[2_many_hobbies]

Normaly stock lens is 50.8mm. I change 38.1mm. You can calculate it. Smaller dot and more power. If you change 75mm lens then you have big dot and small power. I made cutting bed with manual up and down function.

Ahh thanks. I was not sure which one was the stock lense. How many mm of room is their below the stock table?

[miketola]

I check my cutting table and there is room about 95mm with 38.1 lens. I like pintable because now i dont need masking tape below material.

[buddydog]

That might not work with my stock bed conversion (which is working great by the way) since the "up" is limited with the stock bed in as much as it hits the "exhaust" duct that hangs out over the bed. It could be cut back but isn't the stock lens the 50.8? I made two measuring sticks (they are actually calibrated to the mirror mount rather than the end of the lens as that's hidden by the air assist nozzle. I just determined their length by experiment so don't actually know what the actual length is. If the optional one was 38 the I don't have 12mm I could go "up". I would have to go back to "hacking" away at some more metal. I think that 65$ fancy head has adjustable lens length? That would be another plus to it if true.

[buddydog]

Ahh thanks. I was not sure which one was the stock lense. How many mm of room is their below the stock table?

As TMH said "Ahhh". That answers my question about which was the stock lens too. I just measured and on mine there is 10 mm of "up" over stock available before hitting the duct so the adjusters I have made won't bring the table itself "up" enough to be in focus BUT there is a range of actual useful cutting focus distance and so with this setup it will still work especially if you have already set the rafter "clamps" nail things on the bed as they are at about 9 mm tall anyway and you have to lower the bed to use them so just not lower as much. I hope everyone is aware of just how useful those rafter-nail things are?.

[2_many_hobbies]

I think that 65$ fancy head has adjustable lens length? That would be another plus to it if true.

On the adjustable heads the focusing lense appears to be in a moveable tube. I imagine that is there so you can have a calibration block and put it on the material and just lower the focuser assembly on top so your at prime focus right away. I think thats way easier than the bed mod. Of course if you engrave thick objects (laptop covers) I could see the need to lower the bed even with an adjustable focuser tube.

[buddydog]

On the adjustable heads the focusing lense appears to be in a moveable tube. I imagine that is there so you can have a calibration block and put it on the material and just lower the focuser assembly on top so your at prime focus right away. I think thats way easier than the bed mod. Of course if you engrave thick objects (laptop covers) I could see the need to lower the bed even with an adjustable focuser tube.

Since adding even the first mod I have found the adjustable bed very important on these low power machines especially for cutting AND once you get one made you use it continually. By the way this is where having a "jog" button setup would be real nice. There may be a way to disable the steppers so you can move the head around but I haven't really looked for it yet so I just shut the power off to move it. The problem with moving the head for focus is that I think it would mess with lens centering some unless a highly machined 1000$ option and if it does then moving the bed is a way better option. I modified (AGAIN!) the mechanism I built to now have two small knobs, one in each front corner, and adjustment is now easier and topside with two hands. Two hands is a lot better than one as the simple bushing system I'm using is "loaded" against the tension on the ball chain and has some "stiction" to it. Two hands makes it easy. Using real bearings in the mount would of course be easiest but much more expensive and complicated and really not needed for hobby use. Again these are hobby machines and if using commercially you need the motorized bed (besides needing way more room in all axis!) After I finish my beta testing I am hoping to put a complete kit together on ebay with everything but the all thread and nuts for under 20$ (maybe even with shipping?) and still walk away with 10$ in my pocket after ebay takes their30%. The main cost will be "time" on the 3D printer and since mine is another "hobby" machine it seems to require a fair degree of maintenance so not exactly "free". I have another thing I thought of to go with that mod and it's based on chop sticks. I learned a long time ago to keep a large cheap bag of Costco chop sticks near all my machines. I used them to keep from being tempted to reaching in with my fingers to clear chips while running my metal lathe. Over time I started using them for many other things like dribbling oil on a cut or as sacrificial hold downs etc. Anyway I need some kind of adjustable clamp now for the laser and I think I have a good design for something that will be good for that too. Low cost, effective, and sacrificial if necessary! It's all just time! By the way I stuff one on each side in the sloppy slots that mount the exhaust fan on the rear of the machine and it and a piece of scotch tape along the top, tightens the whole thing up real good to help stop the smelly leaks inherent in these. By some Chinese food and try it!

[miketola]

With 38.1 lens effective material thickness is about 6 mm and 50.8 is about 10 mm. That mean you can cut material inside that. So you can cut 2mm and 5 mm material at same bed settings. Because of smaller dot and double power 38.1 is better. If you cut 6mm plywood with normal lens you need few times to cut it. With 38.1 lens you need only one time. Effective material thickness is "only" 6mm, but because of power and small dot you can cut maybe 8mm. Then cutting bed. I have four threaded rod with springs and wing nuts. You can easily move it. One roud is one millimeter. I cut, draw and encrave 2-5 mm material with same bed settings. Then tip. You can put one laser to about 45 angle. When you table and focus lenght is fine burn mark with test button and aling laser pointer to that. Now you can allways burn small test mark and check distance. I hope you understand. If you need cheap and good cutting bed you can buy grill mesh for cars. Google it. I use pintable because i dont want burnmarks to backside. Sorry my terrible english :-(

https://docs.google.com/file/d/0ByJi...p=docslist_api

https://docs.google.com/file/d/0ByJi...p=docslist_api

https://docs.google.com/file/d/0ByJi...p=docslist_api

[buddydog]

[QUOTE=miketola;1612592]With 38.1 lens effective material thickness is about 6 mm and 50.8 is about 10 mm. That mean you can cut material inside that. So you can cut 2mm and 5 mm material at same bed settings. Because of smaller dot and double power 38.1 is better. If you cut 6mm plywood with normal lens you need few times to cut it. With 38.1 lens you need only one time. Effective material thickness is "only" 6mm, but because of power and small dot you can cut maybe 8mm. Then cutting bed. I have four threaded rod with springs and wing nuts. You can easily move it. One roud is one millimeter. I cut, draw and encrave 2-5 mm material with same bed settings. Then tip. You can put one laser to about 45 angle. When you table and focus lenght is fine burn mark with test button and aling laser pointer to that. Now you can allways burn small test mark and check distance. I hope you understand. If you need cheap and good cutting bed you can buy grill mesh for cars. Google it. I use pintable because i dont want burnmarks to backside. Sorry my terrible english :-(

Miketola your english is a lot better than I would do in whatever your native tongue is so "good-on-ya"for trying as I guess the Australians would say! It took a couple of try's but I did finally understand what you were saying. Each turn on your setup equals 1mm of height adjustment. And you mean the head "red pointer" laser at exactly 45* to focal point and then burn a test dot and the test dot AND red laser should hit the same spot. I was aware that two red lasers could do that but I had not thought of one red dot along with the CO2 test spot doing that so thank you for the tip. I don't have a red dot at this point but I have thought of adding one.
I had the spring set up like yours originally on mine (1st modification) and I started engraving many different size objects and found adjusting 4 different corners one at a time was to cumbersome and time wasting so that's why I came up with the ball chain solution. The one disadvantage of course is with yours you could conceivably tilt the table to make angled cuts in one line only if you wanted with the independent setup like you have. I can't do that anymore as I would have to disconnect the chain under the table to allow independent corner adjustment. One other reason I changed is the springs I used to allow freedom of movement had some give to them and when I put a couple of heavier things in the table to engrave it sagged a little. What I have now is solid wherever it is and I have no doubt I could put 50 pounds on it and it would stay still.

[miketola]

First pic.
4 mm plywood. Focus lenght perfect.
Then push test button. Redpoint and burn mark good.

https://docs.google.com/file/d/0ByJi...p=docslist_api

Then change plywood to thin paper.
Do same again.

https://docs.google.com/file/d/0ByJi...p=docslist_api

Now you see that you are too down. Few round up and test it.
When red dot and burning mark contact your focal leght is perfect.

And here is my "air nose" with HD webcam.

https://docs.google.com/file/d/0ByJi...p=docslist_api

[2_many_hobbies]

Now you see that you are too down. Few round up and test it.
When red dot and burning mark contact your focal leght is perfect.

Pictures do speak a thousand words. That is a very smart setup and with the webcam, a very safe way to monitor your projects progress. Thanks for all the help!

[cruch]

Hi!
I have read this post with alot of interesst Lots of great information.
I am in progress of ordereing on of theese 40W machines.
Can you please post an ebay link for this machine that you would recommend? There are alot of different tyoe of theese machines, some with and without lift system / up and down Laser positioning etc..

The 38.1 lens, great info.

I am planning to use this machine to cut and engrave into acryl at 3-5mm of thickness. Will this machine cut acryl without any problem? How about plexi at the same thickness?

Thansk for any feedback

Inge

[miketola]

Few pages before is link of my order. LaserDrw, air blow, red dot and digital power panel is nesessary. I cut alot 4mm acryl with good results. Settings 30% power and 10m/s.

[cruch]

Does it take longvtime to cut 4mm acrylic, say 90x150mm.
Do you have youtube movie?

Thanks for yor reply

[miketola]

I cut 10mm / second. Here is few sample. Material 3.5mm (masked both side)

Laser cut sample2: Laser cut sample2 - YouTube

Laser cut sample: Laser cut sample - YouTube

[cruch]

Wow..Thanks miketola Well, I think I will order one soon!
You cutting bed is awsome!
Thanks again.

[miketola]

If you check my youtube channel there is few video more

Here is plywood and acryl together.

[bricx]

Looking at converting to 38.1 focus. What diameter focus lens does this machine use? Any preferred suppliers or advice on quality of lens needed? Just ordered my machine and loving your mods. Been resisting getting one for a while but looks like it's time to add another bright spot in my life. ;-)

[miketola]

First one i order from aliexpress and second one from ebay. Both same. 12mm CVD ZnSe Focus Lens 10600nm 1 06UM CO2 Laser ENGRAVER Cutter FL 1 5" 38 1mm | eBay

Normaly diameter is 12mm..

/Mika

[2_many_hobbies]

Wow I don't know what the heck happened but all the links you guys gave to machines are now "currently unavailable" and all the ebay prices have shot up $300! The same machines are now $850 + $150 shipping and their is no way im paying $1000 for the base model machine.

I did find one for $900 that had air assist, red dot and height adjusting table but after inquiring and getting more info the emailed pictures where of a totally different machine without any of that, heck it was a different color even! Now I am just plain worried...

[buddydog]

"Bright spot" good one! I really question if one of these is worth 900-1000 although many have paid 2-3 times that but your getting into the area of the 50-60 watt machines which knowing what I know now about needing bigger X Y and Z and having pretty good confidence in my laser repair abilities I would bite the bullet and go for the bigger ones.
Just checked "professionasell" and your right, 25sold in 2 or 3 days? Hmmm maybe were talking these things up to much on here? These remind me of my first motorcycle I bought in 1964, a Honda 50. I went on to own a bunch of Honda's over the years and even a dealership. I still have that original Honda! These are entry level and should be cheap. They are not nearly as bad as some portray, but on the other hand limited by space right away as you get a couple of hours on one and they ARE A LASER (complex machine, not a microwave oven). Their greatest asset I think is cheaply sorting if you are made of the "right stuff" to own and use a laser. I would have failed if I had not had the electrical and mechanical background I have. What I know for sure is that there are a whole bunch of 400-5000 dollar lasers sitting gathering dust because the owners could not figure out the various hurdles then gave up sometimes blaming China, engineering, manuals etc when the actual failure was in the owner themselves. These machine will teach you those things.