I could use some help

fcwilt

@fcwilt I have an inches to metric calculator doing that for me.

No I mean if the bed actually moved 18 inches which is 457.2 mm the DWC should read the same 457.2 mm, assuming the DWC was reading 0 when you started. Which is should have since you execute G92 Y0.

Frederick

A Former User

@fcwilt maybe the question is, what is the relationship between DWC reporting 350, and my metal measuring stick reporting 18 inches?

fcwilt

@mac said in I could use some help:

@fcwilt maybe the question is, what is the relationship between DWC reporting 350, and my metal measuring stick reporting 18 inches?

When converting inches to mm the DWC should read out what you measured.

Frederick

A Former User

@fcwilt we have to subtract the depth of the bed!!!!! Which is 220. I'm getting 247?

A Former User

@fcwilt so, how is 247 350?

A Former User

@fcwilt 467-350 is 117. I wonder where that's coming from?

A Former User

@fcwilt the back of the bed travelled 247 mm. The front did to. But DWC measured 350.0? That's interesting.

A Former User

@fcwilt if DWC is at the center of the bed, could it travel 350.0?

fcwilt

@mac said in I could use some help:

@fcwilt we have to subtract the depth of the bed!!!!! Which is 220. I'm getting 247?

Well, 247 is not 350.

I think you may not be measuring movement with the ruler correctly.

For instance you could measure where the front edge of the bed is, make the move of say 100mm, then measure where the front edge of the bed is then.

BUT the ruler would have fixed in position so it could not move for the measurement to be accurate.

A 100mm move using the Y jogging buttons should move the front edge exactly 100 mm.

IF IT DOES NOT then the value of 100 in M92 for Y is wrong.

If the 247 is correct then the value in M92 would be closer to 70 then 100. I'm not sure about that value but it least it is an integer.

Frederick

A Former User

@fcwilt the END STOP is 2 and a 1/4 inches forwards of where the back of the bed started. That's 58mm, times 2 is 117 mm. 467mm minus 350mm is 117mm, divided by 2 is 58mm forwards from the back endstop, and 58 mm back from the front edge of the bed when it's fully forwards.

A Former User

@DWC is measuring from Endstop to Endstop.

A Former User

@fcwilt Hey, Frederick, I gotta turn in. 4:30 comes awfully early tomorrow morning.

This was a great session. I think we accomplished A LOT.

If you have time tomorrow, let's try some more, okay?

fcwilt

@mac said in I could use some help:

@fcwilt Hey, Frederick, I gotta turn in. 4:30 comes awfully early tomorrow morning.

This was a great session. I think we accomplished A LOT.

If you have time tomorrow, let's try some more, okay?

Glad to and I agree it's time to sleep.

Good night, mac.

A Former User

@fcwilt thanks again!

droftarts

@mac Wow, this thread is a journey.

Another way to get the steps per mm correct is to know what type of belt you have, and count the number of teeth on the pulley. If there's no marking on belt, measure the distance between 10 teeth on the belt, in millimetres, then divide by 10 to get the tooth pitch. This is the distance between teeth. Usually (but not always) it's 2mm. If the manufacturer used cheaper MXL belt, it would be 2.032mm.

The pulley on the Y axis in your picture looks quite small; I'd guess a 16 tooth pulley, but it's worth checking. I'm pretty sure the motors are 200 steps per revolution, and you are now using x16 microstepping.

Then use this formula:
steps_per_mm = (motor_steps_per_rev * driver_microstep) / (belt_pitch_mm * pulley_number_of_teeth)

For example
step per mm = ( 200 * 16 ) / ( 2 * 16 ) = 100

Which seems to be close to what you are seeing, but then that's just me guessing at the numbers from the pictures, so please check.

I'm not sure why when you posted your video yesterday it was going so fast, and I got you to set steps per mm to 40. Maybe settings got changed without restarting. But slow is better than fast and crashing!

Ian

A Former User

@droftarts Good morning, 10 teeth on the Y-belt measures 9/16th of an inch, which converts to 17.4625mm's. Divided by 10 gives my belt a pitch of 1.74625 something or others.

The pulley does indeed have 16 teeth. So, 200 steps X's 16 teeth is 3200 something or others, 1.74625 something or others X's 16 teeth gives us 27.94mm, I think, and 3200 divided by 27.94 equals 114.5311 something or others after a full revolution of the belt? Is that what we have?

I remember you giving me those lower M92 numbers (?), correct? Frederick was surprised by the higher number in that line of gcode in the config.g.

I remember entering your lower numbers into the code. Apparently, I didn't save it after I made the changes?

At this point, Frederick has done an enormous amount of work on this problem. We were working on all of this until late last night measuring the full travel of the Y-axis.

Here are the results: From the endstop at the back of the printer, all the way to as far as the bed can roll towards the front of the printer is 18 inches, or, 457.2mm's. Interestingly, DWC called that travel 350.0 something or others.

So that's where the journey has lead us so far. I'm enjoying it. Coding can be a nail-bitter, but when it works, it's great!

A Former User

@droftarts

A Former User

@droftarts

A Former User

@droftarts you see? It was there! But somehow it was changed. Probably my bad.

droftarts

@mac From your image, I'm seeing around 12.5 teeth to an inch. 1 inch = 25.4 mm, so...
25.4 / 12.5 = 2.032mm. So I think the belt could be MXL, but MXL has a trapezoidal shape to the tooth, and yours look more rounded, so I think more likely it is 2mm GT2 belt.

I'd stick with 100 steps per mm on X and Y for now. You can always measure prints, or the bed movement, if it needs to be more accurate.

Ian