When choosing a foundry, it is critical to choose one that has in-house machining capabilities. In-house machining means that the foundry has an on-premises machining facility.
Watch out for foundries that tell you they offer machining. Many foundries have partnered with machining ‘vendors’, but since these machine shops are not on-premises, they lose the ability to have instant feedback on things like location and datum points that ensure adequate stock, shift, core shift, etc. All these things and more can affect the final outcome of a ‘to print’ product.
You have certainly heard of “Who Shot Who”. That is the situation you will find yourself in if you choose a foundry that does not have in-house machining. Vendors will tell you that it is not their fault. They will point fingers at the other vendor, leaving you in a circular blame game with nothing but a shotty final product.
6 Problems Encountered When Sourcing Casting and Machining to Two Separate Vendors
Increased Lead Times
A large percentage of the time the foundry is late shipping to the machine shop. Now you are negotiating a new lead time with the machine shop. Many times, you are forced to pay overtime to keep your project on track.
Increased Costs
On top of the increased lead times and the costs added because of that, what about the trucking cost to your machining vendor? You would avoid any trucking costs if you placed your project with a foundry that has in-house machining. That freight cost is tacked on to the price of your product.
Increased Inspection
Will your machine shop do an incoming inspection as the castings arrive from the foundry? If not, beware. And if so, have you educated them on what to look for? And if you have, will they not add their cost to inspect your castings before machining, which adds to the cost of your project and also increases your lead time?
Powder Coating
Here at Precision Enterprises, we’ve developed proprietary nylon powders that have an increased nylon additive allowing for more scratch resistance. Our machining division has developed rubber-tipped hold-down tooling to grip the powdered casting without marring the finish. Now we can powder coat the casting before machining. That allows us to get ‘hang and shoot’ pricing from our coater, which is a considerable savings over traditional masking time spent by our coater. No masking…. just hang-and-shoot pricing. This is a considerable savings to you.
Datum Points
In the foundry business, a datum point is a specific point on the casting that’s used as a reference point for all other measurements and positioning during machining and inspections. Datum points matter every step of the way, from setting tolerances to accurate alignment during machining. Have you educated your machine shop about datum points? Are they on your print? Does the foundry know about them? Here is the typical scenario. You have a datum point in mind and have specified it on a parting line. The foundry grinds too much off, the machine shop locates from that datum, and by the time they get to the other end of the casting, they find they have no stock left to machine. Who is at fault? You will still be charged for both the casting and the machining but may not have any product. And what about the lead time to replace your parts?
Porosity Risks
We saved this one for last because all castings have a certain amount of porosity and when it comes to adequately accounting for porosity in an aluminum foundry, there is a lot to be said. Many times, that porosity is found during machining. If the foundry has not done its due diligence to keep porosity at an acceptable level, the machine shop will machine your castings and ship it to you. Now you have a finished product that is unacceptable. What do you do? The foundry will take the castings back, rerun them, and ship the new batch to the machine shop. But the machine shop will still invoice you for their machining time on the bad batch. Not only will this kill your expected lead time but drive your costs thru the roof.
So, if all castings have porosity, how come you don’t ship rejects that show gas?
“Because we know what the critical surfaces are in advance. We discuss and determine these critical areas during our pre-tooling release meeting. Now that we know critical areas, we can gate the pattern accordingly. And during the sampling run, take a machine cut on these areas to prove our process, and then choose a test level on each subsequent pour.”
No foundry is perfect. But our customers never see any casting with porosity. Why? Because if we get a casting that has gas in a critical surface, we scrap it right at the machine. That does not happen with outside machine shops. They machine and ship.
A very large portion of our customers are the medical equipment folks. They cannot have porosity. Blood-born pathogens can find these small pits and may be impossible to detect and therefore impossible to be thoroughly cleaned. Our people are trained to inspect for these pits, and their talents are brought to every casting we pour and likewise machine.
Aluminum Foundry Experience You Can Trust
All of these scenarios are things we have experienced over our 70+ years. There are more items that can bite you, too many to list here. Every single one of these possibilities is listed in our quality manual and our in-house process guide. It is also audited every year by an independent ISO audit team.
Of course, there are several levels of inspection that we do. Not every casting is a critical piece of medical equipment. We produce pump housings, musical instrument parts, and lifesaving medical castings, to name a few. And since we service every industry there is, we obviously are very competitive across the board. The difference is that we ask the questions prior to running hundreds of castings. We document these surface and location criteria, and we track and inspect for it. We solve problems before they happen, both in the foundry and the machine shop.
Work with a foundry that has in-house machining. From multiple vertical machining centers equipped with the 5th axis, to our large horizontal machining centers, Precision Enterprises can process nearly any size casting. We continuously monitor and audit our machining operations. This enables us to conform to all ISO Q9001:2015 Certified procedures and back up our conformance with the required measurements and documentation. We currently have 25+ CNC machines, from large verticals and lathes to our newest horizontal machining center.
Reach out today to get started on your project.
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