New build, some help please

[woody565]

Hi all,

I am starting to build a cnc router that will be used mainly to cut balsa and plywood model parts.

It is based on this design from another forum member


Would that design be capable of some light aluminium work with shallow passes and slow feed rates? Wouldn't be a lot but would like to make some fishing weight moulds like this,


Additional I have been looking at BST linear bearings , would these be better or worse than running skate bearings on the aluminium box section?

Thanks for any help

Dan

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[awerby]

I don't think that design would be suitable for making metal molds like that. If it cut it at all, the finish would be pretty horrible. If that's a major part of what you want to do, consider investing in a small mill, like the Taig. I'm not sure about the quality of the BST brand, but any linear bearing/round rail system would probably be better than the skate wheels, as long as the rails were fully supported.

[wizard]

Hi all,

I am starting to build a cnc router that will be used mainly to cut balsa and plywood model parts.

If limited to that activity then you really have light duty needs. Beyond that model makers aren't often looking for high precision or fantastic surface finish. At least that is the impression I get from people interested in this stuff. In other words making these sorts of parts is just one step to a finished product. Contrast that with somebody building a guitar where the finished product is what comes off the machine. Well finished as nearly as possible machining wise.

To put it another way model makers are happy with a cheap way to spit out a bunch of parts rather than having to loft them by hand.

It is based on this design from another forum member

That may be passable for model making if you have a high tolerance for poor finish and potentially a lot of inprecision in the finished parts. I often use the word expectations in conversations like this. A machine like that would be suitable for somebody with low expectations. I really can't see the machine being useful for even general wood working. In fact im pretty sure some examples of machines built from wood will perform better than that machine.

Would that design be capable of some light aluminium work with shallow passes and slow feed rates? Wouldn't be a lot but would like to make some fishing weight moulds like this,

Well for the most part no. If you are going for a really crude looking sinkers it might work. However if you want precision, decent finish and a part that is finished before the turn of the century then it isn't the machine for the job.

Additional I have been looking at BST linear bearings , would these be better or worse than running skate bearings on the aluminium box section?

Profile rails and round rails would be miles ahead of what I see there. However you really need to consider a stiffer frame all around, as shown that machine would be suitable for crude work in my estimation. In my mind putting linear rails (profile or round) on that machine would be foolhardy.

Thanks for any help

Dan

No problem!

Consider a few things:

How serious are you about machining aluminum? What you are talking about is making a mold for your sinkers. Mold making is considered high precision skilled work. A lead weight mold doesn't require a high degree of precision like is seen in die casting or plastics but I still needs to produce parts that look good. Beyond that most molds I've seen for casting lead are made of steel, I'm not sure how aluminum would work here.

While you can get away with a sloppy machine for model making, do you have aspirations to do other wood working? If so you will likely want a better machine just to support your wood working interests.

What I'm try to zero in on here is how much of your interests would dictate a different design.

[Third-Gen]

At the very minimum I would use some sort of a welded frame and linear round slides. Or another option is get a smaller granite inspection table, drill it for epoxy inserts, and build off of that. Gives a VERY stable and strong base. You can cut AL on a linear guide machine, but trying on a channel bearing machine just isnt built for those loads. I had a belt drive machine I would run at 4 ipm, .010 cut depth, .010 stepover, with flood coolant and a 3 flute bit, and it came out ok, Just took days to get any parts made. If you want to do aluminum a lot, look at a different design IMO.

[woody565]

Thanks all for taking the time to reply, and it's a good job you guys are offering advice as I am now going to change the design.

All though I will primarily use it for model parts, I would love to explore different areas off cnc machining so would ideally like a more versatile machine.

I have been looking at the carving-cnc models so will either buy one of there models or design some thing similar using extruded ali and sbr20 rails for the x axis and sbr16 for y & z.

Cheers again

[wizard]

Thanks all for taking the time to reply, and it's a good job you guys are offering advice as I am now going to change the design.

No problem, just sharing opinions here.

All though I will primarily use it for model parts, I would love to explore different areas off cnc machining so would ideally like a more versatile machine.

More versatile means more money����. Seriously though as a builder you are always balancing wants against resources. A bigger machine equals more money, a stiffer machine means more money or a smaller machine.

Even the word versatile is hard to nail down. To some people that means a big 4x8 machine to others it might mean a smallish machine that is strong enough to allow them to do realistic machining in aluminum and other materials.

I have been looking at the carving-cnc models so will either buy one of there models or design some thing similar using extruded ali and sbr20 rails for the x axis and sbr16 for y & z.

Cheers again

If you do a DIY home build be sure to wake this thread back up with pics.