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View Full Version : First ULS Demo. I have questions.



Michael Simpson Virgina
04-21-2009, 5:36 PM
I went and saw my first ULS demo today. It was a VLS4.6 60Watt system.

All in all I am pretty impressed with the system but....


The main reason I am getting the laser is for cutting small Acrylic parts for my robotics company. I brought some 1/8" Ivory Cast Acrylic with me to cut some gears that I plan on attaching to servos.

One of the things we did was cut a large 3.5" circle so I could see the quality. After I got home and looked at the part closely It was not very good.

1. The cut was not square. Far from it.
2. Pits and grooves. Some were very deep.

First off the Air assist was no on during this cut and I think that it may have helped quite a bit. Also Because the piece was cut twice there may have been a small amount of movement.

We also gut some large 3" gears with the Air Assist turned on and the cuts seemed to be much cleaner and almost Square.

I guess my question is this. Do lasers have the capability to cut fine pitched gears out of 1/8" acrylic. I know I can cut some larger gears for use in wooded clocks n such but I want to cut small gears for use with some of my robotic projects. For instance a servos shaft has a 3/8" diameter gear with 25 teeth and that has to slip into a inside cutout. The outside of the shaft will then be 2" in diameter with say 40 teeth.

The Epilog Rep says this can be done and is bringing a Mini18 to do just that. He says it will be a piece of cake.

If anyone has done this sort of thing I would love to hear from you.

George Brown
04-21-2009, 6:00 PM
I have done some detailed cuts, and for what I needed, it came out fine. The edges are not as super smooth as you can get if it is flame polished, but quite nice. However, almost all of my cutting is wood, quite different from acrylic. Just make sure that you do not let the sales rep leave until you have ALL samples cut to your satisfaction. It would probably help if you had some samples cut whichever way you did them before, to compare the cut quality to. Also remember, the laser cuts are not perfectly vertical. On 1/8 inch material they will be almost unnoticable, but for precision gears, it may make a difference.

Joe Pelonio
04-21-2009, 6:09 PM
When you cut a square from 1/4" thick piece of acrylic or wood and try to stand it on edge you will see how far off the cut is. That cannot be adjusted,
it's the way a laser works, with an hourglass shaped beam. Less noticeable on thinner material. Yes, air assist helps when cutting, and if everything is adjusted and cleaned properly the edges should be very smooth.

When doing a demo a dealer should be showing the best the machine can do,
pits and grooves are not acceptable.

Scott Shepherd
04-21-2009, 6:10 PM
It's all about the settings. You'll never get perfect results the first or second pass. I have materials I do all the time and I'm fine tuning them all the time. It isn't as simple as "set it and forget it" the first time. It takes trial and error.

I am 100% skeptical of anyone telling you their machine vector cuts better than one of the other major brands. I cut small parts by the 100's and I measure them with digital calipers and across the table, sheet after sheet, the variance it never more than .001".

As for the sides being square, that's a function of the focus and the beam itself. You'll always have some angle, but you can focus down into the work and reduce it somewhat.

Send me a file and I'll cut it in acrylic when I get a chance and see if I can get you better results than the demo. Remember, the sales reps aren't masters at using the machines, they are masters at selling them :)

Michael Simpson Virgina
04-21-2009, 6:14 PM
I wont say the gears need to be precision but I did notice there was a difference in cutting something with air assist off verses on.

The main problem is I took a thumb drive With Corel X4 files and they could not read them. They are on X3. That was very disappointing.

We did cut out some wood parts that he had that would be very much like the wood robot parts that I will be offering and they turned out very well.

I have about 6 different job classifications for the laser. The servo gears were just an extra I was working on.


As far as the circle goes I had someone recommend cutting a 3" circle and comparing the different system to see which ones did it the best.

David Fairfield
04-21-2009, 6:22 PM
Agree with Scott on fine tuning the settings. Generally speaking, the lower the speed, the more precision & less wobble. So my settings tend to be a compromise between speed and precision and are the result of experimenting with the particular material & application.

Dave

Dave West
04-21-2009, 6:36 PM
I've cut 1/8" acrylic gears with my 25 watt Epilog and they turned out quite well.
http://www.youtube.com/watch?v=Y8LY--w7ynI

Dave

Mike Mackenzie
04-21-2009, 6:50 PM
Michael,

If you want to send me a file I will cut some of those gears and send them to you for you to evaluate.

Tor Amundson
04-21-2009, 7:01 PM
We cut gears for robotics-style projects all the time with our VLS4.60 (@60W). Air assist is a must. Going with a longer lens helps keep the edges even straighter, too. Remember, the beam is 'hourglass' shaped, centered around the focus point. The longer the lens the taller/skinnier that hourglass is (at expense of the actual focus point's size). Using the long lens and focusing in from the surface just a little gives us the best results.

Mostly we use 1/8" or 3/16" acrylic, depending on what we need the gear for. The bigger you get the harder it is to keep the edges exactly straight.

Dave Johnson29
04-21-2009, 7:02 PM
The outside of the shaft will then be 2" in diameter with say 40 teeth.


Michael,

I am not sure what load is going to be on this but you will need involute gear teeth to transmit any usable power. In your example a rough calculation for Pitch gives 0.078" pitch width per tooth at the widest part.

I believe it is unrealistic to expect a laser to create such shapes accurately enough. Also acrylic is a poor material for a gear, it does not wear well, it does not slide against other acrylic well. Delrin would be my first choice, followed by Nylon-66 etc.

Regardless of material the gears of this size should be machined. If you are making a bunch then it is a simple matter to stack them on a spindle in a CNC rotary Indexer (My Yuasa-5C has 0.0002" positional repeatability) and cut them with gear cutters.

I recently made 30 x 1.5dia x 36 tooth gears in 1/8" Delrin in less than an hour of machine time. That included pre-cutting the delrin and machining to diameter on a lathe before gear cutting.

Kim Vellore
04-21-2009, 7:04 PM
I have done something similar, I mounted acrylic parts to the servo and for the center that goes on the servo I rastered the acrylic, I had to try a few times to get it right, as for the gears if you are trying very fine pitch on the outside I would raster, for 2" dia with 40 teeth you can get good results with vector cutting. I would use delrin instead of acrylic if you want better precision because I have seen, acrylic deforms more with heat than delrin so the edges come out better with delrin.

Kim

Michael Simpson Virgina
04-21-2009, 7:08 PM
@Dave Thanks. Cool project you got there. A lot of the stuff I want to do are along those lines. Moving Art, Dioramas, Robotics. My business makes its money selling the electronics for the kits. I just want to start offering some of the parts that I used to cut out with my scroll saw. Many of my customers don't have access to a scroll saw and have been asking me for parts kits.

Here are a couple links to some articles I did for magazines. I get a lot of requests for the mechanical portions of these projects.

http://www.kronosrobotics.com/Projects/WalkerP1.pdf
and
http://www.kronosrobotics.com/Projects/MegaBotP4.pdf



I even have a workbook shown here:
http://www.kronosrobotics.com/FirstWalker/FirstWalker.shtml

As you can see not a lot of precision but by adding a few plastic gears here or there I can do some real cool things.

Michael Simpson Virgina
04-21-2009, 7:09 PM
@Mike
I will do just that. I have your email. Do you have Corel X4?

Michael Simpson Virgina
04-21-2009, 7:22 PM
@Dave
The only real small gear is not really a gear it just slips over the Servo gear shaft. The others on the outside are larger. I purchased the program called Involute. It does a real good job designing the gears. It should be possible as I have done it in wood and Acrylic with my Dewalt scroll saw. It was a pain and took me forever but they worked.

I'm not trying to carry a payload or create a gear train. I just want to move a cam or two.

@Kim
Would it be too much to ask for that center servo raster image? That would make my day complete. Also Kim what Laser did you use?

@Tor
How long a lens are you using on your VLS4.6?

Mike Mackenzie
04-21-2009, 7:31 PM
Michael,

Yes X4 is no problem

Kim Vellore
04-21-2009, 8:07 PM
no problem, I'll send it to you once I get home...
Kim

Peck Sidara
04-22-2009, 11:34 AM
Michael,

Fellow creekers have offered many good and valid points. I'll throw in my $.02 as well.

Don't beleive the hype. Get demos on both machines, see first hand the capabilities, accuracy, cut quality, ease of use, features and then decide which is the better unit. Consider whom you're buying from, his/her experience, willingness to help, after sales support, factory technical support.

You'll find that the thicker material you cut, the less straight of edge you'll get. As others have stated, this is due to using a focused beam of light. 2" lens is typically the standard and will produce good cuts but if you're looking for a more perpendicular cut, a 4" lens will be the better option (available on the Mini/Helix system).

Another suggestion is to raise the material away from the table using pins or something similar. This keeps the contact points to a minimum offering less tick marks (pits & grooves). Epilog offers a Pin table, optional for the Legend Elite series (Mini/Helix/Legend EXT).

I can also provide samples from the factory. Send me the file, let me know the thickness of acrylic and what system you'd like to have it done on and I'll process and report. Just send me a email or PM.

Scott Shepherd
04-22-2009, 12:07 PM
I agree with Peck (did I just say that out loud?) :)

Anything that requires a nice finish needs to be off the table. I made a table to do it from acrylic some time ago. I posted the file on here somewhere. It holds the material off the table and you can make it yourself in no time.

Peck Sidara
04-22-2009, 12:12 PM
^^^
I'm cutting and pasting that into my sig.:)

Michael Simpson Virgina
04-22-2009, 12:13 PM
Thanks Peck.

I have an Epilog Dealer coming over to my Lab/Studio today. He is going to install the laser on my system and let me try it out first hand in a real production environment. I already have the driver installed installed as well as my Exhaust and compressor so it should be a fast hookup.

While I really like the ULS driver/software as it seems more geared tword production use I cant ignore the dealers willingness to go that extra mile.

....... OH A knock at the door he is here now. I will let you know how it goes.