Getting started cutting non-proofgrade hardwood

[eric12]

I hate to ask, but what is “operating in class 4 modes”? I have a GF Basic and never intend on opening the door while running or anything…

[rpegg]

If the Pro operates without the pass thru shields it is in Class4.

[evansd2]

What @rpegg said. Basically it means “there’s a chance this laser might escape the machine, wear glasses.” If you don’t trick your GF into operating with the door open on a basic, you should be fine.

[eric12]

So this is very interesting…I bought some 1/2" red oak and did the speed test graphic mentioned in other posts and after doing this and some other separate tests, here’s what I learned:

• 100/full in 1 pass went all the way through and gave some flashback
• 125/full in 1 pass went in only maybe .25in. I tried multiple passes and after 7 passes it still wouldn’t go through. So I instead started over and did one pass at 125/full at the full 0.5in focus height, then one at 0.25in. But that pass left about 0.1in left, so I started over and did the 125/full at 0.5in, then 0.25, then at 0.1in (all without moving the part) and it still didn’t go through. So I gave up and just did the 100/full in 1 pass even though I was a bit concerned about fire.

So here’s my questions…

1. Why did 100/full go through (and then some) and yet 125 had major struggles? Are these speeds significantly non-linear in their effective strength or something? I would expect 125 wouldn’t be that dramatically different than 100.

2. Also, do you think I did this right on the multiple prints at different focus lengths? I thought that would have worked.

Thanks!

[jamesdhatch]

@eric12

Are these speeds significantly non-linear in their effective strength or something?

Yes. 50 is not half of 100. 200 is not twice 100.

GF uses its own speed and power setting scale. Part of the reason is so that settings for Basics and Pros can be used interchangeably until you get to Full power - for the Basic that’s 40W and for the Pro it’s 45W.

They did release a spreadsheet back when they switched from their initial scalable settings (and inch per minute speeds) to their current scheme. If you search you should be able to find it and get a better sense of how the numbers scale in relation to each other.

[jbmanning5]

Speed of 100 is 4 inches per minute. Speed of 125 is about 13 inches per minute.

[eric12]

Wow my suspicion is right. That seems odd but thank you for the info. I guess I would need to do some tests with small increments between 100 and 125 to really get this right.

Thanks much to you both.

[evansd2]

@eric12

I guess I would need to do some tests

You can do it in one test.

Has anyone been cutting 0.37-0.40 material?

This post has been moved to its own topic. Click to go there.

Testing is fast and easy, use this method and you’ll be able to test any material in minutes.

[eric12]

Yes, definitely. In fact I used that to determine the 100 vs 125 vs 150 etc. Now I just need to modify it a bit to run 100, 105, 110, 115, 120, 125 now that I know that the speed numbers are non-linear.

Thanks!

[rbtdanforth]

When you are running at full blast with no flame happening the Glowforge will cut much deeper than if there are problems. At first I thought it was variations in the wood but those cuts near the magnets did not go through, When re-cut those parts that were not cutting all the way through, still did not cut through. As best I can tell either or both of two things could be happening : #1 the char itself is more resistant to the laser than bare wood or #2 the wood is hardened by the heat and it takes more to cut it. Whatever is the case there is rather a difference with the second pass that it does not cut as deep as the first, even as the same settings.