Testing Frequency Range on ComMarker B4

Initial Revision 4/10/2023

Property of Paul Ruby of PaulRubyAmplifiers.com

Contents

Introduction. 1

Expected Results. 2

Testing Results. 2

Conclusions and Musings. 8

Deep Engraving Brass. 9

DISCLAIMER. 10

Introduction

The data sheet for the MFP-20W laser source say 30khz to 60khz.

But there is no explanation this range. Is it the min and max allowed setting?

Or, is it the range over which the pulses will be full power?

We’ll find out…

Expected Results

First some math. From previous study, focused dot size is about 50um.

Pulse frequency should be fast enough such that the dots touch each other along a path of engraving.

At the base frequency of 20khz, dots are produced every 50us.

So, the laser path should not move faster than 50um in 50us.

That’s easy math: 50um/50us=1m/s or 1000mm/s.

To run faster, pulse frequency must go up proportionally…

40khz for 2000mm/s; 60khz for 3000mm/s; 80khz for 4000mm/s; etc…

This will vary depending on dot size, which depends on power setting and focus adjustment, of course.

Testing Results

Here’s a full view of the test for frequency versus speed.

The lower right corner is the expected 20khz and 1000mm/s.

The diagonal moving up and to the right are where the speed and frequency should be a match.

Results are not visible at this level. Need a microscope to look closer.

I use a cheap USB microscope to study results. This…

https://www.amazon.com/gp/product/B00XNYXQHE

At 20khz and 1000mm/s the dots are touching each other and are perhaps slightly larger than 50um, so have some overlap.

Individual dots are easy to make out. No surprises here.

Moving to 2000mm/s, 20khz is not fast enough to allow the dots to touch but 40khz just barely touch.

Note the dot size has reduced a little at 40khz, so there is no overlap of dots at 40khz and 2000mm/s. Just barely touching.

The energy in each pulse must have reduced a bit at 40khz. Hmmm…

Now looking at 40 & 60khz and 2000 &3000mm/s.

Dot size has reduced again 60khz. No question that pulse energy is dropping as frequency goes up.

But, the dots are coming in faster as expected.

Dots are not quite touching at 60khz and 3000mm/s because of the reduced dot size.

Moving to 60 & 80khz, 3000 & 4000mm/s, dot size again reduces.

Also, the dot pace does not appear to have gone up as much as expected.

Dots are not touching for either speed at 80khz.

Using a ruler on the image, I get 52khz measured frequency on the 60khz test. Close enough…

But, the 80khz dots only measure to be 60khz. Frequency has gone up but seems to have topped out.

One final image shows 80khz and 100khz. Dot pitch is unchanged, so frequency of pulses is not increasing.

Maximum frequency is about 60khz. If you set frequency to about 70khz or higher, you will get the same frequency, independent of setting.

Conclusions and Musings

Pulse energy clearly drops consistently at 40khz and above.

This behavior can be explained with some math…

The fiber in our B4 laser is rated at 20W power delivery. The pulse energy is 0.68mJ, from the spec.

This seems to explain the behavior I’m seeing well. Here’s the math for power in the fiber:

20khz*0.68mJ = 13.6W ß Well within power rating.

We hit the max power rating at 30khz: 30khz*0.68mJ = 20.4W.

This explains why the energy per pulse is dropping as frequency goes up. It has to drop to protect the fiber.

I don’t know at what frequency the laser will start to reduce the energy per pulse, but it is certainly no higher than 30khz.

At 60khz, the max allowed energy per pulse is 20W/60kHz=0.33mj. ß Less than half the rated energy per pulse.

For maximum pulse energy, run at low frequency of about 20khz and no higher than 30khz.

This also imposes a speed limit for maximum pulse energy of 1000mm/s at 20khz to keep the dots touching.

In previous study, I’ve also found that lines wiggle when moving beyond 500mm/s.

Here’s a plot of max energy per pulse versus frequency to stay under 20W and 0.68mJ.

Deep Engraving Brass

I ran a quick test cutting through brass, 0.3mm think sheet.

Chose 750mm/s, 100% power, x-hatch fill in continuous run to see how many passes cut through.

30khz takes 104 passes (which is 208 since each pass is X-hatch)

25khz takes 106 passes.

37khz takes 91 passes.

45khz takes 90 passes.

52khz takes 92 passes.

60khz takes 88 passes.

25 and 30khz do not seem to deliver maximum energy.

But, just above that, 37khz and beyond are all about the same.

60khz seems to have done the best but they are all within a few percent of each other.

Can't draw any conclusion that 60khz is best unless repeating the experiment many times.

I ran 30khz twice and averaged the two results.

1st time was 100 passes and second was 108. I did not run any of the others more than once.

If I were suggesting what to use…

~35khz to maximize energy delivery without overlapping the pulses.

And run between 500 and 750mm/s.

500 gives perfect path accuracy but a bit more dot overlap. 750 would be closer to optimal dot overlap but line path will wiggle a bit.

Nothing much to see, but here’s a picture of the experiment run.

These are 4mm squares, cross-hatch filled.

I had wood below and ran until I could hear the laser mostly hitting wood.

DISCLAIMER

Last updated April 06, 2023

The information provided by Paul Ruby Amplifiers ("we," "us," or "our") on paulrubyamplifiers.com (the "Site") and this document is for general informational purposes only. All information is provided in good faith, however we make no representation or warranty of any kind, express or implied, regarding the accuracy, adequacy, validity, reliability, availability, or completeness of any information on the Site. UNDER NO CIRCUMSTANCE SHALL WE HAVE ANY LIABILITY TO YOU FOR ANY LOSS OR DAMAGE OF ANY KIND INCURRED AS A RESULT OF THE USE OF THE SITE OR RELIANCE ON ANY INFORMATION PROVIDED ON THE SITE. YOUR USE OF THE SITE AND YOUR RELIANCE ON ANY INFORMATION ON THE SITE IS SOLELY AT YOUR OWN RISK.

The Site and this document may contain (or you may be sent through the Site) links to other websites or content belonging to or originating from third parties or links to websites and features in banners or other advertising. Such external links are not investigated, monitored, or checked for accuracy, adequacy, validity, reliability, availability, or completeness by us. WE DO NOT WARRANT, ENDORSE, GUARANTEE, OR ASSUME RESPONSIBILITY FOR THE ACCURACY OR RELIABILITY OF ANY INFORMATION OFFERED BY THIRD-PARTY WEBSITES LINKED THROUGH THE SITE OR ANY WEBSITE OR FEATURE LINKED IN ANY BANNER OR OTHER ADVERTISING. WE WILL NOT BE A PARTY TO OR IN ANY WAY BE RESPONSIBLE FOR MONITORING ANY TRANSACTION BETWEEN YOU AND THIRD-PARTY PROVIDERS OF PRODUCTS OR SERVICES.

The Site and this document may contain testimonials by users of our products and/or services. These testimonials reflect the real-life experiences and opinions of such users. However, the experiences are personal to those particular users, and may not necessarily be representative of all users of our products and/or services. We do not claim, and you should not assume, that all users will have the same experiences. YOUR INDIVIDUAL RESULTS MAY VARY.

The testimonials on the Site are submitted in various forms such as text, audio and/or video, and are reviewed by us before being posted. They appear on the Site verbatim as given by the users, except for the correction of grammar or typing errors. Some testimonials may have been shortened for the sake of brevity where the full testimonial contained extraneous information not relevant to the general public.

The views and opinions contained in the testimonials belong solely to the individual user and do not reflect our views and opinions. We are not affiliated with users who provide testimonials, and users are not paid or otherwise compensated for their testimonials.

Except where specifically noted, permission must be obtained for reproduction of any portion of the material on this website and in this document. The material may not be edited or altered and must remain unchanged, as published by Paul Ruby Amplifiers. To obtain permission to reproduce material at this website (including text, images, and multi-media files) for any purpose, submit the specifics of your request in writing via contact through PaulRubyAmplifiers.com.

Artwork or images on this website and in this document may be protected under copyright law. The unauthorized use of such material could be a violation of the rights of the copyright owner. The unique branding of the website and various official seals and marks may not be used without permission of Paul Ruby Amplifiers. To use any information on this website or this document not owned or created by CDE, permission must be obtained directly from the copyright owner.

Paul Ruby Amplifiers shall have the unlimited right to use for any purpose, free of any charge, all information submitted via this website and this document, except those submissions made under separate legal contract. Paul Ruby Amplifiers shall be free to use, for any purpose, any ideas, concepts, or techniques contained in information provided through this website and this document.