The new clamping mechanism
We decided to go back to clamping the way it is done at St Olavs. Although, since there were some problems we want an improved version in our final product.
At St Olavs they use 4 prongs to clamp the prostate slices. Often they just use two, since it is hassle to tighten them. We want our solution to incorporate more prongs. This would make it possible to remove one of the prongs for procedures where they want to cut at specific locations near or at the edge of the slice. But we would have to make them easier/faster to tighten, so that we don't let out too much cool air and don't have to rely on the user being very patient.
In addition we want to protect the slice from cracking. The method they use at St Olavs can cause overtightening and that can lead to cracking. We want to create a tightening solution that does not let the user tighten above a certain pressure.
Our current ideas are:
- Making an improved version of the design at St Olavs that solves the problems mentioned above.
- Using pinching in some way. Pinching the slice at different locations around its edge should solve the same problems, since the force will not be applied horizontally.
If we were to go for the St. Olavs design we want to use cam clamps to provide a quicker and easier way of fastening the clamping pins.
https://www.sykkelkomponenter.no/sykkeldeler/cx-gravel/setepinner/setepinneklemmer/pro-setepinneklemme-qr?variant=PR900113
At sykkelkomponenter they are able to provide cam clamps that use M5 screws. They are ... mm wide and ... mm long.
There is stainless steel clamp levers sold with many varying sizes here:
https://www.elesa.com/en/elesab2bstoreoc/all-products/clamping-handles--1/cam-levers--1/Clamping-handles--Cam-levers--GN9275-d2-l2#sortby=0&facetvalue=-70000000000000000937752,-700000000000000000766659583116101101108,-7000000000000000007666695831169710511010810111511532115116101101108
They also exist at RS:
https://no.rs-online.com/web/c/hand-tools/clamps-vices/clamps/?searchTerm=Toggle%20Clamp
The current clamping mechanism
The current is using negative pressure from drawing out air to force the slice down on the mill bed.
The advantage of this is that it is extremely non-invasive. The force applied on the slice is only applied in the downwards direction and is evenly spread on the slice.
The disadvantages of this is several. It draws out cold air from the freezer, adding the requirement for an active cooling mechanism. It also makes it so that we have a solid mill plate, making milling all the way trough impossible without risking milling into the metal base plate. It draws out cold air from the freezer, adding the requirement for an active cooling mechanism. It also makes it so that we have a solid base plate, making milling all the way trough impossible without risking milling into the metal base plate. Furthermore, particles from the slice can enter the air stream and can contaminate the equipment, adding the need for a filter solution.
image
Possible improvements
Changing the design in a way that doesn't make the base plate uneven
Changing the design of the base box and base plate to something that wont cause an uneven milling surface would make extraction easier as it would allow for the CNC to mill further into the tissue without risking hitting the base plate.
Return to the MR Core Labs Setup
Using the clamping solution currently in place would remove this issue, as the head of the CNC mill bit can be below the surface and therefore cut all the way through without risking cross contamination. This clamping solution can probably still be upgraded and included into the CNC to make it automatic.
If we were to go back to this solution one would only be able to mill out one sample before extracting that one sample, as pushing loose samples around on the plate could lead to accidents/errors.
Incorporate a better vacuum/air pump in the system
Switching out the lab vacuum for a new better one is a crucial step in making the product more user friendly.
We believe that perhaps a radial air pump could be worth exploring. These pump often has an external motor and is used for high pressure air flows. Having an external motor would reduce how much the cold air is heated when passing through the pump, being favorable for a closed loop air flow system.
MR Core Labs Setup improvement 1
If we were to return to this design we have several ideas for improvement.
We want to implement an easier and more secure way of tightening the clamps. We want the clamps to go inwards in steps, but skip steps if the resistance is too high. This way we can make sure not to apply more pressure than necessary, reducing the risk for cracking.
We also want to have more than 4 clamps. Perhaps 6 or 8. This way, if you want to drill near the edge, you can simply remove that one clamp, and the others will still keep it in place.
MR Core Labs Setup improvement 2
Another way we could keep the slice in place is to use pinchers instead of clampers. This would possibly reduce the shear stress on the slice.
HeyHey
MRCL Vacuum pump
Testing the mobile vacuum pump down at MRCL with a completely sealed base-box setup and filter gave great success. The slice of ham was heldt firmly in place. The vacuum pump had an air flow of 96 l/min. This was plenty enough, even with a filter mounted. This pump is therefore sufficient enough to replace the vacuum cleaner in terms of air circulation. In addition, it was able to draw a negative pressure of -0.96 bar, which is close to a perfect vacuum. If it's required, a larger, designated vacuum pump with a larger air flow could be puchased for this project.
