Hi

I'm very new to the CNC world. I just bought a machine and got it running yesterday. I primarily bought the machine cut profiles out of particle board, I have done a few tests and made out OK, but I'm using old bits and the old router that came with it (Porter Cable 890 2-1/4 HP) it started off OK but I might have pushed it too much and it doesn't sound to great anymore. I'd appreciate some advice on where to go from here. Keeping in mind my main concern right now is cutting parts from particle board 1/2" - 3/4" (I bought this for work and have orders to fill soon).

1. My first thought was to replace the router with the Porter Cable 7518 (3-1/4 HP). Will this hold up for what I want to do? It is a simple solution for me, just have to change the mounting plate and I'm off and running, but if you think it will burn out in a month I don't want that. If I could get a couple of years out of it that would be great.

2. When cutting particle board (not MDF) what is the best bit to use? How many flutes, up cut down cut, spiral, straight? I assume 1/4" dia or can I go 1/8"? It doesn't need to be a perfect cut but not real rough either (tried a 2 flute up cut and it was to rough for my liking...but maybe a feed speed adjustment would help?)

3. With particle board should I run the router at high or low RPM? Approximately what should the feed speed be?

4. With particle board how deep should I be cutting each pass? Is 1/4" reasonable?

Sorry if the questions seem a bit pathetic but I want to start off right with this and not regret getting into this.

Thanks for the help
Chris

Chris,

Others may offer different opinions but I would suggest the following.

The Porter Cable 3-1/4 hp router is a fairly standard item on light duty CNC routers. It will be a good choice for your system.

I would use a 3/8" 2-flute carbide downcut spiral bit. This will give a clean top edge but will also compress the chips in the cut slot.

By making the cut in 2 passes at 3/8"+ each you will eliminate some most of the compressed chip issues. This could be done in a conventional cut direction. I would recommend stepping the bit 1/16" out from the final edge on the first 3/8" deep pass, then stepping it in and down on the second pass. You should be able to set this up in your CAM software.

If there is any play in your system you should also make a 3rd pass at full depth. In this case the 1st pass doesn't need to be stepped out. Instead run the 1st and 2nd partial depth passes on a climb cut, and the 3rd pass on a conventional cut. Doing this will make your part slightly oversized after the first 2 climb passes and bring it down to correct size on that 3rd conventional pass. Do this type of cut arrangement if you find your parts are coming out slightly small with the 2-pass system.

Lots of good bit manufacturers out there. Don't cheap out with an import bit to save money. Expect to spend about $40+ per name brand bit.

BH Davis

BH said what I think you needed to hear, The 7518 is an industry workhorse as the bushings and bearings can be replaced.

We have a tool store here who repairs them if you get a new 7518 have the old one looked at, having an extra anything can prevent a slow down in work !

Hi Guys

Thanks for your input it is very helpfull. When BH says light duty CNC. I do want to use this for a few hours a few days a week or more. Is the Porter Cable good for this? Or should I be leaning towards a 2.2kw spindle?

Light duty means other than the heavy iron machines. Perhaps a poor choice of words on my part. If you were running 8 hours a day / 7 days a week you might want a more substantial machine. However since you didn't say what machine you had it left me to speculate it was not a heavy iron router. Plus larger and heavier machines typically would come with 10 hp plus tool changing spindles as vs. a 2 hp Porter Cable router.

The Porter Cable router will be fine for what you will be doing. I wouldn't worry about running it several hours a day 5 days a week. Beyond that a spindle might be in order. As James said though the router bearings can always be replaced.

BH Davis

Tossing up a photo or giving some more detail on the actual machine/frame/construction would probably give people more info to guide your decision. The decision to move to a spindle over a router motor seems about a no brainer for many today. While the 7518 will give you some speed control the spindle would give you full control though it may not be a simple swap out so if you need to maintain production the 7518 is probably the best choice for now.

I wouldnt personally go below 1/4" for the particle board in my opinion but your machines capability with regards to feed speed will have a lot to do with how hard you can push the tool.

Do some googling on chipload per flute for various cutters and you can quickly get some ideas of rough starting points for feeds and speeds. After that you can dial up your feed until you see/hear bad juju or break a tool and then back down.

Thanks again for everyone's input. The machine is a 5x10 MechMate. I have attached a few pics. Even though sticking with a porter cable would be easiest I think I'm leaning towards a 2.2kw 3 hp spindle...unless that sounds crazy.

My understanding is that the hp on the spindle is a more continuous rating compared to the router.

View higher quality, full size image (2016 X 1512)

View higher quality, full size image (2016 X 1512)

If it were me I would buy the spindle. You will be able to run the machine harder and turn out parts quicker. The faster you can make your parts then you can be doing something else. In the end you make more money and paying the extra for the spindle easily takes care of itself. There is a lot of difference in a 3hp router and a 3hp spindle. As was said earlier heavy duty machines are heavy duty. Our CNC weights in at over 7,000 pounds.

I have not seen a mech mate in a few years, got the plans and almost built one a decade ago, Lots of South Africans built them !

The big PC router is probably one of the better hand held routers on the market. The problem is they are not made for continuous running. The brushes wear pretty fast.
The tooling companies have feed and speed charts on their web sites to get the correct chip load. If you buy a regular spindle will you have the ability to vary RPM's? If your control doesn't have that ability you can buy VFD's from China pretty cheap.

An easy way to check see if your chip load is reasonable is to (carefully) take hold take hold of the bit right after cutting a sheet. If you burn your hand your chip load was too little. Increase feed speed or reduce RPM's. If your horse power won't permit fast enough feeds you will have to make multiple passes.
Buy high quality bits. They are worth their price. We use Onsurd marathon 3/8", 2 flute compression spirals, 12hp spindle. Always use the shortest bit that will do the job.