Hi
I am playing with making complex forms and punches with a cnc router, and wondered if anyone on here has experience with this? General tips welcome, but also, in particular I am having problems with the plastic (Delrin, I think) forming a fibrous mass attached to the form where the angles are not steep, rather than cutting cleanly. See photo attached for my current project - a star form, the material is visible as very white stuff in the bottom of the form. ps_bond - do you have any experience here?
Thanks Matt
p.s. here is my first attempt at making a tea spoon form: https://m.facebook.com/story.php?sto...00057360741593
This is the latest project outcome- a domed star. You can see the poor cutting on the punch in particular. I suspect the answer will be feed rate and drill speed adjustments.
I think that what is probably happening is that the tool tip is heating up and the plastic is sticking to it. This also can happen when machining aluminium, the chips that come off can become welded to the tool.
Smaller tools with small tips such as the V cutters and ball nosed cutters are more prone to this. Clearing the chips quickly and easily so that the cutter tip remains cooler than the material being machined is the objective. It's difficult to make small cutters with different cutting angles so you are left with speed of rotation of the cutter feed rates as well as using some sort of coolant/lubricant.
What is the size of the star and what thickness of material are you using? Very interesting.
Hi- thanks for your help. I do a rough cut and then a finishing cut. I have only a generic 3018 cnc machine so no option to cool really. I think I'll try a slower spindle speed. Possibly invest in a lower flute cutter too, but I'm trying to keep it cheap The form is 20mm by 10mm deep, and metal thickness is 0.5mm copper, probably going for 0.3mm sterling. I might need to cut a smaller punch to give the metal more room.
Thanks- I dropped my spindle speed from 10,000 to 5,000 and used my larger bits which have two flutes rather than 4 and it was better but not perfect- but a quick sand cleaned it up nice tho. The larger bit wouldn't work so well for the form shape as it wouldn't get inside the tight details. I'll maybe try an even slower spindle in future.
Thanks Matt
It can be a bit of a black art to find the sweet spot for a particular cutter and that can be different when the cutter is new and really sharp and after it has been used for a while.
On a related note: I've seen a video on YouTube of someone pressing 1.6mm steel using 3d printed PLA. He used a hydraulic press. And I've also seen someone using a vice instead of a hydraulic press. He had a multipart mould.
CNC router and plastic forms
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The form is 20mm by 10mm deep, and metal thickness is 0.5mm copper, probably going for 0.3mm sterling. I might need to cut a smaller punch to give the metal more room.
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