I would like to CNC one day but one of my favorite things about machining is finding ways to complete operations manually and accurately. I have wanted a power feed for a while and after learning what I have about steppers and arduino, I thought I could make a better power feed for the same cost. I think the full CNC after all 3 motors, 3 drivers, power supply(ies?), ball screws, PC to run it, mounts, wiring, etc, will cost $600 - $700 which is a good bit more than I have to spend at the moment. The plan is to use this machine manually for another year or two then get a G0704 or similar and do a full CNC conversion on that one.
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Practicality Of Arduino Controlled Precision Power Feed?
- Thread starter shooter123456
- Start date
Looks like the available packages are more than double the price, run slower, and can't be precisely controlled. I think I will go ahead with it since at the very least, I can easily build one that will feed 0-12 IPM and I will get the precise control. The plan is to be able to input a value on the touch screen and have the table jog to that position. If its off a few thousandths by the DRO, ill just send a few more steps.
Regarding the spindle speed, the machine has no tach and its tough to set it to the same speed repeatably. I have been looking for ways to control it better and faster and someone elsewhere said the easiest way was a $5 stepper on the pot then select a few positions and determine the speed, and use a few buttons to control it accurately and quickly. I think installing a tach and stepper control would take about the same amount of effort as just the tach.
Do you know of the best way to mount a stepper to the Z axis? I have seen them mounted to the head or column with a block and a lead screw or on the fine feed with a pulley system. Not sure what the pros and cons of each are.
Shooter - Knowing what you want to achieve, I'd certainly agree with you that the LMS power feed is not quite the right answer. For one thing, it doesn't have a rapid traverse button. For another, as it's now on closeout and about to be discontinued, replacement parts or support might become an issue. OK, closeout price is pretty good, compared with the original price. But as you said, the Arduino parts will come out to considerably less. Plus, you get to feed what sounds like a passion of yours!!!
PS - I have one of these LMS table feeds on my HF mini-mill (same as yours), so I'm pretty familiar with it. I modified it to add rapid traverse (basically a momentary switch across the pot wiper). I also moved the electronics to a remote enclosure. This lowers the profile of what hangs off the end of the table, allows me to quickly and reproducibly mount and dismount the motor (it's more difficult to crank the table with the motor attached!), and keeps (conductive!) swarf away from rapidly moving electrons.
As for powering the Z axis, I'd avoid using the existing knob. There are way too many moving parts and linkages for any kind of accuracy. You've probably noticed this if you've ever compared the scale reading on the Z axis knob to what the DRO says. A separate leadscrew or ball screw is the only way to get any decent results.
Good luck ... and be sure to post the details of your final design!
PS - I have one of these LMS table feeds on my HF mini-mill (same as yours), so I'm pretty familiar with it. I modified it to add rapid traverse (basically a momentary switch across the pot wiper). I also moved the electronics to a remote enclosure. This lowers the profile of what hangs off the end of the table, allows me to quickly and reproducibly mount and dismount the motor (it's more difficult to crank the table with the motor attached!), and keeps (conductive!) swarf away from rapidly moving electrons.
As for powering the Z axis, I'd avoid using the existing knob. There are way too many moving parts and linkages for any kind of accuracy. You've probably noticed this if you've ever compared the scale reading on the Z axis knob to what the DRO says. A separate leadscrew or ball screw is the only way to get any decent results.
Good luck ... and be sure to post the details of your final design!
I appreciate the response. I think LMS discontinued it in favor of a different one here: http://www.littlemachineshop.com/products/product_view.php?ProductID=3387&category=2 which runs $205.
I am a fan of tinkering and adding features to my machines. The end result isn't just to have a power feed, but to make something new as well, I hope that qualifies for a passion! Im sure a lot of people know what its like to start working at 6 and have 7 hours go by in the blink of an eye.
Regarding the Z axis, I will probably put that off for a while. I think I can make a lead screw pretty easily and inexpensively in the future then rig up a nut/block to attach to the head to get it moving. Ill add that to the list of projects but ill stick to manual for now.
Ill be sure to take pictures along the way and post some documentation and the results I achieve.
The problem you'll run into is that the simple stepper driver boards for Arduinos can't handle the rates you're looking for. Stepper motors have a LOT of induction, and even though they only drop a couple volts holding still, getting enough current flowing fast enough to maintain a decent step rate requires some sophisticated electronics and a lot of voltage.
Because of the induction, in order to get the current to make a nice pulsing square wave, you have to supply a voltage that looks like sharp spikes with exponential decay. That's what drivers like the Geckos handle for you, and you'll have to have something like that in your setup.
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Because of the induction, in order to get the current to make a nice pulsing square wave, you have to supply a voltage that looks like sharp spikes with exponential decay. That's what drivers like the Geckos handle for you, and you'll have to have something like that in your setup.
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You are absolutely right. I have been looking into specifics based on what I have learned recently and most of the arduino boards can only handle 36 V. Now I am looking into an interface between the arduino and a proper stepper driver or lowering my expectations. I think at 36 V I should be able to run 75 IPM with the rapids and roughly 20 IPM with the cuts. I haven't worked out all the details yet but thats what this research phase is for.
I used an automation direct stepper driver paired with an arduino mini for my power feed. I used the arduino to enable the drive, rapid and set direction based on a few switches as inputs. I also mapped a pot to pulse outputs for speed. I don't know what size motor I used, but it ended up being under powered- it still is. I don't have it usefully installed. I need to gear it down to get the torque I need. I don't know what size it is, and I'm across the country from it right now so I can't look. I'll get back to you on that. My mill is a rong fu, don't know which model, knockoff. It was a great learning experience on multiple fronts!
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