I’m working up to making an Arduino controlled stepper motor driven cross-feed vise for my drill press. I have several stepper motors. Now I’m looking for a supplier for gears to fit the stepper motors and the cross feed shafts of my vise.
The back story. I have been using a small cross feed vise on my drill press to do a variety of small milling operations in wood. Several months ago I decided that since a lot of set up time was involved it made sense to do a batch of small jobs at once. This means I operated the lengthwise knob many thousands of times over a day and a bit. The next day my thumb had a crick, trigger thumb. The next day I could not move the last joint on my thumb at all. I could not grip anything with my right hand. The implications are far reaching. I could not release the handbrake on my car, I could not open a door knob, I could not open a jar lid. I could hardly hold a drinking glass. Etc., etc. I got a referral for physio but the person was on extended leave so that never happened. There were so many things I could not do with that hand. Then a death in the family had me away for over a month. When I wasn’t doing anything my thumb began to recover. After about 5 months my thumb was working again and I don’t want to go through that again. I put a rubber rim on the knob in question and used a flat stick to push on the rubber to turn the knob without having to grip the knob. But it eventually occurred to me that a stepper motor could do the job. Two stepper motors and a joystick.
Although I have hundreds of gears for many things taken apart not single one fits the stepper motors. Besides that I need two pinion gears the same and two larger gears to match. I figure I need the gear reduction to give some extra power to move the vise left-right & front-rear. I have seen on Amazon stepper motors that cone with a feed screw as the main shaft. That looks good but I’m not sure about how much load it could take.
The left-right movement is the longest about 200mm. The front to back range is about 55mm.
Here is a picture of the thing at work. I need to keep the free play tightened up to eliminate slack so there is some tension to overcome.
I would welcome any ideas or suggestions. Suppliers of gears , etc.
3d printed gears actually work really well, at least from quality 3d printers. I 3d printed a “prototype” gear for the ELS system for my lathe in the middle of last year, thinking that I’d cut one from metal, and I’ve kept the 3d printed one instead. Do you have a 3d printer?
Hello Brian
Here’s my ‘two penneth’. Looking at your picture … have you considered putting a handle on the lengthwise knob, just like the cross slide knob?
If so and you have rejected it and you want to continue down the stepper motor route then I’m sure one of the larger stepper motors (nema 34 and above) will have sufficient torque for your timber machining without the need for gearing. You could control the feed and speed with an arduino and a couple of potentiometers.
Another option, more expensive I’ll admit, is one of the small CNC mills which can easily handle your 255x55mm machining range, my own small mill machining area is 310 in the X direction and 390 in the Y direction and is open both ends of Y so can take much longer work pieces.
There’s a general recommendation not to use drill presses for milling, but I’d think that a sharp end mill in wood probably is probably fine here. But that also means that you don’t want very much torque at all, and using a small stepper motor with low torque would actually be a feature for not hurting the drill press bearings.
You might want to use a timing belt and timing belt gears, instead of gears that mesh directly. You will still have some backlash on the lead screw in your table but I doubt that much backlash matters in wood.
Again the 3d printing idea: You could 3d print a replacement for the table end block that the handwheel is mounted in, and also has a mount for the stepper motor integrated into it, and using a belt gives you more flexibility in placing the motor.
Most inexpensive A axes for mills use a timing belt for this purpose.
I’m already looking at CNC for standardized parts. But I often have need for one-off little jobs that look more sensible to use hand work.
The end knob came with a crank handle but I found it introduced an up/down torque on the table which produced wavy results, so I removed the crank.
My work area is seldom more than 100x30mm x10mm deep.
It doesn’t need to go very fast. It usually takes me a couple of hours to do this job with manual feed.
I am usually using a 4mm flat end mill for what I’m doing. I advance fairly slowly so I’m not very worried about applying much side force on the spindle bearings.
Using the stepper motors is not to speed up the process. It is just to eliminate the repetitive stress on my hands. It takes me a couple of hours to do the job by hand.
The suggestion to use toothed belts is a good one. I have already made things with toothed belts and the associated pulleys and found I could get quite a range of hole diameters on Amazon.
I’m not thinking about torque applied to the spindle bearings but torque required to advance the table movements. I can feel how much force is required to move the table without any cutter in contact. I will have to regulate the motor speed to keep the advance rate slow. Most of the torque will be to overcome friction in the table movements. I will advance slowly so as not to load the cutter or apply too much side force to the spindle bearings.
Things are progressing. I’m accumulating the necessary parts. I have ordered some toothed belt pulleys. My stepper motors have 5mm shafts but my cross-slide screw shafts are 5/16” so I will have to drill them out from the nearest smaller metric size.
I have the Arduino board but the shield has not yet arrived. I realized a problem now that I have received the joystick controller. It is spring loaded to self-centre. I need to get rid of the springs. Having the cutter zoom back to the starting point may be a problem, especially if it plows through an as yet unmilled area. The shaft of the joystick is much too short and the travel too short. It would be difficult to control. I would expect that when I remove my hand from the joystick that everything will remain in the same place. I notice when searching online for joystick controllers that many of the ones that look promising have micro switches rather than potentiometers. But maybe there is another way to control the stepper motors besides the potentiometer method. Perhaps with the micro switch system it would simply mean when I return to the centre position is just means “do nothing”. It seems to be, though, that the joystick with potentiometers would be more nuanced when heading off at some angle between 0 & 90°.
Here is a photo of one of the types of jobs I do with this milling table. This is an irregular shaped polished agate inset on the top of one of my wooden flutes. The bottom of the agate has been flattened. I’m making the inset at about 2mm depth. While operating the two cross feed knobs manually it is too easy to accidentally turn one knob the wrong direction and run “out of bounds” which is untidy. I go very slowly. I start by making the outline of the agate on the wood with an Xacto knife blade. Then mill out the inside space slowly and carefully. Even so, I have yet to do one that I thought was done perfectly.
I think I have all the parts I need now. Here’s the milling table so far with the two stepper motors installed. I’m much more comfortable with cobbling together mechanical parts than wiring stepper motors. Using timing belts instead of gears was a good suggestion so that’s what I did. I have a 16 tooth pinion going to a 40 tooth drive pulley. Everything feels smooth running, by hand. I also added a sealed ball bearing on each lead screw shaft where there was only a bushing.
My next issue is wiring the stepper motors. I have been unsuccessful in finding any data online about these motors. They are 5 wire motors. The only real data I have is that each winding is 75 ohms. No info on current or voltage ratings. I believe these stepper motors came from a couple of 17” Epson printers I took apart.
You can see that black must be the centre tap for both windings. But because the centre taps are joined internally I can’t be sure about how the windings are laid out because they all connect through the same centre tap. Unless I can interpret something by the wire layout of the plug.
Any suggestions for figuring out more details about the coil winding connections?
I have an Arduino UNO R3 board, plus the stepper motor shield, DiGiYes CNC shield V3.0, and some TMC2208 stepper motor drivers and a spring loaded joy stick controller. Look OK so far? I also have several power supplies to experiment with.
Usually you just control those with an H-bridge motor controller, and arduino libraries exist to support that. But yeah they won’t work with the TMC2208s.
New bipolar steppers are cheap — though I do hope on your behalf that they are the same frame as the ones you designed for. NEMA17 are the most common size. What are the physical measurements of the motors you have now?
I appreciate your help with this.
Yes, these motors appear to be standard Nema 17 size. 42.37mm square at the mounting face and the motors are 33mm long. I have other stepper motors but they are all with 4mm shaft and the two I’m using are 5mm shaft and the pinion toothed belt pulleys are also 5 mm.
I have some other smaller (shorter) Nema 17 motors with 4 wires but 4mm shaft and bushings instead of roller bearings.
I also have the original A4988 stepper motor drivers that came with the motor shield.
I got urgent security warnings when I followed the link for stepper motor info. Everything but air raid sirens. It was ok when I turned my VPN back on.
I did not realize my drivers were not suitable for the motors I have. All the parts are cheap enough. Eventually I will end up with a compatible set of parts.
Fortunately, the 5mm shaft is the norm for 3D printers; it’s probably related to the fact that it was easy to find 5mm timing pulleys, also used in lots of 3D printers. Here’s a random example (not a specific recommendation) showing that:
Those will all have proper ball bearings inside. Including if you have any friends with dead or obsolete 3D printers that they want to part out.
The A4988 drivers, like the TMC drivers, won’t work with the unipolar steppers. The TMC drivers are better in every way.
(I don’t know how much electronics background you have, but the A4988 have a problem with current sense around crossover that is somewhat like what you get in a class AB amp if you don’t bias the input to the power transistors somehow; the current sense in the A4988 doesn’t account for the diode drop in the driving transistors. The “TL smoother” was invented to compensate on the output side, much less efficiently, to work around this problem. The TMCs don’t have this design defect. I see no reason to ever use an A4988 or similar stepper drivers now that TMC drivers are cheap and readily available.)
I found that motor on Amazon.ca at $24. It’s bigger than the motors I have (longer) at 48mm. Mine is 33mm.
How does this one look? SIMAX3D Nema 17 stepper motor 42x40.
Anyhow, I get the idea. But it would simplify things if the Arduino stuff snd the stepper motors could run from the same power supply. So a 5vdc motor could be run from the 5V Arduino power supply if it had sufficient current. For 2 motors.
Examining the specs of several motors I found voltage ratings 1.5, 3.6, 5, 7.5, 12, 24. It would be handy if I could use a power supply I already have, like 12v. But running from one 5V supply has its attraction too.
Actually, I studied electronics just after high school. But take into account that was 1970 and they were still teaching vacuum tube circuits at that time. I’ve been an electronics hobbyist on and off, mostly audio circuits, but in between I forget stuff.
The last time I made an Arduino project was 15 years ago to control a motor for a camera glide rail for a 6-1/4 hour time lapse sequence in which the camera panned and rotated to track the incoming tide in the Bay of Fundy.
I especially enjoy the feeling when parts from disparate sources somehow fit together as if destiny intended it, like a 55mm diameter gear from an Epson printer exactly mating with a flat roller thrust bearing from a 1969 Austin Mini automatic transmission to support the weight of the rotating camera head plus camera. And I only had to keep that bearing in stock for 40 years to find a use for it.
Totally depends on how much torque you need. Trade-off between not accidentally overloading bearings and skipping steps. Since you are driving this with an MPG or equivalent, you probably care less about skipped steps? But they exist in myriad sizes, and the tradeoff is primarily torque. I’ve estimated necessary torque with a wrench and a pull scale in the past. For you, you can probably manage torque by how much you tighten the gibs on your table.
You don’t actually want to run the stepper off 5V even if it says it is rated for 5V. That’s max current through it. Use at least 12V; 3D printers where they want to move fast mostly use 24V these days, even if the stepper is rated at, say, 2V. The real rating is the current rating; the voltage rating is just the voltage that will draw the rated current if you apply it across one of the coils directly, with a low impedance source (capable of supplying arbitrary current at that voltage relative to the motor).
You set the current limit on the stepper driver, and then it uses PWM (pulse width modulation) to limit the current to keep the stepper from overheating (which destroys the otherwise permanent magnets in them by taking them past their curie temperature). The steppers should get warm.
So just feed 12V to the arduino (which should have a 12V-capable regulator) and to the motor shield, and set the right current for whatever stepper motors you buy.
Are you saying I should connect 12V to the Arduino 5V input? Would it not be better to connect 5V to the Arduino Uni board and 12V to the shield? I know I said it would be tidier to run just one power supply but a regular 5V supply is not much of a hardship.
I had not thought of trying to measure the torque required to move the table.
On my old 3018 machine I remember being surprised at how much force the stepper motors applied when accidentally run to the travel limits. The milling table certainly doesn’t require that degree of force.
On my Creality Falcon the amount o force required to move the x or y travel seems to require more force than moving the milling table.
I just made a test to try to measure the force required to move the milling table. The feed screw shaft (6mm) has a hole drilled through for a roll pin to secure the original winding knob. I wound the shaft around a few turns until I felt I was against the maximum resistance, with the roll pin hole horizontal. I inserted a 2mm rod through the hole and hung the original winding knob (29.9 grams) on the wire by its roll pin hole. Then slid the knob farther along the rod away from centre. At 143mm the weight of the knob was enough to rotate the shaft. I tried that a few times. Sometimes I had to slide out to 145mm before it started to swing down. Not sure how to convert that to a usable torque value.
Pinching the shaft between thumb and forefinger I can rotate the shaft easily enough but I have to pinch hard enough to get a grip.
The original winding knob had a crank at 15.5mm from centre and that was easy enough to wind along. Not any harder than winding a fishing reel knob with no fish on the line. It’s hard to think up everyday tasks to compare torque. Not as much force as a manual crank operated pencil sharpener when sharpening a pencil.
In addition my toothed belt pulleys add additional reduction in force required. 16 tooth pinion and 40 tooth drive pulley.
Approximate is good enough; it’s likely to be different at different table locations anyway. The rod has some weight too. But (in round numbers) 30g at 150mm is 450 g/cm (gf•cm) which is about 0.044 N•m which is not much! Here’s a thin (thus lower-torque) pancake stepper for $10 (again an example not a recommendation) with 17 N•cm (0.17 N•m) — over 4 times what you need, not even counting your timing belt reduction!
Therefore, nearly any NEMA17 frame bipolar stepper you harvest from a dead 3D printer, or buy cheaply, will be fine. And since you aren’t making a CNC machine, a few skipped steps won’t hurt anything.
