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Topics - ggallant571

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1
General Discussion / Image prep question
« on: March 29, 2018, 07:16:33 PM »
I want to do 9 etchings for a friend in slate. Unfortunately for me he is a talented artist with skills well beyond mine. The panels contain simple subjects with partial black outlines. The subjects proper are drawn with a pastel paint that quite artistically does not match the outline.

Could be etched in wood with varying intensity but need the black/white for slate. It took more than a full day for me to do the first image and I was not pleased with the result. I think they will look best with a simple complete outline.

Looking for ideas on how to reliably extract an etchable image with a uniform fixed width outline. Is there a tool to import a sloppy outline and output a clean one?

2
General Discussion / Etching Granite
« on: February 06, 2018, 08:39:48 PM »
I was at a kitchen counter shop this afternoon and got a couple pieces of scrap kitchen countertop granite. The black (with white speckles) is etchable with a 2.5W laser. Not great and the shine from the stone makes the camera picture useless. Etched their business name on both sides at both 240 and 60 mm/min. The rougher surface (forget the trade name) is less visible than the polished one.

Also got a light (almost white) chunk that I expect will remain unscratched.

Open to suggestions regarding taking pictures of faint images on a shiny background.

BTW - They have a few tons of scrap granite along with a large quantity of scrap birch plywood good for small images or testing.

3
General Discussion / Wine Glass Etching
« on: January 31, 2018, 01:29:06 PM »
I have enter the wine glass etching game. Built a fixture based on a small rotary table, two 8mm rails with linear bearings, and a 1.6W laser module. Glass is held in a vertical position in a 3D printed spring loaded clamp. This eliminates the need to support the far end of the glass.  Currently Y is vertical and X is rotational. Electro/mechanical components working smoothly. Starting on the etching. Questions:

1. Prefered ink/paint.
2. Laser intensity.
3. Burn speed.
4. DPI.
5. How to position/aim the laser.
6. Is it "better" to etch horizontal or vertical.

4
General Discussion / NEMES Show
« on: January 27, 2018, 08:05:44 PM »
For anyone in the New England USA region the New England Model Engineering Society, NEMES, is holding its annual show on February 17, 2018 at the Charles River Museum of Industry in Waltham Massachusetts. I plan on bringing  a 2.5W core-xy flat bed  etched and a 1.6W wine glass etcher. The core-xy has been behaving nicely for some months now while the rotary glass machine is still under construction.

I have small wooden discs (25mm) onto which the visitor can engrave their initials. Also have some NEMES specific images engraved in glass, wood , & slate which will be donated as door prizes for the exhibitors.

5
General Discussion / Slate problem
« on: January 13, 2018, 02:14:29 PM »
I just tried to etch a slate coaster with 2.5W laser and the result was very faint. Not sure that my speeds are accurate but used 900 mm/min at full power. Running a second  pass to see if it improves. The image has lots of lines that are 3 pixels wide in all directions. Etched ok on test cardboard and the final product will be on a mirror. Any thoughts?

6
General Discussion / Lead screw design problem
« on: January 02, 2018, 10:58:12 PM »
I have built a 500x500mm etcher using 8mm lead screws. As I have a similar machine using belts with a core-xy scheme this design was intended to highlight the build complexity and performance of the two drive mechanisms. After a day of testing and tweaking the software & firmware I have a couple of problems to solve:

1. The lead screw design appears to have a max speed of approx 2700 mm/min. Beyond that the motor just chatters.
2. The Y motion is very loud. X is smooth and quiet.
3. The Y step action is very sharp. Very noticable when etching and doing a line reversal.

Distance and speed measurements appear to be very accurate. Cut a 250mm square out of paper and measured the sides and diagonals.

The steps per mm is set at 400 due to the lead screw thread and the 16X to the stepper motor driver. Wondering about:

1. Changing the 16X to 4X (or 1X).
2. Wiring the Y motors on separate driver chips.
3. Adjusting the current limit.

7
General Discussion / Line widths
« on: December 22, 2017, 05:04:54 PM »
I have 8 images that started as clip art. Plan to select 6 and etch a 3D puzzle for my granddaughter. Put 4 of the 50x50x50mm blocks together into a square and etch the 100x100 image across the 4 faces. Then scramble the blocks and put another image on the new faces. A couple of problems/questions arouse.

First - Being the least artistic person in the universe I have no idea if the finished project should have the wood grains aligned or random. Two of the faces will be end grain.

Second - When I test printed the images I noticed that the outline paths are different widths. I recall using a free online service that converted rastor to vector with user specified line widths. That memory cell got zapped.

8
General Discussion / Inkscape question/problem
« on: December 13, 2017, 08:03:17 PM »
I need to add units (mm) to a svg file created by openscad.  A Google search recommended opening in inkscape, changing the units from px to mm, and saving. The basic outline is approx 100 x 160 mm with about 35 holes. When I change the units to mm it also scales the image down to about 25% of the original. I am also concerned about negative numbers as openscad centered the image.

9
Mini CNC / Mini mill kerf
« on: November 20, 2017, 07:06:11 PM »
I have the limit switches working in the mini mill and have been able to cut some 20x20 squares with ok results.

Running at 100mm/min it seems to be limited to 0.25 mm per pass on scrap plywood with a good quality 3mm end mill. 50mm/min and 0.50mm cut chatters a lot.

Also have a plunge drill working with ok accuracy. Added code to the svg file parsing that detects small, less than 8.0mm circles, and turns them into drill operations. Because the mill collets are limited in size I will drill with 3mm bit and bore to size on manual drill press.

The spindle motor is quite weak (along with everything else being marginally crap) so I don't expect to be able to cut any type of metal but am thinking it could make nice picture frames for mirror etchings.

Questions:
   1. What tools are available for compensating for tool width (kerf)?
   2. What is the notation/procedure for setting the Z axis on a tool change.
   3. I use openscad for all my 3d design work and generate stl files for 3d printing. Looking for a utility
       that would take a stl file and slice it into a number of 2d files with user selected layer depth.
   4. What is the proper syntax and units for grbl dwell. I want to pause on every Z change.

10
Mini CNC / Limit vs Home switches
« on: November 09, 2017, 07:28:49 AM »
I added 6 switches to my 3018 mini mill. Set the grbl options to limit switches and reset the CPU. Startup messages indicate that a $H homing cycle must be preformed or an $X override. Did the $X and tried to run the x axis past the limit. It stops with a

 "ALARM : Hard limit"

message. Looks like they are wired correctly.

What I do not understand is:

   1. How to initial a Homing cycle.  It currently runs to the limits and
       freezes or hits the hard stops and bangs on the steppers.
   2. How to recover from the hard limit alarm
   3. What is the process (name) for measuring the Z position of the cutting tool. I would
       like to change cutting tools and know the new depth.
   4. Does the HOME use the same switches as the LIMIT?

There is not much documentation available. It appears to have grbl 9j loaded and there are adds that indicate newer units are being shipped with 1.1. I have no idea if it contains "stock" firmware or if the vendor has played with the configuration.

11
General Discussion / Sad day in Laserville
« on: November 03, 2017, 01:47:23 PM »
After approx 16 months us fairly heavy usage my 5.5V laser module appears to have died. It supplies a very weak beam that will not focus and at times has a solid bar thru it. Was working on a mirror when it just stopped burning.

A 2.5W laser module arrived earlier this week and it is behaving mostly OK on finishing the mirror job.

Something that I have no control over is the backing on the mirrors. Have 760x760mm mirrors from Michaels and Hobby Lobby. Same brand and packaging, different reaction to the laser. They both have 3 layers - glass, reflective, and painted backing.

The mirrors from Michaels burned cleanly thru the paint and turned the reflective material into a flaky char, sometimes very hard to get off.

The Hobby Lobby mirrors are not burning all the way thru the the reflective material, just turning it into a very nice crystal like surface. However, the paint is not being completely removed and is adhering to the groves made by the laser. Looks crappy from the backside.

Would like to hear from other users etching mirrors as to medium, power settings, manual finishing, etc.


12
General Discussion / Etching on mirrors
« on: October 20, 2017, 02:32:48 PM »
I went to "Michaels for Men" and bought some small mirrors with the intent of etching. Questions:

  1. What power settings?
  2. Etching with fine lines ok?
  3. Are the etched surfaces smooth or glazed?
  4. OK to paint? If ok, what cleaner & paint?

13
General Discussion / Problem focusing 1.6W
« on: October 14, 2017, 08:56:12 AM »
I purchased a 1.6W TTL diode module to put on my home brew corexy fixture. Having difficulty getting a sharp focus. Looks like a circle of small dots. The distance from laser lens to waste board is approx 80mm. I have a  number of lenses for my 5.5W diode and think that there is an "ideal" distance for each. Any idea what this might be for the 1.6W?

14
General Discussion / Low pwer with 1.1f
« on: October 10, 2017, 11:41:30 PM »
I have assembled a corexy machine with a 1.6W diode laser. Things are progressing slowly. Currently stuck with setting the PWM from the command line. Have compiled and loaded grbl-1.1f onto a simple Arduino/CNC shield. I am Linux based (unless I borrow a laptop from wife) so T2 & BCL are not a good option. Have read the grbl laser doc and think I have the config.h setup correctly.

I get the laser on full power upon reset and have some control but a "M03 S255" does not appear to generate a very powerful beam. Power supply indicates 12V 0.30A. Letting the PWM line float causes it to consume 0.70A. It is 0.06A when idle.



   

15
General Discussion / Etching in leather
« on: October 04, 2017, 05:53:31 PM »
I downloaded the attached image file from vectorinc.com and scaled to fit a slate coaster with a density of 254dpi and a burn area of 800 x 800 mm. Least amount effort on my part in a long time. Instead of etching in slate I tried some light colored leather that I got from an almost scrap pile at a local junk (antiques) shop. Turned out great for a first attempt. Etched at a speed 1200 power 20 and cut the outline at 800/50 with 6 passes with 5.5W laser. Leather had some stains so a second burn is necessary. Also did a poor job on trimming the outline with knife where the laser did not cut thru.

It was  necessary to have the air turned on for the frame cutting. Leather wanted to catch on fire. Also stunk up the house pretty good!!!!
 




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