Sacrificial board for mini CNC

Discussion
1

Hey all,

I’ve seen a number of questions about cutting through material on the mini CNC so I’ve tried to make it easy for people by making a template for a sacrificial board.

The template and an example (that is thinner than it should be) are beside the linux CNC machine with bolts and washers:

PXL_20240614_114635400
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The board is not symmetrical so sides are marked on the top.

  1. To use trace the template onto some scrap. This must be at least 10mm thick (files attached if you’d like to cnc or laser cut this)
  2. Remove existing work holding from the bed
  3. Add 1 t-nut in each corner of the bed:
    PXL_20240614_111315157
    PXL_20240614_111315157.jpg4624×3472 4.42 MB
  4. Bolt your sacrificial board to the bed and make sure it’s tight (unlike the photo). There is a bit of play in the holes to make it easier to align with the t-nuts.
    PXL_20240614_113955675
    PXL_20240614_113955675.jpg4624×3472 4.01 MB
  5. Attach your stock to the sacrificial board. The engraved area of the board shows the cutting area of cnc so make sure any work holding (e.g. screws) are more than 5mm outside that line. Sorry no photos of this

There are two main methods for attaching your stock to the sacrificial board - screws or masking tape and glue.

To use screws just screw your stock to the board outside the working area. You can add holes in each corner of the

To use masking tape, apply a layer of masking tape to the sacrificial board and to the bottom of your stock. Try to avoid overlapping tape to make a single flat layer. Then add super glue between masking tape and hold in place until dry.

Link to model is here - https://cad.onshape.com/documents/0f9c4b5c4e1bae7cce11881d/w/a0b37307eb5abc095e0dcda2/e/e071a88c131703a266af926f?renderMode=0&uiState=666c3279b2790032a6958400
dxf for the laser/vcarve is here - isel sacrificial board v1.dxf (120.0 KB)

9 Likes
2

Nice work! I’d definitely add TEMPLATE in big letters, less it become a spoilboard itself :slight_smile:

2 Likes
3

Good suggestion!

The template also has holes in the corner of the cutting area to transfer onto the spoil board

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PXL_20240614_145745547.jpg4624×3472 2.53 MB

1 Like
4

Great work!!!

Yeah i agree on the template

5

I’ve already had more thoughts on improvements for the template:

  • use acrylic so you can place it over a spoilboard and double check any screws are outside the cutting area
  • engrave a 5mm boarder around the cutting area to indicate you need to be careful there with larger bits
  • remove the cutting area from the template so it can’t be used as a spoilboard
6

There are some 10mm acrylic under the table saw in the woodshop. I think they are for all techs to use it, @woodtechs am i right?
If correct, Hugo you can use 1 of those as template

7

Yep, go for it

8

Great, thanks. I’m away for a couple of weeks but I’ll take a look when I’m back. Is it laser safe acrylic?

9

Yes, I’ll keep 1 aside this evening ( marked as cnctechs) and it will be under the bigcnc

1 Like
10

Thanks for the template, I used it to create a spoilboard for everyone to use.

IMG_20240618_172423
IMG_20240618_172423.jpg4624×3472 4.07 MB

4 Likes
11

Looks great! How did it go?

12

Haven’t tried yet! Also because I couldn’t figure out how to CNC a shape out of 20m MDF: the bits I saw either had a max cutting depth less than that or the shaft diameter was bigger than the flute diameter, making them not suitable for cutting deeper then the flute length…

13

If you rough the surface you should be able to use the small tools as finishing. It depends on the cad obviously.

14

Do you have a picture?

15

Yeah, this is what I am trying to cut:
com-animated-gif-maker
I was thinking about getting this bit: https://www.amazon.co.uk/gp/product/B0BJ8PBYL7/ref=ox_sc_act_title_1?smid=AIF4G7PLKBOZY&th=1
Screenshot%202024-06-19%20100755 - do you think this will work on the machine )and how do I add it to the tool library?)Do you know if the tool control has been replaced / fixed (i think it was identified as a potential reason for the random loss of contact between the computer and the machine…

16

The inside circle is cut out completely and the outside gets cut off too. There is then a ring with steps. You can do that with e.g. a 6mm or 8mm endmill (which we have on the big CNC). Try it in vCarve and preview.

1 Like
17

The 6mm on the mini should handle 20mm cut, check it i don’t remember by heart

18

Thanks - there are two 6mm shaft, 2mm ball nose bits (no 10)

IMG_20240618_173457%20(1)
IMG_20240618_173457 (1).jpg4624×3472 3.27 MB

IMG_20240619_131021
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, but they dont seem to be in the to tool database. Can I add them as follows and use them?

Screenshot%202024-06-19%20132024

What rpms to use for this one?

19

No i meant tool 23 the big boy

20

They are both in the database already, probably you are looking into the wrong material section