plasma design 8' x 4'

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Any thoughts on this design from all you guru's ?
Will be using Mechmate home ground rails for x and y. The results some of those guys get are amazing (see mechmates forum for some amazing router builds) . rack and pinion of x and y. Will have a water table that can be wheeled in and out. Would also like to use it ocasionally as a router, I appreciate that there will be a fair amount of set up time to convert between the two. Will be using a gear a belt reduction on all axis approx 3:1.

Havent even thought about z yet but it will have THC. Any thoughts here would be greatfully received.

I have a candcnc plas pak 1a kit. Want to have it running by end of december latest.

Cheers.

[mike techserv]

Hi

Looks fun, are the Y (long travel) motors going to be sprung into mesh or fixed?
If sprung Im not too sure if some bearings running on the bottom face would be a good idea to stop the machine tipping under hard accel / decel.

Keep up the good work

cheers

Mike

www.techservcnc.com

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Sprung into rack. I wandered wether bearings running underneath might be needed. Would they "confuse" the sprung tension on the pinion ? if you know what i mean. Mechmate routers do not have the bearings underneath but then their gantry looks pretty heavy.

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Well here it is..
Spent 3 months building this, now ready to plug in.
Will be building a water table to fit under underneath.
Using a plaspak 1a system from candcnc which i managed to pick up on ebay as an uncompleted project.
Now I have the big Mach 3 learning curve to conquer.
Sure hope it all works!

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sorry larger pics here..

[Speedave]

sorry larger pics here..

Hi Ads,

Great pics, thanks for sharing.

I have a couple of questions, I am genuinely interested. Having worked hard on getting rack and pinion / V bearings right, why did you decide to switch to Ballscrew / linear guide for the Z axis?

Also on the X carriage, the ratio of the distance between the wheels left/right to front/back is high. i.e. Its a wide, short carriage. In the past I have had problems with linear rails that stick when the ratio is too high, like the runners in a chest of drawers. Have you ever had anything like this? (probably not a problem because you drive from both sides)

Lastly, what kind of spring tension do you use on the rack? Ever seen it jump?

Best wishes

Dave

[irving2008]

...
I have a couple of questions, I am genuinely interested. Having worked hard on getting rack and pinion / V bearings right, why did you decide to switch to Ballscrew / linear guide for the Z axis?

Also on the X carriage, the ratio of the distance between the wheels left/right to front/back is high. i.e. Its a wide, short carriage. In the past I have had problems with linear rails that stick when the ratio is too high, like the runners in a chest of drawers. Have you ever had anything like this? (probably not a problem because you drive from both sides)
..

There is a rule, known as the 2 to 1 rule, which says that the point at which force is applied should never be further away than twice the distance between the support bearings. So if your bearings are 50mm apart the maximum height of your workpiece is 100mm (assuming the top of the gantry is not constrained). See the video here (if it asks you to register just put in any old rubbish for name and email, it doesnt check). A similar rule applies horizontally, but where both sides are running on rails and the two sides are connected its 4:1 or more depending on rigidity of the connecting piece, so for bearings 50mm apart the maxmimum width between rails is typically around 200 - 250mm. If you look for example at the Igus dryLin carriage plates, they always stick to a ratio between 3 and 4:1

[Speedave]

How about that? that video is excellent.

So the next question is what is the ratio in Ads' machine.

[Lee Roberts]

Looks good mate, well done on getting this far!

I'm liking the sprung tension on the pinion, never seen that before.

[Tom]

That's looking a good 3 month work ads...! When you've got it all tuned up it'll be a nice robust machine.

Just a Q: What are the Vbearings running on on X and Y? It is the proper machined rail, or have you found some alternative (angle iron, or something)? And did you use eccentric bushes to pull the bearings onto the rails, or some other method? Just curious because my next machine will probably be using v bearings.

Anyway, looking good!