Laser engraver/cutter

[jpanhalt]

I have been researching laser engravers/cutters vs. desk top CNC machines for various small tasks, such as cutting out model airplane parts. I am leaning toward the laser, as I have a nice 9X42 Bridgeport mill than can be made into CNC for metal working. It already has DRO. CNC would not increase its capability for me very much, since I have an 11" Troyke X,Y and rotational table on it. It would be neat to be able to mill a complete panel with labels, though, from time to time.

The laser cutters in my price range (<$3000 USD) all seem pretty generic. Is there any real difference between them, except cutting size?

Does anyone have real experience with these 40 to 50W CO2 machines from China?

Thanks.

John

 

[RichTheDude]

A friend at a UK hackspace brought a Chinese laser cutter (50 W). They have it cutting now but he was telling me the default control electronics and software are god awful.

They converted it to LAOS electronics https://redmine.laoslaser.org/projects/laos/wiki/LAOS_Mainboard_v03

Supposedly it allows a lot more software (hence file formats), is no longer windows only, and is a lot better.

 

[jpanhalt]

Thanks for the report. Poor electronics, particularly the stepper motor drivers, seem to be a universal theme. For the CNC cutters, they are even referred to as, "The blue box electronics," meaning trash.

I was worried mostly about the cutting accuracy, whether the laser tube lasts anywhere near what they claim (1000 hours), whether focus stays reasonably set, and whether the rest of the specifications are realistic or exaggerated 2 to 3 fold.

It is good to hear it cuts. The material I will be cutting will not be much of a challenge, namely 3 mm (mostly) and 6 mm plywood and balsa wood.

John

 

[gerty]

I used to work on some 1KW co2 lasers (Coherent General) several years ago. I'm just curious as to what you'll use for a beam delivery system. Ours had 7 mirrors that were a real pain to keep in alingment. We used them to cut 14 ga sheetmetal parts for air conditioners, some of the parts were 42 feet long and we cut from roll stock with the parts going through a roll former as they were cut off.

edit: We cut off of 2 axis using a Anorad Controller. The laser cavity was stationary and we moved the beam, hence all the mirrors. The Super 48 Laser is 10'long x 4 foot square and weighs in at approx 900lbs.

 

[jpanhalt]

The Chinese units use reflective mirrors and a final focusing lens. Kerf is reported to be about 0.005". They will not cut metal.

This past Summer, I had a local shop cut some 5/16 CRS for me, including oversized holes for pins. Sure beats finding a .020 oversize 7/8" drill. His machine could easily handle 3/8". I am not sure whether they were CO2 machines either.

John

 

[gerty]

Sounds like a similliar delivery system. I hope your optics are going to be cheaper, a mirror (water cooled) was $400, and the lens was only $200. Those are 2003 prices.
We used oxygen as a cover gas, and if the pressure was too low when the beam first burns through the metal the back spatter would mess up a lens.

 

[jpanhalt]

These hobby machines operate at much lower power, of course. Mirrors and lenses are not cooled. For cutting "air assist" is used to give a smaller kerf and help remove smoke. From what I have read, some plastics are really bad on the lens and optics from the smoke. PVC is especially bad because of the corrosive gases evolved. My uses will be 95%+ cutting "lite" ply and balsa wood.

I am still debating with myself about going with laser versus a CNC router. Router sellers are pretty well established. As for laser sellers on eBay, I get the feeling that there is a lot more junk, DOA, no support, and fringe. That was another purpose in starting this thread to see if anyone had had experience with the sellers.

My biggest reservation with the CNC router approach is the need to mount the wood relatively securely. Routers also cannot make quite as sharp inside corners as a laser can. I use double-backed tape for mounting when I manually cut out parts, but a burr in a CNC would probably get all gummed up if it tried to cut through such tape. I have thought about adjusting the depth so it doesn't cut all the way through, which would allow the parts to be easily separated and cleaned manually up afterward.

John

 

[Mr RB]

... I have thought about adjusting the depth so it doesn't cut all the way through, which would allow the parts to be easily separated and cleaned manually up afterward.
...

That's usually how I do it when cutting parts from flat sheet stock.

Seriously, if you are weighing up whether to own just a CNC laser or just a CNC router, the router really is superior. For a start it's a 3D machine, where the laser is 2D. The laser can just cut right through or mark the surface. With a router you can cut pockets, slopes, use a rounded or 45' tool and do edge chamfering, use a ball tool and cut extremely complex curved surfaces (true 3D from CAD) etc.

Hold down if thin stock is not that big a deal, you can clamp the sheet at the edges and leave a few small breakout tabs on each part, or what I often do it drill a few holes in the sheet and screw it down to the threaded grid on the router table. Then cutting small parts from plastic I leave about 0.12mm of skin holding parts together (ie don't cut all the way through) the parts break out easy and the skin is removed with a fingernail or other blunt object.

The router could also be used for PCB making, that is a popular use. Seriously have a think and look around the CNC sites before settling on owning just a laser.

 

[jpanhalt]

I am sort of like that mouse you may have seen in rat psych studies with approach - approach conflict. Just today, my bias has shifted back to the CNC router.

I do have a full size mill with nice DRO (Mitutoyo) and will probably be converting it to CNC. It has some other nice bells, like a rotary, X, Y table in addition to the usual X,Y, Z of the mill. The problem is that I use it for metal working and keep it well oiled.

I want something light, table top, and not covered with no oil. It only needs to be 2D.

I have written most of the eBay laser dealers. Gotten only one reply, and even that dealer couldn't/wouldn't give the name of a single satisfied customer in Ohio. That is bothersome, i.e., it adds an element of avoidance to the rat psych experiment. So, I am definitely leaning towards the CNC router again.

Here is a link to a very inexpensive CNC router kit: https://www.inventables.com/
They have had positive reviews.

John

 

[KeepItSimpleStupid]

John:

Just recently I stumbled across these guys: http://fslaser.com/

Their stuff looked interesting and seem to be simple to maintain, however, the add-ons appear to be mostly necessary.

Their forums were interesting too. My laser experience was limited to small HeNe and a few sold state ones and we scanned the beams with mirror galvanometers. I wasn't involved with the 1W laser, nor the laser scriber.

 

[jpanhalt]

Are you sure that is the right link? Isn't a 50W cutting laser a little extreme for smelly feet?

John

 

[Mr RB]

...
I do have a full size mill with nice DRO (Mitutoyo) and will probably be converting it to CNC. It has some other nice bells, like a rotary, X, Y table in addition to the usual X,Y, Z of the mill. The problem is that I use it for metal working and keep it well oiled.

I want something light, table top, and not covered with no oil. It only needs to be 2D.

I agree completely, the right desktop router will be much faster and more pleasant to use than a big CNC mill on flat stock and have a larger working area too.

And you are saying "only 2D" but I think you will very quickly come to enjoy having the ability to pocket instead of always through-cut, and ability to chamfer and v-tool engrave front panels for projects etc.

...
Here is a link to a very inexpensive CNC router kit: http://www.inventables.com/
They have had positive reviews.
...

That kit in full form is about $600 and I think you can do much better in terms of mechanicals. It only uses lightweight rails and rollers, a "proper" machine uses linear bearings, and you really want ballscrews too for good life and accuracy.

Have a look at the machines here (under "Gantry Part Moving" page);
http://cncdiy.org/
Check out the 9060 and 6545, these type machines have proper linear bearings, the main long rails are supported rail type (important) and they even have VFD spindles which may not be that much use to you but it means they will cut aluminium stock even if you need to take a few light cuts to do it. The 4030 and 3020 are popular and being smaller usually cheaper and in the $600 to $800 price range;

**broken link removed**

That type machine are available from a few China suppliers under different brand names. The 4030 shown in the photo above only has unsupported lower rails but I believe they are now shipping with full supported lower rails, or at least another brand is. Expect the machine to need some care and alignment, but after that it should be a reliable and "proper" machine, ie capable of a lot of accurate work.

You should be able to find some owner reviews blogs etc from people that have bought these machines.

 

[jpanhalt]

Thanks for the additional push. The comments in this thread have been helpful. The more contacts I have had with the laser companies, the more concerned I have become.

The engraving aspect of the router is a definite plus; although, lasers can do some of that directly on plastics and indirectly on aluminum, either by removing anodize/paint, then followed by contrast color or etching. Right now, I have definitely decided probably to go the router route.

Ball screws will be strong positive. Some of the vendors have been a little evasive about the type of nut used. Not all ball screw nuts provide effectively zero backlash. I will be looking for one where the nut and end bearings are clearly described. And of course, the rails need support.

As for the spindle motor, I do want a motor, not a flexible shaft-driven design. Some of the low power (≤300W) units look like what we call "can" motors. The bearings are not very good and they are noisy. The larger motors seem to be water cooled, and they look to be heavier made. Do you have any experience with them? Are they noticeably quieter? I will also want VFD. Having retrofitted several machines to VFD, I never want to go back.

Finally, for the bed, what do you think of the bolt together extruded aluminum versions versus those with a machined (e.g., MIC6) aluminum bed? I suspect one uses a sacrificial bed over the machine bed almost all of the time, but for engraving and PCB's, one might want a flatter bed.


Regards, John

 

[KeepItSimpleStupid]

John:

Fixed the link. It's http://fslaser.com/

 

[Mr RB]

...Ball screws will be strong positive. Some of the vendors have been a little evasive about the type of nut used. Not all ball screw nuts provide effectively zero backlash. I will be looking for one where the nut and end bearings are clearly described. And of course, the rails need support.

I've seen user reviews of these Chinese machines, and the main negatives have been about poor alignment and the need to go right over the machine once it arrives. I haven't seen any reported backlash issues. The other common name is "Tonsen" which may help you in googling reviews etc.

Even the cheaper ballascrews only have a couple of thou backlash at worst, which is inline with laser accuracy considering the laser melt can drift a few thou on any laser cut anyway. Also the CNC software always has an adjustment to remove backlash in software which does a pretty good job. If you are after really low backlash it is easy enough to add tension to the ballscrew, there are a number of ways to do this and most are well documented on the CNC sites.

The thing with these Chinese machines is you get a lot of machine for the buck, but expect it to be roughly assembled by an idiot and in need some good engineering on your part to align it and tweak things like backlash and possibly flex. It will still be many times more "pro" than the hobby machine you linked to above that just used roller bearing son aluminium extrusion rails.

...
As for the spindle motor, I do want a motor, not a flexible shaft-driven design. Some of the low power (≤300W) units look like what we call "can" motors. The bearings are not very good and they are noisy. The larger motors seem to be water cooled, and they look to be heavier made. Do you have any experience with them? Are they noticeably quieter? I will also want VFD. Having retrofitted several machines to VFD, I never want to go back.

The 4030 and 3020 look to still use the DC motor spindle, these are pretty good for ridigity and have ball bearings, their drawback is limited power at about 300W and low top speed at about 8000 RPM (from memory). 300W spindle will cut your woods and plastics with a small tool no problem, I have a 850W router on mine and it never goes over about 40% power use, even cutting aluminium.

The DC motor on those machines is already "VFD" as they use a crude variable voltage DC supply with some current feedback, speed regulation won't be fantastic but the speed is fully variable so you can tune out cutting resonances.

"Proper" VFDs can be bought from ebay, they get pricy. Most people in serious hobby or semi-pro use use a router like myself, they are a little noisy but make a ton of shaft power and enable some fast machining. My 850W router was $60 with a 3 year warranty, and I added a home made computerised speed controller for better low speed cutting.

Really it depends on what you are cutting and how "pro" (ie proper manufacturing where time is critical) you need. That DC motor supplied with those machines will be quiet and rugged and accurate, and will cut your 3mm/6mm ply and balsa with no effort at all. What you gain from a higher powered spindle like a router is ability to make more parts an hour, but you get lots of nasty noise, and dust so you start to need cabinets and vacuum dust extraction (more noise!) you get the idea.

...
Finally, for the bed, what do you think of the bolt together extruded aluminum versions versus those with a machined (e.g., MIC6) aluminum bed? I suspect one uses a sacrificial bed over the machine bed almost all of the time, but for engraving and PCB's, one might want a flatter bed.
...

I have no experience with those extruded bed things, but I assume you can align it ok when you setup the machine. Then proibably the first thing you need to do is put a sacrificial bed on there, a piece of MDF is common but I prefer acrylic plastic, both need to be machined dead flat but the plastic is harder, cleaner and not subject to swell or tear.