[erazz]

Hello All,

My company produces 3D moulds for composite applications. Currently we work on a Busselato Jet600 which is not our own and so I'm looking to buy a CNC router.

I need a router to mill MDF and tooling blocks (Sika 960-950).

I'm trying to decide between the following:
1) K2CNC KG3925-GTHK
2) ShopBot PRTAlpha 48 or 96
3) EZ-Router 4'-8'
4) ShopSaber 36x36

All with either a closed loop encoder-stepper motors or with full servo motors.

My main concern is accuracy. The Sika blocks reproduce accuracy errors and are a pain to sand.

Would the lower accuracy of machines 2 to 4 create problems here? Would running the machine at a slower rate help the accuracy?

Also, how much would an increase in Z travel affect the accuracy? The ShopBot setup looks pretty rigid while the K2 does not.

Any other suggestions besides the stated machines? (price < $10K)


Thanks for the help

[turmite]

Hello All,

My company produces 3D moulds for composite applications. Currently we work on a Busselato Jet600 which is not our own and so I'm looking to buy a CNC router.

I need a router to mill MDF and tooling blocks (Sika 960-950).

I'm trying to decide between the following:
1) K2CNC KG3925-GTHK
2) ShopBot PRTAlpha 48 or 96
3) EZ-Router 4'-8'
4) ShopSaber 36x36

All with either a closed loop encoder-stepper motors or with full servo motors.

My main concern is accuracy. The Sika blocks reproduce accuracy errors and are a pain to sand.

Would the lower accuracy of machines 2 to 4 create problems here? Would running the machine at a slower rate help the accuracy?

Also, how much would an increase in Z travel affect the accuracy? The ShopBot setup looks pretty rigid while the K2 does not.

Any other suggestions besides the stated machines? (price < $10K)


Thanks for the help

I think you are confusing accuracy with smoothness of cut and though the two are connected, they are not nearly as connected as you think.

Accuracy would be telling the machine to move 10" and it moves 10". I think what you are looking for is a very smooth product after the machine has finished the carving routine?? Correct? This is accomplished by using a very small step over in your g-code and also using as large a bit as possible to keep the scallop to a minimum. If the machine has any, or at least very much vibration, you will want to run it slow enough to keep that from becoming a problem. The material you carve will also help determine the speed of your feedrates.

If I were going to advise you, I would need to know the minimum and maxium size of the models you carve. Get the smallest machine you can get by with and get that machine as heavy as you can. I have a machine that can cover a 4'X8' sheet of material with two heads but I don't need that kind of machine. I need one less than a 1/3 that size that is 3 times as heavy as the one I have!

Mike

[cbass]

I would consider the rigidity of the machine. Under no load, they may all be accurate. But what happens when they encounter a load? How much will the gantry deflect when the Z is extended?

While I like the K2 machine, it is aluminum, as is the EZ-router I believe. I'd be tempted to go with the Shop Saber. It uses ball screws (or lead screws) and linear guides. I think the shop-bot is a step down in terms of components. I would ask them to put servos on it.

There seems to be a new kid on the block...

http://cgi.ebay.com/ws/eBayISAPI.dll...039936787&rd=1

Made by EBF
I don't know much about them, but damn, that thing looks HEAVY. Much more meat on it than your 4 choices (compare the bracing in the corners of the gantry to the Saber and you'll see a big difference). Its within the same price range, has nice components and is steel, but dosen't have much reputation. You could end up with a great deal, or you could end up being their guinea pig. At least they are in Canada, not China, and they have a phone number. Something to consider.

Good luck!

Carlo

[erazz]

Yup, wording problems.

I should have just stuck to simple English.

You're both absolutly right. When I said "Accuracy" I ment that it cannot have to much "chatter" on the part. It should be (as Mike said) "smooth".

So basically I'm trying to figure out what machine will give me the best finish on the part (assuming equal stepover).

Thanks for the heads-up, Carlo, I'll definitly call the guy.

How about the Shop Sabre? They seem pretty solid.