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Topics - ggallant571

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1
3D Printer Software / 3D printer x/y steps per mm
« on: June 16, 2017, 05:26:32 PM »
I just looked at the motor conversion units on my 3D printer and X & Y are set at 81 while Z is 400. Since these device share components with the laser etchers I find this odd. Measured a 10x20x8 mm cube and it is long on all sides. Any comment?

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General Discussion / Getting started with 3d printing
« on: June 11, 2017, 07:28:23 PM »
I purchased a Monoprice "Maker Select Plus 3D printer" and am not being very successful. Tonight I printed one of their sample files, a swan, that came out perfect. This was via the SD card. I then tied to replicate via Cura and USB from the host. Just strings that did not attach to the print bed. This was with black PLA. Tried again from sdcard with white PLA (printed better than black last week) and nothing. I think there is insufficient filament being pushed thru the nozzle. Also getting error messages on the Cura console that would hint at spelling mistakes in the code.

1. Is it necessary / feasible to clean the extruder?
2. Can the nozzle get clogged?
3. Do different clor filaments need different heat profiles?


3
Z Axis / Laser Beam Alignment
« on: March 02, 2017, 07:18:14 PM »
I have been using a not to precise home-brew z-axis mechanism. It is two vertical side plates with groves. A plate with a a nut on one side and the laser heat sink on the other moves up and down in the grove driven by a low power gear head stepper motor. The UP/DOWN accuracy is more than acceptable. However the slop in the slide causes the head to tilt. The error can be lessened by inserting a small spring. The total range is about 30mm but the typical usage has been less than 3mm.

BTW - this problem can exist on systems without the Z-Axis. Most wheel on V-Grove systems have significant wobble on the X laser carriage. Forcing the lower wheels up tight to the aluminum under frame can reduce it but eventually they become sloppy. Also, there is slop in the bolts used to attach the laser to the plate.

The is a another potential cause of mis-alignment, manually adjusting the focus lens. On my machine the focus dot has considerable variance in both X & Y. I do not know if this at an angle or not.

When doing single pass work such as etching it is probably a non-issue. When doing multipass cuts the effect is non-vertical edges and extra wide cut paths. I first observed this problem when cutting 20x20mm squares in 3mm plywood with 6 passes on a factory fresh machine.

The problem that I am trying to solve is implementing a laser alignment mechanism for both the X and the Y axis's. But first I need a method to measure the current angle. So far I have been cutting squares, examining the edges, adjusting, and recutting. Rather tedious but only needs to be performed after observing problems. The thicker the material, the easier it is to measure the alignment.

Currently thinking about mounting a 45 degree mirror on the top end of a rotating axle. To use:
  1. Position the laser at the center of the axle
  2. Emit a low power laser beam
  3. Measure the height of the laser beam at a known distance (~50mm)
  4. Rotate the axle 90 degrees and remeasure

If everything is perfect the heights should be equal. That is a big "if".

Other ideas:
  1. Use a t-square to align the beam with the base. Inject smoke to enhance the beam.
  2. Add leveling adjusters to the bed and using a level on the heat sink.
  3. Get a thick, easy to burn, non toxic, non-distorting foam material.
  4. Make the jig precise enough so that this becomes a non-issue.

Comments and collaborators wanted.

4
General Discussion / Murphy Lives Here
« on: February 22, 2017, 03:00:36 PM »
My A5 laser has been working great. Recently added homing switches, belt tensionors, and a G2 lens. Order of plate PCV arrived earlier this week and decided it was time to do the job I bought the laser for. The weather is great so I hauled laser, laptop, & plastic to garage so that I might survive the fumes.

Setup with laser near door, inserted card stock do do a test cut, and absolute crap motion. Checked the usual suspects like belts and wheels being tight. All OK. Back to basement for alternate poser supply and simple tools. No difference.

Went and got a stepper motor and it worked on all the stepper motor ports. No load by as expected. Checked the stepper current limits. OK. Switched out stepper drivers. No difference.

Plugged X axis into Y driver. Crap motion on X.

Disconnected Y belt and plugged Y motor into X driver. Works as expected.

Swapped y-motor power cable to x-motor and it works. Appears I have an intermittent open in the cable. Ohms out ok until I flex it. Ordered a bunch from ebay and I may have a beer or two or three and try find and fix the fault. 

Murphy is alive and well and I know his address!!!



5
General Discussion / Belt Tension Adjustors
« on: February 21, 2017, 01:08:36 PM »
I installed 3 sets of 3D printed belt tension adjusters on my A5 gig. Believe they were posted by user Beikeland about a month ago. The Y Axis went on in minutes, the X-Axis took a lot longer, mostly because I tried to do it in place and ended up disassembling just about everything.

It is necessary to cut the acrylic mounting plates to mount the belt to the holders. For the end plates I sawed the plastic the width of the v-grove from the top edge down to the 6mm hole. For the side plates I marked the location of the slot and used a drill press as a milling machine. Not very professional looking but functional.

Within seconds of installing the first y-axis clamp I was convinced these should have been mandatory from day one. Even without the adjustment screw mechanism the ability to place the belt in the holders was fantastic. No effort!!!!!

An unexpected benefit arouse in there is now an additional 1cm of range in both X & Y. Could be 2cm but I currently have limit switches in that space.

If I were to do it again:
  1. make the brackets slightly wider
  2. wider spacing between belt hold down screws
  3. change adjustment screw & nut from US 10-32 to 5mm
  4. smaller bore hole on adjustment screw
  5. uniform mounting holes to loose fitting 6mm.
  6. make out of solid gold.

BTW - They did not improve the quality of the burns, just made it much easier to get there.

6
General Discussion / Painters Tape
« on: February 16, 2017, 10:07:44 PM »
I purchased roll of Scotch blue painters tape in the 72mm (2.83 inch) width at Home Depot. Is there a magic formula for changing the laser intensity while etching? Do you etch twice, once for the tape and again for the wood?

7
General Discussion / Test pattern
« on: February 10, 2017, 03:40:10 PM »
I have been playing with etching slate. First 3 came out great, 4th was horrid. I don't think the laser can etch to the resolution specified in the image when working with slate. Test etches on neon colored card stock at very low laser intensities came out looking good. Wonder if the laser causes small explosions in the slate. As a result I hand generated 2 test pattern gcode files. One to hold the laser intensity constant and vary the speed. The other to vary the speed and hold the intensity constant. Turns out neither makes much difference in the slate. Also etched in wood and picture is attached along with source code.

8
General Discussion / Aligning laser beam
« on: January 30, 2017, 06:14:22 PM »
I have a home-brew Z-Axis. It helps when cutting 3mm plywood but I noticed that the cut was growing wider on each pass. Did some tests and determined that the beam is not exactly vertical, particularly in the X direction. Under an examination lamp, I can see that the slot is not vertical. Slopes the same direction on both sides.

Did the same cut without Z motion and it is much cleaner. Also played with the distance of the work to the lens and get the best cuts up close, 40mm vs 100mm.

I know the mechanism is not great but I have not idea how to align other than loosening, rotating slide, and tightening the screws, and reburning a line. Rev 2 of the z-axis is ready to be made but will hold off awaiting ideas on alignment

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General Discussion / inkscape export
« on: January 18, 2017, 05:12:01 PM »
I have some files in svg format that I would like to convert to dxf. I open and display the files ok in Inkscape 0.91. Then I save as "dxf". The files get saved but the units are off. 10mm  exports as 2.82mm. The ratio is 3.54 which I recall is the pixel to mm at some standard ppi.

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General Discussion / First Slate Etch
« on: January 08, 2017, 05:52:34 PM »
Tried my first etching in slate. Not very good compared to wood. Tried to etch the picture of a tigers head, assume I got it from this forum. The lines are nice and crisp but the texture of the hair came out all flat. I suspect it was a poor example to start with.

Going to try Agastar's Elf with text.

Is there a way to clean (sand) the slate so it can be reused? At least for test pattern.

11
Alternative Applications & Firmware / STM32F303K8
« on: January 08, 2017, 01:59:46 PM »
I purchased a low cost STM32F303K8 Nucleo board in the AVR Nano form factor. Ported my home brew gcode firmware. After a week of setbacks it is working. No visible difference in results from the AVR but the processing speed (72MHz) and the extra RAM (12KB) make for a more comfortable processing environment.

Have started to do some performance measurements. I currently drive the stepper motor update at 40HKz (25 usec). The AVR uses about 14usec and the ST about 6usec. Starting to instrument the time it takes to process a single G01 Xxx.xxx Yyy.yyy command. The AVR was about 1.6msec with the processor idle which goes to about 4msec when actively etching.

If you are wondering if this matters the answer is probably NO for cutting and YES for etching. The faster the processing the shorter the individual etch segments can get. User Beikeland posted an interesting unit (mm/hz) that I want to investigate.

I still need to find the magic recipe to enable hardware floating point.

12
General Discussion / Killing a A4998 stepper motor driver
« on: January 05, 2017, 08:07:15 AM »
I killed a A4988 driver last night. Was playing with new software and had the current limit on the bench supply set quite low, probably less that 0.5A. The X played ok but the Y which drives two motors just consumed all the current the bench supply could deliver causing the voltage to drop low and very sporadic movement on the Y motors. Few seconds and all stopped. Do not know if the bench supply caused random surges but the module is quite dead. Set current limit at 2A and a new A4988 works as expected.

13
General Discussion / Benbox laser Messages
« on: December 14, 2016, 01:22:31 PM »
I am wondering about the behavior of messages in "My Messages". From some users I get a email and not from others. Is this something that the sender selects or I need to configure?

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General Discussion / Power & Weak Laser switches
« on: December 05, 2016, 02:32:49 PM »
I am looking for a manufacturer part number for the latching switches used on the Eleks controllers.

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General Discussion / SVG Files
« on: November 02, 2016, 05:17:42 PM »
I have been using png files for raster etching operation on my Linux application that utilizes the GTK toolkit. When reading the png file I get the number of channels (3 or 4) that represent the R,G,G,A data channels.

I was converting the RGB into gray scale by averaging the 3 color channels. Then I imported a png that was created in grayscale only where RGB are all zero and the intensity is in the A channel.

Note: If there are only 3 channels then it must be RGB.

Both are fine except I don't know how to determine which one is really there. So far I scan the A channels looking to see it they are all 0xFF. If so then calculate the grey from RGB. Or I can scan all the RGB channels for all 0xFF or 0x00 and use the A channel. Problem is what if there is info in both RGB & A or is that an invalid condition?

An acceptable alternative would be a utility that rewrites the file as grayscale only.

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