Ultimaker Community of 3D Printing Experts

# jhinkle

Dormant

54

1 Neutral
1. ## Comments on U1 controller

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. ## Merlin Jerk Speed

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. ## Merlin Jerk Speed

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. ## Merlin Jerk Speed

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. ## Where to buy Stepper Motors?

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. ## Where to buy Stepper Motors?

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. ## E3D All Metal Hotend for Ultimaker

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. ## Monitoring current from extruder motor for feedback?

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. ## Using Pololu DRV8825 Stepper Drivers on a UM1

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. ## where to get glass for build platform in U.S.?

ACE Hardware - \$7.50 .... same as jhertzberg states above
11. ## Monitoring current from extruder motor for feedback?

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
12. ## Cura Gcode has me puzzled

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
13. ## Cura Gcode has me puzzled

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
14. ## Cura Gcode has me puzzled

Diad: Thank you for quickly explaining. Joe
15. ## Cura Gcode has me puzzled

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.
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