Bench test

[martyscncgarage]

the issue you would have with the sherline box is ...it won't work with Acorn.

sherline themselves are not using that box on their new machines, they offer it for sale just as a replacement for older system with failed drive boxes.

they are using these on their new machines.

sherline_new.PNG

John and karl at Sherline have told me it will work. John just told me he has an Acorn sherline mill runing with no issues.

Karl tells me the new industrial controller the are working in is going to be like 5K retail.

If I were to go the route your suggesting what would the cost be? And what is involved can you give me an idea?

You already have them, you might as well try them and report back.
Marty

[cnckeith]

all i can tell you is i had one of those boxes on the bench for a month and yes i could turn motors, but it was not good performance. this is like putting bias ply tires on a modern car,and complaining they don't stop, start or go around corners... why would you? when for same or less money you could have much better gear and smooth performance.

[martyscncgarage]

Bottom line is they are OLD technology.
If you own them, have them, hook them up and prove them to yourself and let us know what you find out.

I won't build a machine anymore with open loop steppers. Closed loop drives/motors are much better and the way to go moving forward. They are not as expensive as they used to be.

Marty

[BillB]

So marty your saying sevo motors right?

Can you guys give me an idea of cost and drives you recommend? I did ask about this with John at sherline and he recommended Geck G203V drives IF I was going to go that way, but did tell me I would need to rewire all servos.

Keith when you say not good performance can you give me a bit more detail as it relates to actually making parts?

[Richards]

There have been a lot of threads debating which type of motor to use.

An open loop stepper has no feedback, so if it stalls the Acorn won't know that there is a problem. It can be used. It's cheap. But, to be safe, you'll have to use a stepper that is larger than necessary because there is no feedback.

A closed loop stepper is better. It has feedback so it can send a fault signal to the Acorn if it stalls.

Servos are normally high performance motors. The ClearPath servos that I use output a fault signal to the Acorn if they stall or lag too much. The ones that I use cost between $260 and $400 each. To me, they're well worth the price.

I stepper motor's performance depends on its inductance and on the driver you use. The lower the inductance, the "snappier" the performance. I've always used steppers with inductance ratings of 1.4mH to 2.0mH. I've run extensive tests using Oriental Motor steppers and the Geckodrive G203v stepper driver. Gary Campbell convinced me to try Leadshine stepper drivers. I've switched to the DM542 driver. It fits the drawer full of NEMA 23 motors that I have on hand and it costs 1/6th the price of the G203v. The Leadshine drives allow the user to select the number of steps per revolution whereas the G203v restricts you to 2,000 steps per revolutuion with a 1.8-degree stepper.

Stepper motors run hot - very hot if their holding power is matched to the job. My servo motors rarely get warm enough to notice. A stepper motor's torque drops off rapidly the faster the motor goes. The ClearPath servos hold their torque to 2,500 RPM on the 2321S-RLN and 4,000 RPM on the 2310S-RLN.

Some people want to build a minimal controller with the least cost possible. If it meets their needs, then that is all that they need. I prefer to build to a higher level so that the first "real" job doesn't bog down the machine. The means that my minimum cost for a "bar-bones" open-loop stepper controller is $1,500 to $2,000. The same controller with ClearPath servos is $2,500 to $3,000. My goal is to match the controller's ability to the needs of the mill, lathe, or router. My little Taig mill runs just fine with open loop steppers. I have some ClearPath servos and an IPC-5 power supply sitting on the bench that I'll install on the Taig someday. The truth is that, without substantial modifications to the Taig's mechanics, the extra power and performance of the servos would be wasted on the stock Taig. The Taig is an incredible machine when I work within its limitations. The goal is to match electronics to mechanics so that they all work in harmony.

[martyscncgarage]

Closed loop steppers are about $150 an axis.
Keith already showed you what Sherline is testing:
https://www.cnc4pc.com/nema-23-2-0-n-m- ... motor.html

I have used these on several Emco PC5 lathes:
https://www.automationtechnologiesinc.c ... e-kl-5080h

Like I said previously, if you already have the motors and drive box, test it. If you can return them and buy a couple of hybrid closed loop steppers, that's what I would do...

Marty

[BillB]

Great input guys, thank you. So let me throw this into the mix and see what you guys think. A bit of background on my needs.

I did not know there was such a thing as a closed-loop stepper? IF it loses steps or has a power failure does it remember where it is and pick up where it left off Or crashed?

The need for a small low cost but capable cnc lathe is to make 1, 2 opp part that is just under .375 OD in 314 stainless, simple features, 1 ID bore, an M5 thread on the end, with a small press-fit end cap and spring loaded push-button, its a small bleeder valve that screws into the top of a motorcycle fork (dirtbike). 1st op is the turning work, 2nd op is 4th axis millwork on the Sherline mill with the rotary table to create hex flats to facilitate tightening into the fork cap.

IF I could do it right now I would buy a Tormach 15L but its out of the equation right now to get me started.

The primary goal is that I'm currently working on is buying a used Tormach 770M OR 1100M OR even an MX if I can find the right deal, but I that probably will not happen with what I have to spend.

So these 2 little machines are really just 1/2 the equation. If my product has a market I will need to do short-run production on them, But that is a whole other discussion and I cross that bridge when I get there. The brunt of the work for this product is millwork on the Tormach in 6061. I just gotta get started somewhere kinda story. Been trying to make this happen for almost 3 years now, I have multiple concepts and products in development so this product is not one trick make or break type of thing. The big hurdle has always been the $$$ aspect of it. I'm not doing a DYI for the fun of it, It is simply to save me some money, BUT believe me, I'm questioning this decision as I get deeper into it. Especially considering changing gears and revamping my whole plan IF I were to go with another drive OR even change the motors. It boils down to all the time spent doing the build is time I could be doing CAD and CAM and actually getting closer to final designs and making parts. Im actually laid up right now after shoulder surgery at home from my regular gig building a custom controller BUT I would really rather be finalizing my CAD, but it is what it is.

One last bit of info. I run a Tormach 440 and a Zenbot at my current gig. I gotta admit I HATE when the dam thing crashes, stalls, loses steps etc. Happens a lot on both machines because I don't run parts every day and when you don't you make small mistakes. It's a real PIA! SO if If I can find a MX Tormach that is what I would like but not sure it's in the budget, either way, I would eventually upgrade it to an MX with the servos to close the loop. I am questing how important it is to have a closed system on these Sherline machines??? Small parts, light cuts, etc just seems like its not as important????? on a small machine???? I don't have huge expectations Im gonna be pumping out a hundred parts a day. Im just trying to get started.

Anyways hope you guys would like to shed some new light IF anything changes on your input based on knowing the need. I do really appreciate your time and input, I tend to write a lot. LOL thanks guys

[tblough]

IF it loses steps or has a power failure does it remember where it is and pick up where it left off Or crashed?

Nope. Still open-loop to the acorn. Benefit of closed loop motors is they can tell the control if they have encountered a problem.

I run a Tormach 440 and a Zenbot at my current gig. I gotta admit I HATE when the dam thing crashes, stalls, loses steps ...

Looks like you are familiar with the problems of open-loop.

Happens I am questing how important it is to have a closed system on these Sherline machines??? Small parts, light cuts, etc just seems like its not as important????? on a small machine????

Light cuts, slow feedrates, easy materials all help to minimize the issues with open-loop.

[martyscncgarage]

Using closed loop drives/motors will stop the control if they get out of position. You may be able to rehome, restart the program and recover.
The motors I suggested should have plenty of power for the Sherline machine.

As for the parts you want to do, as Tom mentioned go light on the feeds and speeds. Prove out a part or two and then have them produced. I think you will struggle a bit using the Sherline size machines, but you won't know until you try. Remember the sherline spindle motor is a bit small, DC brushed motor.

Good luck.
Marty