[Roadstercycle]

Hi everyone, just waiting for my mills to hit the door so I can start my build. Stand is done and I know starting this thread without them here is kind of lame but they should be here today. I do have a question though and don't beat me up for asking this because it's been gone over a thousand times, "what's better servo's or steppers" I know the difference and have used steppers in the past and they have performed great. What I am wondering is has anyone one used the steppers with the encoders that are available now. Do they work the same as the servo type with encoders? I've looked and can't find a good answer.

[dracozny]

Hi everyone, just waiting for my mills to hit the door so I can start my build. Stand is done and I know starting this thread without the here is kind of lame but they should be here today. I do have a question though and don't beat me up for asking this because it's been gone over a thousand times, "what's better servo's or steppers" I know the difference and have used steppers in the past and they have performed great. What I am wondering is has anyone one used the steppers with the encoders that are available now. Do they work the same as the servo type with encoders? I've looked and can't find a good answer.

From my understanding it's about cost in the end. We all know that servos maintain a better torque curve and steppers will lose steps under heavier load, hence the addition of encoders. If you go the stepper route I think it would be better served by getting linear encoders for the table instead of for the motor. It's not a bad idea on the servo side either. Although they tend to get expensive compared to rotary encoders. A user I know over at Hobby-Machinist uses magnetic linear encoder feedback to his system (not the cheap igaging ones). As a result lost steps and backlash are accommodated for easily.
with that said, I have rotary encoders on my servo system. The torque curve was more of a deciding factor for me. Plus they already had encoders on two of the motors I found on Ebay, so I just stuck with that design for the other two.

[CS900]

I am currently using the NEMA34 closed loop steppers from automation technologies on my PM45 mill. They have been working fantasitcally for over a year now. They do not work exaclty the same as a servo. The encoder is not used for positioning feedback like a servo, but as far as I can tell is used as a warning mechanism to detect lost steps. So I THINK the controler monitors the encoder and matches it against the step output. If the two do not match it throws a positioning error. The control boxes do have an error output, so you can hook them up to an estop so if one axis looses steps you dont ruin your work piece, which is a very nice feature. that said the NEMA 34's are a beast of a motor and I have yet to stall one out. I have locked up my spindle, but the steppers never missed a beat.

[Roadstercycle]

Well still waiting for the mills to show up. Last word they where stopped because of snow in Chicago. I did finish the stand though. As you can see I brought the mill up about 6" off the chip pan for 3 reasons. 1. I don't like bending over while working, I found this out after I built my RF31 CNC and just had it on the stand, then one day I wanted to adjust the ball screw backlash and had to lift it up to do it and while doing it I put 4 pieces of 4 " x 6" wood blocks under it and ended up leaving them there because it was so much more comfortable to work the machine, 2. I am able to put the Y axis motor under the machine (sample in pic, not the one I'm using) out of the way and 3. I can get to the Y axis ball screw if anything go awry. I don't think anything will go wrong but I'm a helicopter test pilot so I'm always looking for a soft landing or the safest way out. So here's the pictures of the stand, the bottom shelf will be water sealed wood so I can put my extra 4th axis and other things and not really hurt anything, the wood won't mind a ding here or there. The chip pan I ordered from a company that build them. 36" x 36" with a 2" lip. It was water tight until I cut the holes in it. I run a mister instead of coolant so I'm not too worried. It can be sealed with coolant resistant silicone in the future then I can run coolant if needed.

[Roadstercycle]

Finally got the mills today. 3 weeks but alls good. They are definitely heavy. Tomorrow I should get one on the stand and check the situation out. I decided to put the other mill on Craigslist and just share shipping with someone on the west coast. I'm so busy with other things doing 2 CNC projects seems crazy at the moment. Here's some pics of the machines. Also an added note. If you buy one of these new from Charter Oak don't waste your time taking the top off to check it out and see it. Just unclip the bottom clips (they are same as the top clips) and lift the sides and top right off it. Easy peasy.

[dracozny]

That base looks very narrow to me I suppose it could just be the same width as a zx45 but the length makes it look narrow

[Roadstercycle]

That base looks very narrow to me I suppose it could just be the same width as a zx45 but the length makes it look narrow

Well I don't know if this means anything to anyone but the base is just at 16" across. Maybe the photo did not make it look correct.

[Roadstercycle]

I got my machine on the new base table today so I can start pulling it apart. Pretty big compared to my CNC'd RF31 in the background. That's a 1236 Birmingham Lathe behind it. I really would have liked a shorter x as I really don't need it. 30" would have been fine and fit in the shop better but someday it will come in handy. The Y is awesome though, that's the big winner here along with the square column. Well now comes the hard part, I'm running 1200 OZ steppers on my RF 31 and it's never missed a step, well except once when I had a buddy doing a job and I was cutting something and the high frequency from the Mig welder freaked out the electronics in the mill and destroyed the part. NOTE TO SELF, NO MIG WELDING WHILE RUNNING A CNC PROGRAM.
So anyway again it's the stepper vs the servo decision. I wish there was only one or the other.

[dracozny]

Well I don't know if this means anything to anyone but the base is just at 16" across. Maybe the photo did not make it look correct.

Yea, its the same width as the ZX. I think it was just the length that makes it look odd. The zx is 24.5" long.

[dracozny]

I got my machine on the new base table today so I can start pulling it apart. Pretty big compared to my CNC'd RF31 in the background. That's a 1236 Birmingham Lathe behind it. I really would have liked a shorter x as I really don't need it. 30" would have been fine and fit in the shop better but someday it will come in handy. The Y is awesome though, that's the big winner here along with the square column. Well now comes the hard part, I'm running 1200 OZ steppers on my RF 31 and it's never missed a step, well except once when I had a buddy doing a job and I was cutting something and the high frequency from the Mig welder freaked out the electronics in the mill and destroyed the part. NOTE TO SELF, NO MIG WELDING WHILE RUNNING A CNC PROGRAM.
So anyway again it's the stepper vs the servo decision. I wish there was only one or the other.

Thank you for the heads up about the welding! although I have to wonder if you have a shielding issue on the cables.

[Roadstercycle]

Shielding? what's shielding? Just kidding. He was right next to the machine and all my cables are shielded and grounded but that Mig high frequency starting will blow through almost anything. I keep my computers and cell phone far away when I weld with Mig.

[Roadstercycle]

Yea, its the same width as the ZX. I think it was just the length that makes it look odd. The zx is 24.5" long.

The base is 27.5 inches long on the Charter oak.

[arizonavideo]

The 1200 are really a bit large for the use and the higher inductance makes them a bit slow compared to the 900 oz stepper.

I just removed the servo in my IH because I had a bug and installed a 900 oz 6.1A stepper and it is way fast and so far perfect with no dropped steps.

The Z might be OK with the 1200 direct drive.

[Roadstercycle]

Dave, Thanks for the thoughts on this and you and some others may think I'm crazy but I am actually going to go with a setup I saw another guy build on the Hobby CNC forum. He's running 1600 OZ steppers on his X and Y and a 4200 oz on his Z. He's getting 200 ipm and it is smooth as silk. He's been running over 2 years with no issues and no lost steps. It was really hard after watching and reading about all the CNC setups on the RF45 and I.H. clones and make a decision on which way to go. Servos vs steppers, how many in oz steppers, etc, etc,etc. So after seeing just brute strength and how smooth it runs and cuts I decided to overkill it and do it once and be done. The Z was also crazy, gas springs, no gas springs, counter balance, direct drive, reduction drive, servo, stepper, 1200 oz, 2400 oz. There was no end to it, it seems. It was actually trying to drive me crazy and I've built machines my whole life. So here's a brute force machine build and we shall see how it turns out. I think we both agree that there is more than one way to do something and all of them work, some better than others, but when it's all said and done we got off the couch and actually did something and that's the great part of it all.

[dracozny]

Dave, Thanks for the thoughts on this and you and some others may think I'm crazy but I am actually going to go with a setup I saw another guy build on the Hobby CNC forum. He's running 1600 OZ steppers on his X and Y and a 4200 oz on his Z. He's getting 200 ipm and it is smooth as silk. He's been running over 2 years with no issues and no lost steps. It was really hard after watching and reading about all the CNC setups on the RF45 and I.H. clones and make a decision on which way to go. Servos vs steppers, how many in oz steppers, etc, etc,etc. So after seeing just brute strength and how smooth it runs and cuts I decided to overkill it and do it once and be done. The Z was also crazy, gas springs, no gas springs, counter balance, direct drive, reduction drive, servo, stepper, 1200 oz, 2400 oz. There was no end to it, it seems. It was actually trying to drive me crazy and I've built machines my whole life. So here's a brute force machine build and we shall see how it turns out. I think we both agree that there is more than one way to do something and all of them work, some better than others, but when it's all said and done we got off the couch and actually did something and that's the great part of it all.

My Z servo motor has a constant torque rating of 328 oz-in. They really get up and move fast and hard even with a 2.63:1 gear ratio. Peak rating before demag is pushing 2300 oz-in. I don't ever plan to push them anywhere near that limit. I homed my system from 18 inches away with a 60% override. The one thing it proved to me was I need to improve my stand. I do have a gas spring installed but I could easily run it without

[Roadstercycle]

drac, thanks for that. I'm going the direct drive and the 4200 in oz. stepper. Should never have to worry about it unless the bearings I use don't like 300 pounds hanging on them but I will get good bearings that will deal with the load.

[arizonavideo]

I run Electro Craft servos that are large enough to run a Hurco mill but it was just because I got a deal on them. They do run cool and will last longer but with any of the larger steppers or servos the driver is the power limit not the motor.

That 2300 oz stepper will have in inductance around 26mH or more and will run fine at 200 volts. At 70v the 900 oz will make more power at 150 IPM than it.

What driver do you plan on running?

[Roadstercycle]

The 1600 in oz are running a DQ860MA with 7.8A peak.

The 4200 Driver is a DQ2722 With 8.0A Peak current,7.0A rated current, 110-220VAC,200 Microstep,

[dracozny]

drac, thanks for that. I'm going the direct drive and the 4200 in oz. stepper. Should never have to worry about it unless the bearings I use don't like 300 pounds hanging on them but I will get good bearings that will deal with the load.

Doesn't matter if you do belt or direct drive the AC Bearings will be holding that weight regardless. Try weighing that head if you can. I found using one 150 lb spring was actually more pressure than what was needed to equalize the head. I would guess since it's already mounted that the ZX head minus the quill feed is roughly 125 lbs and not 200+ like I have seen purported by others.

[Roadstercycle]

Doesn't matter if you do belt or direct drive the AC Bearings will be holding that weight regardless. Try weighing that head if you can. I found using one 150 lb spring was actually more pressure than what was needed to equalize the head. I would guess since it's already mounted that the ZX head minus the quill feed is roughly 125 lbs and not 200+ like I have seen purported by others.

Thank you drac, It's really a mute point about the Z axis. I'm going to run the 4200 stepper on the Z axis without any counter weight. The guy I'm modeling the machine after has run his for almost 3 years with no issues so I'm going to give it a shot. His machine runs smooth, fast and solid. I hate to be a copy cat but reinventing the wheel is not always the best solution. I'm making some changes to the design as far as belt drive X and Y to give me more room without the motors sticking out the ends of the axis. One motor under the machine for the Y and one motor parallel in front of the X axis on the right side. If I was left handed it would be on the left side. All the axis will have 4 pole double throw switches so they can be shut off the X and Y at will for doing hand jogging and resetting easy and quickly. I will also have a rotary switch, pulse controller and jog button so I can use the machine quickly and easily without turning on mach 3 or a computer. That will be a big plus for doing quickies so I can move the head. Waiting for parts at the moment, Hate that part.