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Re: Choosing router for steel rule die board application

Posted: Fri Dec 20, 2013 11:50 pm
by TDA
Hi everyone, I thought I would try to clear up a few things. Please keep in mine I don't know the Shapeoko systems very well. So I leave it to you to apply this.

SRD milling overview: Here's how most SRD milling is done. A pair of birch ply sheets .30"-.40" are cut through with a SRD tool. The sheets are then glued together and rule is forced through them. This is done for a couple reasons. First SRD tooling only has around .100" worth of engagement for the rule. Doubling up lets you get a total of .200". The second reason is that you could not do this kind of full plunge routing of a single thicker board. There would be too many issues with tool strength and deflection. This process does come with a few problems though. The biggest issue is that you have very little margin of error for lining up the sheets. This means that you must have little deflection and pretty much no backlash.

Router / spindles:

Overall: The biggest thing you need to worry about is runout. Even as much as a thou worth can make some boards unusable. This is why production machines use high end spindles with runout measured under .0002". That being said we have customers that use routers with our collets without issue. You don't really need to worry about the power too much if you are sticking to 2 point tools (0.0280"). Most units should be able to handle this at decent feeds.

611: The DeWalt 611 is by far the best router in this form factor that we have seen. There seems to be very few units that have any issue with the tapers. Meaning that you should have a good base for low runout. They also seem to have good bearings in them that last a while and are better supported. This makes them better for plunging.

Chinese spindles: Be careful here. While there are definitely good ones we have seen a number of units that have high runout. Most sellers don't even spec it or they list "typical" runout. A company named UGRA does sell tested units. However, their spec is usually around .001". That should give you an idea of where the unlisted units are. Also watch the bearings as we have seen some units out there need replacement after very little run time. Lastly, if you do get one be sure you get a VFD that has English instructions available.

Machine rigidity:

Overall: Basically what you are worried about here is deflection. With these tools designed to go 120IPM @ 40KRPM full plunge there are a lot of forces on the machine and tooling. You will need a very rigid setup or you will have to compensate for the deflection. Most ways of doing this are far from ideal. To give you an example our machine's gantry is 1/2" to 1" aluminium with linear rails and we still see issues that are not present in production machines.

Router mount: Do not use a plastic mount for the router and keep it as close as possible to the gantry. Using plastic or extending out with weak/long supports are very easy ways to introduce deflection into a high stress cut.

I hope that at least helps a little. Let me know if there is anything I can help with.

John Torrez
Think & Tinker / PreciseBits

Re: Choosing router for steel rule die board application

Posted: Sat Dec 21, 2013 1:44 am
by mrtofu
John: Thanks a lot for all that useful information. This is pretty much what i got from you guys when i contacted you.

This pretty much helps the case that the key thing, since i'm planning on using precisebits's collets and 2 point bit made for this task, is the machine rigidity. I would love to know opinions if i could upgrade a shapeoko2 to probably handle the task or not, and since i don't own a previous one or another cnc for that matter, it's really hard for me to work it out by myself. Maybe john has seen a previous shapeoko in the works.

Thanks for all!

Re: Choosing router for steel rule die board application

Posted: Sat Dec 21, 2013 2:03 am
by WillAdams
Yes, you could upgrade a ShapeOko to that kind of accuracy/precision --- but there wouldn't be much of the original machine left, and it would cost more than custom-building a machine --- at least if you got the custom design right the first time, maybe not even then.

The advantage of the SO2 is that it's an affordable entry-level design which is known to work --- you can replace / upgrade a part and be confident the machine will still function.

It'd be neat to see a set of ShapeOko upgrades which could be this accurate on this scale, but they'd be so expensive only a very few might sell.

Re: Choosing router for steel rule die board application

Posted: Sat Dec 21, 2013 11:47 pm
by mrtofu
In this case, do you guys have any recommendations for a system that has the rigidity/precision i would need? I've googled a lot but i either see DIY or 10-20K commercial ones.

Thanks again!

Re: Choosing router for steel rule die board application

Posted: Sun Dec 22, 2013 5:16 pm
by samc99us
Mrtofu,

The Dewalt 611 is too large for the stock SO2. I am working on a highly expanded version, as it appears there is a market. Improbable Constructs machine is essentially what I'm aiming for but his build isn't replicable, since hardened openrail isn't available. I'm planning on sistering hardened steel v rail to Misumi extrusions and using the open builds
Steel v-wheels. Not sure if the GT2 drive system will work, but so far no one seems to have any major complaints with it once properly adjusted. Moving to an ACME or r&p drive system is expensive.

Your best bets for an existing kit in your price range are CNCRouterParts machines and Fine Line Automations, though i woukd pick the former due to customer support. Harrys CastCNC is super nice with the ibeam gantry, something i may replicate on a smaller scale.The Grunblau CNC is really nice but pricey.