CNC Routers for FRC Robotics


#481

It’s router ception!


#482

That is some good photography right there!


#483

Doesn’t look like the correct color blue.


#484

Weird flex but ok.


#485

We recently got a CNC Mill (see here, with 2.2kW spindle and oil-mist) and have been successfully using it for wood in the past few weeks. Recently, we wanted to start milling aluminum so we got high-end aluminum end mills (3 flute 6mm solid carbide). However, when we ran it on aluminum (8k RPM, 300mm/min) it was making weird and loud noises—which we later learned was chatter. Therefore, we ran the following experiments with pockets to get rid of the chatter:

8k RPM, 1mm step-down, 2.6mm stepover, feed rate (mm/min): {300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000}
Feed per tooth 0.033mm, 1mm step-down, 2.6mm stepover, RPM: {4000, 5000, 6000, 7000, 8000, 9000, 10000}
8k RPM, 2.6mm stepover, 800 feed rate (mm/min), step-down: {0.5, 1.0, 1.5, 2.0}

Out of all of the experiments, 8kRPM at 800mm/min seemed the best but it still seems like a lot of chatter… (image attached, video here). We also tried clamping down stronger than what is visible in the video, using 4 clamps and tightening them using pliers till the clamps started bending. We ran out of ideas for what to change, do you have any tips?

The G-Code for the pocket is attached (generated in Fusion 360).pocket.tap (2.9 KB)


#486

Can you not go faster? We run our 6mm cutters between 13,000 and 16,000 RPM. Those spindles have very little torque at any speed below 10,000 RPM. Use a little stick out as possible will also help. For routers you generally want less flutes, clearing chips is hard and for 3 flutes you should be using a lot of air to keep the endmill clear of chips so you aren’t re-cutting loose chips.


#487

Stiffness can also have a huge difference for metals and other harder materials. Your machine appears to have good fundamentals so I would start with RoboChair’s suggestions, but if that doesn’t work, you may have a stiffness issue on hand. Try pushing on your spindle and/or table bed with a dial indicator on the other side and see what deflections you get. Some Small/Hobby CNC routers loose a lot of stiffness in their beds. I saw one instance where someone replaced the aluminum T-Slot with Steel and drilled holes for fixturing and vastly improved the performance of their machine.


#488

We can go up to 24K RPM so we’ll try that, should we keep the feed-per-tooth constant when we increase the RPM (i.e. run at 14K RPM and 1400mm/min) or keep the feed rate constant (i.e. 14K RPM and 800mm/min)?

We have about 15mm stick out now and that’s the furthest up we can put it.

We already spent quite a lot of money on a few 3 flutes as it was recommended to us by the store… Does less flutes mean 1 or 2?


#489

We got a Laguna IQ last year and started experimenting with it. We started by carving out our team numbers from like plywood or something and then moved onto cutting aluminum. We actually cut the bearing holes for our power cube sucker last year with it so the bearings would fit almost perfectly. If your team does not have a CNC router, you should get one, they are incredibly beneficial and allow the creation of complex custom parts.


Best Shopbot Tutorials/Videos?
#490

You can play with both by using the overrides in Mach3 or similar program, letting you just change your values on the fly. 3 flutes is about the max I would consider on any endmill 0.25" and smaller, 1678 uses 1 flute endmills for just about everything because they clear chips very well and are actually possible to resharpen the ends by hand. 3 flutes will give you the ability to run at a higher feedrate(as long as your machine is stiff enough) and give you a much better finish, as long as you can clear the chips. Blasting that endmill with a very focused jet of air will really improve your cuts. If you can take your misting nozzle and aim it a little off to one side of your endmill and use a second dedicated air line that aims right at the cutter while passing THROUGH the mist, pulling all the mist along with it at high speed.


#491

I am learning about CNC router usage and have questions about placing bearing bores in rectangular tubing.

  1. If the tubing is not wide can you use a long router bit and machine both sides without flipping the tube over? What is the maximum tube width when this can be done?

  2. For wider tubes the tubes will need to be flipped over. How do you index the tube to ensure the holes on each side are aligned?


#492

I would think that any flexing in the cutting tool would cause the cuts on the top and bottom to be different and I would imagine the tool would be likely to break if you attempt to machine both sides.

As for flipping, I am sure most teams are using tubing jigs with Vises or some other means of ensuring that the X and Y locations are identical for any tube installed in the jig. There are pictures in the very first post of this thread.

Here are photos of the 4096 tubing jig with tubing installed vertically and horizontally.



The vises are mounted on a 0.5"x6" aluminum plate with 0.03" deep slots cut in the plate for installing the vises. The vise mount plate is bolted to the router frame.


#493

For those of you with VFD drive/spindle combinations, do your spindles accommodate tool holders? 4096 is looking at upgrading to a water cooled spindle but we have been spoiled by having 5 quick change tool holders for our various cutters.


#494

I think I just answered my own question. we can put a 0.5" collet into the ER20 collet chuck that will come with the new spindle and then put our existing tool holders into the spindle collet.


#495

How do you all approach cutting parts with lots of pocketing? We’ve been cutting some gearbox plates and started out just doing profile cuts on the pockets, but found that: a) it could be dangerous since the remaining pieces can be shot out at pretty high speeds; and b) with tight corners the remaining piece in the middle can kick out and wedge the end mill causing it to break.

We’ve since been doing full pocket cuts, which solves those problems, but significantly increases cutting time. For 4 gearbox plates, for example, our cut time went from 40min to 90min.


#496

It depends on the size of the piece in the middle. If it is big enough to accomodate a #8 brass screw, we drill a holes in the middle of each part that will be left behind, move the spndle clear and pause the operation, screw those parts down, then continue.


#497

What toolholders do you use that have a 1/2" shank and would go into a 1/2" collet?


#498

I’ve heard good things about the cheap 4mm Huhao endmills on CD, but I’m having no luck with them. This album shows a comparison of some boring and contouring with the 4mm Huhaos with the 4mm endmills from WCP. Same 20k spindle speeds, same 32ipm feed rates, full WOC, 0.090" DOC. The only apparent difference between the endmills is the lower helicity of the WCP endmills. I’m wondering what’s causing the terrible finish with the Huhao endmills, and should I be adjusting feeds and speeds based on helicity?


#499

We had very similar results initially with the Huhao endmills. Our problem was just not enough chip clearance. Initially we just set up an airblast system and this mostly worked, but the endmill would heat up considerably by the end of long runs, resulting in poor cut quality toward the end. We added in a mister just before build, and so far we’ve had very good results.


#500

I should have been more specific. We have a Velox 5050 with a Porter Cable router and we are using the QCT kits with ER16 collets from Velox which have a 0.5" shank. We also purchased some of these https://cme-tools.myshopify.com/products/er-16-collet-chucks-straight-shanks

We are looking at a cheap Chinese spindle from Amazon that has an ER20 collet. So I think a 0.5" ER20 collet will accommodate our existing ER16 tool holders.