Smooth Surfacing of MDF Using CNC Equipment

Material choice and cutterhead selection affect the smoothness of a CNC-profiled MDF surface. CNC sanding is also possible. May 16, 2005

We route one-piece MDF doors on our nested-base router, which works very well. But compared to the MDF doors I used to buy out, the routed details are much more open-pored and require a great deal of hand sanding.

The tooling is very sharp, however it is brazed carbide, not insert tool type carbide - if that makes a difference. We are using Plum Creek super-refined MDF, which is the most dense available to us (and the same as Cal Door, our door supplier, uses).

So, I am looking for a method of sanding the routed portions of the doors. Turbosand (and perhaps others?) makes a 3" diameter head that seems like it would work for the outside detail, but what about the inside panel/inside edge detail routes?

I read this in the Knowledge Base: "Use an abrasive aluminum head with rechangeable and rejectable profiled inserts in your router or point-to-point machine." Sounds interesting. Does anyone have any feedback on either the Turbosand type heads or this abrasive aluminum head? I am very interested in saving a lot of sanding labor!

Forum Responses
(CNC Forum)
From contributor A:
Have you tried using diamond tipped router bits? We use diamond, and the only style we have to sand are shaker. Keep in mind that the further into the MDF you rout, the more porous it will become.

From contributor X:
What contributor A suggests is very good. Diamond tools are the most adequate tool to cut MDF. The biggest MDF door companies use diamond tools because of the finish and life on the tool. Also, use tools with 1in diameter shank. You must be able to have a door that sanding would take just a little or there is something wrong on your tool speeds or router.

From contributor A:
I agree that 1" shanks are optimum. That is what I use. Also, make sure that your collets are in good working order. Best thing to do if you still have problems, and even before switching anything, is to get your board supplier and tool supplier in together. Show them the issue, ask them to identify the root cause, and get a fix. Check with your tooling supplier for RPM and feed recommendations. I run most of my tools at 18000 RPM and 15 meters (approximately 600 inches) per minute.

From contributor B:
It is possible to sand on a CNC machine. However, you must keep this in mind... You spin sanding heads at low RPM, and at low RPM you have low torque. Lower torque means it is very easy to stall the router, which in turn means you can not sand very hard at all. Therefore you need a machine that has a constant torque router. As far as I know, only Homag has this. Unless you have a Homag, you will have trouble sanding on a CNC.

From contributor X:
What contributor B said is part true, but I've sanded on other brands and done it perfectly. If you need to sand very hard, your finish is bad (must be something else going wrong). It is always better to solve a problem from the origin, not from the end.

From contributor A:
I would add that if you still need to sand, you may save time by having your router operator sand the parts by hand, while the machine cuts the profile of the next door.

From the original questioner:
I will definitely research diamond tooling with 1" shanks for this particular application. I also have been told today that there is, in fact, a grade of MDF that is superior to Plum Creek and I am looking into that.

Lastly, if sanding is possible with my machine, no one has commented specifically about the sanding heads themselves, only that some feel it is possible or have done it in the past. For those of you that have sanded with your CNC router: What brand/type of sanding head are you using? Any comments on this abrasive aluminum head? Again, the key is finding something other than the Turbosand type heads, which will only do the outside profile. My real problem is the inside detail/raised panel route combination. I guess, ideally, I am looking for some sort of secondary bit, that matches the corresponding router bit, but has abrasive qualities (for sanding) rather that cutting qualities.

From contributor J:
Try to find steel or PVC brush head for aluminum grounding and polishing.