What kind of stepmotors to IH mill ?

[Juka]

I get my machine a month ago,it is ZX45 (copy).
Now I want install steppers to that, with straight transmission. I am not sure what size they should be ? Does 8 Nm holding torgue enough ?
I´d like to see pictures too...

Thanks again!

[SMW Precision]

Originally Posted by Juka I get my machine a month ago,it is ZX45 (copy). Now I want install steppers to that, with straight transmission. I am not sure what size they should be ? Does 8 Nm holding torgue enough ? I´d like to see pictures too... Thanks again!

Juka, this is the wrong Forum for the question IH CNC Mill has a Servo System. System is belt driven and has a Ratio versus direct connect Stepper drive system.

[Richards]

Ken,
I disagree. My mill was purchased last year without CNC electronics, giving me the choice of whether to simply attach some steppers to the screws or go 'whole hog' and add ball-screws and motors. Even then, I would still have the choice of using steppers or servos.

I think Juka's question is very valid. Has anyone simply attached steppers to the factory mill without first adding ball-screws? I've been thinking of doing that very thing as a first step before going all-out with a servo/ball-screw CNC controller. Since I have a bunch of Geckos (both G212 and G203v) on hand, a box full of stepper motors (mostly Oriental Motor PK299 series), a licensed copy of Mach 3, and several power supplies, break-out boards, etc. to make a running system, I've been toying with the idea of adding a stepper to the X-axis, a stepper to the Y-axis and using the Z-axis in manual mode. Hoped for accuracy is about 0.003 inches. Hoped for speed is in the 30 to 60 inch-per-minute range. Does anyone have experience with a similar set-up who can tell me if Mach 3, with its backlash compensation turned on, and the basic mill with factory screws can deliver that kind of accuracy? Other than building belt-driven motor mounts, I have everything else on hand. I'm thinking that using what I have on hand is better than waiting forever until I get around to collecting everything that I want. Any ideas?

[Juka]

Originally Posted by Richards Ken, I disagree. My mill was purchased last year without CNC electronics, giving me the choice of whether to simply attach some steppers to the screws or go 'whole hog' and add ball-screws and motors. Even then, I would still have the choice of using steppers or servos.

Thank you for the support, I also have seen IH mill without any CNC components and because of that I ask my question in this thread.
Sometimes is very hard to understand terms and words in there, sorry for that.


I think first that I replace my Z-axis screw by ballscrew 20mm/5mm.
I put top of column 8Nm stepmotor with timing belt, 1:2.5 ratio ( 20-50teeth /T5).

I hate to move Z-axis for the handle up and down, when I change tool.
Handle is "very heavy" to turn and it is in bad location...

And after that if everything works, I replaced X and Y screws by ballscrews 20mm/5mm, I maybe? use 3Nm stepmotors with timing belts, 1:2.5 ratio. Not sure for the motors.

Does 3Nm motor enought to X-Y, and 8Nm to Z ?

Thank you!

[Richards]

I don't know which size motors would work best, but if I've done the conversion properly, an 8Nm motor is about 1,100 oz*in. That would be about the largest size 34 motor with which I am familiar. Then doing the math, a 4:1 ball screw X 2.5 gear ratio = 10:1 gearing. That gives us 11,000 oz*in, or about 700 in*lbs. Assuming that the weight of the Z-axis is around 250 to 300 lbs, that size motor should work fine, especially if counterweights or gas struts were also used.

I think that I would use a 4Nm or 5Nm motor for the X and the Y axes. Again, if I've done the conversion correctly that would be about the same as a 550 to 700 oz*in motor. The Oriental Motor Pk299 series of motors that I normally use range in size from 600 oz*in to 880 oz*in. Those are the size motors that I would try first. A 3Nm motor would be closer in size to the Oriental Motor PK296 series of motors. With the same 4:1 ball screw and the same 2.5:1 gear, you would have about 4,250 oz*in, or about 250 lb*in with a 3Nm motor. That is probably enough, but I would still use the larger 4Nm or 5Nm motor (because I use that size for other things).

Has anyone actually used these sized motors on the IH? How about sharing some of your experiences with the rest of us?

[SMW Precision]

Originally Posted by Richards Ken, I think Juka's question is very valid. Has anyone simply attached steppers to the factory mill without first adding ball-screws? I've been thinking of doing that very thing as a first step before going all-out with a servo/ball-screw CNC controller.

Richard,

It has been done and there are some interesting ways to minimize backlash using lead screws out there.
You still have several other problems to overcome. One is standard leadscrews are at a 10 to 1" ratio versus ballscrews normal 5 turns per inch. So a direct drive stepper could potentially run at up to 80 inches per minute with a leadscrew. Then there is the accuracy problem on movement in length with leadscrews. Either a good ground or precision rolled ballscrew is much more accurate than a lead screw. You may find +/-.003 difficult using existing leads.
Then there is the final and core problem with leadscrews is heat or friction. Many times higher resistance than a ballscrew and remember that leadscrew length changes with heat.
From my own CNC experiences going off the beaten path usually leads to a lot of hours and frustrating results. Even doing a developed kit I found challenging not particularly for mechanicals it was the electronic's to get fully stable and consistent.
Then with an operating machine there is the not so simple matter of Cad/Cam. Along with Mach3 thrown in which I really wonder if I would of ever gotten setup properly without being supplied with a developed operating file. It sounds insane my VFD took over 12 hours to program and install. Try reading a 300 page manual and working through setup. You do it once and it is not difficult but like so many things that first time takes the time.
I have vast respect for anyone who can do a DIY as a first machine. While most of us have some of the needed skill sets we are usually short in numerous areas.
After doing the IH kit I feel comfortable building or modifing other CNC machines on my own. I read groups and studied information for years before I tackled that project. Even then it has been far more difficult than I could of imagined.

[SMW Precision]

Originally Posted by Juka Thank you for the support, I also have seen IH mill without any CNC components and because of that I ask my question in this thread. Sometimes is very hard to understand terms and words in there, sorry for that. I think first that I replace my Z-axis screw by ballscrew 20mm/5mm. I put top of column 8Nm stepmotor with timing belt, 1:2.5 ratio ( 20-50teeth /T5). I hate to move Z-axis for the handle up and down, when I change tool. Handle is "very heavy" to turn and it is in bad location... And after that if everything works, I replaced X and Y screws by ballscrews 20mm/5mm, I maybe? use 3Nm stepmotors with timing belts, 1:2.5 ratio. Not sure for the motors. Does 3Nm motor enought to X-Y, and 8Nm to Z ? Thank you!

I suggest using larger steppers for X & Y-axis. For Z-axis fabricate a new connector to head collar. If you modify existing lead screw nut and mount casting will only be 3 to 4mm thick around ball nut threads and is easily broken. My replacement was made out of 75 x 75 x 75mm 6061 aluminium block then machined to fit.
Problem with using a Stepper motor for Z-axis is head will move down when stepper motor is off. Place a board on table so that it does not become dented.

[Juka]

Originally Posted by SMW Precision I suggest using larger steppers for X & Y-axis. For Z-axis fabricate a new connector to head collar. If you modify existing lead screw nut and mount casting will only be 3 to 4mm thick around ball nut threads and is easily broken.

I have one idea for that, I can show picture later tonight...
Do you have picture of yours replacement part?

Jussi

[Richards]

Ken,
I agree that using the factory installed lead screws are not ideal, nor would using them be a long term option. What I had in mind was to convert the manual IH into a CNC IH using stock mechanicals and then use that version to fabricate parts and pieces to convert to ball-screws. As I see it now, the actual work envelope would be no larger than 8" by 8". Feed speeds would be kept low, which would keep friction caused heat at a minimum. The primary use of the machine would be to drill motor mount bolt holes and recessed pockets required for stepper motor mounts. In effect, the IH would be used more like a glorified drill press than a vertical mill, but, hey, even using it in that minimal configuration is better than letting it sit idle day after day after day.

What I'm really trying to do is to find a good, practical short-term solution. My long-term plans for the mill would be to install ball-screws on all axes, linear rails and block on the Z-axis (at least) and a VFD/motor/belt drive to replace the geared motor that comes with the mill. But, as they say, baby steps; always take baby steps when you're learning to walk. By starting with things with which I have experience (stepper motors, process control computers, power supplies, programming) and taking baby steps into the areas where I have minimal experience (mechanicals), I might be able to finally reach the desired destination.

[SMW Precision]

Originally Posted by Richards Ken, I agree that using the factory installed lead screws are not ideal, nor would using them be a long term option. What I had in mind was to convert the manual IH into a CNC IH using stock mechanicals and then use that version to fabricate parts and pieces to convert to ball-screws. As I see it now, the actual work envelope would be no larger than 8" by 8". Feed speeds would be kept low, which would keep friction caused heat at a minimum. The primary use of the machine would be to drill motor mount bolt holes and recessed pockets required for stepper motor mounts. In effect, the IH would be used more like a glorified drill press than a vertical mill, but, hey, even using it in that minimal configuration is better than letting it sit idle day after day after day.

I understand your problem and desire. Most of fabrication elements you mentioned are easily done with a DRO installation. As you have found manual milling with a stock machine is a tough proposition. A lot of layout and measuring then results that are usually not very happy in the early stages. How are you going to fabricate the initial mechanicals? I also suggest if you do this conversion do only X & Y-axis. Using stock leads for z-axis movement and the weight involved appears likely to result in burned out componets. Unless you cantilever the head which is another project all by itself.
Stay away from belt driven conversion no one who has tried that has had much sucess. Using existing gears and a VFD results a machine capable at very low rpm to quite high rpm. Belt driven conversions seem to only able to run at high rpm. Unless you go are able to change belt ratio's and then you are better off with the existing gears.

[Richards]

Ken,
I already have digital readouts on the X, Y, and Z axes. Even with DRO, it's still a manual mill. I still have to stand there and crank the handles - all - day - long. For my purposes, I've found that a mill with DRO is barely usable. Ever try cutting circles manually? I finally bought a rotary table and a boring head. That was money that had to be spent to do the job manually, but with CNC, it would have only required a few keystokes.

Between by Shopbot CNC router and my manual IH, I can easily fabricate the motor mounts to add the stepper motors and belt drives to the IH.

You are correct about only doing the X and Y axes. You'll note in my first post on this tread that I mentioned adding steppers to the X and Y axes and using the Z in manual mode. If and when I do the Z-axis, I'll first add linear rails and blocks with either gas assist or counter-balance weights.

[SMW Precision]

Originally Posted by Richards Ken, I already have digital readouts on the X, Y, and Z axes. Even with DRO, it's still a manual mill. I still have to stand there and crank the handles - all - day - long. For my purposes, I've found that a mill with DRO is barely usable. Ever try cutting circles manually? I finally bought a rotary table and a boring head. That was money that had to be spent to do the job manually, but with CNC, it would have only required a few keystokes. Between by Shopbot CNC router and my manual IH, I can easily fabricate the motor mounts to add the stepper motors and belt drives to the IH. You are correct about only doing the X and Y axes. You'll note in my first post on this tread that I mentioned adding steppers to the X and Y axes and using the Z in manual mode. If and when I do the Z-axis, I'll first add linear rails and blocks with either gas assist or counter-balance weights.

Richard,

Sounds like you are doing repetative production. I agree circle cutting is difficult in manual machining without a rotary table. But even in cnc operation there are major advantages to using a rotary table as a 4th axis. If you do a cnc conversion the DRO system will make tuning Gecko's and mapping table fairly easy and/or practical.