Driving the MDF Rose Engine with a Stepper Motor
There has been a lot of interest recently in the modifications a few of us have made to drive our rose engine spindles with stepper motors.
If you want to modify your MDF rose engine for a stepper, you’ll need to make some modifications to the lathe first.
MDF Headstock Modifications drawing – The cutout on my headstock is larger than needed, but pics show the general idea below. The drawing has a more minimal size opening you can cut.
MDF Lathe Base Modifications drawing
Stepper Motor Mounting Plate layout drawing – If you have one of the stepper motor mounting plates I’ve made, but your lathe is slightly modified or different, you can print the layout of the motor plate and use it to assess possible mounting options on your lathe:
Touchscreen:
– Most of use have standardized on the Nextion Enhanced NX4827K043
– Generic 4.3'' HMI Touch Display, Model: IM160511006
– ~$50USD
Software, PCB and Other Hardware – Ed French has set up a Github repository with:
– The current Teensy code, both in hex (compiled) and source code (for the Arduino IDE)
– The Nextion touchscreen code, both in compiled form .tft file) and source (.HMI file)
– The Gerber files for the current four-axis PCB
– 3D printable files for a Nextion touchscreen enclosure
– 3D printer files for the two GT2-5mm pitch 12T and 108T pulleys
Details to be added soon...
Printed Circuit Board & Bill of Materials (BOM)
– Printed Circuit Boards – The current 4 driver board is shared on OSHPark, minimum order 3 boards
– Connectors & sockets – TBD
– Teensy 3.5 – The current builds are using the Teensy 3.5 from PJRC.com
– Stepper Driver Options – The two main options are DRV8825 drivers from Pololu or DM542T drivers from StepperOnline
– Power Supplies – Motor power supply is at 24V for best efficiency, and the current rating for the power supply must be at least the sum of your motors (up to 4 supported by the current board), plus some margin of safety overhead. Numerous options exist to provide 5V logic power to the main board and Nextion touchscreen, either from a separate 5V supply, or using a DC-DC converter on the main PCB, or as a separate external component.
– Enclosure – A 3D printable enclosure for the touchscreen is on the Github page above. Other options are work in progress.
— Added “draft” stepper motor & driver info below — 072619
For the spindle on the MDF rose engines we have been using:
- NEMA 23 size stepper motors
- 1.8° or 200 steps per revolution motors
- bipolar (4 wire), or bipolar-series (8 wire) motors
- with about 270 oz. in. (1.9 Nm) +/- of torque
- 1/4” (6.35mm) shafts, either single or dual-shaft
(FYI: 290 oz-in ~= 2 Nm ~= 2,040 g-cm ~= 18 lb-in ~= 1.5 lb-ft)
Look at the specs carefully before you buy.
Other things to note:
- 4 wire motors can only be used at their rated current (or less)
- 8 wire motors can have the two center wires connected together to run in "bipolar series" mode, which typically cuts the heated current in half, but also reduces the acceleration and top RPMs, which is usually unimportant in our application
- ignore the voltage ratings for the motors, they are meaningless in our application, we will always drive them with 24V +/- power supplies, using current-limiting "drivers"
- lower inductance for a given motor translates to faster acceleration and higher RPMs, but is relatively unimportant in our slow speed application
- the small drivers mounted in the printed circuit board sockets ("on-board" Pololu DRV8825's) are limited to about 2.2A maximum
- external (off-board) drivers, like the DM542Ts can be used for any motor rated from 1A to 4.2A (by setting DIP switches)
Here are a few example motors (in no particular order or preference):
Nema 23 Bipolar 1.8deg 1.9Nm (269oz.in) 3A 3.36V 57x57x76mm 4 Wires
SKU: 23HS30-3004S
$22.64
Nema 23 Bipolar 1.8deg 1.9Nm (269oz.in) 2.8A 3.2V 57x57x76mm 4 Wires
SKU: 23HS30-2804S
$22.64
NEMA23 282oz/in 1/4″ Single Shaft Stepper Motor
KL23H276-30-4A
Price $25.95
NEMA23 282oz/in 3A Stepper Motor 1/4” Single shaft
Note: This is an 8-wire motor, used in "bipolar series" wiring, to run at 2.1A instead of 4.2A.
https://www.automationtechnologiesinc.com/products-page/nema-23/nema23-282ozin-3a-stepper-motor-%C2%BC”-single-shaft-kl23h276-30-8a/
KL23H276-30-8A
Price $25.95
NEMA23 282oz/in 3A Stepper Motor 1/4" Dual shaft
Note: This is a dual-shaft, 8-wire motor, used in "bipolar series" wiring, to run at 2.1A instead of 4.2A.
KL23H276-30-8B
Price $25.95
NEMA23 270oz/in 2.8A 1/4″ Dual Shaft Stepper Motor
This 270oz/in NEMA23 stepper motor is well suited to medium sized motion control projects of all types.
KL23H276-28-4B
Price $25.95
NEMA23 185oz/in 3A Stepper Motor ¼” Dual shaft
Note: This is an 8-wire motor, used in "bipolar series" wiring, to run at 1.5A instead of 3A.
KL23H256-21-8B
Price $21.99
Here are two stepper motor drivers we have been using:
DRV8825 Stepper Motor Driver Carrier, High Current (Header Pins Soldered)
https://www.pololu.com/product/2982
Price: $10.45
StepperOnline DM542T
Digital Stepper Driver 1.0-4.2A 20-50VDC for Nema 17, 23, 24 Stepper Motor
SKU: DM542T Price: $30.25 (from China) $35.07 (Free Shipping) $37.17 (from US) $38.99 (Amazon Prime)
This page is intended to help people with information on improvements and modifications to the original MDF Rose Engine design and plans.
Resources
Outdated Info...
Visit the Rose Engine and Spindle and Axis project page on Github site for the latest project details, links and files.