Problems cutting MDF

[tallen84]

I am trying to make a piece out of MDF that has allot of small details and I keep having trouble with my clearing pass breaking off some of that detail. Any suggestions for things that I can do to help prevent this? (Besides removing the fine details). I am using partworks to make the tool paths and these are pocketing paths. Note that for the clearing pass I am using a 1/2 diameter 2 edge straight cutter.

I thought about doing the finishing pass first so the large cutter doesn't get that close to those pieces however I am trying to use a 1/8" downcut on my finishing to minimize edge burs and I dont want to plunge with that.

Attached is an image of the problem. Any suggestions are welcome. Thank you.

[CNYDWW]

What about using a v-carve tool path with the large area clearance bit and a 60 Deg V bit if you have it. It will thicken up the base of the details and give it more strength. Also consider setting your standard pocket up as a raster with a pocket offset of at least half the diameter of the bit used for the finish pass. It actually looks like you're using a box store mdf. I've had a lot of issues with the actual density of it and milling properties.

Regards
Randy

[andyb]

Try doing the profile pass first and ramp into the material or do an inside profile pass with 2 shallow passes. The latter is the way that I have gotten around the problem a couple of times.

Andy B.

[ken_rychlik]

Looks like chatter from a dull or cheap bit to me. The cmt lazer bits seem to work the best for me. There are also several grades of mdf available at my wood supplier. The cheap stuff breaks off more.

I don't quite understand clearing pass.... do you mean flat depth clearance?
If so, I run the flat depth bit first, then the v bit.

If you are leaving a clean up pass for the v bit, that could cause an issue. Let it run full depth one pass and it should do fine.

[adrianm]

I always use spiral bits with MDF. I find that straight cutters are prone to chipping the edge of the work.

[steve_g]

Todd:
If you are buying your MDF at the big box stores you’re not getting good enough quality material to do the job. I’ve switched to “Plum creek” brand supplied locally by “The plywood company”, Fort Worth. This brand is made to be milled and results in much better quality parts. I’m sure that brand or a similar one is available to you locally by a similar wholesaler. The shocker is that I pay less for the good stuff than I do at the HD.
http://www.plywoodcompany.com/application/home/itemdetails.aspx?categoryid=89&itemid=1688

Steve

[tallen84]

Randy,
I thought about using a V carve as you suggested but I found that I wasnt going to get the "deep" look that I would get with straight sides. I am also using MDF from lowes so it isn't the higher quality MDF. How can you tell the difference by looking at them? I am trying to find a supplier near by that has the higher grade but so far no luck.

Andy,
I will give that a try and see if it yields any better results, I was just worried cutting into the MDF without having somewhere for the cuttings to go could cause a problem. That is why I was using the larger bit first to clear out the center and then clean up the edges with the downcut.

Kenneth,
I did check the bit, it is an onsrud that came with my shopbot but I have not used it much. The edges still look very clean and sharp. As for the clearance pass I mean in partworks when you select "Larger area clearance tool" when doing a pocket toolpath and that is not using a v-carve tool.

Steve,
Thanks for the link on the MDF I will look into them and see if there is a location nearby.

Everyone, thank you for the help!

[ken_rychlik]

I understand what you are doing now. I cut the big bit first, then the smaller one when doing that type of work.

I think the mdf quality is your main issue though.

[CNYDWW]

Think of lowes as walmart for materials. Another suggestion would be a ball nose tapered carving bit. I have a couple with a 7 deg taper in 1/16 and 1/8 dia ball. They would do the same thing just obviously maintain the deep look. A couple trips around the inside at a small stepover. One issue is these bits are expensive. As far as quality you can't really tell the difference until it's milled. Good luck with your project.

Regards
Randy

[knight_toolworks]

actually on such things it can be better to do the profile cut first with a small bit and it relieves the stress from the larger bit. the material and the straight bit are your big problems though.