Pro Pallet System
Models: PPS model for Fusion 360 | PPS Base model in STEP format | PPS Pallet model in STEP format (STEP files: Right click and select "Save link as...")
Mini Pallet System
Models: MPS Model for Fusion 360 | MPS Model in STEP format (STEP files: Right click and select "Save link as...")
NYC CNC: Making the MPS part 1 Full Length
John Grimsmo unboxes his MPS Full Length
The Mini Pallet System is built with the same basic components of the Pro Pallet System, but with the roughly half the components and cost. The MPS is best suited for lighter machining applications (spindles under 7 horsepower). The base lacks a perimeter seal so air/mist coolant is preferred over flood coolant but still functions perfectly in any cutting conditions.
The repeatability of the MPS is .0003" - the same as the PPS. However, the MPS lacks a cast iron core which makes it more sensitive to large temperature fluctuations that could change accuracy up to .001".
In short, very rigid. Bolting the base down with 2 included toe clamps is sufficient, but the question arises about the overhang of the pallets. For this reason, we've limited the maximum pallet size to 8" x 14". 2000 lbs of force at the corner of the larger pallet can flex it up to .004" in Z, but stable in X and Y. However, in reality no drill or endmill exerts this much force without breaking.
The MPS uses tight tolerance components that depend on equally tight tolerance machining of the aluminum pallet. For this reason, we prefer to manufacture all pallets in-house so that performance will not be affected. One workaround is to use our pallets as a master in which the user can bolt on other fixture plates.
All of our products can be purchased directly through us. This allows us to establish a close relationship with our customers and provide the best applicaton advice possible. Click here to order online or give us a call to place an order at (800) 352-2894. We accept all major credit cards and company checks.
SmartVac II Vacuum System
Models: Solid models are available after purchase. Please email us at firstname.lastname@example.org.
The US short answer - Multiply a part's surface area in square inches by 14 to find the downward holding force in pounds.
The Metric short answer - Multiply a part's surface area in square mm by .0098 to find the downward holding force in kg.
The long answer - The holding power of any vacuum chuck system is measured by the amount of air it can remove from under a part. You'll see vacuum ratings measured as "Inches of Mercury" or "Hg. A perfect vacuum, like outer space, would equal 29.9" Hg. It takes a lot of energy to create a perfect vacuum on Earth however the SmartVac II vacuum chuck draws a 94% or 28" Hg vacuum using only 0.8 cfm or compressed air! This is equal to 14 psi of downward holding force. This means a 6" x 6" part will be held with a force of 504 pounds (36sq.in. x 14psi = 504lbs) or a 150mm x 150mm part will be held with a force of 221 kg (22500sq.mm x .0098 = 220.5 kg).
The perfect part has a large surface area and with a small thickness cross section. Materials can range from plastics to metals. Harder materials can increase side loads during cutting which can slide a part off the chuck so lighter feedrates and depths of cut should be observed. One tip to overcome part movement is to sandwich a piece of 400 grit sandpaper between the chuck and the part to increase friction. Take a look at this article that explains this concept in further depth: CNCReport.com
The SmartVac II VCU draws a vacuum equal to or greater than convential vacuum pumps. Plus, the system is low maintenance since it does NOT require particle filters or coolant traps. Other systems require an electrically powered pump where the SmartVac II runs off a small amount of compressed air. The chuck portion of the system has nine vacuum inlets allowing up to nine individual parts to be held simultaneously where other systems only hold one part at a time. Pricewise, the system is far less expensive to purchase AND maintain than traditional systems.
This is easily done by attaching a Top Plate to the vacuum chuck surface and milling a gasket groove just inside the part's perimeter. Any through holes in the part need to have gaskets around them so the vacuum isn't lost when a cutter breaks through the bottom surface of the part. If the finished part has very thin features (imagine cutting out the letter O), consider leaving .002" to .005" of material at the bottom (the inside of the O) to maintain a larger vacuum area. Depending on the material, you should be able to easily peel out the center section by hand.
For all sizes of gasket, the groove width should be 95% of the gasket diameter. The groove depth should be 75% of the gasket diameter. This means our 1/8" gasket should have a width of .118" and a minimum depth of .094". The same formula for a 1/4" gasket comes out to .238" wide and .188" deep. For best results, add at least a .015" chamfer to the top of the groove.
Yes! The SmartVac II is perfectly suited to handle large parts. Multiple bases can be setup adjacent to each other using a Twin Base Kit. This kit contains everything needed to chain multiple bases together and operated by one VCU.
All of our products are sold direct. This allows us to keep prices low and to establish a close relationship with our customers to provide the best applicaton advice possible. Click here to order online or give us a call to place an order at (800) 352-2894. We accept all major credit cards and company checks.
Vacuum Workholding Tips
- Vacuum Power has an Upper Limit – The absolute maximum vacuum power any vacuum pump can achieve on Earth is 14.9 pounds per square inch at sea level. This is because the weight of air around us is what actually pushes the part down onto the chuck.
- Vacuum Workholding is Often a Secondary Choice – Yes, vises and clamps are the preferred method of holding a workpiece due to theoretically unlimited clamping force, however thin parts aren't easily held with a vise. A vacuum chuck may be your only choice, but don’t expect to be able to machine a part as aggressively as when using a vise. For example, a 3" square workpiece will only be held with 126 lbs of downward force and a 10" square workpiece is held with 1,400 lbs.
- Use Common Sense – Holding a part that is 1 inch square and 4 inches tall is not going to work. Short and wide parts that absolutely cannot be held with a vise are the best candidates for vacuum workholding.
- Use Workstops Whenever Possible – Side loads are the enemy of vacuum applications! Though vertical holding force may be high, cutting forces can shift a part sideways, especially when machining plastics with a low friction ratings (nylon, teflon, delrin). Adding pins, side rails or best practice of cutting a shallow pocket in one of our customizable Top Plates for the part to sit in will maximize sideways rigidity.
- Use Small Cutters when Possible (if you’re not following tip #4) – Small cutters exert less torque, reducing side forces thereby reducing the chance of sliding a part off the chuck. Instead of taking a 1/2″ wide cut around a part, use an 1/8″ cut with four passes.
- Use Sharp Cutters – Sharp tooling naturally exerts lower side loads which reduces the chances of a part sliding on a chuck.
- Use 45 Degree Helix Endmills – Low helix cutters won't lift a part, but they exert higher side loads. 45 deg cutters split the difference between lifting and sliding forces.
- Flexible Workpieces Might be Problematic – Because the rigidity of the workpiece helps maintain a vacuum seal, very thin or very soft materials may be more likely to flex at the edges and peel off the vacuum chuck. Use reverse helix cutters that have a downward cutting action and follow the 3 C's:
- The 3 C's of reverse helix cutters – Coolant: Have adequate coolant or air to help with chip evacuation since chips are forced downward. Clearance: Also consider milling a trough in a Top Plate along the edge of the cut so chips have a place to go. Corners: Outside corners have minimal support so slow down. Inside corners have good part support but more of the tool is engaged in the cut so side loads are higher than normal so slow down here too.
Models: RotoVise model for Fusion 360 | RotoVise model in STEP format (STEP files: Right click and select "Save link as...")