Plastic is not the first place engineers usually go when designing this kind of machine. Metal rules this kingdom because of its great properties that allow flexibility in design choices. Using plastic, every avenue to strengthen and rigidize the machine needs to be taken. Instead of using a thick steel sheet for a bed, 2 1/8" plates with an iso-grid web in between is used. Instead of a single plate connecting the x carriage to the y carriage, a its a more boxy structure. That's the main premise - if we turn parts into more boxy ones, we can get the necessary inertia to maintain rigidity.
## getting parts ready
### 3d-print
### laser cut
- carriage
- Side plates x2
- side L supports x2
- each 8 mins
- Bottom face x1
- Front facex1
- Diag webs x7
- Needs to be adjusted for kurf A bit of testing
### prepare
- heat insert all connectors and necessary parts.
## Mechanical
The machine can be divided into a few core parts:
- The X-carriage
- The Z-carriage
- The end effector
- The Y carriages
- The bed.
For the remainder of this document, I will refer to specific groups of components by the following:
**webs** - usually 1/8" laser cut pieces used to structurally support main sheets
<imageofwebs>
**connectors** - these are 3d printed pieces used to connect sheets of laser cut plastic together.
Each one is assembled with these connectors:
<imageofdifferentconnectorswithdifferentnames>
Let's talk about how to assemble:
### Bed
The bed is assembled with The HexTrompo connectors. These work as tensioners to sandwich the webs between the two large bed sheets.
1. Place all the female HexTrompos(ones with heat insert) required for the bottom sheet.
2. Place all your webs into the appropriate holes in the bottom sheet. Add the rail webs while you are at it to save time later.
3. Sandwich top sheet on top. You will have to align the webs. Do this from one corner to the other, moving the webs underneath through the holes meant for the HexTrompos. After the sheets are nicely fitted, add the male HexTrompos and tighten using M4x55 flathead bolts.
### X - carriage
Place the appropriate webs into place, and just follow the image. This one is pretty self explanatory.
### Y - carriages
If you have not yet installed the rail webs, do that.
Once webs and rails are together, the whole contraption should fit nicely onto the bed. Make sure the connectors are in the right place before you go to attach it on, otherwise, you won't be able to attach it.
The bearing are setup so that one is static and the other is on a beam H-bar type tensioning system in order to prevent it from jamming with all the other bearings since it is over-constrained. There is a preload of 0.2mm on this bearing
Maths:
$3x^2$
157.68 N of preload for the 0.22mm deflection on a link with width 3mm, height 5mm and depth of 6.50mm
Simple myosotis beam equation
### Notes
The RCAT 0030 is very solid when it comes to the base. The base is quite rigid in all degrees of freedom, however, it is easy to see its weak point in retrospect: the attachment from the x carriage to the bed. There is a diving board effect that happens at the edges and it could lead to major deflections. Thus the search for a more rigid structure is here.
# Side face attachments
The vertical side face needs to attach to the horizontal side face at some point. There is a desire to maintain the base as close to the 0030 as possible. So for the 0040, the edge rail webs will be swapped out to fit a more boxy way to attach rails for the bearings.
