Setting the Axis Settings for a Device
| This page is referenced by the ℛ Settings tab withing Rose Engine Butler on LinuxCNC. |
When working to tune your axis’ settings, you will use the ℛ Settings tab.
Steps for Setting the Scale
The axis' scale is used by LinuxCNC to know how to convert your distance measurement (i.e., inches, mm, or degrees) into pulses sent to a stepper motor for rotation. It is also used for speed (i.e., rpm) on the spindles.
Step 1 - Identify a Starting Scale Value
Use the table below to identify a starting scale value.
| Axis | Unit of Measure | Drive Type | Comments | ||||||||||||||||||||||||
| X | pulses / inch | (any) |
Calculating the Gearing Ratio
Calculating the Leadscrew Ratio
Calculating the Scale
Using the gearing and the leadscrew ratios to identify the starting scale value gives:
| ||||||||||||||||||||||||
| Z | pulses / inch | (any) | Follow the directions outlined for the X axis.
Do note that there will probably be differences between a cross slide and the linear drive on a curvilinear slide. You will need to ensure the values are correct for each (and they will probably be different). | ||||||||||||||||||||||||
| U, V, or W | pulses / inch | (any) | Follow the directions outlined for the X axis. | ||||||||||||||||||||||||
| B | pulses / degree | Direct or Geared | Multiply the noted value by the gearing ratio as outlined above for the X axis.
This will of course need to be adjusted using the gearing ratio:
| ||||||||||||||||||||||||
| Leadscrew | Follow the directions outlined for the X axis for a leadscrew.
If there is a gearing ratio for the driving of the leadscrew, follow those directions outlined for the X axis also. | ||||||||||||||||||||||||||
| Sp0 Sp1 | pulses / revolution | (any) | For the MDF Rose Engine stepper motor bracket designed by Jon Magill, the gearing ratio of the stepper motor’s drive pulley to the spindle’s driven pulley is 12 : 108 so the starting value will need to be multiplied by 108 ÷ 12 = 9 (9 is the value used in the ELFOS application)
This value does not have to be exact for speed, but it needs to be very exact as it also sets the indexing operations for the spindle and the rosette phaser/multipler. Steps 2 & 3 below are really key for this. |
Imperial Values for Metric Leadscrews
Note: whilst LinuxCNC will not send partial pulses, these numbers get used for calculating the number of pulses needed for other distances (e.g., 1.25” x Pulses/Inch = pulses to send to the stepper motor).
| Leadscrew | Metric | Imperial | Leadscrew | Metric | Imperial | |||||||
| Pitch | Starts | Ratio ① | Pulses / mm | Ratio ① | Pulses / Inch | Pitch | Starts | Ratio ① | Pulses / mm | Ratio ① | Pulses / Inch | |
| 1mm | 1 | 1.000 | 6,400.000 | 25.400 | 162,559.995 | 3mm | 1 | 0.333 | 2,133.333 | 8.467 | 54,186.665 | |
| 2 | 0.500 | 3,200.000 | 12.700 | 81,279.997 | 2 | 0.167 | 1,066.667 | 4.233 | 27,093.332 | |||
| 3 | 0.333 | 2,133.333 | 8.467 | 54,186.665 | 3 | 0.111 | 711.111 | 2.822 | 18,062.222 | |||
| 4 | 0.250 | 1,600.000 | 6.350 | 40,639.999 | 4 | 0.083 | 533.333 | 2.117 | 13,546.666 | |||
| 2mm | 1 | 0.500 | 3,200.00 | 12.700 | 81,279.997 | 4mm | 1 | 0.250 | 1,600.000 | 6.350 | 40,639.999 | |
| 2 | 0.250 | 1,600.000 | 6.350 | 40,639.999 | 2 | 0.125 | 800.000 | 3.175 | 20,319.999 | |||
| 3 | 0.167 | 1,066.667 | 4.233 | 27,093.332 | 3 | 0.083 | 533.333 | 2.117 | 13,546.666 | |||
| 4 | 0.125 | 800.000 | 3.175 | 20,319.999 | 4 | 0.063 | 400.000 | 1.587 | 10,160.000 | |||
① Ratio = {$ Ratio_{Leadscrew} $}
Leadscrews with 2mm pitch are commonly found. As noted in the table above, one with a single start requires 4x the number of pulses to move the same distance as a leadscrew with 4 starts. Such diversity in distances is why is is very important to first start with a small number when testing (as noted in step 2.3 below).
Step 2 - Measure the Actual Movement
The process for identifying the actual movement achieved is:
- Enable the axis you will be using.
- Setup a measuring device (i.e., a dial indicator) to identify how far the axis actually moves.
- Using the Rose Engine Butler system, set the axis to move a small distance.
- Once you are satisfied that the magnitude is right, set the movement for the axis to be a distance which makes sense for the device. A good starting point is 0.100” (especially as that is one complete revolution on a dial indicator).
- Use the measured movement in the next step.
Step 3 - Tune the Settings
The values noted above should get very close to the expected movement for a selected axis. But, it is important to ensure the observed movement matches the calculated movement. To do this,
Adjust the Scale value as necessary. This formulas below can help with determining the new values.
| {$ New Scale Setting $} | {$ =Current Scale Setting \times \frac{Planned Movement Distance}{Actual Movement Distance} $} |
An Actual Case
The value from the table above notes that the cross slide value should be
For my cross slide, the calculated value was different than the actual value. Additionally, the two axes were not the same. The values were calibrated using a dial indicator to be:
Recommendation
Once you determine the correct value for a given device, attach a label to that device with the value(s) needed. If you do not want to use a sticky label (e.g., from a Dymo label printer), then attach a string tag to the device.
For example, my Retractor has this label attached to it.
| REB O/S Scale -67,000.00 |
The "," will not be used when entering the value into the menu, but it makes it easier to ensure it is correctly entered.
REB O/S = Rose Engine Butler Operating System
| spacer line |
|
eMail comments to |