ACMER 20W Module — Oversized Laser Spot Along Y Axis (0.2 mm instead of 0.08 mm). Support unhelpful. Anyone else had this?

[Mikalai (Kryvusha)]

Hi everyone,
I’m reaching out to the community for advice and support.

I recently purchased the ACMER 20W Diode Laser Module (ordered directly from their official website) as an upgrade for my ACMER P1 S PRO. I was previously using their 6W module and was very happy with it, but wanted more power.

After installing the 20W module and running some tests, I noticed a serious issue:

• Vertical lines (laser moving along Y) engrave perfectly — thin and deep.
• Horizontal lines (laser moving along X) come out blurry and wide (~0.2 mm) — almost 3× wider than advertised.

They claim a spot size of 0.06 × 0.08 mm, but I’m clearly getting something like 0.06 × 0.2 mm, which causes major distortion, especially when engraving text or patterns requiring precision.

I did all the proper setup:

• Correct Z-height / focus with the original metal gauge
• Tested on MDF and black anodized aluminum
• Tried various speeds and powers — issue is consistent
• The spot shape appears stretched into an oval or bar

I reached out to ACMER support several times, but they dismissed it as “slight deviation due to material burn” or claimed that “advertised spot size is only from optical measurements.” They refuse to acknowledge that this might be a defective module or lens alignment issue.

I’m honestly disappointed — this doesn’t feel like a “slight deviation,” it’s a massive distortion that ruins precision work.

My questions:

1. Has anyone else experienced a similar issue with ACMER 20W modules?
2. Is this really “normal” for diode lasers of this class, or should I insist on a replacement?
3. Any tips on how to escalate this with ACMER, or even adjust/fix the focus if possible?

I’ve attached microscope photos and test results if anyone wants to see them.

Thanks in advance — I’d appreciate any feedback or shared experiences.

— Mikalai Kryvusha (from Minsk, Belarus)

[jkwilborn (Jack Wilborn)]

I hope you bought with a credit card? If so, you should contact them and tell them what they sold and told you, ask for a refund.

It’s clear there is some issue, but without some type of item, scale or measuring tool, next to the burn line, we can’t tell size, except that the X axes is much larger than the Y axes.

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Question, 1.) I don’t have one of these, but I’ve seen a lot of diode lasers and have never seen one this far out.

@Mikalai

Is this really “normal” for diode lasers of this class

2.) These usually have much better results. If they didn’t the wouldn’t sell them.

@Mikalai

should I insist on a replacement?

3.) I’d say yes. I’d say your photo was clear evidence… However you’re dealing with the Chinese

@Mikalai

spot size is only from optical measurements

I think you are doing optical measurements with your posted photo.

I know of no way to correct this, it’s all internal to the diode module.

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A similar problem…

Diode Laser Astigmatism? Blurry Vertical Lines, Sharp Horizontal Lines – AtomStack A24 Pro

Hey everyone, I recently picked up an AtomStack A24 Pro and ran into a concerning issue right out of the box. During a quick test engraving, I noticed something strange: vertical lines were coming out noticeably blurry and wide, while horizontal lines were sharp and clean. To investigate further, I engraved multiple 1cm x 1cm squares at various speeds and power settings. The results were consistent — vertical lines always appeared fuzzy and significantly thicker than their horizontal counterpa…

Good luck

[misken (Melvin)]

0.08 x 0.2 is extreme, though a realistic value for a 20W module is around 0.1 to 0.12 side length. There is no module below 0.1, that’s stupid advertisement of all manufacturers.
Do the wall test, point the beam to a wall and take a picture.

[jkwilborn (Jack Wilborn)]

@misken

point the beam to a wall and take a picture.

I simplicity for simple determination.