Here is a picture of the finished "JH" logo. We painted it with a high gloss oil based paint.

The second picture is of a curved piece of crown mould.
The customer (fellow cabinet maker) made a curved cabinet, then brought us a block of maple with the same radius as the cabinet. I drew the 3d model in sketchup (free edition) then exported the .stl, and did the cam process with freemill (also freeware). I was not expecting to do this with free software.

We ended up needing to buy a extra long 1/2" straight flute bit due to the height of the mould. I used a .060" stepover. It did need some sanding:D
It wasn't perfect, but the customer needed it pronto, and we decided we would do it for the sake of education :)

Not bad for the first 3d project.

You have my attention!

Nice work, Colin. Thanks for sharing.

Wow, impressive. Did you scan the profile of the existing molding for doing the 3d model? Interested in the process. :)

Very nice job Colin! thank you for the chain and sprockets characteristics. Are these with the pinion reduction you have talked about or is it a standalone transmission setting. Thanks again

The last specs are for the chain sprockets only. The belt transmission parts are in post #75.

@ Domino11
That was the trickiest/hardest part of the whole job! I DID trace it on paper then scanned it in, then scaled it to the right dimensions, and imported it to sketchup. However, I still needed to trace that scanned picture with the pencil tool in sketchup. That was trickier than anticipated. The process could be improved somehow.?!? It turned out fairly accurate. The profile wasn't perfect, but that's what practice is for right? :D

Well folks, The time has come.... As much as I hate to do this....As long as I have put this off....It doesn't change the facts. I've decided to fit her with the rack and pinion according to the original design. :cool: I wanted the chain to work. I really did! But, There were some things I didn't like that I decided were not worth "playing with" in a production shop. :D While I think it would work, and be a low cost solution for a hobby user, etc. I was having problems with the chain stretching and binding up the steppers. The cost was not significant enough to prevent us from just doing it like everybody else. I ordered all the parts and had it working again with just under 2 days of down time. Side bonus was that I got a welder out of the deal. :D

We also got the vacuum all hooked up. I divided the table up into 6 zones. Let me tell you. "That table works nice!"

The spindle is also hooked up. Did I mention I've been learning about 3 phase electricity lately?

I Built my own Rotary phase converter for the 15hp vacuum. Fun ;)
I might post pictures of that later on.

I also attached a picture of one of 25 entertainment center that we just finished. We used it to cut the top and bottom, the shelf in the middle, and the bendable plywood for the face.

The rocking chair is a project I'm taking on for an amish friend. :p


P.S. I'm sure some of you could have told me the chain wasn't the best idea.
Please, let me know what you were thinking. I won't be offended. :o

Looking good Colin.. Glad you are honest about the chain thing....and are happy with the original design. In my 3 years I have see a lot of people with some bright ideas. Some locals that I assisted also tried some modifications.... some of them are still not finished after 2 years of building. I have always said to them to keep to the original design as it worked out well for me.
I will say nothing about your chain attempt....too afraid of venom spitting okes on the other side of the world..:D you know what I mean...

Collin,

You gave it a shot and it didn't work the way you wanted it to work. It is better to try than to wonder if it would have work. Thanks for sharing you experiment.

We all learn from others.

Colin, I don't think you're going to get any "I told you so" responses; many of us were pulling for it to work, and we appreciate the feedback on the results. "Failed" experiments are often more educational than "successful" ones.

With the understanding that you've moved on for good reasons (like running a business), I'd like to know if you feel that some kind of dynamic chain tensioner such as a spring or large weight could work, or if other issues render this approach dead.

Collins,

You win some and you loose some. I will never fault anyone for trying something different to meet the needs at the time. I think it is great that you were able to come online and share your experience with everyone here even if it didnt meet your needs.

The entertainment centers do have me scratching my head though. They look great but is the TV of center or is the black area for components and the Tv sits on top?

Hey, give the man a number! :)

Haha, Thanks Gerald! Do I get #62b or something?

@ Brad
Scot had many ideas for making the chain work better too. A high tension spring may work. I Don't think there would be many problems with it on a light duty machine such as a plasma cutter, laser, etc. The Chain needs a lot of tension to eliminate any backlash, and to eliminate that, you basically are going to end up with a stretched chain. However, on a laser or plasma, you could use a lighter chain (like #25) similar to the machines at buildyourcnc.com and it might work very well. I was also thinking that maybe if you fastened the chain to the gantry and made a loop with the steppers on the end of the machine you would eliminate some sprockets too. But, that would be drastically altering the design of the Mechmate. :eek:

It's also good to remind ourselves that it DID work for about 10 months of moderate to heavy usage.

@ Regnar
The entertainment centers get a granite top on them yet, then the TV sets on top, and the components go inside.

Very nice machine. Love the colour as well.

I am only just starting my build but I do like your table.

keep up the excellent work.

michael

Hello collins.

I am french, excuse me for my bad english.

I build my CNC based mechmate, and I wanted to try chain. But I wanted to put the chain on a bar to improve tension and use it as-rack:

http://llcorp.free.fr/autres/SDC12069b.jpg
http://llcorp.free.fr/autres/SDC12070b.jpg

I am disappointed... The chain seemed to work well on videos.

PS: I difusion photos of my CNC once completed.

by the way, using a chain as a rack&pinion isn't as accurate as normal rack&pinion, cause of some play.
But if you do want to use chains, then this is the only way.

If you use a chaindrive for positioning systems, and work with chainwheels, be aware of the polygon effect when using chainwheels. Chainwheels are not perfect circles, but act like polygons, and will give positioning errors!

Chain Drive
 

Hey you guys,
I think Collin is being a little hard on the chain drive. It did work very well for several months under true commercial conditions and was still working very well before the change to the rack drive. I wouldn't say it was a failure just that it has it's limitations. I think for home hobby use it is an excellent way to go.
What do you think Collin? Am i being stubborn?
Louloute30 that is a very fine looking machine let us know when it's running.
Thanks, Scot

Exactly,
I'm not writing it off as a total failure. I Did say that it did work fine for quite a while. I think there are a few options one could try to improve the idea. I simply didn't want to "experiment" with mine right now. But, if I had the time and needed to build another one, I would definitely try some other ideas with the chain.

@ Skillalot
The sprockets not being perfectly round makes sense. I kind of figured as much wich is why I suggested that maybe a loop with the chain attached to the gantry would be better.

Collin,

Thanks for your confirmation.
I'll try then the mechanism of chain.
I'll see, and I will share with you

See you soon

Else I did that

http://llcorp.free.fr/autres/SDC12072b.jpg
http://llcorp.free.fr/autres/SDC12071b.jpg

And, I added a bracket to support the chain and prevent earthquakes