Squaring & Calibration Logbook

Thanks @RobertA_Rieke, ended up adjusting those eccentric nuts some more and was able to further minimize the noise.

I went on to using Easel and as you mentioned the noise wasnā€™t at all apparent when being driven by the stepper motors.

This was my second cut which turned out pretty well. 50x50mm box with a 50x50mm circle; both outline, interior profiles. The box came out to 48.85 wide and 49.75 tall, so quite close for a first attempt.

Something is off with the Z axis however, as my depths of cut were 1mm for the box, 0.5mm for the circle, and 0.2mm for that triangle in the middle.

I ended up measuring the Z depth at: 2.05mm DOC for the square, 1.38mm for the circle, and 0.85mm for the triangle. Onto more reading!

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I have exactly the same sorts of noises pushing in Y, either the belt is thrumming a little or the rails vibrate a littleā€¦itā€™s difficult by hand to push evenly so both sides move exactly the same. I know Iā€™m a tad out of square (the two diagonals arenā€™t exactly the same, but itā€™s hard to be sure how much of that is measurement error) although Iā€™ve started doing some early jobs regardless. I am not so far having any lost step issues in Y doing projects, then again Iā€™ve only milled soft stuff like foam so far so I hardly had any ā€˜sideloadā€™ on the bit or material drag. I upgraded my wiring to 16awg so I havenā€™t adjusted stepper current up yet, or attempted any calibration of steppers or anything. (Just using Easel so far.)

I did hear this loud almost chattering sound at intermittent intervals while carving out a 24 x 10 inch sign ā€¦sounded like a loose metal washer or something vibrating against metal, and I couldā€™ve sworn it came from the vicinity of the carriage. I didnā€™t think my stock spindle could be going bad YETā€¦ I tried touching the limit switch levers, vwheels, the extrusions, belt, drag chain, etc. but none of them stopped the sound. It was definitely louder in either positive X or negative Y movement (and on longer moves) than other directions. I watched carefully because it did seem to modulate related to changing direction of motion but it sort of lagged the actual stepper actuation and pulley rotation, it wasnā€™t timed right along with a motor starting or stopping or visibly slowing down. It was driving me NUTS. I finally looked back in the back corner of my wasteboard and saw Iā€™d left my aluminum framing square laying on the wasteboard, outside the current clamped down material area, and it was ā€˜walkingā€™ around on the wasteboard. Every time direction changed I guess the vibration resonance changed and it moved/slid a bit. Picked it up and the noise went away. Man was THAT a relief. :smiley:

I know Iā€™ve got a number of square issues to sort out myself so Iā€™ll be subbing this topic in case you find anything or elicit a response that can help us both. So far sticking to easy projects with foam since a) itā€™s practically disposable and b) its nice and large so pretty easily shows out of square issues in XY or in depth of cut without runout or bit loading compounding things. (Iā€™m assuming itā€™s thickness is pretty uniform which might not be entirely safe, but Iā€™ve calipered in several places and the 24 x 24 x 1 sheets seem within about 0.05" as long as you have them clamped flat so they donā€™t bowā€¦)

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@Chris314, is your X-carve set up with the proper Z-axis screw? If you have the M8 but it thinks you have ACME, or vice versa, you will get the wrong depth.

It may also just be a Z-axis calibration issue. If you have a dial indicator, you can fudge a mount and attach it to the spindle mount, then calibrate the steps/mm. You can calibrate the X and Y axes also, just need a known accurate source (such as a large steel rule) to compare it to. I ordered a 600mm Shinwa rule for $30 off Amazon, and itā€™s fantastic.

@RichardRemski, you can calibrate the steppers in Easel. Check out this forum page: Z axis not accurate

Thereā€™s a link to the procedure to calibrate X and Y on there, and Iā€™ve got the procedure for how to adjust the settings in Easel a little farther down.

@RobertA_Rieke - Good call! I goofed up and configured Easel with the M8 screw when I ordered the ACME lead screwā€¦ Going to go reconfigure and try another cut.

Do you have any suggestions regarding the rectangular cut being 2% shorter (48.80mm to 49.75mm versus 50.00mm)?

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Glad you got it figured out. :smile:

The rectangle is probably off because itā€™s not accurately calibrated yet. You can calibrate the steps/mm of the stepper motors in Easel. Thereā€™s a video for a good procedure and some instructions for changing settings in Easel in this forum: Z axis not accurate

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@RobertA_Rieke

Thanks for your continued help! I followed those instructions; and re-calibrated the X axis. I moved it 500mm; and measured 508mm.

500/508 * 40 (steps/mm) = 39.37007874 steps/mm
$100 = 39.37007874

So I was going to repeat this in the Y direction and I ran into this problemā€¦

In short small repeated small movements of 10cm (100mm) are fine; however one large movement of 500mm results in a small initial movement and then nothing. The machine believes it has traveled 500mm based on the workspace coordinates; and subsequent commands to move the Y axis in smaller increments (100mm) continue to work fineā€¦

Is this a Y-Axis belt issue? Tried to reproduce this on the X axis and no dice.

Resolved: Y Axis belts were loose in the video. I retensioned the Y axis belts; and added a ziptie to hopefully prevent future detensioning

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@Chris314, I agree with @AngusMcleod that it sounds like something is slipping. After watching to see if the pulley moves, you may want to inspect the teeth on the belt to make sure you donā€™t have a spot where theyā€™re worn off. If the pulley is spinning, you probably need to increase tension on the belt a little bit.

I doubt it, but it may be a potentiometer issue as well. Is your Y-axis pot dialed all the way up or down? It may be hitting a thermal overload if itā€™s dialed too high, but I remember the sound from testing as being more like a crunching, like brakes being slammed on and then taken off. Scary sound.

@RobertA_Rieke & @AngusMcleod, thanks for weighing in.

I went back to investigate. The belts are looser than they were at the beginning of the day; lost that guitar string ā€œsnapā€ which they previously had.

Those potentiometers on the controller are as they were from Inventables; Iā€™ve yet to change thoseā€¦

From a quick overview the belts are otherwise in undamaged shape (couldnā€™t find any missing teeth), and the NEMA setscrews are still in place. Iā€™m going to re-tighten the Y axis belts first thing tomorrow and restart the calibration sequence.

In terms of cutting circular, circlesā€¦ This is my current benchmark; I have high hopes for improvement with the successful calibration of both axis.

Thanks - Will update tomorrow.

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It was the Y Axis belting!

I re-tightened, and added zipties to both the dynamic and static sides, so the belting should stay put.

I repeated the calibration process (moving 500mm on both the X & Y axis). The X axis ended up at 39.499 steps/mm; while the Y axis seemed fine at 40.000 steps/mm.

The problem is Iā€™m still not getting very ā€œcircularā€ circles. The below photo is of the same drawing repeated 3 times, you can see that the ā€œoblongnessā€ of the circle changed a bit between calibrationā€™sā€¦ But Iā€™m still pretty far from an actual circle.

For reference the circle is a fill cut, 10mm in diameter. Measuring the column on the right; the circle(s) are 10mm vertically, and 8.6 to 8.8mm horizontally.

The wheels secured by eccentric nuts on the X axis/gantry are all finger tight, and the X axis belt is secure, roughly the same tension as the Y beltsā€¦ What else could be going on?

It looks like youā€™re not getting microsteps on your X-axis, something Iā€™m currently working out on mine as well. Itā€™ll move large distances, but .001" and sometimes .010" movements donā€™t always happen. To verify this, try moving .001" 50 times or so, and see if there is any change in position at all.

2 possible problems Iā€™ve located are (a) belt tension is wrong, either too tight or too loose, or (b) potentiometer is too low:

To check the belt tension possibility, you can loosen the belt tension up a bit (1 flat increments, keep track of initial tension nut setting) and try to microstep. If that doesnā€™t chance anything, then try tightening it up (again, 1 flat increments).

To check the pot possibility, turn the dial your X pot clockwise about 15-30 degrees from its current setting, and try to microstep. Repeat once or twice more, but donā€™t go too far.

Another possibility Iā€™m dreading is the idea of a stepper motor being weak or bad. I highly doubt it though, since it still works. Thereā€™s no guidance for tension, so right now itā€™s just a ā€œmake it up as you goā€ type thing.

So this machines ability to make a reasonably perfect circle, is honestly not a topic that Inventibles has covered/supports? This canā€™t be rightā€¦

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Inventables hasnā€™t released a ā€œguideā€ to tension. Iā€™m currently working on developing a method to measure it, but until I get it completed itā€™s just something you need to tweak as you go.

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Rethinking thisā€¦

If the Y axis is repeatably making accurate cuts to within <1%, and the X axis is repeatably making cuts that are off by ~14% each time; then I donā€™t see why this would not be an adjustment problem.

So back to the basics, Iā€™ve repeated the pattern for loosening/tightening the eccentric bolts on the gantry, as well as loosened & retensioned the X axis belt clips.

This time Iā€™ve added zipties to secure all of the beltsclips, X&Y axis.

Itā€™s possible/probable that what began as a correctly positioned wheel/belt, worked itself loose with the operation of the machine. I also purchased a bottle of Loctite meant for bolts <6mm which is the color purple. Couldnā€™t find it locally, but Amazon did have it for sale hereā€¦

Going to re-calibrate the steps/mm and see if the cutting accuracy improves this time.

I just wanted to mention that yes, the a well setup machine should make pretty accurate circles. Iā€™ve found the main problems to be

  1. beltā€™s are loose
  2. v-wheels too loose (I make sure they arenā€™t easy to spin by hand, by adjusting the eccentric nut)
  3. missing steps due to not enough motor torque (potentiometer set too low)
  4. pulleys are loose on motor shaft

Personally, Iā€™m usually getting squares to match within ~0.01in by checking for the above 4 items. Sounds like you have you have checked #1 and #2, so my guess would be #3.

What is your depth of cut, and have you tried decreasing it? Decreasing it will directly lower the forces on the motor, making it less likely to miss steps.

1 - Itā€™s possible, the X axis was somewhere inbetween the tension of the Y axis before & after I tightened it up today. It did have some snap to it though.
2 - Checked this, none spin by hand
3 - Is there an established way of checking this? The potentiometer is changing the amount of available current to the stepper motor? So this should be measurable during operation with a multimeterā€¦
4 - you are referring to the grub screws which secure the ribbed wheel - or something else? I just rechecked all of the grub screws holding the short end; theyā€™re torqued so that the allen wrench just begins to deflect (with the long end inserted into the grub screw).

My depth of cut is set to 0.5mm, Iā€™ll try a DOC of 0.2mm after I re-calibrate the steps/mm. Hadnā€™t considered the depth of cut since wood is relatively soft, but this is a really valid point.

Having the V-wheels too tight can cause problems too. Right now I can move the V-wheels by hand if I really try hard, and it made everything a bit better. If itā€™s too tight, then it may be putting extra torque on the stepper motor since the bearings are far from frictionless.

Check out this forum post for some good pot information: New drifting

As for the loose pulleys, itā€™s very possible for the little screws to come loose (or even come out). If that happens, it can cause the shaft to spin in the pulley without actually turning the pulley. Double check that they are tight, and throw some loc-tite in them as well if you notice they start to loosen up. Mine are still solid, but the first time one loosens up theyā€™re all getting locked.

Youā€™ll likely have trouble measuring the current accurately with a multimeter. Using a single mulitmeter while the motor is stationary, you can only read one of the two coils, and donā€™t necessarily know if you have all of the current going through one winding or not.

When microstepping is enabled, the total current supplied to the motor is split up depending on the step differently between the 2 different sets of coils in the motor. Temporarily turning off microstepping can make the measurement easier for testing purposes.

Another thing to consider when tightening the belts (Y axis) is the length of each belt after you have it tight.

For example, if you tighten both to the exact ā€œtoneā€, as a lot of people do, the left belt might be two or three teeth shorter than the right belt. (or more)

What I did, was get one belt roughly where I needed it to be, mark a start tooth and end tooth with a short copper wire (one strand out of the stepper wire). I would then match the other belt, tooth by tooth, and mark the exact same teeth on that belt.

Once I installed the belts and got the right tension, I measured the distance between the two marks. By ensuring these were the identical distances, even though one belt might be slightly tighter/looser than the other, it ensures that both the left and right side move the exact same distance. As long as you get it tight enough not to slip or cause backlash, this would make your X-Carve move in perfect sync along the Y axis, even if one is not as tight as the other.

Before doing this, my left belt was almost 1/8 - 3/16th shorter, so over the distance of the cut, the left side had moved 1/8 - 3/16 further than the right.

Hope this makes sense

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To me, this sounds like either the acceleration or max rate might be set to high, or voltage to low. With short movements, it does not get a chance to accelerate, however with long movements it tries to accelerate to its top speed.

Check your max speed and accel settings. ($120-$122 and $110-$112)