Taking the ShopBot to the EXTREME

[Brady Watson]

Last week I had a friend in a bit of a pickle. He needed a part for his 1955 Buick Century V8, and nobody had one in the US. With a car show quickly approaching (last weekend) he asked me (OK begged me) to make him a replacement part so that his family could all drive down to the show together.

This VERY graphics intense write-up (cable & DSL only) shows how a ShopBot CNC router saved the day, producing a double-sided 3D mechanical part on spec and on time.

While I am not interested in doing production runs of these parts, I was curious...Could the ShopBot do it if I programmed it correctly?

Tune in to find out...

http://www.bradywatson.com/Aluminum.htm

-B

[joe]

Excellent Brady,

Aside from the professional cutting techniques you exercised, I'm also impresed with the 3D model you made. I have to assume you used ArtCam, or was it some other software. Did it take long to make up the file? What was your total cuting time and how many tool changes were there?

When I try something like this I allways call up the "A" team.

Keep up the good work!

Joe

[mmccue29]

wow what a great job.

[rookie432]

nice job Brady!

I knew this was possible theoretically but it is nice to see someone actually take on the challenge. Do you think this would have been possible without the spindle?

Bill

[doglaw]

Nice job Brady. I'm curious, how long did it take you to machine the aluminum?

[Brady Watson]

Thanks for the kudos guys.

Model was created in ArtCAM & took me a few hours to create, mainly because I was measuring the broken pieces while modeling it


All said and done, it took me about 8hrs of cutting time to do the front & back. I probably could have knocked that down to around 4hrs or less if I eliminated the 1/8" toolpath operations in between the fins and eliminated some of the 3D toolpaths that I now see could have been improved upon or are just redundant.

It was a good learning experience & not something that a newbie should tackle. This project required an operator that could govern the machine while it was running...Not someone who would sneek off to get a drink. Speeds & feeds varied across the project, and it needed that kind of attention (or at least my fear of crashing the spindle kept me there).

Do I think it could be done on a router instead of a spindle? I think that it probably could, but you would have to use a very light chipload to prevent the router from bogging down too hard. I ran everything but the 1/8" bit at 13,500 RPM, so there was no advantage to the spindle there, except for non-bogging torque.

-B

[brian_h]

Brady,

I can't tell you how glad I am that you took the time to post that. I'm just *itching* to expand into other materials, like aluminum, but right now it is very far out of my comfort level. This sort of post with the pictures sure helps with building a comfort level.

I'm curious about your technique of lining up the part when you turned it over. How do you know it is exactly where it should be????

[Brady Watson]

Brian,
When doing a double sided radial part I always create the model with 0,0 in the center of the part. You might be able to see where I put an X from corner to corner to use as a reference, plus lines on the spoilboard. I used an engraving bit to line it up to the intersection of the 2 marks. Instead of blindly trusting that the flip would be dead on, I chose to mill all the way thru the part so that I would have a center reference. I then took a 1" bit and verified the 2nd half's center with the bit about 1/2" into the part.

-B

[brian_h]

Thanks, Brady. Pretty straight-forward. I've been working on dreaming up a fixture that'll help me line up flipped-over 3D parts. I have some ideas but haven't tried anything yet.

[sawkerf]

You make me sick! or jealous or something like that. Great job Brady.
Kip

[jim_hansen]

Very nice job Brady. I did my first aluminum milling job yesterday. I made an air cooling tube out of a piece of 3/16 od steel brake line and a starboard collar on the spindle. I learned not to rely on vaccume to hold the part it needs to be fastened to the table. Jim

[Brady Watson]

Brian,
Check out DeskProto...DOwnload the demo when you are ready and run it. It puts 3D tabs on the part and tells you exactly how to line up the material for the flip. It's pretty foolproof and the results are great.

Jim,
By the time I thought to use brake line it was 8PM...so a quick run to Depot is all that the night permitted. Good idea though, since the stuff bends fairly easily and still remains stiff.

You're right about vacuum on smaller parts or parts that will be subjected to vibration and heavy chiploads. AL sheet is fine with a FEIN vac, but larger thicker pieces have trouble, even with correct gasketing and a high Hg (27+) pump.

-B

[normand]

good show! Is there an advantage with the alpha over a prt at those speed. Also does artcam have a radial machining option?

[Brady Watson]

Normand,
The Alpha is better at any speed, since it is microstepping & the PRT only 1/4 steps.

Yes, ArtCAM does. The entire model was created in ArtCAM and toolpathed in ArtCAM. No Rhino, no DeskProto...just ArtCAM.

-B

[mikejohn]

Check out ascension 100 messages to improve PRT resolution and speed.

.........Mike

[dingwall]

Very cool Brady.

Is your bot frame and gantry stock or have you modded/beefed it up?

I won't even ask if you made shop rates on that project

[Brady Watson]

Sheldon,
It is a stock Alpha gantry...no mods. I did adjust the VR a little to 'cushion' starts and stops to reduce shocking the bit. I mod the VR depending on what I am cutting that day. It can make a big difference if you know what you are doing...and a mess if you don't!

This was for a friend & it was worth the excitment and anticipation to see it work out so well. If I had to charge shop rate it would be in the neighborhood of $1200...hence my statement of not wanting to do anything like this in a production capacity on the bot...BUT what is not readily apparent is that I could have made a master & had it cast in AL, then just do cleanup on the hub to bring it to finished size...either way it is pushing the envelope of a CNC router and is probably better suited (either operation) on a CNC mill. It is however nice to know that if I absolutely needed a part and HAD to do it on the bot, I could...What a great tool!!! I still love this thing after 5yrs!!!

-B

[normand]

Brady Thank for the info. I am glad for you that you could make this with only ArtCam, no Proto, no Rhino. But why would you need to, having the best of the best. Another thing and dont be mad (if) you are selling ArtCam how come you dont know their return policy?

Normand

[Brady Watson]

Normand,
Where does it say I sell ArtCAM? That's news to me!

-B

[normand]

I am sorry .Why would I assume that? Anyway good work on the alu.
Normand