Opinions Needed Please

Here is my scenario starting with bottom going up
I am using plywood to protect my board, my bit cuts pretty deep through my initial project into my plywood with each project I have.
My project is being cut on Luan Plywood 5.2MM 2x2 from Lowes
I have my project set as an outline/outside cut my depth is 0.25
My bit is set to 1/8 in upcut
The thickness of my material is 0.250in, type of material MDF
My feed rate is 40in/min, plunge rate is 12in/min, depth per pass 0.05in
The completion time is 19 mins.

Looking at the material I am using, bit, feeds etc… would you change anything???
Also, when choosing MDF as my wood for Luan is that correct?

For a 1/8" 1-flute tool regular wood and MDF could do well with:
60IPM @ 16k RPM
Keep 0.05" depth per cut but if you feel it chews fine you could up it a little bit :slight_smile:

Here are 2 more questions I have, my machine normally will run 4 more passes through my wood after it’s cut all the way through causing the loose wood to rattle & break pcs off my project. I normally can catch this and pull the loose pcs out but I still get broken pcs from my bit from time to time. Is there not a way stop cutting and move on to next section once that section is complete to avoid that?

Have you tried to hold down the pieces with ca glue and tape?

If the machine is make 4 more passes after cutting trough the material change the material thickness by the depth of cut x4 or maybe x3 to give just a little material to hold pieces in place

Phillip I am unsure of what your saying here of changing the material thickness by x3 or x4

Instead of it being .25 change it to .29

I think you need to verify your settings and also where/how you are setting your Z zero position. Something isn’t adding up here at all.

If your material thickness is set to 0.25" and your DOC is set to 0.05", that is only a total of 5 passes that the machine should do.

You state it does 4 passes after it cuts through, that would imply its either cutting 0.25" per pass (not likely) or your material thickness is set to around 0.45".

You should also measure your material. It probably isn’t 0.25" but probably closer to 0.2". That would be one reason why it cuts so deep past.

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5.2 mm ISN’T 0.250 " . It’s just over 0.20".

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The luan I got from Menards measures between 0.185 and 0.195.
Pieces 2’ square may not be flat and hard to clamp down completely.
Try to place them cup down then when clamping the edges it will be flattened better.
Still it can bubble up in places. Also your up cut bit will pull it up some.
The tape and superglue method can help as well.

Yep, and actually thickness could easily vary from that.

That would be why it carves more passes, due to being set at .25" thickness. Also, use tabs for the piece or use painters tape and ca glue to hold it all down.

Based on the picture you are cutting too deep. It looks like you have is set for tabs, but the cut depth is too deep so the tabs are below your work piece which is why it’s breaking.

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You should not have four additional passes after cutting through the material. Something is wrong. Thickness of material is off or z probe inaccurate. If everything checks out then change the thickness of the material by the depth of the extra passes that is cutting after cutting through your material

I sincerely think it has to do with my Z axis, so where do I start with this and please be patient and kind as alot of this is foreign language to me. I will need patience and guidance in this as I am fixing things as I go that were incorrectly set up wrong or put together wrong. Until this machine I had never worked or dealt with anything like this. I am overly appreciative of each of you and your help

Patty

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In your material setup in your CAD Program, where do you have your Z set to

  1. Top of material
  2. Machine Bed

Are you setting your Z zero after every tool change?

Are you using a Flat Depth? Is it only happening on your Profile cuts?

In vcarve pro, if im setting up a profile cut to do my cutout I would set Z to top of Material and set a flat depth to z (This will take what you have inputed as your material thickness and cut to that depth)

This doesn’t have to do with your Z axis.

Your material is 5.2mm or 0.20" thick. You set your material thickness to 0.25" and then 0.29". This will very obviously cut entirely through your material and into your wasteboard.

You need to measure the actual thickness of your material, don’t assume that because it is sold as 5.2mm that it actually is. I suggest using calipers at a few places around the perimeter of your material and using the highest value as your material thickness (probably something like 0.19").

Additionally, use a DOWNCUT BIT. This is thin material and you are making letters with curly-cues and the like. If you use an upcut bit, the bit will have a tendency to lift the material and vibrate those long thin pieces and snap them off.

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You could try spraying the Luan and plywood with contact adhesive and stick them together. This should hold the pieces well enough to cut all the way through, especially if using a down cut bit. I would still use tabs if there are small pieces with not much area for the contact adhesive to hold. The contact adhesive should allow you to sperate the Luan from the plywood easier than if you used CA.

If you notice that one side of the work is cutting deeper than the other, you may need to level your xcarve table, but I think your problem is really getting your z height and material thickness set right as the others said above.

If you haven’t seen it yet, there’s a community-maintained glossary at: https://www.shapeoko.com/wiki/index.php/Glossary which may help with understanding things.