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Messages - ggallant571

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1
Z Axis / Re: Adjustable focus rather than a moving Z-Axis?
« on: March 28, 2017, 09:18:24 PM »
Welcome to the Society of Z-Axis Builders. There have been a few solutions presented, each with its own set of problems. Some issues:

1. Laser beam alignment
2. Home switches
3. Weight
4. Z-Axis motor drive
5. Speed

1. I built a simple mechanism about 6 months ago and it fails miserably on beam alignment. If the beam is not perfectly vertical you will expend energy burning the sides of the cut trough. Looks poor and the cut is extra wide. Really shows up bad when cutting plastic as the walls melt and fill the cut path. A nice test pattern is a large square (50mm x 50mm) where the Z-Axis is lowered 1mm for each 5mm of travel.

2. Home switches are a necessity!!! You will want to focus the laser at a known height and lock it in place.

3. Adding weight mean more mass. My factory supplied stepper motors could not handle the weight of a NEMA17.

4. Extra motor means extra stepper driver and associated firmware. I wrote my own embedded firmware and the ISR for servicing 3 steppers uses about 60% of the CPU cycles on a 16MHz 328 chip.

5. To lower the weight I went with a small motor with internal gear box. Slow. Takes about 30 seconds to move 1mm. Might not sound like much today but when cutting it is a pain. Also, when finished it needs to return to the home position. BTW - make sure you turn off the laser when doing Z motions.

I was designing a "better" mechanism but my interests have changed from cutting to etching. I primarily use the z-axis for focusing and test burns. To etch 3mm slate I focus the laser beam on cheap neon cardstock and do a low power burn. Once OK with the test burn I raise the laser appropriately.

For my next laser (parts on workbench) I am planning on raising/lowering the work surface. It has a few design issues, 4 stepper motors and wiggle, to solve.

Please post your ideas and pointers to purchasable solutions. If we get enough response we could start a z-axis thread (assuming Ralph hasn't already).


2
Projects / Re: Lighting mirror
« on: March 28, 2017, 06:24:43 PM »
They look excellent. Thanks for sharing!!!!

3
T2 Software Updates / Re: Updates
« on: March 27, 2017, 07:19:02 PM »
Gee. I was hoping for a multi-spectral control option so I could etch the wood the same color as the laser beam.

4
If anything, you probably will fry the stepper motor controllers. My controller uses A4988's and it has been handy to have a bunch of replacement modules on hand!

5
Assembly Help / Re: Wiring home switches
« on: March 25, 2017, 10:32:56 AM »
I would securely glue a header to the L7 and run 30 gauge wire from the header to pin 9 on the backside. Then you can  plug/unplug the CPU board without playing with the home switches. You can wire the limit switches to individual I/O pins if you configure the firmware.

6
General Discussion / Re: Is this the z-axis we've been looking for?
« on: March 25, 2017, 10:23:00 AM »
Are you squaring the laser heat sink or the laser beam?

7
General Discussion / Re: Is this the z-axis we've been looking for?
« on: March 24, 2017, 09:08:22 PM »
Please explain how to use the square to align. Mine is off enough that multipass cutting is generating wide angled slots.

A machinist friend has volunteered to mount a mirror on a 45 degree cut in a rotating vertical shaft. Idea is to shine the laser onto the "exact" center of the shaft and measure the burn on a circular wall. X+, Y+, X- & Y- should all be the same if it is vertical. Hoping that there is a math algorithm to evaluate the results and compensate for the beam not being dead center.

8
General Discussion / Re: Is this the z-axis we've been looking for?
« on: March 24, 2017, 08:14:26 PM »
Looks like you have "All the toys". How do you align the laser to be vertical?

9
General Discussion / Re: New lens
« on: March 23, 2017, 07:45:39 PM »
I have that problem and wonder if it means that the beam is not perpendicular to the work piece.

10
General Questions / Re: Use of a SD-card with lasercutting/engraving?
« on: March 22, 2017, 08:06:45 PM »
It also means the user interface for file name etc is going to be missing. How would you synchronize placing the material, laser focus, initial laser position, burn intensity and the burn start operation?

11
General Questions / Re: Use of a SD-card with lasercutting/engraving?
« on: March 22, 2017, 04:17:55 PM »
What about using a small board with USB ports such as Raspberry Pi?

12
General Discussion / Re: What's the advantage to limit switches?
« on: March 21, 2017, 07:17:21 PM »
I put the home switches on X & Y axis and can't imagine using a laser etcher without them. Gets the laser to the exact same coordinates every time. My switches each go to a dedicated I/O pin.

Upon receiving the gcode HOME command the firmware:
  1. Moves both X & Y forward 5 mm. Just to insure that they are not already at 0,0
  2. Run the X slowly in reverse until the switch closes.
  3. Run the X forward very very slowly till the switch opens.
  4. Repeat steps 2 & 3 for the Y axis.
Take about 30 seconds.

I have burned multiple test patterns in cardstock without any visible deviation. Once the switch positions were finalized I used the machine to cut an alignment "L" out of 3mm plywood which makes a quick placement gig.

13
General Discussion / Re: Link for better same spec wheels?
« on: March 20, 2017, 09:31:52 PM »
I think you have the new/better wheels. Must be a softer material than the older ones. Mine are a hard white plastic wheel very similar to those used on sliding shower doors.

14
General Discussion / Re: Is this the z-axis we've been looking for?
« on: March 20, 2017, 09:22:59 PM »
We should be able to etch wooden nickles.

As for better, the heavier motors have more torque but require more current. I just weighed one of the bigger motors and it is approx 12oz or 340g. Enough to induce significant degradation of the smaller x-axis motor performance. The motor I am using weighs about 1oz.

15
General Discussion / Re: Is this the z-axis we've been looking for?
« on: March 20, 2017, 07:08:01 PM »
The motors on my A5 machine have cores that are 16mm across while the motors for a new jig are 24mm. This is the black iron center section not including the aluminum end caps. The orig motors are marginal at best. Fits perfectly with the rest of the fixture components.

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