Hi, I've a problem with my ratrig killerbee 1515, loaded with 2.2kw water cooled spindle. I've probably some deflection in the gantry, because the spindle is quite heavy, but as I only machine plywood sheets, it should not be a problem as long as I surface my spoil board. However, that's not the case! I surfaced my spoil board correctly, multiple times, with enough depth. No ridge or anything, it looks super flat. However, the sides of the surfaced zone are higher than the center compared to my spindle height, with more than 1mm difference. If im not clear, the spindle is closer to the spoil board in the periphery. How is that possible, as the surfacing should have compensated the deflection in the Z axis? Thanks -fx
The sides are higher because there's less downward deflection on the sides compared to when the spindle is in the center. Surfacing wont fix that.
I understand the difference in height in absolute numbers, but surfacing should give equal RELATIVE height everywhere (IE distance between the spindle and the surfaced spoil board), because deflection will also happen when surfacing. However that's not the case here, I can't understand why? Thanks -fx
Francois, How well are the edges of your spoilboard supported? Is the difference in the distance between the spindle and the spoilboard apparent at the front and back or only from side to side? Alex.
The surfacing wizard nor CONTROL would cause that obviously. So its something physical/mechanical in your setup. Might be what Alex is suggesting. It might be that there's more downforce in the weaker (middle) of the gantry when your spindle is on and cutting.
I attached a picture of the aluminium structure below my spoil board. The difference is visible when comparing left/right sides to the center, not front/back (U shaped, and not bowl shaped). Thank for the replies, as I can't figure what is happening. -fx
I suspect that the problem is that your spoilboard is flexing - you said in the Ratrig Facebook group that you only have it fixed to the aluminium extrusions at the front and back - I attach mine at approx 200 mm spacing to all the supports, and I have much more closely spaced supports than you do. See the attached pic of my workbee 1010 spoilboard support structure. Alex.
And here is my spoil board, you can see how it's fixed to the structure, with 3 screw/t nuts on the front and back aluminium rails. -fx
Alex, it shouldn't be able to flex, because there are support underneath, so it can't go any lower. And let's say that for an unknown reason, it was to flex upward because of the tool used, then the deflection would not be in that direction, because of the way I screwed it (it would be rotated 90°). The deviation is present even near the center front screw, where the spoil board can absolutely not move at all (and not at the two other front screws left and right). I really can't understand what is happening. Is there some hardcoded flex compensation for a given machine in the surfacing macro? ( I used lead 1515 as a base) Thanks for the help, appreciate it ☺️ -fx
The only mechanical reason I can imagine would be that the flex is accentuated by the weight of the surfacing bit, and when I switch to regular cutter, there is less deviation. But what are few grams compared to the weight of the spindle itself? Would it be sufficient to cause almost 1.5mm deviation? I may try to surface with a smaller bit, the smaller/lighter I can find, and see if it makes a difference. -fx
This is the bit I use to surface, maybe it's too heavy : https://m.aliexpress.com/item/4001140417861.html?_fs_=true -fx
My bet would be that the substantial size of that bit is causing it to skate more at the center where the stiffness of the X-gantry is at its lowest. Retry the surfacing job with a 6mm bit using the same height and offset spacing you used with the 57mm bit. If it removes nothing at the sides yet cuts grooves through the center, you'll have your answer.
I'll try to find higher quality surfacing tool, and lighter, something around 1" / 25mm diameter. Any suggestion? I saw a CMT/orange tool, but the 25mm version is out of stock, only the 34mm remain. Thanks
