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Everything posted by jhinkle

  1. I'd like any positive/negative comments people might have. I started on this 1.5 years ago but it got shelved because of illness. I'm back into the development and wanted to see if anyone else is possibly working on something similar or has information/comments on my direction. I purchased a U1 almost two years ago. I have a habit of redesigning things to make them better for me -- for it it was redesigning the U1 control board. I designed a hi-end stepper motor controller that can be programmed to micro-step up to 128 or 256. That was phase one. Phase two was the controller that drives
  2. I figured it out -- Thanks. All is well. Here I thought this was all magic -- now I know it's just fishy! -- Merlin vs Marlin.
  3. Reprint from Merlin code: // The speed change that does not require acceleration (i.e. the software might assume it can be done instantaneously) #define DEFAULT_XYJERK 20.0 // (mm/sec) #define DEFAULT_ZJERK 0.4 // (mm/sec) #define DEFAULT_EJERK 5.0 // (mm/sec)
  4. I'm going through the Merlin code to get a complete understanding of its control over the steppers. I believe JERK is defined as the instantaneous allowed change in velocity (mm/sec) that can ignored at a junction so that the speed does not have to go all the way to zero. Merlin has the default XY jerk defined as 20mm/sec. Merlin has the default XY acceleration defined as 4000 mm/sec2. Kinematics states that v(i) = sqrt(((v(i-1) * (v(i-1)) + (2 * Acc)) If we want to see the delta change in speed (v) we can choose v(i-1) to be 0 therefore DeltaV = sqrt(2 * Acc); Placing the Merlin values
  5. Don't look at what I'm doing for electronics. I'm a retired embedded hardware/software guy who does not like Arduino. I'm designing a arm based controller with my own stepper controller which provides 255 sub-steps.. I would stay with what is currently in the UM1 or UM2. That way you have a lot of support from this forum. The UM1 uses the Marlin board -- don't know what's in the UM2 --- someone else can share that.
  6. Be careful what you buy when it comes to steppers. There are a lot of "cheap" motors positioned for the 3D printer market. I am building my own printer and wanted motors -- I'm using my own control system. I purchased these from Amazon: http://www.amazon.com/Signstek-Printer-4800g-cm-Resistance-Electric/dp/B00H98FKVK/ref=sr_1_1?ie=UTF8&qid=1403048294&sr=8-1&keywords=Signstek+3D+Reprap+Printer+CNC+Nema17+48mm I returned them and wrote a 1 start review review. I suggest staying away from motors built by WANTAI motors in China. Hi torque motors are built with tight tolerances.
  7. The inside needs to as clean and polished as possible to reduce friction. That is why many hot-ends used PTFE tubes inside - low friction to the melted plastic and hi melting point of it's own. I suspect this will be one area where a cheap clone will not properly do the required work to reduce cost --- You the user will probably never look or know but the performance of the head will suffer.
  8. The actual voltage that appears at the sense coil will be the voltage on the "Part" of the sin wave that is associate with the associated microstep. Peak voltage will only appear at FULL step positions --- any microstep location will be less -- depending on where you are on the sine wave. Internally, the IC uses a lookup table as it steps through the microsteps. It measures the voltage across the sense resistors, amplifies them and then does an analog compare. When the voltage across the sense resistors reaches the internal values associated with the associated micrstep, the current thru t
  9. You might run into a problem moving from 1/16 microsteps to 1/32 microsteps. That change requires Marlin to process interrupts twice as fast. I don't know if the micro has additional headroom to do that. Marlin already has code to deal with too fast of interrupt times --- halving that time might produce strange behavior.
  10. May I make two replies - one on measuring stepper motor current and the other on a feed sensor that I have been pondering. Stepper Motor: Most stepper motor ICs have an internal clock (usually around 10khz) that determines when coil current is applied to the stepper motor. They have a sense resistor in each coil path to ground to measure coil current. Internally they have an amplifer and comparator that will trip when a specific voltage appears across the sense resistor thereby turning coil current off. This mythology allows the board designer to set max coil current and coil current only
  11. Thanks. Yes - micro-stepping does not provide a linear movement between full steps. Standard Stepper chips don't let you directly control the steppers current --- but if you could you can drive the coils NOT with a sine wave but with one which included specific harmonics that would linearize it's movement --- but THAT is much more complicated driver. Personally - I'm looking at 1/255 for better control over the extruder and smoother motor operations overall. You are at 78.7402 micro-steps per mm when driving 1/16 micro-steps. That increases to 1259.8 micro-steps per mm when driving 1/256
  12. Diad: Does Cura ALWAYS generate gcode with X/Y/Z to two decimal places and E to 5 decimal places? Do you see the precision increasing in the future? Do you know what precision the other slicers generate? Thanks. Joe
  13. Diad: Thank you for quickly explaining. Joe
  14. I'm getting old ... I looked at those large volume segments many times and did not see the delta from zero. This was a quickie test and I missed it -- nice catch on your part. The real intent of the post was the HALF volume segments as they might be some of the under extrusion concerns people are posting about.
  15. I just received my UM1 in the last 30 days. I purchased the UM1 because of its printing resolution and ability to be modified. I intended from day 1 to replace the marlin control system with one of my own design that would allow me to micro-step all steppers at 1/256 - or 16 times finer than Marlin does today. Towards that end, I have been analyzing the Gcode that Cura produces since THAT is what drives the control system. I have found two types of code generated by Cura that does not make sense to me --- I'm hoping someone can explain. First -- an assumption on my part. I am assuming th
  16. I appreciated everyone's help and input. The hardest part in solving an issue is finding what the root-cause is. Once that is known - the rest is usually easy. I would have thought UM would have updated their assembly instructions on line about the new tool they provide. If not for this forum, I'd still be using 3B or the several other tools I was coming up with to do the job. Again --- thanks to all in helping resolve my issue. Joe
  17. It squared nicely once I got the rods in the print head to be 90 degrees. I loosened the print head's clamping screws and the adjoining bolts. The print head was still a very solid and no flexing anywhere was perceived. Using my drawing of perpendicular lines and the rods as lever arms, I attempted to get to 90 degrees. I felt nothing move at all. but after a couple of times on the rods applying force in the correct direction, the rods measured 90 degrees. I felt no movement -- but it moved. With the print head rods now at 90 degrees I inserted the print head into the printer. Set belt
  18. I believe the current UM process of squaring the axises of the printer is severely flawed. If every thing was built to precisely 90 degree angle or rods parallel to one another -- then there would not be a squaring requirement. The proper way is to have alignment adjustments -- but that would add cost and complexity. Forcing a sliding block so that it becomes square and holding that square by tightening the pulley set screw--- DOES produce a square system but adds a twisting force to the bushing associated with the sliding block. The induced side forces produce friction which requires more
  19. I just confirmed that the rods in the print head are not 90 degrees to each other. I drew a line on a piece of paper and then, using drafting tools, -- drew a line perpendicular to it. I placed the rods in the print head and placed it on the drawing. Getting my eye over the middle of the print head, I aligned one rod with the horizontal line in my drawing. I then expected the other print head rod to align itself with the perpendicular line --- but is is off by 1 to 2 degrees. So .... THAT is my issue ... Now ... how to adjust the rods in the print head to get them close to 90. Comments?
  20. I totally understand and agree with what you say. Explain if you can, .... All frame located rods are square. Assume rods in print head are 90 degrees. If all of that is true --- then securing the print rods to the sliding blocks should also produce square. If its not ... then the only logical piece that could be off would be the print head. Assume for a minute that they were 89/91 degrees to each other. You will set the first print head rod parallel to its related frame rods. The other print head rod would not be 90 degrees and would produce a difference when using the alignment tool.
  21. Robert: FYI ... as to why I was calling it an extruder ... taken from the assembly instructions. :-P :-P :-P :-P
  22. Robert: Yes --- I did you what you suggested. -- Still issue. I have now taken the print head (sorry for the wrong reference- I knew I had my head where things smelled funny) -- completely off and was going to go through the step-up/assembly again. Problem is ... if I did make a mistake ... and don't understand its a mistake -- my reassembly will probably end up with the same issue ..... that is why I'm trying to get a clear understanding of the process. Joe
  23. Not quite following you. The premise of this whole squaring process is that the drive rods and slide rods in the frame are 90 degrees to each other. Using the tool -- you are attempting to set the extruder rods parallel to their associated drive rods. If they can not be set parallel the something is off. The only flexible attachment points are where the small extruder rods enter and are secured to the sliding block. Those are almost a press fit which then locks the extruder rods to the "slide" rods which are expected to be 90 degrees and parallel to the drive rods since they are all p
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