Q. Can I request vacuum or vent blocks with a larger gap in the teeth?
A. Midland Valve-Less Vacuum and Vent Blocks have been designed with a tooth gap found to be most effective for a broad range of casting processes. We are able to provide blocks with larger tooth gaps upon request. We recommend filling out our Valve-Less Vacuum/Vent Block Sizing form (or download) so that we may provide a recommendation on needed evacuation area. Our technicians can then work with you to determine the optimal tooth gap to block size ratio for your process.
Q. Why evacuate the die cavity?
A.The air and gas present in a die cavity, runner system, and shot sleeve in the case of a cold chamber machine, must be evacuated by some means. These include conventional venting, vent blocks, or vacuum-assist. If gas is not evacuated sufficiently, part quality can be degraded, both in terms of function and cosmetics.
Q. Why select vacuum?
A. Vacuum-assist provide a positive pull to evacuate the largest volume of air and gas in the shortest amount of time from the die cavity. This can help to reduce scrap, and to cast more complex shapes. Not all dies require vacuum to achieve low porosity levels that meet customer specifications. In these cases, a vent block can provide the greatest area to achieve air and gas evacuation.
Q. My parts are too small for vacuum to be effective, what is my option?
A. It is true that not all dies require vacuum to achieve low porosity levels that meet customer specifications. In these cases, a vent block can provide the greatest area to achieve air and gas evacuation while helping to reduce excess material loss.
Q. Are there specific area requirements for utilizing vent blocks or vacuum-assist effectively?
A. Yes, we calculate the needed evacuation area as a function of fill time to volume. In order to do this we utilize PQ2 and proprietary calculations developed internally and proved out over years of real life applications. Note that vacuum-assist requires a smaller area in relationship to venting than either conventional venting or vent blocks due to the positive pull that it provides.
Q. How are the needed vacuum or venting areas determined?
A. We calculate the required vacuum or venting area based on a number of factors related to the die casting machine capabilities, casting volume, cavity fill time, slow shot time, and gate area.
Q. How can I obtain the required area for a specific tool?
A. By submitting a completed Valve-Less Vacuum/Vent Block Sizing form (or download) provided by Midland Technologies to be used in calculating the required area for a specific tool.
Q. How long will it take to obtain a sizing calculation for vent or vacuum blocks?
A. If we receive a completed information sheet in the morning, we can often have the results the same day.