[KTP]

Hi,

I am starting a project log to build a very low cost laser engraver out of an old HP7550A plotter and some other bits from printers and copiers. The motion of the carriage in the HP7550A pen plotter is extremely fast, and well suited for a flying optic mirror/lens system.

Here is the donor, obtained locally for $15. These plotters can be found at computer salvage stores and on ebay. The 7550A uses Pittman DC servo motors with quadrature encoders...perfect!

[KTP]

Ok here are some pictures of disassembly (my favorite part!). You can see the Y axis Pittman servo in one picture, the other servo which moves the paper is hidden. Note the very nice alumining timing belt gears and the wide timing belt...looks very promising!

[KTP]

Ok, at this point it looked like the motion assembly and paper feed were one giant unibody construction, but ahah! there are some hidden screws which allow the Y axis carriage to be separated, reducing the size drastically. After removing the belt, pen carrier and motor, the Y axis assembly was presented to the band saw for a bit more disassembly

On the plus side, I have increased the travel to over 14 inches by using the space where the plotter used to pick up pens!

[KTP]

Ok, so now I have reassembled the Y axis after trimming off some plastic that was in the path of the soon to be added lens/mirror. I added a aluminum angle to strengthen the assembly which makes up for the plastic I needed to remove. The whole axis is very lightweight (good) and extremely fast (great). It should allow for insanely high IPS travel rates which is nice when you are rastoring a large image with the laser. Next step is to hook it up to an AMC servo amplifier, Pixie P100 controller, and Mach 3 to see how it moves. I will post a link to a video of this.

[KTP]

Ok, as promissed, I have made a video of the carriage moving under Mach3 control using a Pixie P100 step/dir to analog controller board and a AMC 12A8 brush servo amplifier. I am quite pleased with the results, the Pixie P100 lets you pull every little ounce of energy out of the Pittman motor. The motor is surprisingly strong for it's size, and the top speed should be well above the 2640 IPM (44 inches per second) seen in the video. The Pittman motor/belt reduction drive assembly seems to have 4000 steps per inch of travel. I have set the Pixie P100 step multiply to 4, giving 1000 dpi resolution. Using Mach3 at about it's maximum step rate of 44khz, this gives the 2640IPM feedrate I used in the video. I have also attached a tuning graph running on the Pixiecom software showing the response of the Pittman servo mounted in the carriage. You can tell the motor responds very well to a 50 step impulse error in the test.

video: http://www.skyko.com/videos/HP7550A.wmv

[miljnor]

Awsome thread man will be following it with baited breath!

What servo amps do you use? (I see you are the maker of the Pixe100 nice job)

thanks
Michael

[KTP]

Thanks for the kind comments Michael!

The amplifier I am using at the moment is an Advanced Motion Controls 12A8D, which is a bit overkill for these smallish motors. I bought quite a few of them very cheap on ebay and they work well with the Pixie, so why not?

The laser I am going to use initially is a small air cooled Synrad J48-1 10 watt unit. It is RF excited, powered by a 30 volt 7 amp DC supply and currently is outputting 16+ watts at 95% duty cycle. I have included a couple of pictures of it cutting some 1/8" balsa stick crudely waved in front of the focusing lens by hand

[thuffner3]

If I may ask kind sir, Where and what cost is the laser you mention above?

Thank you
Neil

[KTP]

Hi Neil,

The laser in the picture is made by Synrad (www.synrad.com). This unit sells for around $2450.00 new from Synrad, but can be found used on ebay and other places for $800 to $1300 or so. Unfortunately, they are so rock solid and they last so many TENS of thousands of hours that they hold their value on the used market. Lucky me, I got this laser for free out of a scrapped semiconductor machine that was going to the landfill. Unfortunately, I didn't get the rest of the machine.

[KTP]

Here is a quick frame I threw together using 8020 extrusion. I think I may have overbuilt it a bit It has inside clear dimensions of 24 inches by 48 inches, though my Y axis only has 14 inches of travel at the moment. Building for the future I guess...

The x axis linear rails are mounted as you can see in the picture. I found these IKO rails and carriages brand new on ebay for $125, so might as well use them rather than round rail. They have VERY little resistance to movement, which will be nice. Low mass too!

There will be 3 cross bars bolted to the underside of the top platform to hold the engraving honeycomb table. I will fashion a vacuum/exhaust box out of 1/8" something and attach it below the honeycomb. The lower shelf will contain the RF excited CO2 laser, dc supply, motor controls, air pump, and computer.

[KTP]

Yesterday I ordered the pulleys, bearings and drive shafts for the x-axis. I already had 19 feet of XL (.2" lead) 3/8" wide belt, so will use that for now. It is neoprene with kevlar tension members. Getting what I wanted in pulleys was a bit of a puzzle. I wanted all the pulleys to have a 3/8" ID so I could use 3/8" shafting running inside the 8020 extrusion to link the two drive belt pulley systems together. Several pulleys were out of stock for 5 to 6 weeks at SDP/SI, but I ended up with four 14 tooth pulleys, one 15 tooth pulley, and one 42 tooth pulley. The x axis drive belts will ride on the linked 14 tooth pulleys, which will be driven by a brushless servo geared down through the 15 and 42 tooth pulleys. This gives a final ratio of 1 rev of the servo motor shaft equals 1 inch of x travel (14/5 = 42/15). The brushless servo has a 2000 line encoder, so resolution will not be an issue. The final question is will the brushless servo be able to drive the x axis at speed and with enough acceleration? Some scratch calculations give:

1.5 Newton-meter stall torque rating of the servo motor. Using a hopefully conservative 1 Newton-meter running torque and noting that the 14 tooth pulley pitch circle radius is about 0.5 inches, we get a force of 79 Newtons on the belt, or roughly 17.7 pounds of force. For the acceleration, noting that F=ma, and taking a total guess of the mass of the y axis gantry and the drive components to be 4kg or less (under 9 pounds) we get a acceleration figure of 19.7 meters/sec^2. Enough?

I like the try it and see if it works method better, especially when using cost saving "what I have on hand" components.

More to come.

[KTP]

Decided to go looking for more information on the brushless servo I plan to use for the x axis. I found the specs at:

http://www.apicontrols.com/newapi/pr...rbo_mbt23.html

The motor I have is MBT-N233-BCNC Actually, I have 2 of them Ebay $15 each brand new...glad people don't know how easy brushless servo motors are to drive...oops (chair)

Looks like the Continuous stall torque is 13.6 lb-in (1.537N-m) and the peak torque is 40.8 lb-in (4.611N-m). The rated voltage seems to go up to 230VRMS at a whopping 6380RPM, but I am going to use an AMC B25A20AC brushless amplifier and Pixie P100 so will be limiited to the 115VRMS input to the B25A20AC with max RPM of 3190. So really this justifies the 1 revolution of motor shaft to 1 inch of belt travel, since the maximum IPS rate I could theoretically achieve would be 3000/60 = 50IPS. Not slow, but not much more than what the high end commercial flying optic laser engravers can do. I know they have optimzied the mass of the moving components much better than I have, but I want to shoot for the best I can with available funds and equipment. But really I need to keep the mass of the y axis much lower than the 4kg I used in the crude calculations...slinging even 2kg back and forth at 50IPS is going to bounce the machine I fear. Time will tell.

Will be interesting to see how this motor performs. Can't beat the price.

[pyroplotter]

Thank you for your sharing of information about your design. The videos are particularly informative. I have a CNC table that is a subset of a Torchmate kit sold by Applied Robotics. I first built this table in 2005 for use in wood sign engraving onto full sheets of plywood when we were living on our horse ranch. This year we sold the ranch and are now living in a house in a town and I have a garage. So the table was reduced from 1100 pounds, 5' x 8' x 14' down to a 5' x 6' gantry / platform instead.

I'm now working with 36" x 48" wood pieces so far and using hot points like irons and nichrome wire to burn into the wood. The results are accurate but not stellar and I need not worry about ever becoming a threat to anyone's livelihood. But the gantry system can use different heads for drills, routers, engravers, and my own version of a pyrographic burner and I'm still experimenting with what I can do with the tool.

And at this point your own work becomes a guide.

I like your use of the J48-1 laser which is what I'd like to duplicate here. Cutting a gear from denim relates to something that I'd like to try here in arts and crafts activities. I have Engravelab Photo Laser software which lets me create inlays and such and using a laser to cut fabrics leads to some possibilities for the Xmas season.

So my questions are ... do you use the UC1000 controller ? And do you use it in pulsed mode for your power control ? What settings burned the wood without the lens ? And did you have to jump through any hoops regarding safety when buying the device ? ( ie ... and certifications / licenses / authorizations that I need to get to buy and use such a device ? )

Thanks in advance for any answers and best regards.

Wil

[KTP]

:wee: :wee: :wee: :wee: :wee: :wee: :wee: :wee:
:banana: :banana: :banana: :banana: :banana: :banana: :banana: :banana:

My plotter just got a laser upgrade! I bought a known broken Synrad 48-5-28W 50 watt laser and spent all day today repairing several fried circuits and damaged components on one of the two control boards. Someone had evidently miswired the unit as one trace leading to the DB9 connector was vaporized!

Reinstalled the circuit, powered up the included! UC-1000 controller and switching power supply and presto 64 watts of power with a really great beam profile! I am so happy now...my engraver project was in need of a bigger laser and this should fit the bill.

I took a picture of it blasting through a piece of balsa into a brick (which took about 0.01 seconds for the unfocused beam ) but the laser melted the brick and turned it incandescent so all you really see is what looks like the worlds most impressive white light laser (chair) I took another picture with the laser off so you could actually see things. Yes, I know this laser needs water cooling. It came with the hoses and connections, but it is perfectly fine to run it for a few seconds for the testing and pictures. There is actually quite a bit of aluminum that has to get warm before the laser would start complaining.

[KTP]

Wtawtaw:

Up until today, I didn't have a UC-1000 controller, but now I do. I probably will not use it since I will have several embedded microcontrollers in the final engraver machine and will generate the tickle pulse with them. It is very nice to have if you are not familiar with digital electronics.

If speed is not an issue, you can totally get by with a little J48-1 Synrad. Air cooled and so very easy to use. They put out quite a bit more than the stated 10 watts too. You could cut fabric, paper, rubber, acrylic, wood, foam, and lots of other stuff. I even carved a foam halloween pumpkin with one! Stepping up to the bigger power mostly allows an increase in speed, but also thickness to some extent.

You need to use a lens to do any usefull work. A lens will provide you with a small spot for fine detail but more important will drastically increase the power density (which is why you are using a laser instead of a flashlight no?) allowing the material to be vaporized without heating the surrounding material (little char and burning). Lenses happen to be all over ebay now...just search for ZnSe.

Hmm, the only license I can think of that you need to buy a CO2 laser might be a driver's license if you happen to be in a small town in Alaska where UPS doesn't deliver. Seriously, there are few regulations about industrial lasers...though if kids keep shining pointers at planes and helicopters, there will be soon.

[Laser Guy]

KTP
I saw your other post but had no idea you were building a beam delivery
system.I have a 2.0" focal length lens with your name on it. Some chips on the edges but it will definitely work to get to off ground. I'll send it in a mount used with Epilog laser engravers,You pay for the shipping and it's yours.

[KTP]

Thanks very much for the kind offer Laserguy, but I have this addiction to collecting lenses so I am probably covered in that aspect (see picture below). The main problems I am having are decided if I want to go to the trouble of making a galilean beam expander (I have enough optics for it) or just bounce the raw beam from the output of the Synrad around my mirrors. The beam expander might give me a smaller spot size...

Edit: I had not read your other post. Is the lens you have meniscus?

[Laser Guy]

I use Plano Convex

[KTP]

Most excellent! A 0.004" spot size from a plano-convex lens with no beam expander optics...EXACTLY what type of performance I hope to achieve.

Thanks for the information!

[Halfnutz]

Very cool. You have many talents!

A stupid question for you, How does the beam travel and remain focused? Do you use some type of flexible fiber optic link to allow the beam to be moved so easily? I'm sure that the entire laser body doesent have to be moved around, or does it?