How fast can I push a PRT?

[Greybarn]

How fast can I push a PRT with a 4G control box? I am going to be cutting some meranti plywood. For the chip load factor, with a 2 flute bit, running at 11,000 RPM, it looks like I want to have a feed rate of 6 IPS. Can I push this machine that harder?
Regards
Peter

[bleeth]

probably not. For extremely accurate cutting an old gantry will restrict your speed well below that. The 4-g box will allow much faster jogging but cutting speeds (depending on the needs of your cutting, bit, etc) are restricted to 1.75 to 4 ips.

[erniek]

I have a PRT with the 4G controller, I cut melamine and plywood at 5 IPS in two passes, first pass 95% depth climb cut second pass convential to clean up the edge. I use a single fluted 1/4" cutter, I've tried a double fluted at that speed and I lose position. I've tried 6 IPS but found that it would occasionally loose position so backed off to 5 and no issues. ( though I think it was 3/4 melamine I was cutting at the time) I suppsose I could probably try 6 IPS with 5/8 but it just such a pain when it loses position it's not worth the risk for the small time savings.

[Greybarn]

Thanks for the replies. I am going to try 4IPS, at 9000 RPM to start out with and then go from there. Accuracy is not super critical but I don't want it loosing position, as that would be a pain.
Regards
Peter

[harryball]

hmmm... does it have wheels on it and are we level or uphill?

sorry, when I read the title that was the first thought in my head.

The depth of the cut vs. the diameter of the bit changes the target chipload a little.

If better chipload (less heat etc...) is your goal and not time, it may be better to take shallow cuts on multiple passes to reach a more suitable chipload.

/RB

[richards]

Keep in mind that on many routers, reducing the speed also reduces the torque. Before I bought a spindle, I used a Porter-Cable 3-1/2 HP router, thinking that I could select the best speed between between 9,000 and 21,000 and then adjust the move speed to get the proper chip load. What I had not counted on was the loss of torque as the RPMs slowed down.

With my Colombo spindle, the torque curve is constant between 12,000 and 18,000 RPM, so it's much easier to match the feed speed to the spindle speed to get the proper chip load.