originally said and it took a day less to arrive at the terminal. This worked out really well since it arrived on MLK day and I was able to pick it up without taking off work. I rented a U-Haul open trailer and hauled it home with no problems.

The only negative thing I have to say about Charter Oak so far is that you have to have a special spline wrench to hold the spindle when tightening the drawbar and it wasn’t included. They included several tools I don’t need like a cheap flat tipped screwdriver and a normal metric wrench but not a spindle wrench which made the mill useless until I got one. I ordered it from Charter Oak and they gave me a $5 discount. This was really not a big deal. I just wish they would have at least asked me if I need one when I bought the mill so I could have ordered it at the same time.

Getting it off the trailer was interesting. I had to do it late at night after I got home since I had to return the trailer the next day. Basically, I hoisted the crate up off the trailer with my 2 ton hoist and drove the trailer out from under it. That’s my 11 year old son helping me in the photo.

There it sat in the middle of my shop floor for several weeks before I had time to build a stand. I ordered 4 heavy duty 1000# leveling castors from Hand Trucks and Castors on ebay and bought some steel from a local supplier. I based my stand design loosely on Bob Warfield’s. My stand design has an open bottom so I can get to the y axis mechanicals without lifting this beast off the table and trying to work under it while it hangs from a hoist or disassembling it every time. I used 3/16”-1/4” thick steel on the legs and cross braces. The legs are 4x4 and the cross braces are 2x4. I intended this to be way overbuilt in order to add mass to the whole thing and I wanted plenty of safety factor since it depends on my welding ability. I finally found the time to build the stand over a couple weekends and it went together pretty well. I finally got to use my Harbor Freight Mig 170 and learn to mig weld. I have dabbled in stick, gas, and tig welding over the past 10 years or so. This welder did a pretty decent job and I have no real complaints. Mig was way easier and faster than Tig would have been, especially for those inside corners. I used pure Argon since I use my gas bottle for Tig also. I found it works much better if you keep the torch clean with the waxy cleaner stuff. I had to break a couple pieces back apart once or twice that had shifted in their alignment while welding. After that ordeal, I’m not too worried about my welds anymore. They may not be the prettiest but they were rock solid and a pain to grind through.

I ordered 12”, 24”, and 38” AccuRemote digital scales from Anytime Tool on Amazon. All 3 were around $260 delivered. These are pretty cool scales. I set up a DRO on my mini-mill using digital calipers several years ago and it was the best thing I did with it before converting it to CNC. I’ve already used the longest one to calibrate my router. I haven’t yet tried to mount them on the IH mill. I hope I can come up with a good way to do it and protect them from coolant when I finally get a coolant setup. At any rate they should help me use it as a manual mill to make the motor mounting parts and to calibrate the CNC movements.

I ordered the Nema 34 3-axis servo kit from Keling (AutomationTechnologiesInc.com) and received it yesterday. I special ordered it with the KL34-180-72 motors which are 1125 oz*in, 72V motors. I got the 72V version since the power supply is 72V and the Geckos are only rated to 80V. I don’t know why they usually sell 90V motors with this kit. I asked questions about it but never really got an answer from Keling. I have bought quite a few motors from them over the past few years and I’ve always gotten good service from them. They always answer my emails very quickly but aren’t so good at answering the questions I ask. They did assure me that this combination should work fine. I know these motors are waaay bigger than I need but the price difference was marginal (only $60 more than the 600s) they have almost the same max rpm (4000 vs 4200 as compared to the 850s), and their listed current draw is only ~5-7% higher but they have a 33% higher constant and max torque over the 850s. The 600s don’t have a 72V version available through Keling and I didn’t want to have to gear down the 6000 rpm. I wish I had contacted DMM about their AC servos but I couldn’t really figure out how much they would be and I didn’t bother to contact them.

I ordered 7202B angular contact and 6202zz radial bearings from VXB. They don’t even list an abec rating so I’m sure they are abec 1 or less. I might have gotten some better ones but these were cheap enough that I’ll give them a try and I can always upgrade later if needed. Most of the higher quality ones were way more expensive or only had a 15 deg contact angle.

I ordered ballscrews and nuts from linearmotionbearing2008 a week and a half ago. I ordered straight from Chai to get the lengths and sizes I wanted with end machining. I just emailed him yesterday to see if they had shipped yet. He sent me a tracking number and I found that they should be here tomorrow. I thought his prices for everything were very reasonable. I ordered a 2005 screw for the x and 2505 screws for the y and z. I got 2 of each ballnut. They are supposed to be zero backlash (.0006”) but I’m skeptical and wanted the option to make a double nut setup. If nothing else, I’ll have some spare nuts in case there are some bad ones or I lose some of the bearings. Chai said they have anti backlash double nuts already made up but I didn’t get them since I wanted more flexibility in mounting. I can always order them later if I change my mind. The prices on the nuts are pretty reasonable and shipping them shouldn’t be too bad. I also ordered some 1900mm 2005 screws for yet another CNC hotwire machine I’m working on. I sure hope they make the journey intact.

I ordered timing belt stuff from SDP/SI yesterday. I thought long and hard about making my own but finally decided to save the time and buy them. I got all 5mm HTD stuff since that’s what IH uses on their conversion kit. I wanted a 4 to 1 ratio so I got a piece of 15 tooth stock and 3 x 60 tooth pulleys. The 15 tooth stock was cheaper than 3 pulleys and it will allow me to make a better hub design to fit my ½” motor shafts. I got belt lengths that would allow me to set up the motors on the side of the machine and table like jid2 and others have done instead of sticking way out in the way like the IH conversion kit. I just hope this doesn’t cause problems with belt vibration.

Well, that pretty much catches me up to the present and that's plenty for now.

[tauntdesigns]

Nice looking machine

Pulling up a chair

[Bubba]

Yup, I'm along for the ride also so I can see how someone else does things. Always learn something new!

Good luck with your build.

[Ahab345009]

Ok, broke into the CNC servo kit today. A few observations and a few questions....

All appears to be well packed and in good order. There are no manuals for anything except the encoders which have short manuals that tell how to install them. Other manuals seem readily available on Automation Technologies Inc's website and Gecko's website. I don't know which G-320X revision these are since it doesn't say anywhere but I think it's safe to assume they are the latest rev 10s since they have a QC pass date on them of 0314 and the last revision on Gecko's website was in 2011. Man, these geckos are tiny. Much smaller than my single axis stepper drivers on my router.
Looking at the Gecko manual it says to set all the trim pots to 11 o'clock. Is that supposed to be based on the tiny little dots on the dials that I didn't even notice were there until I took the photo below and zoomed way in?

Attachment 230834

The encoders don't come with mounting screws but they are just little 4-40s and luckily I had some on hand.

Attachment 230836

Why are there 2 rectifiers on the power supply? All the photos on ATIs website only show 1 rectifier. Should I hook them up in parallel? Sure would be nice to have complete documentation. They do have a nice wiring diagram on the page for the power supply but it doesn't say anything about how to hook up the 2 rectifiers. Maybe this will become more clear when I power this beast up and see what the output voltages are.

Attachment 230840

[Ahab345009]

Oh, didn't notice this giant label before. I guess I will have to parallel them to get 20 amps.
Attachment 230844

[Bubba]

yup, there are two different voltages on that power supply. IIRC, one will be the main for your servos and the other will be 5v for powering your BOB

[Ahab345009]

Hmmm, for some reason they moved this thread to the Charter Oak Automation Support page. That doesn't make sense since this is not their conversion kit. I just bought the base mill from them.

The screws were supposed to be here today but they didn't make it. Looks like they are in Memphis.

The 2 rectifiers are each 72V and will provide up to 10 amps apiece. Each one has 2 + terminals, 2 - terminals and a C terminal. I get ~72.3V between + and - and half that between either + or - and ground. I think I'm supposed to tie them together with the C terminals if running in parallel but I'm not sure. I couldn't find anything about it in the documentation so I emailed Keling. Haven't heard back from them yet.

Worked on the servo drives more today and got 1 axis up and running. I set up the Geckos per the Gecko Manual. I set up the encoders for 400 based on the calculations given in the manual. This was based on my kernel speed of 25kHz in Mach 3. I can probably set it faster so I can use a higher resolution but didn't mess with the kernel speed today. I just used step and direction pulses from the breakout board on my CNC router.

I was a little unsure as to what the 11 o'clock position was on the Geckos. There are 2 dots on 1 side but they are otherwise symmetrically marked. I put the dots in the 11 o'clock position as shown in the photo below and it seemed to work as advertised.

Can't get the photos to attach with this computer. I'll attach them later.

[Ahab345009]

Here's the photos:
Attachment 231026
All set up and ready to run

Attachment 231030
The little dots on the trim pots are hard to see unless the light hits them just right. Then it is unclear which end of the pointer they are marking. I used this setting and it seemed to work correctly.

Attachment 231028
Make sure you set the dip switches before attaching the encoder to the motor. This is set for 400 which should be fine for now.

[Ahab345009]

I'm thinking of buying an inexpensive oscope to tune the servos and who knows what else. I've always wanted one but I've never used one before. Anyone have any good suggestions? Not sure what frequency range would be practical. The PC based ones look like they would probably work fine for me. There are a bunch of these and other mini oscopes for <$100 on ebay. Are they junk or will they work ok?

[arizonavideo]

You can set them by ear with a little practice.

The adjustments are to get the feed back loop not to over react and be stable. The higher the gain the higher the damping needs to be. The screws and table add a little damping that help prevent ringing.

Generally you end up with the drive set close to the point where it becomes un stable. To test a setting you can energize or excite the motor shaft and listen to the motor response. It should make a single rebound and settle with almost no bounce. A pulley or the like mounted to the shaft helps with this so you can see whats going on. A quick jar to the motor shaft and you can hear the reaction.

Many people like to get the gain way up because the servo is more rigid that way but it also cause more wear and heat on the servo. They also make much more noise that way.

The way I have mine set you can hardly hear them and they make almost no heat. I would think they will last forever at the current settings.

You get to pick the gain level to give the desired level of stiffness V noise. They also fault easier at high gain setting because the stiffer settings ask for higher instantaneous currents during direction reversals and the drive can only deliver 20A max so the second you go over it faults. A slower reversal time makes the current spike lower.

The main problem is the Z with all that mass. The table is fairly fast and easy with less problem faulting.

[Ahab345009]

Man, you are ruining my excuse to get more tools!

I'll have to look into doing that later. I tweaked the pots a little and can get them to quite down but I don't really know what I'm doing at this point. I've built quite a few stepper based machines but this is my first attempt at servos other than the model airplane variety.

I got 2 axes up and running at once under Mach 3 control. I would have had all 3 but one of the encoder brackets has a broken clip. I emailed Keling about it and they already have a new one on the way. They still haven't answered my question about paralleling the C terminals on the power supplies though. I did test all 3 geckos and the C10 BOB. I am having issues with pins 16 and 17 on the BOB. When I use them to drive a Gecko, the servo motion is rougher and it faults often, especially in one direction. Not sure if this is a BOB problem or a Mach3 setting. I'm starting to think it is the BOB since I switched to pins 8 and 9 and it works fine. This is my 2nd C10 BOB and this is the first issue I've had with one of them.

Got my ballscrews today from linearmotionbearing2008. They didn't drop them off at the house because I had to sign for them. This is the first time I've had to sign for a FedEx package in ages. Anyway, I was able to get them dropped off at a local FedEx location and then picked them up after work. The box they came in was pretty beat up. When I opened the package I found that there was no support for the screws other than the screws themselves and a single layer cardboard box. It came as no big surprise to find that my both of my 1900mm long 20 mm ballscrews were bent. These are both for a different project that I had hoped to tackle before the mill. Even my 1900mm X axis ballscrew is slightly bent. The Y and Z axis are both 25mm screws and they appear straight from a cursory examination. I emailed Chai already and I'm waiting to hear back. I'm very interested to see what he'll be willing to do about it. Before I bought them I specifically asked if he could ship these without them getting damaged and he said he could. So much for that. I would have thought he would have taped them to a board or shipped them in a much more rigid tube or something. Other than this issue, they appear to be exactly as I ordered. The ballnuts don't seem to have any perceptible play. Certainly way less play and backlash than some Roton screws I have on other machines.
Attachment 231086Attachment 231088

[arizonavideo]

Pull the seals out and rock the ball nuts by hand. If you can rock them by hand you will need to repack the balls. I'm on screw 12 or so from Chai and all have needed to be repacked to have any real preload and zero backlash. The are dirty too.

The lead error does look to be vary low which lets you get them tight.

I just finished straightening another screw that was out by .015" It is a real pain to get them under .004" or so but I think .004" is OK for a longer screw.

I used the mill and the quill with a 16mm screw, larger ones might require more force. I had the V blocks about 8" apart. For larger screws placing the V blocks further apart would help.

I got the idea from this video.

https://www.youtube.com/watch?v=dzIsR4Mg158

I start from the highest point. So far I have only had a screw with one bend in one direction but I bet I will find more bends.

[Ahab345009]

Thanks arizonavideo. That was an interesting video.

Chai responded telling me he was upset that they had been damaged and gave me this link to Roton's instructions on screw straightening which looks a lot like what the above video shows. Looks like I need to order a set of V blocks since I only have 1. I think my long screws are out by .15" or so. Haven't actually measured them since I don't have V blocks but the bend is obvious when you roll the screw on a flat surface. I'll see if I can straighten them when I get some V blocks.

I did a lot of not working on my mill this weekend as I'm trying to finish up some other projects. I did buy an enclosure for the electronics that I think will work well. It's a 125 A outdoor load center. I measured my power supply, Geckos and BOB when they were laid out on the table and it looked like the min size should be ~14"x7"x4" which would be pretty tight and didn't include any extra room for fans or anything. The enclosure I bought is 18.92"x14.75"x4". I will probably have to trim off about 1/4" of the extra bit of bolt that protrudes from the torriodal transformer in order to close the door all the way but I think it will fit well otherwise.
Attachment 231286

[maker of things]

Did I read that right, multiple z axis screws?

[Ahab345009]

Did I read that right, multiple z axis screws?

No, I only plan on using a single 25mm Z-axis ballscrew.

[Ahab345009]

Finally... the CNC zone administrators got this thread posted in a good place. They kept moving it around to various places it didn't belong. I finally convinced them to open a new sub-forum on RF-45 clone mills. Thanks, this is much better! Hopefully some more of my RF-45 clone brethren will join me here.

Been pretty busy working on various random projects and not much with the mill. I did do a fair amount of work on the bent ballscrews a couple weeks ago. I used the basic method shown in the video from Arizonavideo above. I found that it is a very tedious process but I was able to get the couple that I worked on pretty straight. So, bad news is that linearmotionbearings2008 does an absolutely pathetic job in packaging long ballscrews and then doesn't even insure them but the good news is that I learned a valuable skill to fix them. Thanks again arizonavideo for posting that video. Already, posting on this site is paying off. I made my own video showing how I straightened one of my screws using the mill as a press. I will post it when I figure out how to post videos.

[Ahab345009]

Here is the video I made of straightening the ballscrews.



One note...it would be a good idea to put some padding on the v blocks to keep them from scratching the ballscrews.

[maker of things]

Good job getting the rf45 forum created. It has been driving me crazy trying to find the rf 45 posts. Not everybody uses the same name or spacing or hyphenation etc. Hopefully this will help. I hope to be starting my own 12z thread soon, my mill is supposed to arrive today.

[maker of things]

What are you thinking for oiling system? I have been scouring the site and so far I am leaning towards copying cowanrg http://www.cnczone.com/forums/bencht...pm-30mv-4.html. Having a hard time stomaching $500 for oiling considering I do not intend to run coolant or production.

[Ahab345009]

I haven't worked out any details yet but, yes, I was planning on doing the same thing. I don't want to tear the mill down yet since it is a valuable tool as a manual mill right now. I hope I can get my saddle and Z-axis slide on my X2 to mill the grooves but I may have to take it to a machine shop since it is a bit bigger than the PM-30MV.

Speaking of using this as a manual mill, I milled some 1/4" thick 6061 the other day with a 3/4" end mill. 1st of all, I've been so spoiled with CNC on other machines that turning those handwheels seemed like a real chore :violin:...however, man it went through that plate like butter. I was taking cuts of up to about .25" deep with ease. My X2 would have been vibrating and trying to tear itself apart at half that. As much as I like my X2, It sure is nice to have a machine with some mass and rigidity. I'm convinced this thing will take my machining to a whole new level.