I was attempting to surface my MDF for the first time yesterday. Initially I surfaced a 10x10 inch square with zero issues. I went back into CarveCo and created a file so I could surface 48x46 inches. The first few passes were great. However, I noticed the spindle would sound like it was bogging down in one area on the MDF and go back to normal when it was out of that cutting area. A pass or two after hearing this sound the spindle completely stalled out. I will attach a picture for visual reference, and if it will be helpful I can attempt another cut and try getting a video of my issue.
I am a beginner when it comes to CNC. All advice and suggestions are welcome, as well as greatly appreciated!
My machine is an Elite Foreman with PWNCNC’s 1.5kw 110V ER20 80mm 2-pole 400Hz water-cooled spindle.
I was surfacing with a 2.5 inch diameter by .5 inch shank, 4 wing bit from SpeTool (W05003).
I attempted this cut two separate times with the spindle stalling out the same way for both. Once at a feed rate of 200 and the other at 140. Both cuts were done at 18,000 RPM’s with a cut depth of 0.0312.
If it’s happening in one spot that’s a high spot and it just doesn’t have enough power to plow thru it. Recommend zeroing z there and trying again, once you level out all the high spots you should be able to get it all at the same level.
18k also sounds really fast for the tool, and I couldn’t find the feed/speed rates of that tool on the website. This is where it took me which was an empty selection. Feed and Speed of SpeTool Router Bits (spetools.com), 200 sounds way too fast, and 140 may even be too.
I also imagine you’re getting error 34 on the VFD whenever it stalls. Err34
Getting the high spots leveled is the first step in flattening your spoil board (in the above video link, Mitchell thought he zeroed Z at the high spot, but did not), especially when using a large diameter bit such as that one.
Yes, it happened in the same area on both cuts. I had that thought. However, given my experience level I preferred to get some advice before moving forward.
I thought the 200 feed rate seemed high. I did end up finding the suggested rates from spetool for their surfacing bits. Based on the chart (added below) I assumed I would be good to run at the recommended feed rates. Especially since I am only trying to surface off 1/32 of an inch.
I didn’t even see the note on PWNCNC about using 1/2 inch bits and the expectations with the ER20 spindle. Out of curiosity, can you or anyone please go into more detail about that paragraph. Like what should my expectations be for my spindle, as well as the recommendations for general feed rates and RPM speed. I have looked at a bunch and understand the material plays a big role. For most of my bits I utilize the application IDC woodcraft has to get RPM and feed rate suggestions.
Thank you again for you time and help! I greatly appreciate it.
Hi Cody,
The 1.5kw is like 1.75HP. Even the 2.2kw is just shy of 3HP. There are machines out there with spindles that have 3 and 4+ times that amount of power. When manufacturers talk about feeds and speeds like that, those are the machines they’re talking about, not our hobby machines.
Material, mass (of bit) and machine regidity are some of the considerations when using oversized bits in undersized (relatively speaking) motors. If your machine didn’t require a fork lift and come preassembled, rigidity is a consideration. My opinion is using a smaller surfacing bit will be faster and get you better results.
If it’s happening in the same spot, your unlikely to be cutting 1/32nd off there. Zero Z there and try again.
2-1/2" is pretty big for a 1.5kw motor. I have never used more than 1" personally, including in my 2.2kw.
Another principle to bear in mind as you’re working out this stuff is the cutters effective surface speed. This isn’t the feedrate (ipm) but rather the speed at which each actual blade is moving through the material. Think about standing on the outside edge of a moving carousel, and how fast that is compared to standing close to the center. When you spin a 2.5" diameter cutter at 18k rpm, the blades are being pushed through the material MUCH faster than when you’re spinning a 1/4" cutter.
