CNC router to cut and tap holes in aluminium box section?

honestone · Jan 21, 2018

Hello everyone! I am looking at manufacturing mobile robots to my design. I have no background in manufacturing. I understand that my needs can be served by a CNC router, but there are so many to choose from that I'm totally lost.

It comes down to cutting and tapping a lot of holes in aluminium box section, up to 4mm thick. The hole diameter will be 80% of the smallest dimenstion of the box section. For example, for 200x100mm box section (the largest) holes will be 80mm, same for 100x100mm box section. For 100x50mm box section holes will be 40mm, etc. Holes are evenly spaced and cover all surfaces of the box section. The thread size will scale as needed according to diameter. The length of the box section will be 1m.

What are the critical router characteristics that I need to check before buying one?

Dan from Oakland · Jan 21, 2018

if you re going to use a CNC router to tap holes, plan on thread milling the threads. Most router spindles do not have enough low speed torque to tap. We successfully thread mill 6-32 holes. But this means your control must be able to do helical interpolation or use a cam system that breaks the moves up into time straight line segments.

gundog · Jan 21, 2018

To get a router that can tap holes you will spend a lot of money. To tap holes you need to reverse the spindle and have spindle orientation. You could get by with a tapping head but that is not ideal and I doubt the router would work most have high speed spindles and very low torque at low RPM so tapping is completely out unless someone on here knows something I don't about this. This is also probably not the forum for this type question. What do plan to spend?

Finegrain · Jan 21, 2018

I don't understand your description -- are you making 40 & 80mm threaded holes, or are you making small threaded holes 40 & 80mm apart? If the former, then it doesn't make any sense to tap, you should be threadmilling. Following from that, you should be looking at a standard VMC, not a router.

1m part length might be challenging for a standard 40x20 VMC if you need to reach both ends of the part, although you can fixture the parts diagonally and then they will fit nicely in a 40x20 VMC work envelope.

Regards.

Mike

gundog · Jan 21, 2018

Dan from Oakland said:
if you re going to use a CNC router to tap holes, plan on thread milling the threads. Most router spindles do not have enough low speed torque to tap. We successfully thread mill 6-32 holes. But this means your control must be able to do helical interpolation or use a cam system that breaks the moves up into time straight line segments.

I would like to know more about the tooling you are using. I have a CNC router with a 5HP HSD spindle I make a part from 6061 T6 that I hand tap 4 1/4-20 holes in it would be nice to thread mill the holes I did not think I could get a thread mill small enough to do this on my machine.

Finegrain · Jan 21, 2018

gundog said:
I would like to know more about the tooling you are using. I have a CNC router with a 5HP HSD spindle I make a part from 6061 T6 that I hand tap 4 1/4-20 holes in it would be nice to thread mill the holes I did not think I could get a thread mill small enough to do this on my machine.

Harvey makes single-form threadmills down to .032" diameter, and multi-form down to 2-56.

Regards.

Mike

B-Mathews · Jan 21, 2018

gundog said:
I would like to know more about the tooling you are using. I have a CNC router with a 5HP HSD spindle I make a part from 6061 T6 that I hand tap 4 1/4-20 holes in it would be nice to thread mill the holes I did not think I could get a thread mill small enough to do this on my machine.

Does your HDS spindle have an encoder on it? If not you may be out of luck. Also are your holes blind or through? Other than that 1/4-20 is very common thread mill size depending on thread depth.

You ready for the Sportsmen Show yet? LOL

Mooner · Jan 21, 2018

honestone said:
Hello everyone! I am looking at manufacturing mobile robots to my design. I have no background in manufacturing.

...

characteristics that I need to check before buying one?

First of all, apologies that I’m not going to directly answer your question. But I have been exactly where you’re at and would advise against what you’re considering - until you’ve proven the success of your product line and ability to sell it. The last thing you need to do right now is also learn how to CNC machine your parts...

Start by finding a local shop that can make your parts for you - local shop will help since you are not familiar with manufacturing and it will help you to be able to walk in and have a face-to-face conversation with the expert taking on your work. You might even learn a bit about machining in the process - or at the very least, learn what issues an experienced machinist runs into while making your parts.

You would be better off spending your time and effort on other operational aspects of getting your business up and running. Once you are stable and growing, you can reassess and figure out if it makes sense to bring machining in-house. You’ll also have been exposed to how an experienced machinist would make your parts, so you’ll be better equipped to make that decision. If your business is healthy, then you’ll have all the money-related data to decide if investing in a machine makes financial sense.

For me, I ran my business for 2+ years on solely outsourcing machining work - then after I bought my own machine, it still took 6-7 months to get production to a reasonable level of output. Bringing manufacturing in-house is no small task - think about tooling decisions, tooling vendors, material vendors, finishing vendors, making your own fixtures (probably more than a few times), CAM (not to mention CAD), labor to run your CNC, figuring out your total cost so you can price correctly, etc... You’ll still need to do all the other business related stuff too - so it could help you a lot to not take on too much up front...

Good luck!

Comatose · Jan 21, 2018

Why are you trying to drill and tap with a router? Routers don't typically have tool changers, don't have a lot of torque, don't usually have tapping cycles (and certainly not rigid tapping cycles) and even if they do, the spindle Accel/decel is glacial.

You're only a meter long. Get a 1996ish Fadal 4020 for the same 15 grand and do it right. Plus then you can mill the rest of your parts too.

B-Mathews · Jan 21, 2018

Mooner said:
First of all, apologies that I’m not going to directly answer your question. But I have been exactly where you’re at and would advise against what you’re considering - until you’ve proven the success of your product line and ability to sell it. The last thing you need to do right now is also learn how to CNC machine your parts...

Start by finding a local shop that can make your parts for you - local shop will help since you are not familiar with manufacturing and it will help you to be able to walk in and have a face-to-face conversation with the expert taking on your work. You might even learn a bit about machining in the process - or at the very least, learn what issues an experienced machinist runs into while making your parts.

You would be better off spending your time and effort on other operational aspects of getting your business up and running. Once you are stable and growing, you can reassess and figure out if it makes sense to bring machining in-house. You’ll also have been exposed to how an experienced machinist would make your parts, so you’ll be better equipped to make that decision. If your business is healthy, then you’ll have all the money-related data to decide if investing in a machine makes financial sense.

For me, I ran my business for 2+ years on solely outsourcing machining work - then after I bought my own machine, it still took 6-7 months to get production to a reasonable level of output. Bringing manufacturing in-house is no small task - think about tooling decisions, tooling vendors, material vendors, finishing vendors, making your own fixtures (probably more than a few times), CAM (not to mention CAD), labor to run your CNC, figuring out your total cost so you can price correctly, etc... You’ll still need to do all the other business related stuff too - so it could help you a lot to not take on too much up front...

Good luck!

I could not agree more!!!! I have also been in your shoes as well. In todays age it is best for a one man start up to contract out everything you can while getting off the ground.

honestone · Jan 21, 2018

Finegrain said:
I don't understand your description -- are you making 40 & 80mm threaded holes, or are you making small threaded holes 40 & 80mm apart? If the former, then it doesn't make any sense to tap, you should be threadmilling. Following from that, you should be looking at a standard VMC, not a router.

1m part length might be challenging for a standard 40x20 VMC if you need to reach both ends of the part, although you can fixture the parts diagonally and then they will fit nicely in a 40x20 VMC work envelope.

Regards.

Mike

It is 40mm and 80mm holes. Large holes to thread, I know. The 1m part can be "broken" in two and each done separately as long as the part is allowed to stick out of the work area. I've seen some vids where they thread large diameters with a router. For example: CNC Router Thread Milling - YouTube This is wood, but can't aluminium be done in this way?

adama · Jan 21, 2018

IMHO you need a 4th axis, some sutable plugs - mounting and you can really haul ass on jobs like this, i would question the idea of fine large diamiter tapped holes in box section though, the threads are easily damaged, very easy to stuff up and crossthread a 80mm hole especially one so thin.

honestone · Jan 21, 2018

B-Mathews said:
I could not agree more!!!! I have also been in your shoes as well. In todays age it is best for a one man start up to contract out everything you can while getting off the ground.

Thanks for advice, but my situation is not typical. For once, I already run a business, and any company savings I don't spend by end of May will be hit by 20% capital gains tax. So it makes sense to invest in tools. Another thing, it will probably be at least 2 years before I have the time to focus on this thing. In the meantine, I don't mind spending some evenings learning about CNC. I'll hire a machinist if I need to.

I already made the parts in question in a manual way and it wasn't hard. These are the only machined parts, the rest will be purchased or 3d-printed.

honestone · Jan 21, 2018

adama said:
IMHO you need a 4th axis, some sutable plugs - mounting and you can really haul ass on jobs like this, i would question the idea of fine large diamiter tapped holes in box section though, the threads are easily damaged, very easy to stuff up and crossthread a 80mm hole especially one so thin.

The thread doesn't need to bear a lot of load. The holes will be mostly plugged with PVC threaded lids.
If the usual router torque is too low for threading, can the router head be replaced with some low-speed one, just for this purpose?

Sarah Loyd · Jan 21, 2018

I think the others have nicely summed this up - Don't buy a CNC router, it's the wrong tool for the job.
A router may drill the holes but it will fail on the tapping requirement. You could do the tapping part by a pneumatic tapping arm but if you insist on doing the manufacturing yourself then a VMC will serve you better and offer you so much more for prototyping your designs. Perhaps the most "critical characteristic"'s you mention are ones you have to have rather than ones a tool has to have.

Manufacturing isn't something you can throw a cheap Chinese router at and expect to get good results. Good luck and best Regards

DDoug · Jan 21, 2018

honestone said:
Thanks for advice, but my situation is not typical. For once, I already run a business, and any company savings I don't spend by end of May will be hit by 20% capital gains tax. So it makes sense to invest in tools.

Doesn't purchasing parts show up as a debt ?

Another vote for subbing it out.

honestone · Jan 21, 2018

digger doug said:
Doesn't purchasing parts show up as a debt ?

Another vote for subbing it out.

Not in UK where I'm based, but don't know about the US. Thanks everyone, I don't think I will be buying a router. VMC's are very expensive unless you buy used which I'm not prepared to do. Perhaps I'm better off with a manual process for now, I'm only in the proptotyping stage anyway.

itsallkuhlmann · Jan 21, 2018

honestone said:
The thread doesn't need to bear a lot of load. The holes will be mostly plugged with PVC threaded lids.
If the usual router torque is too low for threading, can the router head be replaced with some low-speed one, just for this purpose?

You'll be thread milling those holes? torque would not be an issue at all.

Andy St · Jan 21, 2018

honestone said:
Thanks for advice, but my situation is not typical. For once, I already run a business, and any company savings I don't spend by end of May will be hit by 20% capital gains tax. So it makes sense to invest in tools. Another thing, it will probably be at least 2 years before I have the time to focus on this thing. In the meantine, I don't mind spending some evenings learning about CNC. I'll hire a machinist if I need to.

I already made the parts in question in a manual way and it wasn't hard. These are the only machined parts, the rest will be purchased or 3d-printed.

honestone
Just curious but how were you making the thread "in a manual way"?

Mooner · Jan 21, 2018

honestone said:
The thread doesn't need to bear a lot of load. The holes will be mostly plugged with PVC threaded lids.
If the usual router torque is too low for threading, can the router head be replaced with some low-speed one, just for this purpose?

If you're plugging the holes with lids, you might consider using a "bayonet" style mount instead of threads. If there is not much load on the cover, you'd probably be much better off and it would be easier to insert / remove the cover with a 90° - 120° twist instead of trying to correctly line up the lid on conventional threads. It would also be much easier / quicker to machine the thin aluminum parts (2D profile only). Flip side - you would need to make a slightly more complex geometry on the PVC part instead of simple threads.

Not to sound like a broken record, but these are the kinds of design changes that an experienced machinist could help you make correctly the first time, instead of suffering through trying to implement less than ideal early decisions.

CNC router to cut and tap holes in aluminium box section?

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