[PHSS]

So we have a CNC router (Precix) in our school and I am trying to get it set up properly. The table is not flat, or the MDF spoil sheet is not though it is very well bolted down.

I decided that I would try to just machine it down flat, so I programmed a facing operation, 0.05" deep. Feedrate at 250 IPM, rpm @3500 and put in a 7/16 HSS endmill (brand new). These are the settings I use on my CNC mill in the metalshop with no problems.

It started cutting great but after about 20 trips around the top (programmed to cut all 4 sides then step in width of tool and repeat) it as about 4-6 inches in and it was starting burn the wood and even seem to ride up on top instead of cutting.

So I decided to run the figures through G-Wizard and it said I should be moving at 104 ipm. My handbook says I should be using Carbide for this. I really need to get this top dead nuts flat so I can do some fine engraving. Anyone have suggestions on settings that will allow me to face down a 48x96 sheet of MDF

It would appear that I can change a setting and bump up my RPMS to theoretically 10000 rpm but the machine came default capped at 3500. I need to look into this.


Oh and yes I have a vaccum system removing the chips.

[ger21]

Feedrate at 250 IPM, rpm @3500 and put in a 7/16 HSS endmill (brand new). These are the settings I use on my CNC mill in the metalshop with no problems.

You're cutting metal at 250ipm and 3500rpm? I'd like to see that.

Are you sure it's 3500rpm? A router should rarely be spinning less than 10,000 rpm.
250ipm @ 10,000 rpm would still be a fairly aggressive cut.

At 250ipm and 3500 rpm, I wouldn't expect to see any burning, but rather tearing of the MDF due to the incredibly high chip load. Unless you're using a 4 flute tool??

Try a 2 flute carbide tool, at 250ipm and 10,000 rpm, and you should get much better results.

[PHSS]

not metal, mdf

I will check but I am pretty certain shes running at 3500 rpm

[fixtureman1]

MDF will dull a HSS bit real quick. Use a carbide bit and run it again at the same speeds and feeds.

[PHSS]

Will a 3/8" carbide bit at the same speeds and feeds last a whole facing operation of 45x96" of material? Or should I buy a few bits to complete this task?

[ger21]

It should last through 10 sheets. But your rpm is way too low.

[PHSS]

Assuming I can ramp it up to 10000 rpms like it is said on the motors plate what feedrate should I run it at? It will be a 3/8 carbide 2 flute endmill.

[PHSS]

Turns out it told me it was running ay 3500 on the screen but was aways at 18000 RPMs. Anyways I changed to a carbide and it ran fine after two hours at 250 IPM I now have a perfectly "dead nuts level" top. God bless carbide.

[ger21]

At 18,000 rpm you can crank up the feedrate to around 500 ipm.

[PHSS]

I tried it at 400 IPM and it was cutting nice and smooth on the top, but the edges were tearing soI slowed it down as I though it would be a problem. In the future when we replace this spoil sheet I will try if faster. As it will probably last for the next 5 years I doubt I will have a problem. Thanks guys.