I have not been keeping up with regular posts regarding work on my 3D printer, so I will post my notebook contents this time. I learned some important facts about the machine and how it works. As of 19 January 2013, I am happy to say that 8 hours in to an important print, it appears to be working well. Here are my workbook notes with pictures added.
Even at 100% current, the X axis still binds toward the edges (ends of the lead screw). This seems surprising since it is not pushing a load as it would if it were cutting in a mill configuration. Moving the extruder should be an easy job.
The present controller definitely did work at some point, so what has changed? I should go back in my notes to the point when I abandoned the Smooth Stepper and the machine started working so well.
The Y axis motor makes a relatively large amount of noise. Is it bad or possibly mounted wrong?
Turning the lead screw has no mechanical advantage compared to lead screw turning pushing a cutting tool (2 pi r x turns versus linear motion), so any resistance directly from the leadscrew might challenge the stepper motor torque.
6 Jan 2013
I tried several things to fix the 3D printer
1. I put in all new bearings on the Y axis, but I did not replace the motor. I installed 3x 5mm wide bearings at each end since I could not replace the original 12.5 mm long bearing exactly. The bearings have ID 6 mm and OD 16 mm.
2. I tried switching X and Y on the machine wiring, after which the machine screwed up in X AND Y.
3. I configured my new laptop to run Mach 3 through the Smooth Stepper.
I still saw a jump in Y, so does that mean I have a mechanical problem with Y, or a controller problem. There would only be the 4 axis Chinese controller and the Smooth Stepper to blame if there is no possible problem with the signal coming from the new laptop running Mach 3.
The last thing that worked was an older PC running the controller directly through the parallel port. I think I must have tried the parallel port directly with the old laptop. I recall that it did not work as well as the green PC that later crashed.
I have ordered the Gecko 540, and it is on the way.
I can try replacing the Y motor, but the jumping problem makes me think that I have a controller problem. Friction caused missed steps and print tilts, not jumps.
How could a bad or incorrectly specified motor cause the jumping problem? I have seen sudden movement up to 1 cm.
The problem did not just transfer from Y to X when I switched the leads, so that points away form the controller board.
I had to cut out body to accommodate new motor. I made lots of dust, which is very bad for leadscrews. I cleaned the whole system.
Adding more lubrication to a dirty system probably makes things worse, not better. Silicon lubricant was suggested – used for aircraft parts.
Compressed air (most important), isopropyl alcohol – to not damage nut I did not use acetone, vacuum cleaner, wire brush, at least 20 soaked paper towels made leadscrew cleaning possible. Later I learned that spraying with silicone spray at that point would have really finished the cleaning job.
How can a Nema 23 motor bog down? It skips at the ends of lead screw, even at 100% current, 24V. Moving the extruder gives almost no mechanical resistance
What can the problem be? Computer, controller, cables, motors, lead screws, bearings
Smooth stepper. Does the age of the PC no longer matter? I tried my brand new laptop and still had problems right away.
Stepper motor jumps of several mm – what is happening? Will the cleaning fix it? Will the new motor fix it? Has the controller failed? How do they work and then fail? How can I diagnose the problem?
I switched X and Y axis, then BOTH started to lurch and/or skip. Is there something about direction reversal that goes wrong?
How do I set velocity and acceleration properly other than maximum before failure? What should be my maximum G force? How is it related to motor torque?
Motors do not warm up at all at 100% current setting. The controller also does not heat up.
Gecko 540 and Smooth Stepper – what else could I possibly do?
The new motor turns so easily by hand compared to the old motor. Why? Is that good or bad?
The system worked at some point. Old PC, parallel port control of 4-axis Chinese controller at 50% –> 20% current setting.
I tapped out the 7mm mounting holes, which had stripped to 8mm to hold down Z axis. I did not need to drill first.
I need to put a two channel oscilloscope on the Y axis and check it out. Should I look at voltage in parallel, or view current across a low value resistor? Look at voltage drop along the feed cable (milli Ohms will give milli volts) to see the effects of motor inductance. Compare input voltage signal to current?
7 Jan 2013
I installed a new Y axis motor. I had to cut the body of the unit to accommodate its larger size.
Interlocks should be normally CLOSED. That way if they are detached, your system will not proceed. That would have saved many crashes for me. Mine are normally OPEN, so if I detach them all, my machine runs happily. Next time I flip the machine, I can at least make the X and Y interlocks normally closed. I can change the setting in Mach3 and then any time I detach the interlock for any reason, I will be REQUIRED to reattach it before I can continue machine operation.
One problem is that all the interlocks need to be tied together in series if I use NC instead of NO unless I make just one or two NC. I could also make a shorted loop on one channel so that a disconnected plug prevents the machine from running. Basically, that’s an additional interlock checking to make sure the rest are plugged in.
The lead screw cleaning seemed to work for the X axis, but not Y. I still saw the jump.
Next I want to remove the bearings on the motor end and also in the future try turning the lead screw shaft inside of the flexible coupling. The motor is obviously misaligned since I can feel it precessing as the lead screw turns. There used to be solid coupling from the motor to the lead screw, so I can not figure out what must be going wrong. I can try turning the set screws away from the flat part of the shaft.
The X axis only has bearings at the far end of the lead screw, away from the motor. Then again, the original motor might not have had any play along the axis, and the original configuration did not use a flexible coupling. I can move the lead screw back and forth by hand a little bit on the X axis. This should not be a problem for 3D printing since there is no force pushing against the extruder, but it would be a problem for machining.
I can reach under and loosen the bearing clamp for now. Next time I flip the machine, I can remove the upper end bearings.
Do the new motors have less or no play in the axial direction?
I assume that the Y motor must be struggling given how much it precesses. High V and A values probably depend on low resistance to motion. Then again, it turned pretty easily with my fingers…
A bit of humor:
Here are notes I wrote about my old 3D printer on 7 December 2012
Old 3D pinter: What else to try
1. Slower speed 1900 -> 1400 (tried today)
2. Lower acceleration
3. Full current to motors
4. Start drinking heavily
16 Jan 2013
What I learned today about my 4 axis Chinese stepper motor controller.
If the front (all) AND BACK (top) screws are removed from the end covers, the top slides off, giving full access to the circuit board.
Because of that, I could carefully verify all switch positions.
I switched to 100% decay from 0% decay based on this web article.
I switched X, Y, and Z from full steps to half steps based on recommendations from the same article.
I kept X, Y, and Z at 100% current
Note: X and Z are 5A stepper motors, but even 100% current is 3.5A, to torque will be reduced to 70% of its printed rating.
The X axis still bound at the edges, and that is the reduced torque motor.
Things to try:
1. 35,000 to 25,000 interface speed
2. Replace X stepper motor with lower current model
3. Determine how to affect delay 0 usec to 5 usec while using the Smooth Stepper
4. Direct parallel port connection is what worked well before. I should try it again.
5. Try silicone spray lubricant. Is the problem lubrication or debris?
When the system worked well, it was set for 0% decay. I am not sure if it was set for full steps. I think it was set for 50% –> 20% current. I used a different PC with a direct parallel port interface. So why did it work well then and not now? How can I make it work that well again?
One aspect is that I lost my Mach3 settings after the computer crash. I never touched any Smooth Stepper settings, so those should never have changed. The Smooth Stepper was abandoned when the machine worked best however.
Perhaps I should replace the controller with exactly the same model. I found a place that shipped two to me for $60 each with $28 shipping total. The lowest cost with shipping on eBay is around $80 each.
If Y is now working, but X is flawed, I should replace the X motor.
What about current sense resistors? The bare Chinese boards had these I think. There is a row of large resistors on each of those boards. I see no siilar resistors on the enclosed board. How does it operate without them?
The Gecko board also does not appear to have large resistors on it.
The machine was screwing up really badly with ~ 1 cm jumps. That’s not a friction problem or a weak motor problem, is it?
How does that happen? Now I am tilted, but no jumps. Why?
Here are the possible reasons:
1. The controller board may be damaged.
2. The new computer is not working as it should, which implies that the Smooth Stepper does not really solve this problem. My new laptop running through the Smooth Stepper still had problems.
Rewiring to try the Gecko seems kind of hellish. I want to try buying a new Chinese controller like the one that worked before I really give up on it. That was part of my best configuration so far.
If big jumps ever occur again, here are my options:
1. Switch to the Gecko controller
2. Buy a new Chinese 4 axis controller
3. Use a new (old) PC directly through its parallel port with a fresh installation of Windows XP and NOTHING ELSE!
If the controller was damaged, how was it damaged?
During the computer crash?
Power supply startup surges?
Defective controller? Poor quality?
I switch the AC side on and off, and I do not hard switch the DC. The Gecko manual warns against this.
Switching X and Y seemed to prove that I do not just have one bad channel. When I switched, both X and Y were messed up.
The Y axis has aways been a trouble maker, across several controllers.
All I can affect are bearings, clean lead screws, good alignment, correct motor torque. Take a look at the specifications of the original VEXTA motor.
18 Jan 2013
Note that I am hearing no bumps and thumps like I used to before going to the green PC with direct parallel port before it crashed.
Remember that I switched to the little four axis controller because it came in an aluminum box and I thought that electrical noise might be one of my problems.
I used silicone spray lubricant.
Wow! This stuff really takes off the black grease. I cleaned and lubricated the X lead screw, and could only spray lubricate the Y lead screw. The X axis still sounds funny at the edges, but it does not bind at all.
I think the silicone spray was more important as a solvent than as a lubricant. It broke up and removed some of the thick, black grease on the lead screws. I read that my antibacklash nuts for this machine are supposed to operate with no lubricant at all.
Note that I spotted the fact that the X axis has only a bearing on the end of the lead screw opposite from the motor. The motor shaft of the currently installed motor can move a bit along its axis, so the leadscrew on X can move back and forth a bit. That’s probably OK for 3D printing, but if I ever convert it back to a CNC mill, I will need to make sure this play is removed or reduced. The flexible shaft coupling adds to this movement. I think I can use the solid shaft coupler on X since alignment has never been a problem. I may consider removing the upstream bearings on Y so that the motor does not precess so much as it drives the Y axis.
19 Jan 2013
Running Power Spec PC with fresh install of Windows XP
Ran out of black filament during this last run.
Had one big jump in Y.
Turned off screen saver
Turned off fire wall
Turned off Automatic Updates
Disabled internet connection
Re-leveled and cleaned the platform
Loaded red filament
7 hours in it looks great!
I am wiggling the mouse every once in a while. I have not verified that all BIOS power saving features have been turned off.
19 Jan 2013
I am printing a quad copter part now that I think I finally have my 3D printer working correctly.
I went on line to get quotes for having the part printed professionally. I was surprised to find the following. It seems better to have your own 3D printer!
FDM $342 (This is the process I am doing at home today.)
Cast Urethane $2239
Zprint $150 (glued together powder)