TL;DR Am having issues with my router "wandering" mid job.

General CNC CNC Routers
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TL;DR Am having issues with my router “wandering” mid job. Possibly due to blunting 1/8’ single flute cutters?

I started cutting a largest job I’ve attempted so far this past weekend. The total cut time around 2 hours in 1/8’ single flute end mill at 770mm/min in 2 sheets of 15mm plywood, 1.5mm per pass (10 passes).

The first sheet of the job went fine, cutting good chips. The second sheet started fine, the first part cut the “chips” where getting stringy and I wasn’t sure if this was due to the end mill dulling, or poor quality of the plywood I’m using.
About half way into the second part, I came into the shop (after dropping some rubbish in the bin outside) to find the router had wandered and started cutting right through the middle of the job.

Following the cutting path back I could see this started as a small deviation that compounded until the cutter had enough force to wander completely off course, something I have had happen before, but I was blaming the cuts and machine setup. It’s always possible the material moved, but I had 4 screws holding it down, so I doubt that is the issue.

How long should a 1/8 inch HSS single flute last cutting ply?
Have I got incorrect settings somewhere?
Is there any trick to check if the end mill is dull? it “feels” sharp after cleaning it, but I’m no expert.
Should I be dipping my cutters in Methanol first? (or is that mostly for MDF?)

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Check your belt tensions and pulley setscrews. “Wandering” as you put it, can be caused by loose or skipping belts, or loose pulleys.
As the belt goes one direction, its fine, but when it reverses direction, the loose pulley will rotate freely and the machine will lose position.

It may also be caused by losing steps due to too fast cutting speeds, too high acceleration, or, as you say, the bit becoming dull and the machine not having the power to move the bit through the work at the commanded speed.

MG

3

@Darrell_n looks like you are spot on, belt tension is good, but the pulleys are loose again. I re-tightened them not very long ago. Time to drill and tap then to M3.

Edit: and they are already M3, so a new grub screw and loctight, until I can buy an M4 tap and grub screws.

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That may be prudent. Going to M4 is certainly an option. I usually replace the setscrews with actual 4mm long round head screws, as they have a bit larger hex key, 2.5mm rather than the 2mm setscrew. This give a bit more leverage when tightening. I found that the setscrew hex is easily stripped and then you are in trouble. Also, a dab of loktite on the screw helps immensely.

MG