PEKO Precision Products

Four Concerns for BIG Parts CNC Machining and Assembly

Posted by Scott Baxter on Aug 18, 2015 11:49:31 AM

cnc machine shop largeLarge Parts CNC Machining and Assembly:

In the world of CNC Machining, Assembly and Fabrications, parts and features can range from the palm of your hand to the size of a tractor trailer and then some.  Different CNC Machine Shops are suited for many different size ranges.  High volume shops can produce millions of small parts in a short amount of time.  But today I wanted to talk about the big stuff.  Those large parts and assemblies that are not only hard to source for the OEM, but also hard to produce without all the right capabilities.  Large CNC parts and assemblies create very specific problems for the manufacturer but with smart planning and good equipment, the manufacturer can provide excellent value to the OEM without causing too much pain.     

Concerns when dealing with Large Parts:

1. Large CNC Machines and Assembly Fixtures

Large metal parts need to be processes by large CNC Machines.  Machines like gantry mills, horizontal boring mills and other large envelope equipment is very expensive and not easy to come by.  Finding a supplier with such large machines is no easy task.  Most shops have machine envelopes in the 30" range.  Anecdotally, I would guess that machines with 50"+ work envelopes are probably 10-20x more rare.  Furthermore, it is important that the large machines in question are of the highest quality and rigidity.  For many parts, it is critical that tight tolerances are held across long distances.  Rigid, accurate and repeatable machinery is very important especially in the case of large parts.  Fixturing is the same way.  In my opinion, in house fixture building is key to success with large part staging.  Machines like boring mills have huge tables and the fixtures must be built appropriately to ensure the part is stages correctly and the spindle clearance is accounted for.  When assembling large products, it is also important to have great fixtures that can reduce the assembly time and ensure perfect fitment of the product.  The fixtures in these cases should also be designed for maximum safety and have the ability to let the assemblers move freely easily about the product. 

large CNC machining

2. Real Estate

One thing most people don't think about regarding large parts is the amount of real estate the production takes.  In all operations, a huge amount of space is needed.  One needs to store the raw materials, then find a huge machine with a large footprint to put the parts on, then another large area for assembly and testing, then lastly final storage until shipment.  Even in low quantities, the amount of real estate used up can get very excessive.  States like California and Massachusetts where space is scarce and expensive fall victims to this dilemma often.  That's why outsourcing work like this makes a big difference for them. 

3. Operating Capital For WIP

Of course let's talk about who's going to fund all of this.  Buying a dozen billets of thousand pound stainless steel is not cheap.  OEMs must choose companies with strong financials so they can easily absorb the cost of WIP while processing big parts.  The last thing a customer wants to hear is that the contract manufacturer can't get material because of a financial issue. 

large parts assembly fixtures

4. Materials Handling

How are we going to move these big parts around the shop?  What size are the fork trucks in the building?  Is there a gantry built into the ceiling?  Is there sufficient equipment to move the parts and the fixtures into the machine?  Can we move this to assembly and packaging?  These are the questions one must ask in regards to materials handling of very large parts.  A great contract manufacturer will have all the answers and all the equipment to back it up.

large contract assembly




At the end of the day, many OEMs have large products in low volumes that they need machined and fabricated.  There is usually some difficult welding and post machining involved.  A well prepared machine shop or contract manufacturer will be able to handle all the difficulties that come with large part manufacturing.  Whether its the handling, machinery, cash or real estate a well prepared contract manufacturing firm like PEKO, although rare, will be a valuable resource to any OEM that has large parts and assemblies for outsource.

precision cnc machine shop services


Topics: CNC Machining, Contract Assembly, machine shop, large parts