Darkly Labs Community

Cutting MDF and Acrylic

Hi, 

I have some questions after my experimentation with 3mm Bunnings’ MDF (CustomWood brand). It is probably the cheapest MDF there is, at $3.50 per 3mm 900x600mm sheet. Note that the thickness is actually about 3.35mm (edited: fixed actual thickness)

I don’t have air-assist either.

With 1.5mm tool offset, I tried 10 different settings:

Top row: 2 passes at 180mm/min and 2mm pass height, starting height of 12.5mm, 13.0mm, 13.5mm, 14.0mm, and 14.5mm
Bottom row: With 3 passes at 180mm/min and 1mm pass height, starting height of 12.5mm, 13.0mm, 13.5mm, 14.0mm, and 14.5mm

From the cutting side, the lines all look very similar to me, so I don’t think kerf is a problem at all.


On the other side, none of the two passes manage to cut through. Here is the picture (the picture is flipped, so we are still looking left to right).

image.png
Of the ones that did actually cut through, the best one was the one with starting height 14.0mm (2nd from right). The 14.5mm also cuts well, but if you see carefully, it’s not fully cut (there’s a bit of MDF laminate that I had to rip off). 

Question: I used tool focus of 1.5mm, and since the material is 3.5mm and starting height it 14.0mm, I’m guessing that my tool focus should actually be 2.0mm, (or 3.0mm, but I’ll just set it to 2.0mm since I will always use the silicon tray, so I only need to input actual material height).

Based on this results, I tried one more time with 170mm/sec using the best starting height (14.0mm), and it cuts it through no problem.

However, there are other posters who can cut MDF 3 passes at more than twice the speed (380mm/min), with Emblaser1!!!. Even 3 passes at 180mm/min won’t cut it for me!

 Acrylic 2mm, black opaque (2.15mm actual thickness)

I am still experimenting with this. I’m cutting the acrylic with the protective sticker still attached. Tool focus is still set at 1.5mm

start height 12.5mm, 100%, 2 passes at 180mm/min, 1mm pass height – cuts through
start height 12.5mm, 100%, 2 passes at 200mm/min, 1mm pass height – cuts through
start height 12.5mm, 100%, 2 passes at 240mm/min, 1mm pass height (doesn’t cut the bottom protective sheeting, and I don’t think it fully cuts the acrylic either)

start height 13.0mm, 100%, 2 passes at 200mm/min, 1mm pass height – cuts through 
start height 13.0mm, 100%, 2 passes at 240mm/min, 1mm pass height – doesn’t cut bottom sheeting either, and more noticeable damage at bottom of acrylic, which means it wasn’t cut the whole way through. 

The problem about cutting acrylic is that, well, they’re not that cheap. However, I think it’s safe to say that 2 passes at 200-220mm/min is the best setting.

 Acrylic 3mm, yellow opaque (3.25mm actual thickness)

I tried cutting at 100%, 3-pass, 200mm/sec with 1mm pass height, and it didn’t cut it the whole through, so I restarted the job with another 3-pass at 0.5mm pass height. I will give it another try soon. Looks like it needs 6-passes. 

Acrylic 3mm, green opaque (3.25mm actual thickness)

It took 10 passes at 100%, 200mm/sec with 0.3mm pass height. The top layer was a bit chamfered by the end. 

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I haven’t tried with 0 pass height because I assume that would give me a worse cut. Any thoughts on this?

Daniel,

You mentioned Bunnings so I’m assuming you are in Australia.  I’m in Victoria and over the last week the relative humidity in my workshop has been 80% and above.

With humidity so high, it makes it very difficult to cut any timber based material with a E1 or E2.  Timber and especially MDF acts like a sponge and takes on moisture as the humidity rises.

This moisture in the material increases the difficulty of cutting.  I ran a job with 3mm MDF from Bunnings in my workshop last night and it didn’t cut through with my standard settings. I will just wait until the humidity drops and run the job again.

You will also see posts on this forum where Emblaser owners have an issue where all of a sudden they can’t cut today what they could yesterday and go looking in depth at the cause.  In my opinion, the most likely cause is a large increase in humidity between the two days.  I have a cheap digital humidity meter (Hygrometer) in my workshop and constantly monitor relative humidity(RH) as it affects a lot of my work - gluing timbers, painting, E2 cutting etc.

This may of course may have no bearing on your testing at all but may be one of those “nice to know” things.

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Hi Daniel,

Thank you for the very informative post. Excellent testing and reporting.

We have run many tests cutting with both lowering the height with every pass and also leaving it fixed. We have found that the depth of focus of our beam is wide enough to achieve good results leaving the height fixed for up to 6mm materials. You may want to run some tests with this in mind.

The tool offset value from the current calibration test is sometimes difficult to determine. If you are achieving better cutting results with a higher value, then this is probably a more precise value for your machine. We attempted to make the calibration process quick and simple to perform and are actually working on a new calibration test that should yield more accurate results.

Please keep us informed of your results.

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Daryl, thank you for that comment. I didn’t think about humidity at all, but I will now. I’m in Sydney and it rained for the first time in a week yesterday when I was cutting, so I will assume the above setting is for dry MDF. 

Domenic, I’ll definitely give the MDF another go this weekend. Any comments on the green acrylic taking 10 passes, or does this sound reasonable?

Hi,

I ran another test to see the difference between 0 pass height and 1 pass height. The setting is still for 170mm/min, 3-passes, 100% power. Surprisingly it cuts better with 0 pass height. Why is this?

Here are the pictures. As you can see, there is much less burn with 0 pass height, on both sides.

Top (laser) side:

Bottom side (one piece fell off when I flipped it). You can see some charring with 1mm pass height setting.

Any suggestion on what to try next? I’m guessing I should retry different starting heights with 0 pass height.

 

Hi Daniel,

The reason why zero pass height works better with this thickness of material is related to the shape of the laser beam. 

You need to imagine the beam shaped like an hour-glass (yes the light beam is curved), with the thinnest part of the beam (the waist) not being a specific point, but rather a region that can cut effectively.

If you lower the height of the laser on this thickness of material, you are in effect moving the effective cutting region to somewhere below the material and hence not achieving as good results. This is evident with the more charring on top of your piece as in the photo.

I would recommend you experiment with increasing the height of the laser incrementally until you notice the performance going down. Use this number to recalculate your tool offset (based on the current value you are using).

 

Thank you for that information, Domenic. How wide is this best cutting region, or is it different for each laser?

Here’s my tests with pass height 0mm for various starting positions. My tool offset is 2mm and material thickness is around 3.35mm.

Front face:

It may not look that obvious, but the lines start to get darker at 13.5mm

image.jpg

Back side (13.5 to 14.5 break away easiest):

image.jpg

Only one piece broke off easily (the one with 14.5, and only one piece out of three). The 15.0mm start height is still not fully cut. 

So what do you think? I wonder if 15.0mm starting height with 1mm pass height will give me a nice result?

It may also be worthwhile to try 15.5mm, 16.0mm, and 16.5mm starting height until I see thicker lines.

Hi Domenic,

Here is a more thorough test. Tool offset still at 2mm, material height 3.35mm. Somehow it is a different result from the previous run. Hopefully you can help me decipher it.

For the 1-pass, the lines start to get thicker at 13mm and 17mm.

For the 2-passes, I think it’s easy to see that 13mm and 16mm are when it gets thicker. 

For the 3-passes, 14mm and 15mm looks best from the cutting side, but surprisingly 13mm and 14mm are easiest to pop out (15mm one didn’t cut through). 

For the 3-passes with 1mm pass height, the 15mm starting height actually cuts best, though still not ideal. I don’t quite understand this: if I set pass height to 1mm, I expect one of them to have a good cut, but none are better than the 3-passes, 0 pass height ones.

Hi Domenic,

I could not respond to your earlier comments - grandkids, etc.

 

re 3mm (3.2mm) mdf:

I have been following posts and,

I ran some test cuts and came up with 100% / 2 passes / 13.2mm start / 0mm Pass depth /  120mm/m with Air Assist.  This worked for most of the next job, a small switch box.  However:

1.  The part nearest the Zero point cut less well.  The only possibles I can think of are that there is a slight bend in the mdf (I had flat strips of lead flashing holding it down - I wonder if that introduced an up-curve at the left end?)

 

2.  For this cut, and other long cuts, (e.g. a complicated one in 0.3mm heavy paper) the laser became staccato, or stopped entirely while the air-assist and fans continued and a message window popped up with a lot of code which I tried to copy to add to this  text - would not paste.

After a while the laser started up again and the job finished.  I will try to email you the Work Space file (Laserweb-Workspace MPJ SwitchBox)

I have done the machine calibration again, starting from zero offset.  the first complete cut is debatable;  each from 2mm on have at least some tiny bits left in.  This time I chose 3mm as it had the least.

 

One other thing:  The exhaust air tube is too short to reach the outside from where I set up my work area so I got some more 50mm flex tube.  The total is about 12 metres run.  I have made up an inline fan-box, using a couple of small, 12vDC CPU  fans to help push the air along and keep the E2 clear inside.,  The resultant flow is not strong enough to turn the E2’s own fan when it is turned off, but the nett effect with all running seems to keep the interior of the E2 clear (though the laser (?)  is sometimes still a visible streak  in the smoke raised) and I have a smoke and smell-free work area.

 

Re the E2 Manual.   A user’s comment - critique, not criticism.    I found the online version to be correct on several readings,  but not easy for me to understand  and put into use first time, or on repeated jobs,   e.g. the bits about the calibration file are near the end;  this Luddite assumed they were an appendix for later reference.  So, I have written a manual in a step-by-step format for your consideration and use in the community, or the trashcan, as you see fit.

 

Ideas please?

 

Mike

I looked around for some E0 MDF today, and managed to get a few sheets from a supplier in Sydney. E0 MDF has less than half formaldehyde parts compared to E1 MDF, which is more commonly found (e.g. Bunnings). Plus, these MDF sheets actually are truly 3mm, as opposed to Bunnings’ 3.3mm MDF sheets. 

With Bunnings’ MDF, after 3 passes at 170mm/sec, I am still not guaranteed a clean cut. With these MDFs, after 2 passes at 170mm, I cut right through (even 180mm/sec is good enough). I am going to try a few 1 pass settings tomorrow. 

Moral of the story: get a good MDF.

 

Daniel, who is your supplier?

I would like to try this E0 MDF as well. I agree with you about the quality issue.

Hi David, 

I don’t think the supplier really matters as long as it’s E0 MDF (and true 3mm). I’m in Sydney, and I went to FA Mitchell at Lidcombe (https://www.famitchell.com.au/). Nice blokes, considering people buy the pallets and I only asked for 2 sheets of MDF ($20) when I first talked to them. 

The cutter at the factory mentioned that they got their MDF from Borg if I heard correctly, which is weird because that’s the same place Bunnings got their MDF from. 

I got some 4mm E0 plywood as well, at 10 times the cost of MDF ($75 a sheet I think), but I haven’t tried cutting them yet. 

I attach 2 pictures of comparison between Bunnings MDF and the MDF I got from FA Mitchell (notice colour and thickness). 

 

*edit*: Unfortunately I haven’t managed to cut them with one pass successfully, but 2 pass at 200mm/min is good enough for me.

Hello Daniel,

Thank you for posting all this information. I have been chasing my tail like you trying to perfect settings.

New out of the box I could cut Bunnings 3mm MDF with 1 pass, 100% power and 100mm cut rate.
Then after several test cuts and mucking around I needed to reduce speed down to 90mm cut rate and even with two passes couldn’t cut through the same 3mm MDF

I think the problem is dirty lenses.I actually already have a Lenspen (as recommended by Domenic) but found it hard to get onto the lens. So I used some Isopropyl alcohol and a cotton bud.

I have cleaned the laser lens and can now cut the same 3mm MDF with 1 pass, 100% power and 150mm cut rate.