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Hi, I've recently gotten into RC airplanes and I also play around with 3D graphics and I've built quite a few CG airplane models using Rhino and MoI. Both are NURBS surface modelers. I thought I'd combine both hobbies and eventually build a 3-axis CNC machine to carve airplane models out of foam. I'll probably use a Dremel tool for the router. It's going to be a while before I can get started, but I thought I'd start gathering some info now.

I stumbled onto one site that showed how to build one using parts scavanged from old dot matrix printers. I remembered that I had an old Okidata in the ­base­ment so I took it apart (see pic below.) It has a step motor with 1.8 degrees/step. Will stepping motors be suitable for creating compound curved surfaces, or will I need to go with servos.

I can also use the ­meta­l bars for the guide rails. The plastic part that slides along the bar has virtually no play. A local store sells old computer stuff so I should be able to pick up a couple of more printers dirt cheap.

Also, I no longer have access to Rhino and I don't feel like shelling out the big bucks for it. Is Google Sketchup suitable for this type of model building? I've seen some pretty nice airplane models over at their website.

Thanks for this site,

Steve S.

Here are a couple of 3D models I've built, a Spitfire and a Messerschmitt Libelle. I'd love to build a RC version of the Libelle someday.

Spitfire
http://www.photochimps.com/pp/data/604/spitfire.jpg

Me Libelle
http://www.photochimps.com/pp/data/604/screenshot.JPG

Steve S

Hello Steve s!!

Sorry i can't help you with your questions but i must admit that i really like your 3d models.Especially the Messerschmitt Libelle.Nice work.
I am really fond of aircrafts models too!!

Thanks, Mik. Here are a couple more.

B-17
http://www.photochimps.com/pp/data/604/B-17_2.jpg

Fiat G55
http://www.photochimps.com/pp/data/604/Fiat2.jpg

BTW, I answered my own question about Sketchup. I did some searching over there and someone said he uses a freeware app called FreeMill to convert to Gcode.

Another question, the printer also had a 7.5 degree/step stepping motor. Is this usable, or is that too much? Each step is 1/48 of a circle. If I use a threaded rod with 10 threads per inch that's about 1/500 inch per step. Since I don't need incredible accuracy, that might be enough. And is it a problem mixing a 1.8 motor with a 7.5?

Steve S.

Very impressive Steve s!
These models where made in Rhino?What is your experience with Cad programs?
I ask you that because i just started learning Rhino with almost none experience in Cad programs.

The Spit, B-17, and Fiat were modeled in Rhino. The Libelle was modeled in MoI (http://moi3d.com/), which is a more friendly version of Rhino. Back in the mid '90s, I started modeling with apps like Truespace and Ray Dream. Then I got into Rhino for a while. I've recently played around with MoI until the Beta expired. I might buy it if Sketchup doesn't work out. I haven't downloaded Sketchup, but it looks similar to Ray Dream's freeform modeller. You've got 3 walls to draw on (floor, back, and side) to define the model.

Steve S.

Hello Steve,

First, you have some modeling skills. I really like the different airplanes you have done.

"Will stepping motors be suitable for creating compound curved surfaces, or will I need to go with servos."

Yep, I use steppers on my CNC Router and they work fine for 3D stuff. There are also a lot of other people that use them for their simplicity.

I would also be interested in your Sketch Up Journey and what you think of it. I like the idea of it, but I don't have the time right now to learn another platform.

Here is a link to some Sketch Up Video Tutorials:
http://www.youtube.com/user/SketchUpVideo

"This is the official source for online learning of Google SketchUp, brought to you by the folks who make this wonderful software."

Have a good one,
Ivan

Thanks for the reponse, and sorry for the delay in getting back.

The step motor that was in the printer is only 0.9 amps (4 Volts.) Is this powerful enough to cut foam, or should I look for something else? Do larger printers have more powerful motors?

There's a business not too far from me that recycles old computers. Some of the material is sold for scrap to be melted down again, but they also have a parts store. I haven't had a chance to stop by but hopefully they'll have what I'm looking for, and for a lot less money than buying new.

Steve S.

Hello Steve,

First, the steppers your finding should be large enough to handle CNC Foam Cutting. I have met a few people who used printer steppers with some success.

I am guessing the steppers you are finding are similar to the ones at the top of this page:
http://steppercontrol.com/motors.html

I have also came across people using Exercise Equipment Servo Motors on larger milling machine conversions. Keep that in the back of your mind for later.

Here is a good link on selecting the proper size stepper motor:
http://zone.ni.com/devzone/cda/ph/p/id/223

I realize you are working this out in reverse. Find a deal on steppers and make it work for you application.

Here is a useful PDF file on Stepper Basics:
www.solarbotics.net/library/pdflib/pdf/motorbas.pdf

It explains some of the NEMA Sizing, which I found valuable.

Have a good one,
Ivan