MDF Feed Rates?

[wizard]

Please understand that i hate MDF and the dust that comes from working with it. However the referenced European countries and for that matter the state of California are totally insane with their regulation of every substance known to man!

" An extractor is needed to take away dust or fumes from the cutting area, especially when machining MDF.

Nothing was said otherwise. The use of compressed air or flood coolant for other materials to clean swarf from a channel is normal practice. You have to do something to prevent chip recutting.

MDF is a harmful substance and a classified carcinogen, it contains among other things, formaldehyde. and is a banned substance in many European countries."

That may be true or maybe the result of some government employee trying to justify his job. If you consider that just about every product now marketed in the USA has a sticker on it claiming that the state of California knows that this product causes cancer you have to question the credibility of the designation.

In any event in this case it doesnt matter because dust extraction would still be used, the compressed air is there to lift the swarf out of the cut to be vacuumed up.

https://the-cnc.blogspot.co.uk/p/sim...extractor.html

By the way im not trying to dismiss the fact that there are all sorts of hazzards out in the world. MDF bothers me so much i try to avoid it at all cost. What frustrates me is materials being designated hazardous by default with out any sound evidence or massive overreach to address known problems.

Lead is a perfect example of massive overreach. Yes very dangerous to people, especially children. However that lead has to get into their bodies some how and frankly it wont come from the solder on a circuit board. Regulation needs to match the risks involved.

In a nut shell when working with machinery one should assume that all dust is a problem and act accordingly. Otherwise we get into labeling some dust as bad or worse than others.

[shujaa]

hi jerry

i configured everything again. now i can go up to 2600 mm / min. what shall be the proposed RPM now !!

best regards.

[shujaa]

hi Gerry,

thanks. i checked outer motor tuning. now it goes upto 2400mm/min without losing steps.

Dea sir, for straight cuts high feed may be ok but what happens to chips on sharp curves ??

[Stuboy]

You should cut MDF just about as fast as your machine will go in X & Y! If you look at any commercial chart for bits most have a MINIMUM speed of 5500mm/minute! (up to about Now my machine will only traverse at that speed not cut! I cut a lot of MR (Moisture Resistant) MDF and cut usually in 3 passes 4mm each pass at around 3500 to 4500mm per minute. If your machine starts squealing then keep the speed but do 4 cuts, My spindle is 2,2HP 3 phase Chinese water cooled and is a massive step up on the Kress i was using before. I have seen the cabinet makers that produce our production cabinets rip thru 18mm MDF in a single pass but they have 11HP spindles!

This table below is from a bit manufacturer, note for average machining at 18000 rpm with a 2 flute cutter you should be travelling at 29metres a minute. Now I've seen some fast machines but that is REALLLLLLLY shifting!

Fine machining:- 0.3 mm per tooth Speed (r.p.m.) 3000 4500 6000 9000 12000 15000 18000 Single Flute 1 1 2 3 4 5 5 Twin Flute 2 3 4 5 7 9 11 Average machining:- 0,8 mm cut per tooth Speed (r.p.m.) 3000 4500 6000 9000 12000 15000 18000 Single Flute 2 4 5 7 10 12 14 Twin Flute 5 7 10 14 19 24 29

Remember kids speed is your friend, just adjust depth of cut to stop anything bad happening!

Cheers
Stuart

[shujaa]

Hi Stu,

What a precious table you shared. Thanks.
what is your feed when you have to cut tight curves like in dovetails or text ??

[shujaa]

Hi Stu and Gerry,

Mach 3 automatically reduces the feed rate for tight curves due to reasons of acc and dec. How will this affect the tool life if spindle rpm is fixed ? is it possible to carve a name 1 inch tall gothic font at a feed of 3000 mm/min

[ger21]

How will this affect the tool life if spindle rpm is fixed ?

Cutting small parts, where the feedrate will be lower, will result in shorter tool life, but there's not much you can do about it.

For maximum tool life, you should cut as fast as the machine will allow.
For the best finish, you may need to cut slower.

A variety of things can affect how fast you actually cut, and it's up to you to decide what's most important.

I would keep your rpm at about 10,000, and adjust the feedrate as required, trying to keep it as high as possible.

[ger21]

This table below is from a bit manufacturer, note for average machining at 18000 rpm with a 2 flute cutter you should be travelling at 29metres a minute. Now I've seen some fast machines but that is REALLLLLLLY shifting!

Cutting at that rate requires at least a 10HP spindle, and very good hold down, or your parts will be flying off the table.
Also, tool geometry and diameter will have an affect on feedrate. At 29m/min, I suspect that the bit is 1/2" (12mm) or larger?

We cut MDF and melamine with a 1/2" compression bit, typically at about 20-22m/min and 16,000 rpm, with a 15HP spindle.

[shujaa]

Hi Gerry,

you know i was almost waiting continuously for your advice. Thanks for clearing up my clutter.

so that is nice . thanks and best regards.

[wizard]

At some point you end up with a feedrate that is never achieved. This would be due as you note the accel and negative accel that each move requires. Im not sure about Mach but some controllers can blend moves and plan such that the accelerations arent as dramatic. Even so you will not make feed rate if there isn't space or time to do so.

So what happens, you suffer with the consequences. It is no different than what happens with a manual router if you can not hold feed rate. If you happen to be working cherry you get those ""beautiful"" burn marks. At least with a CNC you get a few more parameters to adjust.

Hi Stu and Gerry,

Mach 3 automatically reduces the feed rate for tight curves due to reasons of acc and dec. How will this affect the tool life if spindle rpm is fixed ? is it possible to carve a name 1 inch tall gothic font at a feed of 3000 mm/min

[killersoundz]

My half ton 4x8 steel router is limited by the DeWalt 618 router I'm using for a spindle I was just doing mdf for the first time, the first .25" deep cut it won't go faster than 45ipm without bogging the router down... After the first cut it'll do 70ipm on the next ones but I'm still leaving it pretty slow. I'm sure if I only did .125 deep cuts it would do better. A real spindle will make a world of difference for sure I hope to do .25 deep cuts at 100ipm when I get one

[ger21]

You're goal should be closer to 300ipm.

[shujaa]

Hi killersounds

I don't see half ton anywhere on your machine. What matters is the gantry weight. I observe that it should be around 20 kg.

[killersoundz]

Hi killersounds

I don't see half ton anywhere on your machine. What matters is the gantry weight. I observe that it should be around 20 kg.

Looks are deceiving! the 2x6" 3/16 wall steel tubes alone are a couple hundred pounds by themselves. add up the rest of the steel and junk the thing is at least 800lbs probably more

[killersoundz]

You're goal should be closer to 300ipm.

what kind of spindle do I need for 300ipm jeez. I do plan on getting one of those ebay water cooled 220v deals

[ger21]

A 2-1/4 HP router should have no trouble cutting 1/4" deep with a 1/4" bit at 300ipm. You just need a sharp, spiral router bit.

[killersoundz]

A 2-1/4 HP router should have no trouble cutting 1/4" deep with a 1/4" bit at 300ipm. You just need a sharp, spiral router bit.

I haven't milled anything but particle board and MDF on my machine yet but I could see maybe particle board or soft woods/plywood but the mdf clogs up the kerf badly on the first pass even with a brand new upspiral bit. I get scared when the router bogs down and starts to sound heavily loaded so I slow it down. It really won't go over 50ipm the first .25 deep pass on MDF without sounding very stressed...maybe my router is getting tired

[ger21]

I cut at 150ipm with a porter cable 690 all the time. That's as fast as my old machine will go.
The dust packed into the cut shouldn't be adding to the load at all.

[shujaa]

HI Gerry,

Please give some views on the following thoughts.

I want to enlarge my cnc router from 1100 X 550 mm to 3000 X 2000 mm. Should i go with ball screws on the long axis or rack and pinion. I prefer rotating nut Ball screw. Will 25 mm dia 10mm pitch 1 start with pulley drive 1:3 make it fast enough with 8 Nm closed loop stepper motor.

[shujaa]

Hi killer soundz,

again i am stuck on it. the heavy tubes are not moving i think.