High Accuracy Dovetail Stepper Slide

##28BYJ-48 Mechanical Actuator #3
I thought it would be cool to see what kind of Mechanical Actuators we could make using the 28BYJ-48 stepper motor and mostly 3D printed parts. The 28BYJ-48 is the motor that comes with most Arduino kits. It's a 5v dc motor with a max rpm of 15 and is capable of around 4 oz force/in of torque. You can get these motors with the driver for around $2 each.

##Dovetail Stepper Slide

This version is similar to the previous slide with the exception of two major changes. It’s no longer directly driven but instead there is an integral bearing made with standard .177 (4.5mm) caliber steel BB’s. There was some inaccuracy built into the previous design as its driven directly by the stepper motor and there is some play in its internal gearing. This remix resolves the issue by utilizing a bearing to handle the thrust loads.

I also added an anti-backlash feature to the threads on the carriage to allow for adjustment to reduce the amount of backlash between the nut and the drive screw. It actually works pretty good! Just tighten the anti-backlash set screw until it removes the backlash but still rotates freely.

If backlash is not an issue I would suggest going with the original slide as it requires fewer parts

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Dovetails slides are not really good at long travels or fast speeds but they are very accurate with the addition of a gib to the dovetail way allows for adjustment of the clearances between the ways and the carriage reducing backlash. This is a direct drive slide as the drive screw is clamped directly to the shaft of the stepper motor. The downside to this is that there is a lot of slop in the motors shaft as it’s not designed to carry an axial load. The v3 slide I plan on making will address axial loads as it will use an integral bearing flange.

The max RPM of the motor is 15, the pitch of the drive screw is .5" so the max speed will be 7.5" per minute. The motor can move roughly 7 lbs of weight on the carriage. The load capacity and life cycle can be greatly increased by using grease on both the drive screw and the way. The video shows the repeatability of the slide, after running for a few hours it was only .01" off location.

The mounting holes on the base, carriage, and the endplate all match up so multiple slide assemblies can be bolted together to make a two or three axis cartesian system.

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##Required Components
- M3 Nut (14x)
- M3 SHCS x 10mm lg. (4x)
- M3 FHCS x 10mm lg. (2x)
- M3 SHSS x 16mm lg. (3x)
- M3 SHSS x 25mm lg. (1x)
- .177 BB’s (8x)
- 28BYJ-48 Stepper Motor

Here is my amazon affiliate link to a set of five of these stepper motors and drivers. They are a little more expensive from amazon but you will get them a lot quicker.
https://amzn.to/2KJI6yz

##Assembly
First put the screw in the carriage and set the anti-backlash screw to the desired fit. Then remove the screw from the carriage and place the carriage in the way with the gib key and use the set screws to adjust for the proper fit. Once the fits are correct you can build the screw into the bearing flange.

##Update
3/12/18 - When I first uploaded the files I accidently put in a triple lead screw instead of a double. The new file; "DT-V3-SCREW-1_2-DBL.STL", has a double lead to match that on the carriage.

https://youtu.be/Yq39Y9Z1tzk
https://youtu.be/WCNtUWE9mQ0